Social Development: Life History Theory and Human Behavior PDF

6 Social Development Key Concepts life history theory ontogenetic adaptations deferred adaptations conditional adaptations attachment styles C-F continuum fast versus slow life history principle of allocation shared environment non-shared environment behavioural genetics cooperation morality Some of the early developmental psychologists were influenced by Darwinian thinking. John Bowlby, for instance, proposed that the child is born with certain biological needs and that normal development is dependent upon these needs being met. Failure to do so could result in a wide range of problems in later life including criminality, intellectual under-achievement, promiscuity and psychological disturbances. More recently an evolutionary approach known as life history theory has been used to understand human development. This perspective suggests that some individual differences might be the result of children deploying different evolutionary strategies based on their childhood environment. Behavioural genetics research has also been crucial in unravelling the ef- fects of nature and nurture on the developing child. This has led to a controversial theory which states that socialisation is carried out in peer groups. Finally, we discuss evolutionary approaches to the development of cooperation presenting research suggesting even infants have a desire to coordi- nate their intentions and that young children prefer to engage in joint activity. We further discuss the notion that morality evolved for the express purpose of supporting cooperation. What Is Childhood For? Many organisms have more than one distinct stage to their life cycle. Consider the life history of the butterfly (or moth) which has two stages of relevance here: that of the immature caterpillar and the adult, each of which has a specific physiology and function. A caterpillar is an eating machine. Pow- erful jaws and an efficient digestive system allow it to eat up to 27,000 times its initial bodyweight and increase its weight by as much as 1000 times (James, 2017), the equivalent of a human baby reaching 3.5 tonnes by the end of childhood. To prevent predators interrupting this binge-fest, some caterpil- lars have intimidating eye markings or spines containing skin-dissolving poisons (see Figure 6.1). A butterfly on the other hand is a sex machine. Its function is to mate with other butterflies in order for them to mutually propagate their genes. Butterflies spend a lot of time in flight; they need to eat but they don’t need to bulk up, so the mouthparts of many are designed to sip only nec- tar – nature’s high-energy drink. Why the need to fly? Because flying allows butterflies to disperse, mate with non-kin and lay eggs in new regions to give their offspring the best chance of survival. The life cycle of a butterfly might seem a strange place to start a chapter on human de- 138 Social Development Figure 6.1 Fake eyes on the lackey moth caterpillar (Malacosoma neustria) may be used to ward off predators. described in a theory known as life history theory (Stearns, 1976). This suggests that at any point in time an organism invests effort in order to maximise fitness. Fitness, however, consists of a number of components that can be grouped into two categories, somatic effort and reproductive effort. Somatic effort includes feeding, avoiding predation, learning and – for juveniles – growth and mat- uration. Reproductive effort, on the other hand, includes finding a mate and producing offspring. Because they cannot reproduce, it might appear that juveniles can only engage in activities directed towards somatic effort, but this is not the case. According to life history theory, juveniles often have their eye on reproduction. Furthermore, according to developmental psychologist David Bjorklund (see Myers and Bjorklund, 2020), juveniles have adaptations specifically designed for this purpose. Bjorklund describes three different categories of adaptation present in childhood which he calls ontogenetic, deferred and conditional. Ontogenetic adaptations are adaptations that help the child survive in their current environ- ment which disappear later in life when they are no longer needed such as milk teeth and various forms of neonatal reflexes such as the rooting reflex. Here a baby when stroked on the cheek will turn towards the stroke and make a sucking motion: an adaptation with obvious benefits for feeding. Likewise, the protective spines or colouration helps caterpillars survive to adulthood. Ontogenetic adaptations are directed towards somatic effort: building bodies, obtaining food, avoiding predators and so on. Deferred adaptations are adaptations that have no immediate evolutionary benefit at the time they are deployed but are instead focused on the future when the child becomes an adult. An ex- ample of this is play (see Box 6.1) which is thought to foster the development of life skills. Similarly, the jaws and digestive tract of the caterpillar are designed to put on bulk so to produce more effective adults; caterpillars that fail to put on enough weight don’t make successful adults, if they become adults at all. So deferred adaptations are all about reproduction. Certainly, play is fun and provides immediate gratification for children, but the reason why it is fun, evolutionists argue, is to motivate children to What Is Childhood For? 139 Box 6.1 A Life History Account of Play If life history theory is correct and animals are under pressure to allocate their time and resourc- es adaptively, then how do we account for the prevalence in all higher mammals of apparently functionless behaviours such as play (see Figure 6.2)? After all, play seems to provide no direct benefit to the individual in terms of inclusive fitness. Is play purely functionless (in which case its existence is a serious challenge to life history theory), or does it have some hidden benefit? Evolutionists have addressed this question by suggesting that play is a strategy designed to en- hance future reproductive success by fostering the development of skills that will be important in adulthood. Play fighting, therefore, provides a safe way to practise skills that will be useful in adulthood (although, as we shall see later, the most useful type of play might depend upon factors such as the sex of the individual). According to life history theory, an animal investing in the future is doing so at the expense of maximising current fitness (e.g. survival) so play should only occur in situations when the environment is comparatively stable and unthreatening. Consistent with this prediction is the observation that when times are hard, juvenile mammals play much less than when times are good (presumably because they are allocating their time and energy to maximise their immedi- ate survival (Fagen, 1981)). Research on kittens apparently contradicts this finding. Bateson et al. (1990) found that female cats who had been placed on restricted diets weaned their offspring earlier than those on normal diets. This is sensible because the best thing for cats to do in food- reduced situations is to discharge any additional demands on their metabolism – such as hungry Figure 6.2 Kittens, like many mammals, like to play. 140 Social Development Box 6.1 (cont.) kittens – as quickly as possible. However, the early weaned kittens actually played more than those of mothers whose diets were normal and were therefore weaned for longer. This is appar- ently in contradiction to the predictions of life history theory: the kittens should be maximising their current survival chances not their future reproductive chances by engaging in play. This result, however, is only superficially counter to the predictions of life history theory. Bateson et al. found that early weaned kittens engaged in more object play, which is important for the development of hunting skills, at the expense of social play which has a longer-term re- productive benefit. The kittens were therefore maximising their immediate survival chances by allocating their time and effort to activities that enabled them to survive in a situation where they could not rely on their mother to provide them with food. Such studies undermine the miscon- ception that genes must necessarily lead to behaviour that is fixed and inflexible; as we can see, flexibility is often built into the system, with behaviour being contingent upon the environmental. Finally, conditional adaptations are sensitive to environmental conditions and can change the way an organism develops. The Arizona caterpillar is sensitive to the food it consumes in the first three days of life. Food available in the spring leads it to grow to resemble a flower, food in the sum- mer leads it to resemble a twig. These different forms allow the caterpillar to match seasonal variation in vegetation, thus evading predators (Canfield et al., 2008). Similarly, it has been suggested that in children, maturation and subsequent sexual behaviour may be affected by environmental riskiness. Conditional adaptations are again about reproduction and this is the topic that we turn to next. Parents’ Choices: Offspring Quality versus Offspring Quantity One particularly pertinent decision that many organisms have to make relates to the trade-off dis- cussed above, between maximising the quality of offspring over quantity. Why is this a trade-off? Simply because resource and time limitations mean that the more offspring you have, the less you are going to be able to devote to each individual: one of the fundamental laws of nature is that time and resources are always limited. In Chapter 7 we will consider how an organism’s reproductive strategies can be classified using something called the r–K continuum (don’t, for the moment, worry about what r and K stand for). Organisms adopting the r-selected strategy focus on producing as many viable offspring as quickly as possible and investing minimal resources in their upbringing. This strategy is employed by many species of fish that produce many millions of fry – the technical name for baby fish – and leave them to their own devices. Only a small percentage will survive to sexual maturity, but because the initial number is so large, enough will reproduce for it to be a worthwhile strategy (if you’ve ever seen the film Finding Nemo, you will be familiar with this situation). At the other end of the scale is the K-selected strategy. Here only a small number of offspring is produced, but the parents invest heavily in the care and upbringing of each individual such that a high percentage of individuals will make it to adulthood. Whether a species employs an r- or K-selected strategy depends primarily on the chances that the offspring will die as a result of harsh conditions (e.g. being eaten); when this is high, r-selection is optimal (see Chapter 7). Parents’ Choices: Offspring Quality versus Offspring Quantity 141 The r–K continuum is mainly used for classifying reproductive strategies between different species. When describing different strategies that occur within a species, life history theorists use a related scheme (known as the C–F continuum) that specifies whether the organism should maxim- ise current reproductive fitness or future reproductive fitness. Having a large number of offspring maximises parent’s current reproductive fitness (because there are immediately many copies of their genes), whereas investing heavily in few offspring maximises parent’s future reproductive success (because they are ensuring that the offspring survive to reproductive age). The best-of-all-possible- worlds strategy to invest heavily in many offspring is not possible for the majority of individuals because of resource and time constraints; you cannot have your cake and eat it. Box 6.2 Infanticide as an Adaptive Strategy Not every baby is nurtured and protected by his or her parents. Infanticide – the deliberate killing of young offspring – has existed throughout history and is not unknown today, even in industrial society. Stories of parents killing babies or allowing them to die are greeted with bewilderment: how could someone behave in such a callous manner, surely there must be something psycholog- ically wrong with such people? Research suggests that the answer to this last question is that it depends on how old the child is when it is killed. Technically (although not legally) infanticide can be divided into neonaticide (the killing of a newborn) and filicide the killing of babies and children older than one day. Why make such a distinction? Isn’t each act equally immoral and repugnant? Certainly that is the view of most peo- ple, but the distinction was made because research indicates that whereas mothers who kill older infants and children have frequently suffered psychological problems prior to the killing (e.g. depression), mothers of newborns have not (Resnick, 1970). Daly and Wilson (1984) argue that infanticide – as cruel as it might seem – might be the result of an implicit cost–benefit analysis made by a parent who believes her baby is unlikely to reach maturity either because it possesses abnormalities, or the particular conditions are unfavourable (e.g. famine, many other children, death of a spouse). Rearing children is an expensive business and under such circumstances the best strategy in terms of inclusive fitness might be to focus attention on other children, or wait until times are better and try for another child. Daly and Wilson’s data indicate that the women who commit neonaticide tend to be those who are least likely to be able to rear their offspring to maturity because they are themselves either young or unmarried or lack other social support (see Chapter 7). To further confuse things, a more recent terminology uses the term fast life history to refer to the situation where there is a tendency to maximise current reproductive success, and slow life history where the focus is on the future. For the rest of this chapter we will use the ‘fast vs. slow’ terminology as this is the most intuitive and the most commonly used in recent research on humans. Again, the best strategy for an individual to adopt is dependent upon the nature of the envi- ronment. The claim is that when the environment is uncertain and the chances of offspring reaching maturity are low, it is often optimal to maximise current fitness. Conversely, in predictable environ- ments where there is a high chance of offspring surviving to maturity it might be best to maximise future reproductive fitness. Under extreme circumstances there is evidence that parents might adopt the cruellest strategy of all, infanticide (see Box 6.2). 142 Social Development Maximising Fitness from the Point of View of Offspring Imagine that you are the captain of a crippled spaceship stranded an unimaginable distance from home. You are safe but fed up and want to be back with your family. Fortunately, you have an escape pod. Unfortunately it is low on fuel and it is 50-50 that you will get back safely. You can siphon fuel from ship to pod but this will take several months to complete. Do you leave now and risk it, or do you sit tight until you are certain to have enough fuel? If you are like most people who read this your answer will be to hang on to maximise your chances of getting home safely. Now imagine that your instruments inform you that there is an as- teroid heading towards you with a 95 per cent chance of collision, swiftly followed by obliteration. Do you change your mind? When presented with this, most do change their mind reasoning that it is better to bet on the ‘leave now’ option with a 50 per cent chance of survival than the ‘stay put’ option which has only a 5 per cent chance. The purpose of this little thought experiment is to encourage you to adopt the genes’ per- spective on reproduction. Children cannot reproduce so in a very real way genes are imprisoned in a child’s body in the same way that the crew are imprisoned in the spaceship. According to some life history theorists, such as Jay Belsky (1997) genes have engineered the physiology of the developing child in order to hasten the advent of their departure by reproduction. A crucial factor, he suggests, is environmental riskiness. If the environment is relatively risk free and parents are available and investing in the child, then the best option for the genes is for reproduction to be delayed and the focus to be on somatic effort. This means that the child can acquire useful skills, build networks of friends and develop deep and lasting relationships so that when they grow up and have children themselves, they are able to invest in them. This is a slow life history and is described by the first part of the dilemma above. Conversely, if the environment seems risky, such as in the second part of the dilemma, then it might be best to speed up the developmental process to more quickly usher in the point at which the genes can escape the body. In their 1982 paper Patricia Draper and Henry Harpending explored environmental riski- ness by investigating the effects of being reared in a home where the father was absent. Previously it had been noted (Whiting, 1965) that being reared in a home where the father is absent following divorce leads to precocious sexual development. In particular, boys in father-absent homes show more aggression than those who grow up in homes where fathers are present, are more rebellious and, in adulthood, view women in a sexually exploitative way. Girls in father-absent homes show a precocious interest in sex, have negative sexual attitudes towards men and have difficulty maintain- ing long-term monogamous relationships. Draper and Harpending suggested that the economic disadvantages and uncertainty caused by living in a single-parent compared to a two-parent family meant that maximising current repro- ductive fitness would be more effective than maximising future reproductive fitness. Children in fatherless homes, by maturing earlier and showing an early interest in sexual activity with multiple partners, are simply adopting a reproductive strategy designed to maximise their inclusive fitness by producing offspring early and at a high rate. Such tendencies, they argued, are formed in response to the presence or absence of an investing father during a critical period between the ages of five and seven years. Life history theory has also been applied to an area of psychology known as attachment. Attachment has been one of the most widely researched areas of social development over the last 50 Attachment Theory 143 years. Before discussing life history approaches to attachment, we shall spend some time describing the background to the theory and its key predictions. Attachment Theory British developmentalist John Bowlby (1951; 1969), was concerned with the factors that affect emotional and social development. Human infants are particularly helpless (technically known as altricial) and the attachment system evolved as a means of increasing the infant’s chances of survival and thus ultimately enhancing reproduction (see Chapter 7). Central to Bowlby’s theory of attachment was the idea that children form a working mod- el of the self and others as a result of their early experiences with the mother. The working model is a mental representation that includes both cognitive and affective components and is used to guide the child’s subsequent behaviour. Bowlby proposed that children who grew up in secure environ- ments with responsive and sympathetic mothers would establish a working model that included the belief that relationships were worthwhile and that people were generally to be trusted. Children who grew up with unresponsive or abusive mothers, or if the mothers were absent, would have working models that led them to view relationships and other people with suspicion. The formation of a working model was thought by Bowlby to have a critical period between the ages of about six months and three years. This means that experiences within the critical period are all important when it comes to the formation of the working model, with later experiences being much less im- portant (see Figure 6.3). Figure 6.3 Bowlby believed that being deprived of human contact could negatively affect future relationships and mental health. 144 Social Development Table 6.1 The three principal attachment styles Type of attachment Typical behaviour in Typical behaviour in Approximate ‘strange situation’ later childhood and proportion in adulthood each category Secure attachment Cries when the mother disappears, Generally form long- 2/3 (Type B) seeks attention when she returns and lasting and stable resumes playing following being relationships comforted Insecure-avoidant Shows little attention to mother; does Generally form more 1/4 (Type A) not show much distress when she ephemeral relationships disappears and as easily comforted by than securely attached stranger as by mother individuals Insecure-resistant Infants remain very close to mother; Generally tend to 1/10 (Type C) show anxiety when she disappears overcommit to few and is not easily comforted when she relationships returns Note: The different forms of attachment are sometimes thought of as a continuum, with anxious avoidant individuals at one extreme, anxious resistant at the other and securely attached individuals somewhere in the middle; hence they are also known as Types A, B and C. Despite recent criticism, Bowlby’s ideas have stimulated a great deal of research and many developmentalists today draw on his model of attachment; one such researcher was psychologist Mary Ainsworth (1967), who developed a procedure known as the strange situation in which the immediate effects of maternal separation are studied under laboratory conditions. Children are tak- en into a room which contains a number of toys. When the child is comfortably playing a stranger enters the room and shortly afterwards the mother leaves. The mother returns a little later and engages the child in play while the stranger slips out. The mother then leaves once more and the stranger returns. Finally, the mother returns once more. The infants frequently cry when the mother disappears. This is quite normal – what is of interest is how they respond when she reappears. Based on their response to the mother’s disappearance and reappearance, Ainsworth originally classified infants into three categories secure attachment, insecure-avoidant and insecure-resistant (see Table 6.1). Subsequently other categories were added based upon observation, such as disorganised attachment, but for the purposes of this discussion these additions are not relevant so we do not discuss them further. As you can see from Table 6.1 the majority of infants are categorised as securely attached, although the actual proportion varies from culture to culture, indicating perhaps that cultural differ- ences in childrearing practices has an effect on infants’ behaviour. Applying Life History Theory to Attachment The attachment theories of Ainsworth and Bowlby, and the resulting evidence is clear: insecurely attached children – whether as the result of maternal deprivation or poor parenting – are more likely Applying Life History Theory to Attachment 145 to suffer from mental illness, engage in deviant activities and are generally less successful in life. Although securely attached children are in the majority – accounting for around two-thirds of chil- dren studied – this still means that one-third of people are insecurely attached in one way or another. Children and adults with insecure attachment styles are often seen as dysfunctional as they tend to have less successful relationships, as we shall see, than those with secure attachment styles. If this were the case, a third is a high number (most dysfunctional behaviours, such as mental illnesses, are much lower than this). One possibility is that rather than the behaviours that accompany inse- cure attachments being thought of as deviant and maladaptive, they might have some evolutionary benefit given the environment in which they grew up (Belsky, 1997; Belsky et al., 1991; Chisholm, 1996; 1999). Ainsworth’s attachment styles can be seen as adaptive reproductive strategies given a particular environment. Attachment experiences provide children with information relating to the amount of risk in their environment, which is used as an index of their reproductive value. Put blunt- ly, attachment enables the child to predict the future. Or at the very least it provides information that enables the child to guess at future circumstances and adjust his or her behaviour appropriately in order to select the optimal reproductive strategy. The stress felt in early childhood as a result of a disruptive family life might indicate that the parental environment is risky, and hence serves to trigger a different strategy from that of a low-stress family life. Jay Belsky’s Life History Theory of Attachment Psychologist Jay Belsky (1997) proposes the following adaptationist account of the three principal attachment styles which we discuss in turn. SECURE ATTACHMENT Belsky argues that the parenting style that leads to secure attachment rep- resents the emphasis of parenting over reproduction or, put differently, of maximising quality rather than quantity of offspring. Parents will therefore bring up few children but spend a great deal of time, effort and resources providing for them. For their part, children respond to this high-invest- ment environment by forming the beliefs that the world is a benevolent place, that other people can be trusted and that relationships are emotionally rewarding and enduring. These beliefs would orient children towards forming close relationships with others, including romantic relationships. When they reproduce, such children are likely themselves to be sensitive parents who invest heavily in their children, so long as the economic situation allows it. Research into adults classified as securely attached by the Adult Attachment Interview indicates that they tend to report higher levels of relationship security than do insecurely attached individuals. Secure men engage in more supportive relationships with their partners (Ewing and Pratt, 1995); the romantic relationships of secure men and women are longer lasting than those of insecure people (Hazan and Shaver, 1987); and secure partners are more likely to marry in the first place (Kirkpatrick and Hazan, 1994). INSECURE-AVOIDANT ATTACHMENT Recall that children who are categorised as insecure- avoidant tend to treat the mother with some indifference: they show little distress when she leaves the room in the strange situation experiment, and little joy when she returns. What use might such a strategy be with respect to that child’s inclusive fitness? Belsky (1997) proposes that 146 Social Development in situations when the predicted availability of resources is low and others cannot be trusted, maximising future reproductive fitness might be inefficient. What is the point, for instance, of getting married and bringing up a few children if your spouse leaves you and either takes away the children that you have invested in so heavily, or fails to contribute his (or her) resources to your offspring? With this in mind, it might be profitable to adopt a lifestyle ultimately direct- ed towards maximising current reproductive fitness. Such individuals might therefore engage in opportunistic relationships not fully committing to their partners and perhaps even exploiting them. Furthermore, such individuals might have a series of sexual partners and might begin mat- ing at a comparatively young age. Evidence suggests that insecure-avoidant individuals are more willing than others to en- gage in sex in the absence of an enduring relationship (Brennan et al., 1991), are more likely to have dated more than one person (Kirkpatrick and Hazan, 1994) and are more likely to have experienced the break-up of a relationship (Feeney and Noller, 1992). Furthermore, avoidant mothers are more likely to be ambivalent and unsupportive towards their children and show the least responsiveness and affectionate behaviour when reunited with their children during the strange situation (Crowell and Feldman, 1988; 1991). There is some evidence that insecure-avoidant children reach sexual maturity earlier than do those categorised as secure. Moffitt et al. (1992) presented evidence that family conflict at age seven was predictive of earlier onset of puberty in girls. It seems that envi- ronmental cues might influence biological aspects of maturation as well as psychological charac- teristics. INSECURE-RESISTANT ATTACHMENT Insecure-resistant children are the least numerous of the three main attachment categories and tend to be very clingy and attention demanding. In particu- lar, they seem to be very demanding of the mother, and it is difficult for anyone else to comfort the child. Belsky proposes that such children are being driven into a null reproductive strategy, where they are destined to have no children. Superficially, this might seem like a maladaptive strategy, as the individuals will pass on no copies of their genes directly. Recall, however, that you don’t need to reproduce yourself in order for your genes to go forward to the next generation (see Chapters 2 and 7). Having a child might ensure that 50 per cent of your genes go forward to the next generation, but a niece or nephew carries 25 per cent of your genes as a result of you sharing 50 per cent of your genes with your sibling. Thus helping the offspring of a close relative can help to increase your inclusive fitness if, for whatever reason, you are unable or unwilling to have children yourself. Belsky’s life history explanation for this form of attachment is the most speculative of the three although there are precedents in the rest of the animal kingdom. For example, it is known that other animals born either physically or behaviourally sterile will help their siblings or parents to rear offspring (Dawkins, 1976; 1989; 2006; see also Chapter 7). However, there is little direct evidence for this particular part of Belsky’s theory, partly because comparatively few individuals fall into this category. Some evidence is found in questionnaire studies. Females classified as anxious resistant tend to admit to ‘mothering’ their partner, rather than engaging in a typical romantic relationship (Kunce and Shaver, 1994). Furthermore, firstborns, particularly if they are female, are more likely to be resistant than children born later – consistent with the idea that some children may be behav- iourally ‘sterile’ to help out with their younger siblings. Evaluation of Life History Explanations of Attachment 147 Table 6.2 How the three principal attachment styles arise out of an interaction between the parent’s reproductive strategy and the child’s resultant developmental strategy Attachment style Parental reproductive strategy Child’s developmental strategy Secure long term maximise long-term learning, quality able and willing to invest of development high parenting effort maintain investment from ‘rich’ unconditionally accepting, sensitive, parent responsive to the child Insecure-avoidant short term maximise short-term survival unwilling to invest avoid rejecting, potentially high mating effort infanticidal parent dismissing, rejecting of child Insecure-resistant short term maximise short-term maturation unable to invest ‘quantity’ of development parenting effort with inadequate resources maintain investment from ‘poor’ inconsistent, preoccupied but not rejecting parent of the child Source: Chisholm (1996). Evaluation of Life History Explanations of Attachment The life history approach has strong similarities with that of Darwinian medicine (see Chapter 12) which also makes the claim that many apparent forms of dysfunctional behaviour are perfectly func- tional when inclusive fitness is used as a currency rather than society’s expectations. Further recall that the currency of inclusive fitness is the number of genes that are passed on to the next generation rather than the well-being of the particular individual whom the genes use as their transient vehicle. A strategy that maximises the number of genes that replicate themselves will win out even if this ultimately leads to an individual who is miserable and is frowned upon by society. It might help at this point to consider the suicidal tendencies of the male red-backed widow spider we discussed in Chapter 1: he dies to give his genes the best possible chance. Remember also that the claim is that such strategies would have been adaptive in the an- cestral environment rather than the environment in which the overwhelming majority of individuals is studied (e.g. industrial or post-industrial society). This presents a particular difficulty in testing these theories. If we were studying non-human animals most of whom, we assume, are living under circumstances close to those in which they evolved than the average twenty-first-century human, we could do the appropriate cost–benefit analysis and work out whether each of the strategies was adaptive given the particular conditions under which the offspring was raised. Because cultural evo- lution has changed our environment so much, it is difficult to do the same thing with human beings. However, Waynforth et al. (1998) investigated the pre-industrial Mayans of western Belize and the Aché of eastern Paraguay to test the effects of – among other things – father absence. The Aché and Mayans were used because, it is assumed, living in a pre-industrial society their culture is thought to be closer to that of our ancestors than that of Europeans and North Americans who are usually 148 Social Development the subject of such studies. The results were mixed. Most importantly they found that the patterns of father absence and age at first reproduction did not fit the simple life history model. Individuals reared in father-absent families did not tend to reproduce any earlier than those reared in families where the father was present. They suggest that more complex models need to be formulated that take into account mediating factors such as kin help, mating effort and parenting effort. More recent evidence has shown a fair amount of support for Belsky’s theory. For example, Belsky et al. (2010) found that 65 per cent of girls categorised as insecure at 15 months of age using the Strange Situation test experienced menarche (onset of puberty) at less than 10.5 years of age compared to 54 per cent of those categorised as secure at 15 months. The insecure group also com- pleted puberty early as well. A similar study by Belsky et al. (2010) found that maternal harshness at 15 months predicted early menarche – as before – but also greater sexual risk taking in adolescent girls. Measurement of maternal harshness was achieved by the responses that their mothers gave to a questionnaire. ‘Harsh’ mothers tending to spank their children for doing something wrong, believed that children should respect authority, should be quiet when adults were around, believed that praise spoiled the child and did not give many hugs. In a study of 4553 British women Nettle et al. (2011) found that early pregnancy was accounted for by environmental risk factors such as low birth weight, short duration of breastfeed- ing, separation from mother in childhood, frequent family residential moves and lack of paternal involvement. Social economic status and the age of the participants’ mother when they were born were controlled for in this study. Not all evidence supports Belsky’s theory, for example studies by Ellis et al. (1999) and Miller and Pasta (2000) failed to find results in the predicted direction. But the weight of the evi- dence currently supports the hypothesis. There is however one important consideration. This is that it is possible genes that lead to early menarche and/or sexual risk taking are somehow associated. We know that most, perhaps all, genes have more than one phenotypic effect (a property known as pleiotropy) so it is not beyond the realms of possibility that sexual risk taking and early menarche are both influenced by a single gene or a combination of genes that tend to be inherited together. If this were the case it would give a similar pattern of results. This is not as far-fetched as might be imagined. To take the pleiotropy version of the story (one gene with multiple phenotypic effects). Imagine that there was a gene which led females to display the characteristics described in Belsky’s theory (early menarche, early sexual activity, risky sex, multiple partners etc.). Further imagine that this gene also had the effect of making mothers treat their children harshly (beating them, showing them less love than is typical and so on). Now a mother who has this gene is likely to pass it on to her daughters. The researchers measure the mother’s maternal harshness at time 1 and find that she is harsh, they measure her daughter’s age of onset of puberty at time 2 and find that it is early and conclude that mother’s behaviour at time 1 is causing her daughter’s behaviour at time 2. In fact, it could be that the daughter’s behaviour has nothing to do with her mother’s behaviour. Underlying both the mother’s and the daughter’s behaviour is the effect of our hypothesised gene. If you think that the traits of maternal harshness and early age menarche are unlikely bedfellows you could consider the gene(s) to be gene(s) of low parental investment which maximise current rather than future reproductive success which leads to women having more children (as a result of earlier and greater sexual activity) and invest in them less (which manifests itself as maternal harshness). We can consider this as there being two phenotypes – although really it is more likely to be a continu- um – when times are harsh the environment favours the low-investment, fast life history strategy, when times are good it favours the high-investment, slow life history strategy. In an attempt to sep- arate these two entirely different explanations, Mendle et al. (2006) conducted a children-of-twins Evaluation of Life History Explanations of Attachment 149 study. They recruited a group of adult female identical twins all of whom had daughters. They were selected so that one twin had experienced family disruption, such as divorce, and the other had no disruption. They then compared the age of menarche of the disrupted twin’s daughter to that of the child from the twin with the intact family. The logic here was that if early menarche was genuinely a response to environmental disruption the daughters from the disrupted family should show earlier menarche than those from the intact family. On the other hand, if early menarche were the direct effect of low-parental-investment genes, as discussed above, there would be no difference. Children of twins were used to maximise the genetic similarity of the children. The study failed to find any support for the hypothesis as there was no difference in pubertal timing between the two groups. A different methodology found evidence for Belsky’s hypothesis, however. Tither and Ellis (2008) compared older and younger sisters from the same disrupted family, the families were select- ed such that the older sister had reached or was close to reaching menarche at the point at which the disruption happened while the younger sister was still some way from puberty. The prediction was that the younger sister would show earlier puberty as she had longer in the disrupted environment than the older sister. In support of the hypothesis they found that for disrupted families the younger sister experienced menarche significantly earlier than the older sister, whereas for non-disrupted families it was the older sister who experienced (slightly) earlier puberty (see Figure 6.4). The effect of disruption on menarche was enhanced when the family showed serious paternal dysfunction. Again, in line with the predictions. It has to be said that although the principal results were signifi- cant, the effect sizes were small. Notwithstanding this, it is difficult to explain these results without assuming that family disruption plays some role in accelerating puberty, although it remains a pos- sibility that some combined genetic and environmental model offers the best explanation of the data. Some children may be predisposed to develop more rapidly in the face of a disrupted childhood than others. So far this has not been tested. 13 12.9 12.8 12.7 12.6 12.5 12.4 12.3 12.2 12.1 12 Biologically intact families (N=93) Biologically disrupted families (N=68) Younger sisters Older sisters Figure 6.4 Data from Tither and Ellis (2008) showing the age of menarche (in years) for sisters of families that broke up or stayed together (see text for details). It should be noted that the effect is very small, with the difference between younger sisters in disrupted families attaining menarche just over three months earlier than those from intact families. 150 Social Development Finally, there needs also to be more work developing the model with respect to differences between males and females as to what constitutes an optimal reproductive strategy. As we saw in Chapter 4, there are substantial sex differences in mating strategy because men and women are subject to different constraints. It seems likely that the same environmental circumstances (e.g. fa- ther present or absent, parents maximising quality or quantity of offspring) might have differential effects on the best strategy for males and females (Maccoby, 1990). This argument is very important from the perspective of evolutionary psychology. In Chapters 3 and 4 we discussed how males and females might be under different pressures with respect to reproduction. Females are much more restricted than are males in the number of offspring that they can produce, they typically release one egg every month and should they fall pregnant are then ‘infertile’ during the subsequent period of gestation and lactation. For their part, although men can potentially father thousands of offspring – and therefore have much more to gain – they are also less likely to obtain a sexual partner (because other men might be ‘commandeering’ more than one woman) and therefore have much more to lose. Furthermore, a woman is always certain that she is the mother of her child, a man is always less than 100 per cent certain that he is the father. Such differences indicate that the optimal reproductive strategy might be different for males and females under the same set of environmental conditions. Behavioural Genetics: Separating Nature from Nurture One of the big problems in studying the effects of parental behaviour on offspring is that parents po- tentially influence their children in two entirely separate ways. First there is the effect of the genes: a biological parent shares with each child 50 per cent of his or her genes by common descent so parents obviously exert a genetic influence on their children. Second, in most families, there is the social influence on children of growing up in close proximity to their parents. The fact that these two influences frequently co-occur means that if children resemble their parents in their behaviour we don’t know whether it is due to shared genes, social learning or some combination of both. This is what psychologists call a confound. Behavioural genetics attempts to remove this confound by conducting research on twins and children that have grown up in adopted families. Identical twins are the result of a single fertil- ised egg that splits into two early in development, they therefore share 100 per cent of their genes (hence they are also called monozygotic twins ‘mono’ means single and ‘zygote’ is the term for a fertilised egg). Non-identical (or dizygotic) twins are the result of two separate fertilisations (two eggs, two sperm) and therefore share 50 per cent of their genes just like regular siblings. By compar- ing the similarities and differences between these different types of twins, it is possible to estimate the effects of nature and nurture on individual differences in behaviour. For instance, the amount of variation between individuals can be calculated by looking at the differences between identical twins reared apart on the trait because, since they are genetically identical, it follows that any dif- ference between them must be due to the environment. The results of such studies estimate that the environment accounts for between 50 and 60 per cent of the variation among them on a variety of traits (see Chapter 12). It therefore follows that genes account for 40–50 per cent of the variation. It is important to point out that such statistics do not differentiate between the direct effects of the genes and the indirect effects of the genes. For instance, people judged to be attractive are generally more assertive, a finding that is explained by the observation that attractive people are generally treated with more deference than less attractive people (Jackson and Huston, 1975; see Box 6.3). Even if there were no direct genetic influence on assertiveness, we can see that there is an indirect Evaluation of Life History Explanations of Attachment 151 Figure 6.5 Richard Lewontin’s thought experiment showing how heritability can be misleading. one; genes influence attractiveness which leads to individuals being treated differently, which affects their personality. In the data of behavioural genetics research, both show up as effects of the genes. Adoption studies look at families who have adopted two or more unrelated children, ideally from birth. Researchers can then investigate the correlation between adopted siblings on some trait (say extraversion; see Chapter 13) and then compare that correlation between two unrelated chil- dren raised in different households. If we find a higher correlation between adopted siblings than those reared in different families then it provides evidence that growing up in the same household makes children more similar (we have removed the confound of genes because they are unrelated). Furthermore, researchers can also explore correlations between parental traits and those of their adopted children and, in some studies, compare this relationship between that of the child and their biological parent who played no role in the child’s upbringing. Before we move on it is important to point out that estimates of heritability can sometimes be misleading (see Chapter 2). Consider the example presented by Richard Lewontin (see Chapter 2). He asks us to imagine buying a packet of seeds from the local garden centre (see Figure 6.5). The seeds are genetically diverse rather than clones. We divide the seeds in half and plant them in two identical trays. Both these trays are treated exactly the same (the same light, temperature etc.) but one tray is given good nutrients, the other poor nutrients. The seeds grow into plants and after a period of time we observe two things. First, that the average height of the plants in the tray contain- ing good nutrients is greater than the average height of the plants in the poor nutrient tray. Second, if you examine the plants within each tray some are taller than others. So the answer to the question ‘why are some plants taller than others’ is ‘it depends on which plants you are comparing’. The between-group difference is entirely due to the environment (one rich, one poor) since there is no net genetic difference between the two groups (we divided the packet randomly, remember). However, if we wish to explain the within-group difference then this is entirely due to genetic differences among the seeds; some are genetically taller than others. 152 Social Development We know this because all the seeds within a tray were treated identically. So here is the lesson. Re- search on a particular population – let’s say middle-class children – might reveal that there is very little environmental contribution to differences in intelligence, most of the variation is explained by genetic differences. This might lead you to conclude that any differences in intelligence between groups – say middle-class children and working-class children is also genetic. But this may not be the case, as Lewontin’s thought experiment demonstrates, differences within groups may be genetic, but differences between groups could be entirely environmental. A study by Turkheimer et al. (2003) shows that this is not just hypothetical. He studied several hundred identical and non-identical twins and found that the environment accounted for most of the variation in intelligence for poor children with genes having little effect, but for well-off children the situation was reversed. One possible explanation for this is that for poorer children, even small differences in their environment might have large effects on intelligence (the availability of books, parental involvement etc.) but the environment for well-off children is already so good that any differences in the environment have little effect. To return to Lewontin’s example, giving a plant some fertiliser is going to improve its growth but there comes a point where improvements in the environment cease to have any additional effect, at this point any differences in plant size will be down to genetic differences. The overall message, however, is that the results of behavioural genetic studies are complex and can be misinterpreted and maybe misused. Imagine that a government took the results from a behavioural genetics study that was conducted only on the children of well-off families. Such data might show, as they do in Turkheimer’s study, that genes are by far the most important aspect of educational achievement which may then lead governments to cut funding to schools because ‘the results show that they don’t have much of an effect’ with disastrous effects for the un-tested children from poorer backgrounds. It is important, therefore, to have some understanding of this influential type of research for political as well as scientific reasons. Box 6.3 Behavioural Genetics and the Effects of the Genes on the Environment Many think of the contribution that genes and the environment make to development as being independent. The genes have some initial effect and then the environment has its own separate effect uninfluenced by the genes. This is not the case, however. Behavioural geneticists show how the genes can have a radical effect on the environment that the child experiences. There are three types of gene–environment interactions. Passive interactions occur because, in cases where children are reared by their parents, they will tend to be similar in personality, intelligence and temperament to their parents. Hence, an intelligent child will, on average, be reared in a household with intelligent parents who might surround the child with books or engage the child in intelligent conversation. Children inherit not just ‘intelligent genes’ from their parents, but also an environment that is intellectually stim- ulating. In reactive–evocative interactions, children with a certain genetically influenced trait will tend to be treated differently by people. We know, for example, that children who are judged attractive are punished less harshly for misdemeanours than those who are more homely (Dion, Evaluation of Life History Explanations of Attachment 153 Box 6.3 (cont.) 1972; Landy and Aronson, 1969) and that people judged attractive are generally more assertive (Jackson and Huston, 1975). Thus, the way that people treat a child (which constitutes part of a child’s environment) will be, in part, affected by genetically linked dispositions. Finally, active interactions occur because children tend to seek out people who are similar to them. Thus, active children who like sport will tend to band together, as will children who like intellectual pursuits and so on. If any of these traits are associated with some underlying genetic influence (like the two just mentioned), then we might say that the genes are influencing the en- vironment in which children grow up. Having sounded a note of caution against oversimplistic interpretations of behavioural ge- netics we can further explore the way that behavioural geneticists explore environmental influence. Behavioural geneticists divide the environment into two separate forces: the shared environment, which consists of the influences common to all siblings (the fact that they have the same parents, or might go to the same school), and the unique or non-shared environment, which consists of all the influences that are specific to an individual (experiences with teachers, peers, childhood illnesses and also differences in the uterine environment). These three effects – the genes, the shared envi- ronment and the non-shared environment – are considered to be the only effects on development, and therefore sum to 1 (or, if you prefer, 100 per cent). The effect of the shared environment can be estimated in a number of ways. One is by comparing the difference between identical twins reared together (who share genes and the same environment) with those reared apart (who share only their genes). Any difference between these two groups would give the effect of the shared environment. Another is to measure the similarity between adopted ‘siblings’ – unrelated individuals adopted at an early age by the same family. The assumption here is that because they share no genes by com- mon descent any similarities between them must be the result of their shared environment. The results of these diverse pieces of research lead to the same conclusion: the shared en- vironment accounts for little or none of the variation left over when you take out the genetic effects. One might think that identical twins reared in the same household would be more similar to each other than those reared apart. In fact, there is very little difference between them (Plomin et al., 1994). Other research indicates that unrelated children who are adopted and brought up as siblings in the same family environment are no more similar to each other than any two unrelated children chosen at random from a population (Plomin and Daniels, 1987). The measures in these studies were the heritability of personality, cognitive skills and mental illness. At most the data suggest that the shared environment accounts for 10 per cent of variation among people (Turkheimer, 2000). Adoption studies also reveal another startling fact: adopted children resemble their biological par- ents (whom they haven’t met in any real sense) almost as much as if they were brought up by them (Plomin, 2018). The message from behavioural genetics is that within normal limits (i.e. if we ig- nore abuse) parental behaviour has startlingly little effect on how children turn out. The only traits of the many hundreds studied which show a less-than-negligible influence of the shared environment are political and religious beliefs which are around 20 per cent (Hatemi et al., 2014). If genes account for 50 per cent of the variation among people and the shared environment between 0 and 10 per cent, what accounts for the missing variation? Given that the three causal fac- 154 Social Development tors on variation among people – genes, shared environment, non-shared environment – sum to 1, it stands to reason that it must be the non-shared environment – each child’s unique experiences – that is accounting for these differences. So, Do Parents Make a Difference? Above we have presented two seemingly contradictory theories. Life history theory suggests that genes build mechanisms that enable children to use their parents’ behaviour as a way of choosing (unconsciously) a reproductive strategy designed to maximise genetic fitness based on environ- mental riskiness: in short, parents make a difference. Behavioural genetics research, on the other hand, suggests that identical twins reared apart are no different from one another than those reared together and adopted siblings no more similar than two people randomly plucked from the popula- tion: in short, parents do not make a difference. In 1998, psychologist Judith Rich Harris caused a storm of controversy when she made this very point in her book The Nurture Assumption. Rather than parents, she believed that children were socialised by their peers – something she called ‘group socialisation theory’ and which we discuss further in Chapter 13. So how can we reconcile these apparently contradictory findings? Belsky suggests that some children might be genetically more susceptible to parenting than others (Belsky, 2005). If this were true, however, identical twins would be equally susceptible to parenting and it would therefore show up as a genetic effect (as an effect of an effect of genes shows up as a genetic effect). It would not, therefore, account for why identical twins are not, behaviourally, identical. When focusing on attachment security, behavioural genetic evidence demonstrates that the shared environment has an effect on preschool children, with a third of identical twins reared by the same parents showing different attachment styles (Gervai, 2009). However, this effect seems to disappear in later childhood and adolescence (Fearon et al., 2014) with genetic influences of around 40 per cent on attachment style, the non-shared environment contributing around 60 per cent and a negligible influence of the shared environment. So behavioural genetics research suggests that the shared parental environment has lit- tle effect on how children turn out. Does this mean that the life history approach to reproduction is incorrect? Not necessarily, for three reasons. First, it is possible that life history theory works its effects through the non-shared environment, those parts of the environment that differ between children. The research by Tither and Ellis, described above, showed parental divorce might have different effects depending on the child’s age. Even if both children have the same experience, the experience might have different effects on the child: younger children might be more able to respond to the trauma by switching to a fast life history. Second, an assumption of the shared environment is that parents treat all of their children the same. While this makes some sense (you would think that good parents would be good to all their children and the same for bad parents) there may be subtle or not so subtle variations in parenting style which might lead to important effects on development. Again, this would manifest itself as an effect of the non-shared environment. We return to this issue in Chapter 13 when we discuss individual differences. The Development of Cooperation As we see in Chapter 7 creatures such as ants, bees and naked mole rats show extremely high levels of cooperation, so high, in fact, that these animals are referred to as eusocial (the prefix ‘eu’ simply means ‘good’, as in ‘eutopia’). However, all these animals achieve such high degrees of sociality by So, Do Parents Make a Difference? 155 being very closely related to one another which means that their cooperation can be explained by Hamilton’s rule of inclusive fitness (see Chapter 2). Humans also cooperate with relatives, perhaps the best example being parental care, but we are unique in the extent to which we cooperate with non-relatives (see Chapter 8). Look around or pick any human-made object at random, it will al- most certainly have been the result of many hundreds, if not thousands, of people working together, even if most of these people have never met. A wooden chair, for example, is, as objects go, a pretty simple one and may even have been made by a single person, but many others will have supported the carpenter. They would have cut down the trees to obtain the wood, made the glue that holds it to- gether, manufactured the paint that protects it, made paint brushes, the paint can, the woodworking tools, generated electricity, looked after her children while she worked and many, many others. And that is just for a humble chair (see Chapter 14). Think of the number of people involved in making a mobile phone, a car or a jetfighter. So enmeshed are each of us in cooperative networks that many have suggested that it didn’t occur by accident: somehow evolution must have played a role. So, what are the fundamental aspects of cooperation and how does it develop? SHARED ATTENTION AND SHARED GOALS According to a team led by Michael Tomasello, one of the fundamental attributes of cooperation is the ability for individuals to identify shared goals and coordinate action in order to achieve them. The philosopher Jean Jacques Rousseau (1712–78) identified a problem in cooperation known as the Stag Hunt problem (see Grueneisen and Wyman, 2020) in which people have to choose between hunting hare on their own, which yields a small but certain return, or cooperating as a group and hunting stag which yields a large but uncertain outcome; uncertain because everyone has to pull together if they are to be successful. Formally, the Stag Hunt problem is known as a ‘coordination game’ as it is only successful if people agree on a particular course of action and stick to it. Another example of a coordination game is whether we drive on the left- or right-hand side of the road. It doesn’t matter which we choose, so long as we all choose the same. Crucial to coordination games are shared goals. So long as we all share the same goal, such as not wanting to die from a head on collision, then people will generally fall into line. (As we shall see when discussing the ‘chicken game’, it is when goals differ that problems arise, but children can still negotiate a solution.) The origins of goal sharing, and coordination begin early. As we saw in Chapter 5, from birth babies are interested in social stimuli, and through the first year begin interacting with adults and show evidence of turn taking in interactions, sometimes referred to as ‘proto-conversations’ (Trevarthen, 1979). At around 12 months infants will engage in ‘proto-declarative’ pointing where the child will direct an adult’s attention towards something of interest and monitor the adult’s gaze. Only when the infant is certain that the adult is attending to the same object will the child lower its hand (Lizkowski et al., 2004). Shared attention is an important constituent of shared goals which, as we saw above, is itself a crucial component of coordinated action. From a young age, children are sensitive to shared goals. When adults and two-year-olds agree to engage in joint activity such as rolling toy trains down an incline and the adult fails to join in (either because they are unwilling or unable to participate) then the child will try to reengage their partner by gesturing or vocalising rather than giving up the task or continuing alone even when the task could easily be completed alone (Warneken, Gräfenhain and Tomasello, 2012). This shows that even at two years of age, children have an awareness that the goal of the exercise is to share the effort, not just to complete the task individually. Three-year-old chimpanzees, on the other hand, respond to an adult’s disengagement by carrying out the task alone, indicating that they do not have the same understanding of coordinated action as 2-year-old children (Warneken, Chen and Tomasello, 2006). 156 Social Development Figure 6.6 By cooperating, children can achieve things that they could never achieve alone. Interestingly, in these studies, the adults made a verbal commitment to joint activity; in sit- uations where adults participated but made no prior verbal commitment and then withdrew, children were less likely to encourage their partner to reengage and more likely to carry on alone (Gräfenhain et al., 2009). This suggests such commitments change the nature of a task, serving as a promise to the child that the adult undertake certain cooperative obligations. Understandably the child is puz- zled and perhaps disappointed when the adult reneges on their promise because the adult has broken the rules of collaboration. A further difference between children and chimpanzees is that, given the choice between solitary and collaborative action, children prefer the latter, even when it makes little difference to the rewards gained (children would prefer to hunt ‘stag’ even when there was little advantage over hunting ‘hare’). Chimpanzees, on the other hand, prefer to act alone and only switch to cooper- ative action when the goal cannot be achieved alone (Bullinger, Melis and Tomasello, 2011). As Grueniesen and Wyman (2020) note, when chimpanzees collectively hunt for smaller primates it seems that it is just a group of individuals working together, rather than a group with one shared intention. It is almost as if chimpanzees understand only ‘I’, whereas children understand the collective ‘we’. COOPERATION IN LARGE GROUPS ‘We’ can encompass a number of entities, from temporary alliances gathered together to complete a specific task, such as hunting parties or experimen- tal situations such as those described above, through small but more enduring and close-knit So, Do Parents Make a Difference? 157 groupings such as families or friendship groups, to large conglomerations, often involving strangers, such as a tribe, a society, a culture or a religion. One of the defining features of all these groupings is that they have norms that regulate behaviour: ‘that is not the done thing’, ‘We do it like this’. There are good reasons for the existence of norms as adhering to them can enable us to behave appropriately without having to work everything out from first principles. Some norms are explicit and enshrined in rules and laws, such as driving on the correct side of the road, which has obvious benefits for safety; others are implicit, such as queueing in a bank, which ensures fairness. But some norms seem to have no real underlying rationale to them (they don’t ensure safety or fairness, for example) they are just the ‘done thing’. There is no good reason why some cultures shake hands when they greet and others kiss, they are just conventions that remove the need to work out what to do when you meet someone. (Although getting it wrong can lead to a great deal of awkwardness.) In short, norms are little more than what the majority of people within a particular group do. From an early age, children are sensitive to the majority way of doing things. In a study by Grueneisen, Wyman and Tomasello (2015) five-year-olds watched other groups of children perform a task. The majority of these groups used one method of solving the task, a minority used a different method. When it was their turn to perform the task, the erstwhile observers used the majority meth- od. While this might seem as if the children were showing conservatism or a lack of imagination, in fact it makes sense for two reasons. First, in the absence of any other information as to which method is best, it is reasonable to assume that the method favoured by the majority is the better one. Second, and as discussed earlier, doing what others do is a good way of avoiding criticism or social awkwardness, as we shall see later. Older children can establish their own norms of behaviour. One study used a paradigm called the ‘chicken’ game. (The name derives from a ‘game’ where two drivers drive towards each other, the first driver to swerve to avoid collision, the ‘chicken’, loses.) In the study, two toy trucks each controlled by a child are moving towards each other. Each truck contains rewards, but if the trucks collide neither child gets anything. If one child swerves out of the way then some of the re- ward due to that child is lost (the child who does not swerve gets the full reward). Understandably there is a pressure not to swerve because everyone wants the full reward, and sometimes it is better to have nothing than to see someone else benefit from your being chicken. Because the game is played repeatedly there is therefore a chance that both children will leave empty handed. However, this is not what happens. Eight-year-olds take the opportunity to discuss and establish norms to en- sure that each child gets approximately equal payoff overall, often by establishing a turn-taking rule (‘you swerve first and I’ll swerve on the next go’). Although children realise that norms are somewhat negotiable, even at 3 years of age they also realise that there is often a right way of doing things. When seeing a puppet violating certain norms that children are familiar with, children will tell the puppet that he’s doing it wrong and try to teach him the correct method (Rakoczy, Warneken and Tomasello, 2008). Such policing of norms is commonplace in society. Norms are highly moralised, and their contravention can of- ten lead to the perpetrator being judged harshly or even punished, even when the contravention has no direct effect on those witnessing it. History is rife with people being persecuted for doing things differently whether these be religious practices, sexual behaviour or how a person dresses. A possible evolutionary explanation for this enforcement is that it helps increase group cohesion (Reader and Hughes, 2020). There is evidence that groups which are more cohesive tend to per- form better when in competition with other groups (Choi and Bowles, 2007) encouraging defectors 158 Social Development within a group to fall into line would increase cohesion. If norm enforcement is intended to increase in-group cohesion, then we would expect in-group transgressions to be judged more harshly than similar transgressions by the out-group. After all, why would members of the in-group want to make the out-group more effective cooperators? A phenomenon known as the black sheep effect (Marques and Paez, 1994) shows exactly this pattern of results, with participants punishing in-group transgressions more harshly than out-group transgressions (the name comes from the phrase ‘black sheep of the family’ which describes a family member who is different from everyone else in the family). Children also recognise that norms are often limited to the in-group rather than having uni- versal relevance and, like adults (see Chapter 8) show a preference for favouring in-group members when allocating rewards (Dunham, Baron and Carey, 2011). By eight years of age they also show less tolerance for in-group compared to out-group transgression (i.e. the black sheep effect; Abrams et al., 2014). SUMMARY OF THE DEVELOPMENT OF COOPERATION Humans are super cooperative and the above discussion of research shows that the motivation to cooperate with others is present from the earliest years through mechanisms such as turn taking and attention sharing. As children de- velop, they acquire skills such as the ability to decide on and follow norms of cooperation, and to encourage others to do the same. No doubt there are cultural variations in the development of co- operation, and many of these children would have acquired methods and values from their parents, teachers and older peers to help them to arrive at mutually beneficial conclusions. It is also the case that under certain conditions, such as perceived anonymity, that children can behave selfishly, and one cannot ignore the fact that in many of these studies children wanted to appear to ‘do the right thing’ in the eyes of the experimenters. We should therefore see the above as a description of what children can do under the right conditions rather than seeing it as a description of the way that children actually are all of the time. Perhaps the most important finding from the above research is the way that children see themselves as part of a collective ‘we’ rather than just as individuals. Surely this is an important factor in enabling humans to have developed a cooperative ability ri- valled only by the eusocial animals. Indeed, it could be said that humans have achieved eusociality via a different route. MORALITY For a long time, it was thought that morality contradicted the principles of evolution- ary theory. If genes build brains to ensure their future survival, then it makes no sense for them to help copies of genes in other people, unless those people happen to be relatives (inclusive fitness). The previous section, however, might give a clue as to how morality evolved and its purpose: coop- eration. As we discussed above, although other animals, such as chimpanzees, cooperate with non- kin, none do it as completely as humans. And children (as well as adults) prefer working together, even when it is no more profitable than working alone. The anthropologist Alan Fiske proposes that morality exists to regulate relationships with others to enable harmonious cooperation (Rai and Fiske, 2011). Fiske proposes that there are three basic types of human relationship: community sharing where members of a group share effort and resources; authority ranking which specifies a hierarchy within the group: leaders and followers, carers and dependents, the strong and the vulnerable; and equality matching which governs one- to-one reciprocal relationships: tit-for-tat, an eye for an eye, one good turn deserves another. (There is a fourth type of relationship in Fiske’s scheme, market pricing, which is largely an extension of equality matching but using tokens such as money, but this is not evolutionarily fundamental so we will not discuss it further.) So, Do Parents Make a Difference? 159 These three relationship types govern how cooperation operates on a number of different levels and each has its own associated moral principles in terms of rights and wrongs: Community sharing determines obligations towards their particular group (perhaps best thought of as an ancestral tribe) which permits group-minded cohesion, enabling their group to compete with rival groups. The morals of community sharing relate to respecting the history and traditions of the group, the identification of individuals with the fate of the group and rules governing the equal sharing of food and other resources (Bowles and Gintis, 2000). The morals of authority ranking relate to the hierarchical organisation of members within a group. Subordinates are expected to obey and respect superiors – whether they be parents, leaders or gods – and to punish those who defile or show disrespect to superiors. For their part, superiors are expected to guide, nurture and protect those who are subordinate to them. The morals of equality matching specify how individuals should relate to each other within their group in terms of equality. Unless someone happens to be of a different status, in which the morals of authority ranking will apply. Group members are expected to reciprocate in kind: if one person cooks another a meal, it is incumbent on the recipient to repay the favour in some way. People who cheat, steal or lie about others should be punished. So, Fiske’s view of morality is that it evolved in order to regulate behaviour to facilitate group living. It recognises that our selfish urges have to be off-set by community-based morals so that we all reap the benefits of group life. Interestingly, Fiske also argues that most of the bad things people have done to each other throughout history, and continue to do today such as genocide, female genital mutilation, honour killings and war, are done for moral, rather than immoral or amoral reasons. Morality, it appears, has a dark side. Evolutionary psychologist Oliver Curry similarly argues that morality evolved to facili- tate cooperative endeavour but points out that, among other things, Fiske’s theory lumps together cooperation with kin with cooperation with non-kin. Curry presents his own theory of morality- as-cooperation which rectifies this and other omissions from Fiske’s theory and those of others (e.g. Haidt moral foundations theory; Haidt and Joseph, 2011). In Curry’s opinion, previous attempts to explain morality as a way of solving problems of cooperation suffered from two main problems: they were too narrow, and they were too arbitrary. So Curry broadens out the set of problems that morality was designed to solve beyond those put forward by Fiske and he bases morality on game theory which he claims, maps out the set of social dilemmas that morality should solve. A discussion of game theory is beyond the scope of this chap- ter, as it is discussed in Chapter 8, but in a nutshell, it is a way of treating various social dilemmas in a precise mathematical way. The hawks and doves game (see Chapter 1) is identical to the chicken game described above, with the hawkish strategy being aggressive and the dove-ish strategy being submissive. When driving towards each other if one plays dove and the other hawk, Dove swerves and loses the game. If both play hawk then neither swerve and both lose. As we shall see adopting hawk and dove strategies is one way in which Curry believes conflicts can be resolved. The results of this and various other games has led to a variety of social dilemmas that Curry believes specifies the set of social problems morality has evolved to guide. These are kinship, mutualism, exchange and three different situations which require conflict to be resolved: contests, division and possession (see Table 6.3). Of these, mutualism is similar to Fiske’s community sharing and exchange is similar to equality matching. Kinship, as has already been mentioned, is part of Fiske’s community sharing, the main difference is that Curry’s framework highlights conflict resolu- tion as separate domains of morality (see Table 6.3). 160 Social Development Table 6.3 Oliver Curry’s ‘periodic table of morality’ Problem Examples Morals Kinship kin detection and incest avoidance, obligations to kin, duty of parental parental investment, rules against care, prohibition of incest incest Mutualism coalitionary psychology, common friendship, loyalty, conformity knowledge, theory of mind; in-group favouritism Exchange trust, gratitude, cheater detection, reciprocity, punishment, trust, revenge and forgiveness gratitude, apology, forgiveness Conflict resolution status, dominance and deference, virtues and excellences, Hawkish virtues (Hawk-Dove) contests (fortitude, bravery, skill, generosity, beauty), Dove-ish virtues (humility, respect, deference, obedience) Conflict resolution (division) equal sharing or sharing based fairness, negotiation and compromise on need Conflict resolution (possession) territoriality, property law property rights, theft Source: Adapted from Curry (2016). Conflicts over resources can be solved by dominance and submission (hawk-dove), divid- ing the resource equally, or by morals relating to ownership rights which gives rise to the negative moral attitude towards theft. Both Fiske’s and Curry’s theories have their roots in different worlds: Fiske’s in cross- cultural anthropological studies of relationships, and Curry’s in the arcane mathematics of Game Theory. In reality they have more in common than they differ. Fiske underplays the differences between kin and non-kin interaction, and Curry underplays the hierarchical structure of human societies which, surely, is one of the most important reasons why, for good or for bad, humans dominate the globe. Which of the above theories of morality is correct is, at the moment, uncertain. Science, being what it is, it is likely that none is the complete story, that said, both are surely correct when they emphasise cooperative endeavour as the driving force behind the evolution of the moral sense. Summary A life history theory of development claims that, from an early age, children are monitoring their environment and making decisions about their future reproductive value. Based on their assess- ment of the environmental conditions, they can choose to maximise current reproductive success or future reproductive success. Attachment theory (Bowlby, 1969) claims that early attachments (relationships with caregivers, usually the mother) can have a substantial effect on subsequent personality and behaviour. Central Questions 161 to this theory is that a child forms a ‘working model’ of the self and relationships that is used to guide subsequent behaviour. Secure working models generally lead to more satisfactory and stable relationships in later life than insecure ones. Ainsworth proposed that there are three attach- ment styles, secure (Type B), insecure-avoidant (Type A) and insecure-anxious/resistant (Type C). A large amount of evidence suggests that individuals exhibiting insecure attachment styles will generally suffer more psychological and relationship problems later in life. Life history theory applied to attachment theory suggests that rather than insecure attachments being dysfunctional (as was often thought) they might be considered adaptations. In the ancestral environment, insecure attachments might have led to children adopting strategies that were de- signed to maximise their fitness. If the level of risk is low, they will tend to adopt a strategy that maximises future reproductive value (a slow life history), if it is high they will attempt to maxim- ise current reproductive value (a fast life history). Behavioural genetics research using twin and adoption studies suggest that not only do all traits have a degree of heritability (often around 50 per cent), but the remaining variation in traits is accountable to the non-shared rather than the shared environment. Whatever effect parents are having on children, being reared in the same family doesn’t seem to make them any more similar. Children are born wired for social interaction and quickly develop the motivation and skills to share their experiences and their goals with others. Unlike chimpanzees, which prefer to act alone unless it is impossible to do so (such as a hunt) children prefer to cooperate with others, even when it is not strictly necessary. Children tend to follow the majority when it comes to doing new things and will enforce norms when they see others doing things differently. By around eight years of age they will create and enforce their own norms. They also recognise that the norms governing other groups may be dif- ferent from their own. Cooperation is strongly linked to morality. In fact, morality is one of the forces that drives us to cooperate. The reason why people cooperate fairly is either because they feel bad if they don’t or because they fear being punished if they are caught cheating. Questions 1. To what extent do you think parents and peers influence children’s development? Think of exam- ples of influences that your parents might have had on you, and also influences that might have come from your peers. 2. To what extent are environmental risk factors of early sexual behaviour merely triggers to adaptive developmental trajectories rather than direct causes? How does this differ from the way that it has traditionally been thought of? Assuming that this is true, how might this affect public policy and the way that such individuals are viewed? 3. Between and within species reproductive strategies can be explained by the extent to which an individual is following a slow or fast life history. How does this relate to research and theory of sexual reproduction explained in Chapter 3 such as the red queen hypothesis? 162 Social Development 4. What factors might affect whether a child (or adult) cooperates with others or acts on their own? When might self-interest override cooperation? 5. Choose a set of rules such as the Ten Commandments or the laws of cricket and see whether you can work out whether each rule can be categorised using Fiske’s scheme of community sharing (relating to the traditions and obligations of group membership), authority ranking (relating to the responsibilities of members to a higher power, and the obligations of the higher power to the members), and equality matching (relating to the rules that govern how members should treat each other). What rewards and sanctions are specified if the rules are followed or broken? Further Reading Fiske, A. P. and Rai, T. S. (2014). Virtuous Violence: Hurting and Killing to Create, Sustain, End, and Honor Social Relationships. Cambridge: Cambridge University Press. Harris, J. R. (2009). The Nurture Assumption: Why Children Turn Out the Way They Do (Rev ed.). New York: Simon and Schuster. A still controversial book that unleashed group socialisation theory to a general (as opposed to technical) readership. This version is revised with additional material. Pinker, S. (2002). The Blank Slate: The Modern Denial of Human Nature. London: Allen Lane. The chapter on children is a lucid discussion of many of the themes discussed here. Plomin, R. (2018). Blueprint: How DNA Makes Us Who We Are. London: Penguin. An update on research into behavioural genetics: everything you have been told about development is wrong (unless you have read this chapter).

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