Theories of Human Development PDF

CHAPTER Theories of 2 Pavel L Photo and Video/Shutterstock Development LEARNING OBJECTIVES BIOLOGY AND EVOLUTIONARY 2.7 Identify...

CHAPTER Theories of 2 Pavel L Photo and Video/Shutterstock Development LEARNING OBJECTIVES BIOLOGY AND EVOLUTIONARY 2.7 Identify the conflict associated of proximal development influence THEORIES with each of Erikson’s psychoso- cognitive development. cial stages. 2.14 Describe Bandura’s concepts of 2.1 Describe the structure and function of genes. 2.8 Describe the basic concepts of modelling, reciprocal determinism, humanistic theory. and self-efficacy. 2.2 Describe the ways genes influence development. LEARNING THEORIES SYSTEMS THEORY 2.3 Describe how epigenetic 2.9 Explain how classical conditioning 2.15 Describe how contexts influence mechanisms regulate genes and occurs. development from Bronfen- development. brenner’s bioecological 2.10 Explain the process of operant 2.4 Describe how evolutionary theories conditioning. perspective. explain individual differences. 2.16 Explain why ecobiodevelopmen- 2.5 Describe how biology and COGNITIVE THEORIES talists endorse early intervention evolutionary theories contribute 2.11 Describe how cognitive strategies. to our understanding of disease development progresses, processes and interventions. according to Piaget. COMPARING THEORIES 2.12 Describe information-processing 2.17 Determine the distinguishing PSYCHOANALYTIC THEORIES theory processes. characteristics of human development theories. 2.6 Summarize the main ideas of 2.13 Describe how Vygotsky’s Freud’s psychosexual theory. concepts of scaffolding and zone  26 U N IT 1 FOUN D ATIO N S E very parent knows it’s a constant struggle to keep babies from putting everything in their mouths. Whether it’s an attractive toy or a dead insect they encounter while crawling across the living room floor, infants seem to be driven to use their mouths to explore. Have you ever wondered why? An inborn drive to explore the environment may be responsible, or babies may find the physical sensation of mouthing an object highly pleasurable. Perhaps babies use their mouths more than toddlers and preschool- ers do because they don’t yet have the ability to fully control other parts of their bodies. Clearly, there are many possible explanations. As you learned in Chapter 1, developmental psychologists use theories to formu- late hypotheses, or testable answers, to such “why” questions. For this reason, you’ll be reading about theories in every chapter of this book. To help you make sense of all these theories, this chapter will introduce you to five influential families of theories that have quite different ways of answering questions about development—the biological and evolutionary theories; the three “families” of psychological theories; and systems theory, which integrates multiple theoretical perspectives into a comprehensive theory of human development. Theories in these families will come up again and again as you make your way through this book. LEARNING OBJECTIVE 2.1 Describe the structure and BIOLOGY AND EVOLUTIONARY THEORIES function of genes. A knowledge of biological processes is an important foundation for understanding Watch evolutionary theories of development. Both genetic and epigenetic factors interact with How the Human Genome Map Affects You environmental variables to shape our level of health and well-being across the lifespan. We are just beginning to understand how epigenetic processes integrate nature and Explore Building Blocks of Genetics nurture—epigenetics is positioned to profoundly change the way we think of human development in the 21st century. Evolutionary theories propose that the genetic and physiological processes that underlie human behaviour changed gradually over time through genetic mutation and natural selection. Evolution is used to explain cognitive and, by extension, social and cultural behaviour. chromosomes strings of genetic material in the nuclei of cells GENETICS deoxyribonucleic acid (DNA) Our body cells’ nuclei contain 23 pairs of chromosomes that are made up of about, a chemical material that makes an astounding, 2.0 metres of finely coiled deoxyribonucleic acid (DNA) molecules (see up chromosomes and genes Figure 2.1). Each chromosome is divided into segments, called genes, each of which influences a particular feature or developmental pattern. A gene controlling a specific genes characteristic always appears in the same place (the locus) on the same chromosome in complex chemical units of a every individual of the same species. For example, the locus of the gene that determines chromosome that control or whether a person’s blood is type A, B, or O is on chromosome 9. A genome is all the influence inherited traits DNA an organism possesses. To appreciate the complexity of the genome, consider genome that, in humans, each of our 46 chromosomes contains anywhere from 231 to 3141 all the DNA that an organism genes (read about genetic disorders in Chapter 3). In all, each human body cell nucleus possesses possesses an estimated 23 000 genes. An essential function of genes is to instruct body cells to combine 20 standard proteins organic compounds, consisting amino acids to build the 35 000 or so proteins that our bodies need to function prop- of amino acids, that perform erly. Proteins are organic compounds that form the structures of the body and regulate most life functions and make its maintenance. Basic structural elements of our bodies—for example, muscle, brain, up the majority of cellular and bone—are made up of different proteins. Proteins also control all biological pro- structures cesses ranging from metabolic and immune functions to intercellular communications.  C HA PT ER 2 T H E ORIE S OF DE VE LOP M ENT 27 FIGURE 2.1 Four essential organic compounds, A – adenine, T – thymine, C – cytosine, and G – guanine, are organized into base pairs that form the double helix structure of DNA. The human genome—the DNA contained in the nuclei of our body cells—comprises 23 pairs of chromosomes contain- ing strands of genes. DNA is wound around histones (a protein material) to form what resembles beads-on-a-string, called the nucleosomes. Deposited along the nucleosomes are epigenetic markers, which, collectively, make up the epigenome. Epigenetic markers control gene expression by either opening up or tightly packing nucleosome clusters (chromatin). When chromatin is loosely spaced, gene expression is possible, but when chromatin is tightly packed, genes are silenced. Thus, when epigenetic markers signal chromatin to open, genes (segments of DNA base pairs) are ready to be transcribed and translated into proteins. (Source: Nevid, J.S., Greene, B., Johnson, P.A, & Taylor, S. (2009), Essentials of Abnormal Psychology, 2nd Canadian Edition. Toronto, ON: Pearson Education Canada. Figure 2.1. Artwork copyright © Alexandra Enns. Printed with permission.) GENOTYPES, PHENOTYPES, AND PATTERNS OF INHERITANCE LEARNING OBJECTIVE 2.2 Describe the ways genes influ- The genotype is the actual DNA material that determines each person’s unique genetic ence development. blueprint. The phenotype is the individual’s whole set of observable characteristics. One way to remember the distinction is that the phenotype can be identified by directly genotype observing the individual. For example, you can easily see that a woman has brown eyes, an individual’s unique genetic which are part of her phenotype. Her genotype, though, can’t be so easily determined. blueprint In many cases, you would have to know the eye colour of her parents and offspring to phenotype determine whether she carries genes for another eye colour, because complex rules gov- an individual’s whole set of ern the way genotypes influence phenotypes. Three principles of genetic transmission observable characteristics explain such patterns of inheritance. DOMINANT AND RECESSIVE GENES The simplest genetic rule is the dominant- dominant-recessive pattern recessive pattern, in which a single dominant gene strongly influences phenotype. a pattern of inheritance in (Table 2.1 lists several normal phenotypical traits and indicates whether they arise from which a single dominant gene dominant or recessive genes.) People whose chromosomes carry either two dominant or influences a person’s phenotype two recessive genes are referred to as homozygous. Those with one dominant and one but two recessive genes are necessary to produce an recessive gene are said to be heterozygous. associated trait If a child receives a single dominant gene for a trait from one parent, the child’s phenotype will include the trait determined by that gene. In contrast, a child’s phenotype  28 U N IT 1 FOUN D ATIO N S TABLE 2.1 Genetic Sources of Normal Traits Dominant Genes Recessive Genes Polygenic (many genes) Broad lips Thin lips Height Nearsightedness Flat feet Eye colour Coarse hair Fine hair Body type Curly hair Red hair Skin colour Dark hair Blond hair Personality Types A and B blood Type O blood Rh-positive blood Rh-negative blood Freckles Dimples (Source: Tortora, G., & Grabowski, S. (1993). Principles of anatomy and physiology. New York, NY: HarperCollins.) will include a recessive trait only if she inherits a recessive gene from Critical Thinking both parents. For example, geneticists have found that the curliness of hair is controlled by a single pair of genes (see Figure 2.2). The Think about your hair type and that of your sib- gene for curly hair is dominant; therefore, if a man has curly hair, his lings. What does your hair suggest about your genotype includes at least one gene for curly hair and at least half of parents’ genotypes? his sperm carry this gene. Conversely, straight hair is recessive, so a straight-haired man’s genotype must include two straight-hair genes for his phenotype to include straight hair. Geneticists also know that the only kind of hair type a straight-haired father can pass on to his children is straight hair, because all his sperm carry recessive, straight-hair genes. MyPsychLab In addition, human geneticists have learned that both dominant and recessive genes Explore the concept Dominant and differ in expressivity, meaning that the degree to which any gene influences phenotypes Recessive Traits on mypsychlab varies from person to person. For example, all individuals who have the gene for curly hair don’t have equally curly hair. So, even when a child receives a dominant gene for curly hair from her father, the amount and type of curl in her hair probably won’t be exactly the same as his. Blood type is also determined by a dominant-recessive pattern of inheritance. Because a person must have two recessive genes to have type O blood, the genotype of every person who has this type is clear. However, the genotype of people with type A or B blood is not obvious because types A and B are dominant. Thus, when a person’s phenotype includes either type A or type B blood, one of the person’s blood type genes must be for that type, but the other could be for some other type. However, if a type A father and a type B mother produce a child with type O, each of them carries a gene for type O, because the child must receive one such gene from each parent to have the type O phenotype. polygenic inheritance POLYGENIC AND MULTIFACTORIAL INHERITANCE With polygenic inheritance, a pattern of inheritance in many genes influence the phenotype. There are many polygenic traits in which the which many genes influence dominant-recessive pattern is also at work. For example, geneticists believe that chil- a trait dren get three genes for skin colour from each parent (Barsh, 2003). Dark skin is domi- nant over light skin, but the skin colours also blend together. Thus, when one parent is dark-skinned and the other is fair-skinned, the child will have skin that is somewhere between the two. The dark-skinned parent’s dominant genes will ensure that the child  C HA PT ER 2 T H E ORIE S OF DE VE LOP M ENT 29 Straight-haired Curly-haired Curly-haired Curly-haired mother I father mother II father Parent’s Curly Straight Straight Curly Curly Curly Straight Curly genotype Possible Straight Curly Straight Curly Straight Curly Straight Curly Curly Straight Curly Curly Curly Straight Curly Curly offspring genotype Curly hair Curly hair Curly hair Curly hair Curly hair Curly hair Curly hair Curly hair Curly-haired Curly-haired Curly-haired Straight-haired mother III father mother IV father Parent’s Straight Curly Straight Curly Straight Curly Straight Straight genotype Possible Straight Straight Straight Curly Curly Straight Curly Curly Straight Straight Straight Straight Curly Straight Curly Straight offspring genotype Straight hair Curly hair Curly hair Curly hair Straight hair Straight hair Curly hair Curly hair FIGURE 2.2 Examples of how the recessive gene for straight hair passes from parents to children. will be darker than the fair parent, but the fair-skinned parent’s genes will prevent the child from having skin as dark as that of the dark-skinned parent. Eye colour is another polygenic trait with a dominant-recessive pattern (Liu et al., 2010). Scientists don’t know for sure how many genes influence eye colour. They do know, however, that these genes don’t cause specific colours. Instead, they cause the coloured part of the eye to be dark or light. Dark colours (black, brown, hazel, and green) are dominant over light colours (blue and grey). However, blended colours are also possible. People whose chromosomes carry a combination of genes for green, blue, and grey eyes can have blue-grey, green-blue, or blue-green eyes. Likewise, genes that cause different shades of brown can combine their effects to make children’s eye colour phenotypes different from those of their brown-eyed parents. Many genes influence height, and they are not subject to a dominant-recessive pat- tern of inheritance. Most geneticists believe that each height gene has a small influence over a child’s size (Tanner, 1990). Thus, a child’s height will be the sum of the effects of all these genes. Height, like most polygenic traits, is also a result of multifactorial inheritance—that is, multifactorial inheritance it is affected both by genes and by the environment. For this reason, doctors use a child’s a pattern of inheritance height as a measure of his general health (Sulkes, 1998; Tanner, 1990). If a child is ill, affected by both genes and the poorly nourished, or emotionally neglected, he may be smaller than others his age. Thus, environment when a child is shorter than 97% of his age-mates, doctors try to determine if he is short mitochondrial inheritance because of his genes or because something is causing him to grow poorly (Tanner, 1990). a pattern of inheritance in which a cell’s mitochondrial MITOCHONDRIAL INHERITANCE Scientists have discovered some additional princi- DNA (mtDNA) is inherited from ples of genetic inheritance. In mitochondrial inheritance, children inherit genes that are the mother’s egg and not the carried in structures called mitochondria, which are found in the fluid that surrounds father’s sperm  30 U N IT 1 FOUN D ATIO N S the nucleus of the ovum before it is fertilized. Consequently, mitochondrial genes are passed only from mother to child. Geneticists have learned that several serious disor- ders, including some types of blindness, are transmitted in this way. In most such cases, the mother herself is unaffected by the harmful genes (Chinnery, 2006). LEARNING OBJECTIVE 2.3 EPIGENETICS Describe how epigenetic Recent genetics research has revealed that our genome accounts for only one aspect of mechanisms regulate genes heredity influences. In particular, one question has remained unanswered until now—if and development. each of our cells carries the identical genome, how is it that the cells of our body can be epigenome so different? Put another way, how can cells that have the same genotype differentiate the sum total of inherited into specialized cells (phenotype), such as liver, heart, or brain tissue? The answer comes and acquired molecular to us from the discovery of molecular biological compounds that overlay our DNA, modifications to the genome known collectively as the epigenome (Callinan & Feinberg, 2006) (see Figure 2.1). that leads to changes in gene Possessing the gene for a specific trait does not guarantee that it will be expressed. regulation without changing the Although each cell in our body contains the same genetic code (the same genotype), DNA sequence of the genome our unique set of epigenetic markers regulate gene expression (our phenotype). Epi- gene expression genetic markers work by signalling some genes to “turn on” (gene expression) and when a gene sequence is others to “turn off” (gene silencing). For example, soon after conception, epigenetic activated (“turned on”) and ready to be translated into gene markers “tell” “brain genes” to be active in brain tissue but inactive in liver tissue. Epi- products—proteins, for the genetic structures also control ongoing cellular functioning in a similar way. They most part signal a gene or polygene to turn on (e.g., when a cell needs to produce a specific gene silencing protein) or turn off (e.g., when protein production needs to stop until further notice). when a gene sequence is made In this way, epigenetic mechanisms regulate normal bodily processes, such as regulat- inactive (“turned off”) and is ing blood sugar levels, activating immune functions, or controlling brain cell activity. prevented from being translated Moshe Szyf and Michael Meaney, two pioneers in the emerging field of epigenetics, into gene products—proteins, and their McGill University colleagues have found that epigenetic factors play a piv- for the most part otal role in development across the lifespan (McDevitt, 2006; Rutter, 2007). Through epigenetics animal studies, they were the first researchers to demonstrate that maternal care can the study of the gene regulation physically alter molecular epigenetic structures in offspring. For example, a mother patterns that alter gene function rat’s increased postnatal levels of feeding and grooming of her pups resulted in calmer (phenotype) without changing rat pups by actually altering the molecular epigenetic structures in the rat pups (Weaver gene structure (genotype) et al., 2004; Weaver et al., 2007; Weaver, Meaney, & Szyf, 2006). In follow-up studies, epigenetic factors they found that although these early-life epigenetic changes persist into adulthood, they inheritable and acquired gene could be reversed experimentally (Weaver et al., 2005). regulation patterns that alter Although epigenetic modifications acquired during the lifetime of the parent are gene function (phenotype) typically expunged during the earliest stages of prenatal development of subsequent without changing gene generations (Kimmins & Sassone-Corsi, 2005), recent studies have shown that some structure (genotype) acquired epigenetic modifications can be passed on. For example, animal studies have shown that epigenetic changes to liver, heart, and brain proteins in mice and endocrine, repro- ductive, and behavioural changes in rats acquired during the lifetime of the parent can be transmitted to the offspring (Anway, Cupp, Uzumca, & Skinner, 2005; Roemer, Reik, Dean, & Klose, 1997). Even epigenetic changes caused by changes to maternal diet have been shown to transfer across generations in mice populations (Cropley, Suter, Beckman, & Martin, 2006). In addition, some preliminary evidence shows that acquired epigenetic traits linked to chromosome structure alterations may be inherited in humans (Amor et al., 2004; Peaston & Whitelaw, 2006; Whitelaw & Whitelaw, 2006). LEARNING OBJECTIVE 2.4 EVOLUTIONARY THEORIES Describe how evolutionary Evolutionary theories attempt to explain our differences as individuals and our com- theories explain individual monalities as a species. These theories often focus on the genetic and environmental differences. mechanisms that underlie development throughout the lifespan and across generations.  C HA PT ER 2 T H E ORIE S OF DE VE LOP M ENT 31 ETHOLOGY Ethology emphasizes genetically determined survival behaviours that are ethology assumed to have evolved through natural selection. For example, nests are necessary a perspective on development that emphasizes genetically for the survival of young birds. Therefore, ethologists say, evolution has equipped birds determined survival behaviours with nest-building genes. presumed to have evolved Similarly, ethologists believe that emotional relationships are necessary to the through natural selection survival of human infants (Bowlby, 1969, 1980). They claim that evolution has pro- duced genes that cause humans to form these relationships. For example, most people Ethologists assert that the first two feel irritated when they hear a newborn crying. Ethologists say the baby is geneti- years of life are a critical period for cally programmed to cry in a certain way, and adults are genetically programmed to the establishment of relationships get irritated when they hear it. The caretaker responds to a crying baby’s needs to between infants and caregivers. remove the irritating stimulus of the noise. As the (Photo: Bryan Creely/Fotolia) caretaker and infant interact, an emotional bond is created between them. Thus, genes for crying in an irritating manner increase infants’ chances of survival. BEHAVIOUR GENETICS A related area of study, behaviour genetics focuses on the effect of hered- ity on individual differences. Traits or behav- iours are believed to be influenced by genes when those of related people, such as children and their parents, are more similar than those of unre- lated people. Behaviour geneticists have shown that heredity affects a broad range of traits and behaviours, including intelligence, shyness, and aggressiveness. behaviour genetics SOCIOBIOLOGY Sociobiology is the study of society using the methods and concepts the study of the role of heredity in individual differences of biological science. When applied to human development, sociobiology emphasizes genes that aid group survival. Sociobiologists claim that individual humans have the sociobiology best chance for survival when they live in groups. Therefore, they claim, evolution has the study of society using provided humans with genetic programming that helps us cooperate. the methods and concepts To support their views, sociobiologists look for social rules and behaviours that of biology; when used by exist in all cultures. For example, every society has laws against murder. Sociobiologists developmentalists, an approach believe that humans are genetically programmed to create rules based on respect for that emphasizes genes that aid group survival other people’s lives. Evolution has selected these genes, they claim, because people need to respect each other’s lives and to be able to cooperate. EVOLUTIONARY PSYCHOLOGY Evolutionary psychology is the study of how geneti- evolutionary psychology cally inherited cognitive and social characteristics have evolved through natural selec- the view that genetically tion. Accordingly, cognitive abilities that underlie social relations and interactions are inherited cognitive and social a major focus. Evolutionary psychology is an interdisciplinary approach to explaining characteristics have evolved human behaviour that involves biology, anthropology, cognitive science, and neurosci- through natural selection ence (Cosmides & Tooby, 2000). Harvard psychologist Steven Pinker (1997, 2002), a Canadian from Montreal, has been a leading advocate of evolutionary psychology. His basic premise is that, through a process of biological evolution, the mind, like the body, has been shaped by natural selection to serve adaptive functions and promote survival. Moreover, Pinker (2002) contends that we have hard-wired inherited patterns of thinking and feeling shaped over time by the demands made on the species for survival. Today, this “human nature,” as he calls it, affects every aspect of our lives, from child-rearing practices to the forma- tion of our political views to our taste in art and music.  32 U N IT 1 FOUN D ATIO N S EVOLUTIONARY DEVELOPMENTAL PSYCHOLOGY The proponents of this view say that, contrary to what philosopher John Locke thought about infants (refer to Chapter 1), a newborn’s mind is not a blank slate. Rather, the mind has been genetically pro- grammed with a predisposition to learn and develop in certain ways—for instance, it has a readiness to learn language and recognize human faces (Bjorklund & Pellegrini, 2002; Pinker, 2002; Tooby, Cosmides & Barrett, 2005). evolutionary developmental Evolutionary developmental psychology theorists agree that nature (genes) and psychology nurture (environment) interact in determining individual intelligence, personality, and the view that genetically social behaviour (Bjorklund & Pellegrini, 2002). But they also suggest that we need the inherited cognitive and social ability to display different forms of behaviour at different times over the course of our characteristics that promote lives. For example, the cognitive and emotional abilities that help infants and children survival and adaptation appear adapt and survive are qualitatively different from those that adults require to adapt and at different times across the lifespan survive. Specifically, infants need to form attachments while adults must contend with mating and, once children arrive, parenting and, later, grandparenting (Buss, 1999). From this perspective, then, evolutionary forces have contributed to the development of age-dependent traits that promote survival and adaptation across the lifespan. EVOLUTIONARY PRENATAL PROGRAMMING AND ADULT HEALTH AND DISEASE Changing one’s lifestyle habits later in life to reduce the risk of disease may be a case of “too little, too late.” In addition to genetic and lifestyle factors, the risk of developing noncommunicable diseases such as heart disease, diabetes, and obesity may have its roots in very early life influences. This is the case according to evolutionary theorists, Peter Gluckman of the University of Auckland, NZ, and Mark Hanson of the Univer- sity of Southampton, UK, and their colleagues, who have proposed some intriguing ideas (Gluckman & Hanson, 2006a, 2006b, 2007; Gluckman et al., 2009; Gluckman, Hanson, & Beedle, 2007; Gluckman, Hanson, & Spencer, 2005). They suggest that the prenate (i.e., the fetus) picks up cues about existing environmental conditions from its mother and is thereby able to predict what kind of environment it can expect to live in after birth. In response, the fetus undergoes epigenetic changes that ensure the best chance for survival in the anticipated future environment. These so-called predictive-adaptive predictive-adaptive responses are adaptive only if the forecast is correct. Where there is responses a mismatch between the early (prenatal) and later (postnatal) environment, physiologi- the prenate’s ability to use cal adaptations may be ill-suited to the postnatal environment and thus contribute to information about the current lifestyle-related diseases in adulthood—the greater the mismatch, the greater the risk. environment to adjust its Figure 2.3 depicts an example of how these mismatches predict metabolic disease. physiology in anticipation that it Some responses of the embryo or the fetus to its environment may, however, be will match future environmental conditions and optimize developmentally disruptive with no adaptive value—for example, a response to an envi- the chances to survive and ronmental toxic agent that goes beyond the organism’s ability to adapt (Gdluckman reproduce in adulthood & Hanson, 2004a; Heindel & Lawler, 2006) (you’ll read about these teratogens in Chapter 3). Epigenetic changes in the DNA made prenatally can persist throughout the lifespan and the response made to the predicted future environmental conditions in one generation may also extend over several generations (Gluckman, Hanson, & Spencer, 2005; Waterman, 2006). The Research Report illustrates how a gene variation, which may have aided adaptation for generations, can suddenly give rise to an epidemic when lifestyle behaviours are altered. LEARNING OBJECTIVE 2.5 APPLYING BIOLOGY AND EVOLUTIONARY THEORIES Describe how biology and Biological principles that underlie genetics and epigenetics are expanding our under- evolutionary theories contribute standing of disease processes. Scientists are discovering the complex role that inheri- to our understanding of disease tance plays in human health and the related importance of early intervention. processes and interventions.  C HA PT ER 2 T H E ORIE S OF DE VE LOP M ENT 33 Deprived Cues, e.g., undernutrition, Matched (healthy) adjust metabolic setpoints Ma tur Inherited genotype ric ee he nv and epigenotype r th iro an nm pre en dic t ted Mismatched (enhanced risk of metabolic disease) Matched (healthy) Adequate Developmental environment Mature environment FIGURE 2.3 The developing organism senses maternally transmitted environmental cues, such as undernutrition, during pre- natal and early postnatal life. Developmental flexibility in response to these cues modifies the default trajectory defined by the inherited fetal genome and epigenome according to whether the environment is perceived as adequate (dark background) or deprived (light back- ground), resulting in metabolic adjustments. If the eventual mature environment, whether adequate or deprived, matches the prediction, then the risk of metabolic disease in later life is low. If there is a mismatch between the predicted and actual mature environments, particularly if the mature environment is richer than anticipated, then the risk of metabolic disease is enhanced. (Source: Gluckman, Nansen and Beedle, 2007. American Journal of Human Biology, 19 (1), 1-19 (pg8). Reprinted with permission of Wiley–Liss, Inc., a subsidiary of John Wiley & Sons, Inc.) DISEASE CONTROL Advances in human genomics will likely play a vital role in human genomics predicting and preventing diseases in the 21st century (Collins & McKusick, 2001). the study of the human genome Some scientists claim that developments in relatively rare single-gene diseases, such as including the location of genes, hemophilia, Huntington’s disease, and sickle-cell disease, will have a limited impact their function, and their role in on overall national health care (Hall, Morley, & Lucke, 2004; Holtzman & Marteau, disease processes 2000). In total, these types of genetic diseases account for only about 5% of all human disease in developed countries (Khoury, 2003). Other scientists predict that the great- est impact of advances in human genomics will likely be seen in the treatment of multifac- toral diseases, such as heart disease and cancer. In these cases, having a genome-wide perspective will be an advantage (Hall, Morley, & Lucke, 2004). For example, the British Columbia Cancer Agency research team headed by Samuel Aparicio recently decoded the 3 billion letters in the DNA sequence of a type of breast cancer that accounts for 10% of all breast cancers (Shah et al., 2009). Shortly after this discovery, Canadian scientists joined an international partnership that intends to decode the genomes and epigenomes of some 25 000 cancer samples, with the aim of develop- ing new strategies for early detection and prevention (International Cancer Genome Consortium, 2010). Although the study of the relationship between the epigenome and human health is still in its infancy, early indications suggest that both external and per- sonal factors influence epigenetic mechanisms (Esteller, 2006; Fraga et al., 2005; Hiltunen et al., 2002; Luch, 2005; Mathers & Hesketh, 2007; Rossman, 2003; Weinhold, 2006). In turn, epigenetic changes alter gene expression, which can 34 U N IT 1 FOUN D ATIO N S increase the risk for developing both physical and psychological disorders (Petronis et al., 2000; Petronis, 2003, 2004; Schumacher & Petronis, 2006; Szyf, 2006). Epigenetic markings on DNA are continually modified throughout the lifespan (Heyn et al., 2012; Martin, 2005) and any acquired epigenetic traits may be passed onto the next generation (Feil, 2006; Jablonka, 2004; Jablonka & Lamb, 2005). Epigenetic research is rapidly contributing to our understanding of the inheritance factors involved in vulnerability and resilience and may one day lead to new ways of diagnosing and treating diseases and disorders in humans (“Learning With- out Learning; Epigenetics,” 2006; Jablonka, 2004; Meaney & Szyf, 2005; Wong, Gottesman, & Petronis, 2005). Indeed, newly discovered epigenetic factors may prove to be the proverbial “missing link” that helps us explain how nurture inter- acts with nature. EARLY INTERVENTION Evolutionary theory and research are making scientists more aware of the relative importance of early-life events in making accurate predictive- adaptive responses that match expected future environments. This growing awareness has focused attention on the need to promote early interventional strategies during Research Report TYPE 2 DIABETES EPIDEMIC IN A REMOTE COMMUNITY Prior to the middle of the last century, type 2 diabetes was rare among The type 2 diabetes epidemic demonstrates how we can study Aboriginal populations (Health Canada, 1999a). By the 1970s, however, the interaction between genes and behaviour and suggests that a research suggested that an epidemic might be emerging; two decades genetic susceptibility interacts with multiple environmental factors. later, this was confirmed (Young, Reading, Elias, & O’Neil, 2000). Today, The sudden increase in the incidence of the disease may be related in Canada, type 2 diabetes is three times as prevalent (and the inci- to a significant change in lifestyle. For instance, the Oji-Cree’s tradi- dence rate is escalating) in First Nations Peoples as in the general tional low-carbohydrate diet has been replaced by a “junk food” and population. An estimated 20% of all First Nations Peoples currently live high “fatty” content diet and is coupled with a more sedentary level with the disease (Picard, 2010). of physical activity. This modern lifestyle encourages obesity of the Type 2 diabetes generally occurs later in life and carries with mid-body area in Oji-Cree who have the G319S mutation, and this it serious health and social ramifications. It leads to conditions such is connected to a higher risk of diabetes (Hegele et al., 1999; Young as heart disease, blindness, kidney failure, and gangrene (Young et al., 2000). et al., 2000) and is a leading cause of death and disability among First This new understanding of the interplay between genetics and Nations Peoples (Health Canada, 1999a). environment has led to a complex health care initiative. Community- Robert Hegele and his research team at the John P. Robarts wide prevention and health education programs that actively involve Research Institute in London, Ontario, discovered a strong genetic effect Oji-Cree residents and demonstrate an appreciation for their language related to a single gene variant. This genetic mutation was discovered in and cultural concerns begin in Grade 3. The focus is on healthy lifestyle the Oji-Cree, who reside on the Sandy Lake Reserve in Northern Ontario. practices that include a balanced diet and physical exercise. Moreover, The adults of the community were found to have a high incidence of the a screening program for detecting diabetes and a lifestyle support pro- G319S mutation, which affects the structure of a specific liver protein. gram for those who are living with the disease were both established The incidence of type 2 diabetes was found to be five times higher than to decrease the severity of its effects (Health Canada, 2010a; John P. it is in the general Canadian population. This rate is the third highest in Robarts Research Institute, 2000). the world (Hegele, Cao, Harris, Hanley, & Zinman, 1999).  C HA PT ER 2 T H E ORIE S OF DE VE LOP M ENT 35 prenatal development (e.g., to support good health and nutrition in females of repro- ductive age) versus those instituted later in adult life. This important element will prevent chronic disease in future generations across the globe (Gluckman & Hanson, 2004a, 2004b, 2006b). test yourself before going on 1. Match each term with its definition. (viii) inheritable and acquired gene regula- _____(a) chromosomes tion patterns that alter gene function without changing gene structure _____(b) heterozygous (ix) individuals whose chromosomes carry _____(c) epigenetic factors one dominant and one recessive gene _____(d) phenotype for a given trait (x) the unique genetic blueprint of each _____(e) proteins individual _____(f) genes 2. Match each theoretical approach to its emphasis: _____(g) gene expression _____(a) evolutionary developmental psychology _____(h) polygenic inheritance _____(b) behaviour genetics _____(i) mitochondria _____(c) ethology _____(j) genotype _____(d) sociobiology (i) organic compounds, consisting of amino _____(e) predictive-adaptive response acids, that perform most life functions and make up the majority of cellular (i) genetic traits that aid group survival structures (ii) relative effects of heredity on individual (ii) strings of genetic material differences (iii) pieces of genetic material that control or (iii) genetic traits that aid individual influence traits survival (iv) when a gene sequence is activated (iv) genetically inherited age-dependent (“turned on”) and ready to be translated cognitive and social traits that promote into gene products, such as proteins survival and adaptation (v) a pattern of inheritance in which many (v) the prenate picks up on environmental genes influence a trait cues to adjust its physiology in anticipa- (vi) DNA-bearing structures outside the tion that it will match future environ- nucleus of the ovum mental conditions (vii) an individual’s particular set of observed characteristics PSYCHOANALYTIC THEORIES One theoretical approach to explaining babies’ fascination with mouthing objects psychoanalytic theories might suggest that infants derive more physical pleasure from mouthing objects than theories proposing that from manipulating them with other parts of their bodies. Such an approach would most developmental change happens likely belong to the family of psychoanalytic theories, a school of thought that origi- because of the influence of nated with Sigmund Freud (1856–1939). Psychoanalytic theorists believe that develop- internal drives and emotions on mental change happens because internal drives and emotions influence behaviour. behaviour  36 U N IT 1 FOUN D ATIO N S LEARNING OBJECTIVE 2.6 FREUD’S PSYCHOSEXUAL THEORY Summarize the main ideas of Although much of Freud’s formal theory remains contentious, his ideas still influence Freud’s psychosexual theory. our understanding of personality development. One of Freud’s most distinctive con- cepts is the idea that behaviour is governed by both conscious and unconscious pro- cesses. The most basic of these unconscious processes is an internal drive for physical libido pleasure that Freud called the libido. He believed the libido to be the motivating force in Freud’s theory, an instinctual behind most behaviour. drive for physical pleasure present at birth that forms the PERSONALITY DEVLOPMENT Many of Freud’s patients had memories of sexual feel- motivating force behind virtually ings and behaviour in childhood. This led Freud to believe that sexual feelings are all human behaviour important to personality development. Based on his patients’ childhood memories, id Freud also argued that personality has three parts. The id contains the libido and oper- in Freud’s theory, the part of ates at an unconscious level; the id is a person’s basic sexual and aggressive impulses, the personality that comprises which are present at birth. The ego, the conscious, thinking part of the personality, a person’s basic sexual and develops in the first two to three years of life. One of the ego’s jobs is to keep the needs aggressive impulses; it contains of the id satisfied. For instance, when a person is hungry, it is the id that demands food the libido and motivates a immediately, and the ego is supposed to find a way to obtain it. The superego, the person to seek pleasure and portion of the personality that acts as a moral judge, contains the rules of society and avoid pain develops near the end of early childhood, at about age 6. Once the superego develops, ego the ego’s task becomes more complex. It must satisfy the id without violating the super- according to Freud, the thinking element of personality ego’s rules. The ego is responsible for keeping the three components of personality in balance. superego Freud’s term for the part of According to Freud, a person experiences tension when any of the three components is personality that is the moral in conflict with another. For example, if a person is hungry, the id may motivate her to judge do anything to find food, but the ego—her conscious self—may be unable to find any. Alternatively, food may be available, but the ego may have to violate one of the super- defence mechanisms ego’s moral rules to get it. In such cases, the ego may generate defence mechanisms— strategies for reducing anxiety, ways of thinking about a situation that reduce anxiety. Without defence mechanisms, such as repression, denial, or Freud thought, the degree of tension within the personality would become intolerable, projection, proposed by Freud leading to mental illness or suicide. MyPsychLab FIVE PSYCHOSEXUAL STAGES Freud proposed a series of psychosexual stages Explore the concept The Id, Ego, and through which a child moves in a fixed sequence determined by maturation. In each Superego on mypsychlab stage, the libido is centred on a different part of the body. In the infant, the mouth is the focus of the drive for physical pleasure; the stage is therefore called the oral stage. As maturation progresses, the libido becomes focused on the anus (hence, the anal stage), and later on the genitals (the phallic stage and, after a period of dormancy called the psychosexual stages latency stage, the genital stage). Freud’s five stages of personality Optimum development, according to Freud, requires an environment that will sat- development through which isfy the unique needs of each period. For example, the infant needs sufficient oppor- children move in a fixed sequence tunity for oral stimulation. An inadequate early environment will result in fixation, determined by maturation; the libido is centred on a different characterized by behaviours that reflect unresolved problems and unmet needs. Thus, body part in each stage emphasis on the formative role of early experiences is a hallmark of psychoanalytic theories. LEARNING OBJECTIVE 2.7 ERIKSON’S PSYCHOSOCIAL THEORY Identify the conflict associated Apart from Freud, Erik Erikson (1902–1994) is the psychoanalytic theorist who has with each of Erikson’s had the greatest influence on the study of development (Erikson, 1950, 1959, 1980b, psychosocial stages. 1982; Erikson, Erikson, & Kivnick, 1986; Evans, 1969). Erikson, like many of Freud’s other early followers, accepted many of Freud’s ideas but later went on to expand  C HA PT ER 2 T H E ORIE S OF DE VE LOP M ENT 37 on them. For instance, Erikson claimed that development results from the interaction psychosocial stages between internal drives and cultural demands; thus, his theory refers to psychosocial Erikson’s eight stages, or crises, stages rather than to psychosexual ones. Furthermore, Erikson thought that develop- of personality development in ment continued through the entire lifespan. which inner instincts interact with outer cultural and social demands to shape personality EIGHT PSYCHOSOCIAL STAGES In Erikson’s view, to achieve a healthy personality, an individual must successfully resolve a psychosocial crisis at each of the eight stages of development, as summarized in Table 2.2. Each crisis is defined by a pair of oppos- MyPsychLab Explore the concept Erickson’s First ing possibilities, such as trust versus mistrust or integrity versus despair. Successful Four Stages of Psychosocial Develop- resolution of a crisis results in the development of the characteristic on the positive side ment on mypsychlab of the dichotomy. A healthy resolution, however, does not mean moving totally to the positive side. For example, an infant needs to have experienced some mistrust to learn Explore to identify people who are not trustworthy. But healthy development requires a favour- Erikson’s Last Four Stages of able ratio of positive to negative. Of the eight stages described in Table 2.2, four have Psychosocial Development been the focus of the greatest amount of theorizing and research: trust in infancy, identity in adolescence, intimacy in early adulthood, and Critical Thinking generativity in middle adulthood. In which of Erikson’s psychosocial stages would EIGHT CRISES TO RESOLVE Erikson believed that the behaviour of you place yourself? Does Erikson’s description the major caregiver (usually the mother) is critical to the child’s reso- of this stage correspond to the challenges and lution of the first life crisis: trust versus mistrust. To ensure successful concerns you are confronting? resolution of this crisis, the caregiver must be consistently loving and TABLE 2.2 Erikson’s Psychosocial Stages Approximate Ages Stage Positive Characteristics Gained and Typical Activities Birth to 1 year Trust versus mistrust Hope; trust in primary caregiver and in one’s own ability to make things happen (secure attachment to caregiver is key) 1 to 3 Autonomy versus shame and doubt Will; new physical skills lead to demand for more choices, most often seen as saying “no” to caregivers; child learns self-care skills, such as toileting 3 to 6 Initiative versus guilt Purpose; ability to organize activities around some goal; more assertiveness and aggressiveness (harsh parental criticism may lead to guilt) 6 to 12 Industry versus inferiority Competence; cultural skills and norms, including school skills and tool use (failure to master these leads to sense of inferiority) 12 to 18 Identity versus role confusion Fidelity; a unified and consistent sense of self that inte- grates pubertal changes into a mature sexual identity, assumes adult social and occupational roles, and estab- lishes personal values and attitudes 18 to 30 Intimacy versus isolation Love; person develops intimate relationships beyond adolescent love; many become parents 30 to old age Generativity versus stagnation Care; people rear children, focus on occupational achievement or creativity, and train the next generation; turn outward from the self toward others Old age Integrity versus despair Wisdom; person conducts a life review, integrates earlier stages, and comes to terms with basic identity; develops self-acceptance  38 U N IT 1 FOUN D ATIO N S must respond to the child predictably and reliably. Infants whose early care has been erratic or harsh may develop mistrust. In either case, the child carries this aspect of per- sonality throughout her development, and it affects the resolution of later tasks. Erikson’s description of the central adolescent dilemma, identity versus role confusion, has been particularly influential. He argued that, to arrive at a mature sexual and occu- pational identity, every adolescent must examine his identity and the roles he must occupy. He must achieve an integrated sense of self, of what he wants to do and be, and of his appropriate sexual role. The risk is that the adolescent will suffer from confusion arising from the profusion of roles opening up to him at this age. In the first of the three adult stages, the young adult builds on the identity established in adolescence to confront the crisis of intimacy versus isolation. Erikson defined intimacy as “the ability to fuse your identity with someone else’s without fear that you’re going to lose something yourself” (Erikson, in Evans, 1969). Many young people, Erikson thought, make the mistake of thinking they will find their identity in a relationship, but, in his view, only those who have already formed (or are well on the way to forming) a clear identity can successfully enter this fusion of identities that he called intimacy. Young adults whose identities are weak or unformed will remain in shallow relationships and will experience a sense of isola- tion or loneliness. The middle adulthood crisis is generativity versus stagnation, which is “primarily the concern in establishing and guiding the next generation” (Erikson, 1963, p. 267). The rearing of children is the most obvious way to achieve a sense of generativity, but it is not the only way. Doing creative work, giving service to an organization or to society, or serving as a mentor to younger colleagues can help the mid-life adult achieve a sense of generativity. Failing that, the self-absorbed, nongenerative adult may feel a sense of stagnation. The key idea underlying Erikson’s theory is that each new crisis is thrust on the developing person because of changes in social demands that accompany changes in age. The fourth stage of industry versus inferiority, for example, begins when the child starts school and must learn to read and write. If the child fails to read and write at grade level, she is often still able to advance with her same-aged peers. As the child enters the higher grade levels lacking the essential reading and writing skills, she may experience an increasing sense of inferiority. This evolving negative self-image may adversely affect the child’s transition to the next stage of psychosocial development— the formation of a healthy identity. Thus, childhood crises set the stage for those of adolescence and adulthood. LEARNING OBJECTIVE 2.8 THE HUMANISTIC ALTERNATIVE Describe the basic concepts of In addition to criticizing the fuzziness of some psychoanalytic concepts, psychologists humanistic theory. have taken issue with the psychoanalytic emphasis on atypical development. Some have proposed alternative theories that focus on the positive aspects of development while accepting the psychoanalytic assumption that behaviour is motivated by internal drives and emotions. These humanistic theories share Jean-Jacques Rousseau’s basic prem- ise of innate goodness (refer back to Chapter 1), and they begin with the optimistic self-actualization assumption that the most important internal drive is each individual’s motivation to the process of fulfilling one’s achieve his or her full potential. A key figure in the humanistic tradition is Abraham unique personal potential Maslow (1908–1970), who used the term self-actualization to describe this ultimate motives goal of human life (Maslow, 1968, 1970). internal factors or conditions that tend to initiate, direct, or MOTIVES Maslow’s greatest interest was in the development of motives, or needs, sustain behaviour which he divided into two subsets: deficiency motives and being motives. Deficiency  C HA PT ER 2 T H E ORIE S OF DE VE LOP M ENT 39 motives involve drives to maintain physical or emotional homeostasis (inner balance), such as the drive to get enough to eat or drink, the sexual drive, or even the drive to obtain sufficient love or respect from others. Being motives involve the desire to under- stand, to give to others, and to grow—that is, to achieve self-actualization. In general, the satisfaction of deficiency motives prevents or cures illness or re-creates homeostasis. In contrast, the satisfaction of being motives produces a general sense of well-being. The distinction is like the “difference between fending off threat or attack and positive triumph and achievement” (Maslow, 1968, p. 32). Maslow described these various needs or motives in his famous needs hierarchy, shown in Figure 2.4. He argued that the various needs must be met in order, from the bottom of the pyramid up. For example, only when physiological needs are met do safety needs come to the fore; only when love and esteem needs are met can the need for self-actualization become dominant. For that reason, Maslow thought that being motives were likely to be significant only in adulthood, and only in those individuals who had found stable ways to satisfy both love and esteem needs. In esteem needs this sense, Maslow’s theory sounds very similar to Erikson’s stages of intimacy and the need for a person to generativity. have a sense of value and acceptance based, in part, on their experience of respect and PERSONAL GROWTH Another prominent humanistic psychologist, Carl Rogers admiration from others and on (1902–1987), talked about the capacity of each individual to become a “fully function- their perceived self-confidence ing person,” without undue guilt or seriously distorting defences (Rogers, 1961). Early and self-worth experience with caregivers whose acceptance of the child is conditional on the child behaving in an approved manner can diminish the child’s sense of self-worth. The child Being motives Need for Self-Actualization Esteem Needs (need to gain superiority and respect, including self-respect) Love and Belongingness Needs (need for affection from others; Deficiency need to be with others rather than alone) motives Safety Needs (need for stable, predictable environment, freedom from anxiety and chaos) Physiological Needs (need for food, water, sex, oxygen, sleep, elimination) FIGURE 2.4 In Maslow’s view, needs operate from the bottom up in this needs hierarchy. Until physiological needs are met, no other need will be prominent; until love needs are met, esteem needs will not emerge; and so on. Similarly, there is a developmental aspect: A baby is primarily dominated by physiological needs, a toddler by safety needs, and so forth. Only in adulthood may the need for self-actualization become central. (Sources: Maslow, Abraham H., Frager, Robert D., and Fadiman, James. Motivation and Personality, Explore 3rd Edition, © 1997. Adapted by permission of Pearson Education, Inc., Upper Saddle, NJ, Pearson Education.) Maslow’s Hierarchy of Needs  40 U N IT 1 FOUN D ATIO N S begins to think of himself as worthwhile only when he behaves in approved ways. In Carl Rogers’s view, it is never too late to overcome early conditioning or the residue of unresolved dilemmas. He believed people have the potential and motivation to try to do just that—a concept known as personal growth. test yourself before going on 1. Psychoanalytic theories share the belief that _____ (i) interaction between internal drives and __________ and __________ shape development. cultural demands 2. Write “F” for each concept or term that belongs to 3. Match each humanistic concept to its emphasis: Freud’s theory, and “E” for each concept that belongs _____ (a) self-actualization to Erikson’s theory. _____ (b) deficiency motives _____ (a) psychosocial _____ (c) self-esteem _____ (b) psychosexual _____ (d) personal growth _____ (c) id, ego, superego (i) the drive to maintain physical or _____ (d) eight stages from birth to death emotional homeostasis _____ (e) five stages from birth to adolescence (ii) a sense of value and acceptance (iii) the potential and motivation to _____ (f) libido is driving force behind development become a “fully functioning person” _____ (g) development consists of a series of crises (iv) the process of fulfilling one’s unique _____ (h) defense mechanisms personal potential LEARNING THEORIES learning theories In general, learning theories assert that development results from an accumulation of theories that assert that experiences. Learning theories are aligned with the philosophy of John Locke who, development results from an as you recall from Chapter 1, said that children are born with neither good nor bad accumulation of experiences tendencies, but their behaviour is shaped, for better or worse, by their environment. behaviourism Thus, in contrast to psychoanalysts, learning theorists would say that infants repeat the view that defines the behaviour of putting objects in their mouths because they find the sensations it development in terms of produces rewarding. Alternatively, when they put something in their mouths that tastes behaviour changes caused by bad, infants learn not to mouth such an object again. environmental influences A central learning theory, known as behaviourism, views development in terms of classical conditioning behaviour changes caused by environmental influences—a process called conditioning. learning that results from the As you will see, there are two ways that conditioning changes our behaviour. association of stimuli LEARNING OBJECTIVE 2.9 PAVLOV’S CLASSICAL CONDITIONING Explain how classical Russian physiologist and Nobel prize winner, Ivan Pavlov (1849–1936), discovered conditioning occurs. that organisms can acquire new signals for existing responses (behaviours). The term classical conditioning refers to this principle. Each incidence of learning begins with a biologically programmed stimulus–response connection, or reflex. For example,  C HA PT ER 2 T H E ORIE S OF DE VE LOP M ENT 41 salivation happens naturally when you put food in your mouth. In classical condition- Explore ing terms, the food is the unconditioned (unlearned, natural) stimulus; salivating is an Three Stages of Classical unconditioned (unlearned, natural) response. Conditioning THE CONDITIONING PROCESS Stimuli presented just before or at the same time as the unconditioned stimulus are those that are likely to be associated with it. For example, most foods have odours, and, to get to your mouth, food has to pass near your nose. Thus, you usually smell food before you taste it. Food odours eventually become conditioned (learned) stimuli that elicit salivation. In effect, they act as a sig- operant conditioning nal to your salivary glands that food is coming. Once the connection between food learning to repeat or stop odours and salivation is established, smelling food triggers the salivation response behaviours because of their consequences even when you do not actually eat the food. When a response occurs reliably in connection with a conditioned stimulus in this way, it is known as a conditioned reinforcement (learned) response. any immediate consequence that follows a behaviour and increases the likelihood that the EARLY CONDITIONING Classical conditioning is of interest in the study of develop- behaviour will be repeated ment because of the role it plays in the acquisition of emotional responses. For example, punishment things or people that are present when you feel good will become conditioned stimuli any immediate consequence for pleasant feelings, while those associated with uncomfortable feelings may become that follows a behaviour and conditioned stimuli for a sense of unease. Classical conditioning is especially important decreases the likelihood that in infancy. Because a child’s mother or father is present so often when nice things hap- the behaviour will be repeated pen, such as when the child feels warm, comfortable, and cuddled, the mother and father usually serve as conditioned stimuli for pleasant feelings, a fact that makes it possible for the parents’ presence to comfort a child. LEARNING OBJECTIVE 2.10 Explain the process of operant conditioning. SKINNER’S OPERANT CONDITIONING Another type of learning is operant conditioning, a term coined by B.F. Skinner (1904– Watch 1990), the most famous proponent of this theory (Skinner, 1953, 1980). Operant condi- B.F. Skinner Biography tioning involves learning to repeat or stop behaviours because of the consequences they bring about. Reinforcement is any immediate consequence that follows a behaviour Laboratory research involving ani- that increases the likelihood that the behaviour will be repeated. Punishment is any mals was important in the develop- immediate consequence that follows a behaviour that decreases the likelihood that the ment of Skinner’s operant conditioning behaviour will be repeated. theory. (Photo: Everett Collection Historical/Alamy) REINFORCEMENT Positive reinforcement entails adding a consequence (usually some- thing pleasant) that follows a behaviour and increases the chances that the behaviour will occur again. Some kinds of pleasant conse- quences, such as attention, serve as reinforcers for most people most of the time. But, strictly speaking, reinforcement is defined by its effect; we don’t know something is reinforc- ing unless we see that its presence increases the probability of some behaviour. Negative reinforcement entails taking away a condition (usually something unpleas- ant) following a behaviour and increases the chances that the behaviour will occur again.  42 U N IT 1 FOUN D ATIO N S For example, coughing is an unpleasant experience for most of us, and taking a dose of cough medicine usually stops it. As a result, the next time we begin to cough, we reach for the cough syrup because the behaviour of consuming a spoonful of cough syrup is reinforced by the cessation of coughing. In other words, we make the unpleas- ant experience of coughing go away when we engage in the behaviour of swallowing cough syrup. Thus, the behaviour of taking cough syrup is learned through negative reinforcement. Definitions and simple examples of positive and negative reinforcement may be misleading when it comes to understanding how the two operate in real-life contexts. For example, most people understand that paying attention to a preschooler’s whin- ing is likely to increase it. This case shows positive reinforcement—a child’s whining is reinforced whenever a parent shows attention. At the same time, however, a parent learns to attend to a whining preschooler because whining is irritating, and responding to it usually makes it stop. As a result, the parent’s behaviour of responding to whin- ing is negatively reinforced by its consequence—namely, that the child stops whining. In this case of negative reinforcement, parental attention is reinforced when the child stops whining. PUNISHMENT There are two general forms of punishment but, in contrast to both kinds of reinforcement, both forms of punishment stop a behaviour. Sometimes punish- extinction ments involve eliminating nice things, for example, taking away TV privileges. This is the gradual elimination of a referred to as negative punishment and entails taking away a condition (usually some- behaviour through repeated thing pleasant) that follows a behaviour and decreases the chances that the behaviour nonreinforcement will occur again. Negative punishment can be considered a type of extinction, which is the gradual elimination of a behaviour through repeated nonreinforcement. If a teacher succeeds in eliminating a student’s undesirable behaviour by ignoring Critical Thinking it, the behaviour is said to have been extinguished. However, punishment may also involve unpleasant things such as Describe instances in your everyday life when scolding. A positive punishment entails adding a consequence (usu- your behaviour is affected by classical or oper- ally something unpleasant) that follows a behaviour and decreases the ant conditioning, or when you use these prin- chances that the behaviour will occur again. Like reinforcement, how- ciples to affect others’ behaviour. ever, punishment is defined by its effect. Consequences that do not stop behaviour can’t be properly called punishments. CHANGING BEHAVIOUR Such examples illustrate the complex manner in which rein- forcements and punishments operate in the real world. In laboratory settings, operant conditioning researchers usually work with only one participant or animal subject at a time; they needn’t worry about the social consequences of behaviours or consequences. They can also control the situation so that a particular behaviour is reinforced every time it occurs. In the real world, partial reinforcement—reinforcement of a behaviour on some occasions but not others—is more common (see Development in the Real World). Studies of partial reinforcement show that people take longer to learn a new behaviour under partial reinforcement conditions; once established, however, such behaviours are very resistant to extinction. shaping Shaping is the reinforcement of intermediate steps until an individual learns the reinforcement of a complex behaviour. For example, you wouldn’t start learning to play tennis by intermediate steps until an challenging a skilled player to a match. Instead, you would first learn to hold the individual learns a complex racquet properly. Next, you would learn the basic strokes and practise hitting balls behaviour hit or thrown to you by an instructor. Next, you would learn to serve. Finally, you would put all your skills together and play an actual match. All along the way, you would be encouraged by the sense of satisfaction gained from accomplishing each step toward the goal.  C HA PT ER 2 T H E ORIE S OF DE VE LOP M ENT 43 Development in the Real World LEARNING PRINCIPLES IN REAL LIFE Let’s consider how principles of learning work in some common real-life mother complies, two things happen. First, the mother has just situations. For example, suppose your 3-year-old daughter repeatedly strengthened the child’s hollering behaviour through positive reinforce- demands your attention while you are fixing dinner. Because you don’t ment by giving him what he wanted when he hollered; in this case, the want to reinforce this behaviour, you ignore her the first six or eight school lunch bag. Second, the child has just strengthened the mother’s times she calls you or tugs at your clothes. But after the ninth or tenth obliging behaviour through negative reinforcement by taking away repetition, with her voice getting whinier each time, you can’t stand it something the mother finds distressing; in this case, hollering. any longer and finally say something like “All right! What do you want?” We would predict that the next time the boy wants something from Since you have ignored most of her demands, you might think his mother, he is more likely to holler and, unfortunately, his mother is you have not been reinforcing them. But what you have actually done more likely to comply if the boy stops hollering once his mother gets is create a partial reinforcement schedule. By responding to every ninth him what he wants. As you can see, we can easily and inadvertently or tenth demand, you have in essence, taught her that persistent whin- set up reciprocal patterns of reinforcement and expectations that can ing will eventually be rewarded with attention. This intermittent pattern benefit one person, but disadvantage the other. Moreover, once such a of reinforcement helps create behaviour that is very hard to extinguish. pattern of reciprocal parent–child interaction is established, it can be So your daughter may continue to be overly demanding for a very long very difficult to break, especially if you are not aware of the reinforcing time. sequence of events. Another thing we know about reinforcement is that, when two If such situations are all too familiar to you, then it may pay to people interact, they mutually shape each other’s behaviour—for keep careful records for a while, noting each incident and your re- better or for worse. For example, if a child begins to holler at his mother sponse. Then see whether you can figure out which principles are re- to fetch his school lunch bag before he goes out the door, and the ally at work and how you might change the pattern. test yourself before going on 1. Choose the correct options to complete the following 2. A consequence that causes a behaviour to be repeated sentence: is a __________; one that stops a behaviour is a Pavlov’s experiments addressed (classical/operant) __________. conditioning; Skinner’s dealt with (classical/operant) conditioning. COGNITIVE THEORIES The group of theories known as cognitive theories emphasize mental aspects of devel- cognitive theories opment, such as logic and memory. A cognitive theorist might propose that babies use theories that emphasize mental their senses, including the sense of taste, to build mental pictures of the world around processes in development, such them. Thus, infants mouth everything in their environment until they have learned all as logic and memory they can from this behaviour, and then they move on to a more mature way of interact- ing with the world.  44 U N IT 1 FOUN D ATIO N S PIAGET’S COGNITIVE-DEVELOPMENTAL THEORY For Jean Piaget (1896–1980), as you should remember from Chapter 1, the central question of interest in developmental psychology was “How does thinking develop?” (Piaget, 1952, 1970, 1977; Piaget & Inhelder, 1969). He was struck by the fact that all children seem to go through the same sequence of discoveries about their world, making the same mistakes and arriving at the same solutions. For example, all 3- and 4-year-olds seem to think that if water is poured from a short, wide glass into a taller, narrower one, there is then