PSYC205 Evolutionary Psychology Introduction PDF

PSYC205 Evolutionary Psychology Introduction The Origin Story of the Human Mind Edison Tan Evolutionary Psychology Singapore Management University  Let us introduce ourselves How should...

PSYC205 Evolutionary Psychology Introduction The Origin Story of the Human Mind Edison Tan Evolutionary Psychology Singapore Management University  Let us introduce ourselves How should everyone address you? Which year are you in? What are your interests and hobbies? What do you hope to learn from this class? Edison Tan Evolutionary Psychology Singapore Management University Hello! I’m... Research Interest Edison Sora Tan Evolutionary Psychology Cultural Selection Murdoch University (2019) Evolved Individual Differences BA (Psychology) (Web Communication) Evolutionary Mismatch Life History Theory Singapore Management University (2022) Behavioral Ecology MPhil (Psychology) Darwinian Medicine Singapore Management University (2025) Cultural Psychology PhD (Psychology) Cultural Values, Practices, Norms and Beliefs Motivated Cognition Misinformation and Conspiracy Theories Contact Me Email: [email protected] Teaching Interest Evolutionary Psychology Telegram: Individual Differences and Personality Cultural Psychology @edisonsoratan Quantitative Psychology and Research Methods Edison Tan Evolutionary Psychology Singapore Management University  01 Course Outline Edison Tan Evolutionary Psychology Singapore Management University Learning Outcomes By the end of the course, students would be able to: Explain the ultimate causes of various human cognitions, affects, and behaviors. Apply evolutionary principles to think about various psychological phenomena in modern humans. Edison Tan Evolutionary Psychology Singapore Management University Assessments Class Participation – 20% Discussion Questions – 10% Mid-Terms – 30% Finals – 40% Edison Tan Evolutionary Psychology Singapore Management University  Marks Criteria Description Awarded Assessments The student was willing to participate in Discussion 0.5 class discussions when called upon or by Participation volunteering their views. The student showed a motivation to 0.5 Keen Engagement drive at least part of the discussion in Class Participation – 20% class. Graded weekly 0.5 Elaborated Expression The student’s participation was well- thought-out, demonstrating that they Students are expected to have engaged well with the course materials. read class readings prior to The student had shown enthusiastic class to facilitate discussion. interest during class participation by 0.5 Beyond Expectation engaging in related materials beyond expectation. Edison Tan Evolutionary Psychology Singapore Management University  Example of a Discussion Question Assessments Evolutionary Mismatch Theory describes how evolved psychological mechanisms are designed to process ancestrally relevant environmental inputs that are now forced or hijacked to differ in quantity and intensity or no longer have the same fitness associations, thereby leading many mechanisms to produce maladaptive output. Discussion Questions – 10% On the other hand, Robertson & Chalfoun (2016) describe the existence of undervalued resources as the opposite of evolutionary mismatch, Please send at least one well-thought-out question such that there are inputs that present themselves as fitness- based on the week’s reading by Saturday, 12 PM, the enhancing opportunities that the organism has not evolved to exploit. week before class. Submit on eLearn. Would there be undervalued resources that human’s evolved psychological mechanisms are not designed to process? When writing your question: provide the specific points of the course reading, the question is crafted to address the context of the question the question itself. Please elaborate on your question if you are called upon in class. Edison Tan Evolutionary Psychology Singapore Management University Assessments 70% of testable content will be based on: Required readings Lecture slides Class discussions Mid-Terms – 30% Finals – 40% 10% of testable content will be based on specific books or journal article details covered in the slides or class discussion 20% of testable content will be structured as short essay questions based on the demonstration of critical thinking regarding the application of course content. Details to be provided before assessments Edison Tan Evolutionary Psychology Singapore Management University  Class Schedule Core Long- Kinship Recess Cognitive Evolutionary Revision Concepts Term Biases Mismatch Sexual Strategies Week 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 (Today) The Short- Cooperation Behavioral Mid-Term Darwinian Finals Introduction Hostile Term & Ecology Medicine Forces of Sexual Aggression Nature Strategies Edison Tan Evolutionary Psychology Singapore Management University Ground Rules Be respectful Disagreements are okay – tell us why you disagree. Have an open mind Edison Tan Evolutionary Psychology Singapore Management University  02 Landmarks of Evolutionary Sciences Edison Tan Evolutionary Psychology Singapore Management University  Discussion What do you know about Evolutionary Psychology? Edison Tan Evolutionary Psychology Singapore Management University  “If I really have as bad an expression as my photograph gives me, how I can have one single friend is surprising.” In Darwin’s personal letter to botanist and close friend Joseph Dalton Hooker about the below portrait. “In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history.” ― Charles Robert Darwin, 1809 - 1882 The Origin of Species, pp 499 – 489. Edison Tan Evolutionary Psychology Singapore Management University  Pre-Darwnian Concept of Evolution Biologists have made observations before Darwin regarding striking anatomical and developmental similarities between various species. Hommids, including humans, chimpanzees, and orangutans, all have five digits on their hands and feet Human embryos develop strikingly similar to other mammals, birds, and frogs before distinctive characteristics develop Anatomical characteristics are also observed to be functional, serving a purpose. Giraffe’s long neck and turtle’s shells Life is not fixed and unchanging – but how did organisms change? Edison Tan Evolutionary Psychology Singapore Management University  Pre-Darwnian Concept of Evolution Jean Baptiste Lamarck (1744 – 1829, left) Believed that organisms tend to progress toward higher forms Features and characteristics of organisms are inherited Léopold Chrétien Frédérick Dagobert Cuvier’s (1769–1832, right) catastrophism. Proposed that species are extinguished periodically by sudden catastrophes to be replaced by another species Edison Tan Evolutionary Psychology Singapore Management University  Portrait of Charles Darwin, aged 27, shortly after his return to England. Painted by George Richmond (1840) The Legend of the Beagle Following graduation from Cambridge University, Charles Darwin, aged 22, traveled the world abroad HMS Beagle, collecting numerous samples from the Galápagos Islands. On his return, he observed that Galápagos finches, formerly presumed to be the same species, varied so much they constituted a different species. *There are some historical disputes regarding the role of some details in this story towards the development of the Theory of Natural Selection, HMS Beagle Edison Tan Evolutionary Psychology Singapore Management University Galápagos’s Finches Darwin determined that these different finches had a common ancestor but had become distinct from each other because of the local ecological conditions on each island. Darwin concluded that species are not immutable and can change over time. What could account for why species change? “The Struggle for Existence.” Favorable variations tend to be preserved, and unfavorable The ground finches (Geospiza) has a thick beak adapted to feeding ones tend to die out. When this process is repeated generation on a variety of crunchy seeds and arthropods, whereas the warbler finch (Certhidea olivacea) developed a slender, pointy bill after generation, the result is the formation of new adaptations. to catch tasty insects hiding between the foliage. Edison Tan Evolutionary Psychology Singapore Management University Theory of Natural Selection 01 Variation 02 Inheritance Organisms vary across a multitude of Some of the attributes that vary are dimensions of attributes (e.g., structural inherited and reliably passed down to complexity, anatomy, cellular structure, offspring over generations physical and psychological abilities, traits) 03 Selection (via differential reproduction success) Organisms with heritable attributes reproduce and have more offsprings as those attributes help overcome the problem of survival and reproduction Important note! Reproductive success is the bottom line and the end-all of selection. “Fitness” in evolutionary sciences refers to the odds of an organism with a certain attribute surviving till reproduction. Edison Tan Evolutionary Psychology Singapore Management University Sexual Selection Survival is a necessary but not a sufficient prerequisite to reproductive success. Specific attributes that appear to serve no survival function or even be costly to survival would not have been favored by natural selection but persisted in several organisms. E.g., Male peacocks’ plumage Dakin et al. (2016) The existence of these traits can be explained by an alternate selection process: Sexual Selection. Adaptation that arose as a consequence of successful mating – not survival. Edison Tan Evolutionary Psychology Singapore Management University  Boys of a Feather by Kasia Babis Sexual Selection Intra-sexual Inter-sexual Competition Competition Competition between members of the same Manifest as preferential mate choices sex. Individuals who display superior Individuals of the opposite sex with characteristics during intrasexual advantageous characteristics are preferred competition gain sexual access to mates as mates. directly or indirectly (e.g., controlling e.g., ability and willingness to offer territory or resources). gifts of food and other resources to desired mates Superior attributes that are inheritable are Individuals who do not possess passed down to offspring, conferring advantageous characteristics are less likely offspring with intrasexual competitive to be chosen as mates, reducing advantages. reproductive odds. Edison Tan Evolutionary Psychology Singapore Management University Important Notes about Natural and Sexual Selection Natural and Sexual Selection is not the only driver of evolutionary change – random changes (i.e., genetic drift) can occur Mutation Founders Effect Genetic Bottleneck Selection is not “intentional.” Selection merely acts on variances that exist based on recurrent advantages for survival and reproduction that the characteristic confers Selection cannot anticipate future demands Selection is gradual, some rapid, others over generations. May depend on the complexity of the organism (e.g., changes happen to viruses faster than mammals) Edison Tan Evolutionary Psychology Singapore Management University Darwinism after Darwin Classic Darwinism Variation Inheritance Selection Modern Synthesis (Neo-Darwinism) Integrated Synthesis Mendelian Post-Synthesis Genetic Inclusive-Fitness Mutation and Kin Selection Genetic Inheritance Ethology Etc. Evo-Developmental e.g., Life History Theory Theories Multilevel Selection e.g., Cultural Selection Adaptive Lags e.g., Evolutionary Mismatch Etc. Edison Tan Evolutionary Psychology Singapore Management University Mendelian Genetics Darwin’s Theory of Natural Selection did not define by which mechanism inheritance occurred. From 1856 to 1863, Gregor Johann Mendel (1822 – 1884) carried out pioneering experiments on heredity in garden peas. He crossed-bred peas with seven pairs of pure-bred traits by painstakingly transferring pollens (reportedly with a paintbrush) and vigorously documenting the characteristics of their offspring. He proposed that there are hereditary elements that determine traits (now called genes) and established the law of inheritance. Edison Tan Evolutionary Psychology Singapore Management University The Ethology Movement Chittka (2004) Although more typically associated with physical characteristics, Darwin had envisioned that natural selection could be applied to behavior. There is a clear association between the existence of physical characteristics and the existence of behaviors: Behaviors require support from anatomic and biomechanical infrastructure for enactment. Capacity and propensity for behaviors have been demonstrated to be heritable. An adaptation in the form of a physical characteristic requires organisms to enact behaviors that make use of the adaptation so that organisms can Honeybee workers perform the waggle dance to indicate the range benefit from it. and direction of food. Edison Tan Evolutionary Psychology Singapore Management University The Ethology Movement In 1935, zoologist Konrad Lorenz described a form of learning behavior in young ducklings and goslings known as imprinting. They learn to follow real or foster parents at a certain critical stage (i.e., soon after hatching). By showing that imprinting occurs shortly after birth, Lorenz demonstrates the innate nature of imprinting Served an adaptive function of keeping close to caregivers that would ensure the duckling’s survival Later understood as fixed action patterns – a stereotypic behavioral sequence an animal follows after being triggered by a well-defined stimulus Edison Tan Evolutionary Psychology Singapore Management University Inclusive Fitness William D. Hamilton reasons that what constitutes fitness – how well an organism successfully passes on their genes through reproduction – in classical Darwinism is too narrow a definition. If the bottom line of reproduction is the survival of the gene, natural selection ought to favor characteristics that support the survival of the gene, regardless of whether the organism produces offspring. Survival of the gene can be ensured by aiding genetic relatives. Inclusive Fitness = Classical Fitness + (Effect of the Organism’s Action on the Fitness of The Hamilton Rule Genetic Relatives × Genetic Relatedness) Altruism is favored by natural selection when: Forms the foundation for understanding kin-altruism – the solution to the longstanding problem of how altruism could have evolved when it imposed cost onto self Benefits to genetic relatives must have been greater than the cost to self (The Hamilton Rule) rB >C r – proportion of shared genes B – fitness benefits in terms of how many offspring are produced C – fitness cost to self Edison Tan Evolutionary Psychology Singapore Management University Group Selection Group selection is a now-disfavored proposal of a mechanism of evolution in which natural selection acts at the level of the group instead of at the level of the individual or gene. An organism may reduce reproduction effort to keep the population low, thus preventing the destruction of common food source Imply that only organisms with characteristics beneficial to the group survive; selfish organisms will perish with the group. Selection George C. Williams pointed out the problems with the concept of group selection: Altruistic organisms that sacrifice themselves for the benefit of the group are less likely to survive. Selfish organisms are more likely to survive and reproduce. Selections at the genetic level work against selection at the group level Edison Tan Evolutionary Psychology Singapore Management University Clarifying the concept of an Adaptation Adaptations are evolved solutions to specific problems that contribute directly or indirectly to successful reproduction. George C. Williams established the criteria for characteristics to be considered as an adaptation: Reliability – Does the mechanism regularly develop in most or all members of the species across all “normal” environments and perform dependably in the contexts in which it is designed to function Efficiency – Does the mechanism solve a particular adaptive problem well and effectively? Economy - Does the mechanism solve the adaptive problem without extorting huge costs from the organism? Adaptation is invoked to explain improbable usefulness – are the characteristics too precisely functional to arise from mere chance? Edison Tan Evolutionary Psychology Singapore Management University  Robert Triver’s Three Seminal Theories (1971) (1972) (1974) Theory of Reciprocal Parental Investment Parent-Offsprings Altruism Theory Conflict Theory Defined the condition where Sex that invests more in its Resources invested in altruism – the act of helping offspring will be more offspring are resources not unrelated others while selective when choosing a available elsewhere (e.g., other incurring a cost to self – mate offspring). could have evolved. Less-investing sex will have Parents look to maximize Altruistic helping may be intra-sexual competition for fitness benefits from parental beneficial when there is access to mates resources invested, while potential for repayment for offspring look to maximize the altruistic act in the future. parental resources gained from parents. Edison Tan Evolutionary Psychology Singapore Management University  The Sociobiology Controversy In 1975, Edward O. Wilson published a highly controversial book, Sociobiology: The New Synthesis, which attempted to integrate various batches of evolutionary and biological science, Claimed the integrated principles can be applied to all organisms. Claimed that Sociobiology will “cannibalize psychology” Forgo many important psychological principles (e.g., learning, reasoning, culture) that form the foundation of psychology and focus mainly on behaviors Evidence being primarily from non-human sources Imply that humans possess mechanisms with the goal of maximizing their inclusive fitness, that is, maximizing their gene representation in subsequent generations. Edison Tan Evolutionary Psychology Singapore Management University  The Sociobiology Controversy Sociobiology is to evolutionary Sociobiology psychology, like behavioralism is to Ancestral Natural Selection Behaviors psychology. Environment Conflated the origin of human psychology with the Evolutionary Psychology nature of human psychology Ancestral Environment Sociobiologists skipped or neglected the "psychological level" of analysis. Natural Selection Current Psychological Many go directly from principles of evolution to end- Environment Mechanisms Behaviors product without specifying the psychological operation by which the end-product is generated. Operations of the evolved psychological mechanisms Edison Tan Evolutionary Psychology Singapore Management University “If men had as a goal the maximization of fitness, then why aren't they all lined up to give donations to sperm banks?” ― David Buss (1995) Edison Tan Evolutionary Psychology Singapore Management University  02 Common Misconceptions about Evolutionary Psychology Edison Tan Evolutionary Psychology Singapore Management University “Human behavior is genetically determined.” 01 Genetic determinism is the view that genes determine phenotypes, such as morphology, psychology, or behavior, with little or no Genetic environmental influence. Environment influence is apparent at all stages of Determinism evolutionary processes: Environment as selective pressure Environment as developmental inputs Environment as triggers of psychological mechanisms. Evolutionary Psychology is an interactionist approach. Evolutionary Psychology rejects any claims of genetic determinism. Edison Tan Evolutionary Psychology Singapore Management University “If human behaviors are evolved, it’s impossible to 02 change it.” Evolved characteristics and behaviors require triggers to activate (e.g., calluses). Some changes are easier than others. The extent to which change can happen depends on the extent to which plasticity is favored by natural Inflexiblity selection – adaptive plasticity. Understanding the operations of evolved psychological mechanisms and the environmental inputs allows us to introduce changes via interventions. Evolved characteristics are not necessarily unchanging, static, or permanent. Edison Tan Evolutionary Psychology Singapore Management University “Adaptations that organisms possess today are 03 optimally designed over generations of selection.” Evolutionary or Adaptive Time Lag (i.e., Evolutionary Mismatch) Optimal Changes in the environment outpace the time required for adaptation. Results in adaptations being suboptimal in the Design modern environment E.g., Preference for sweet food and modern diabetes Cost of Adaptation All adaptations carry a cost in some forms Adaptations are only beneficial in so far that fitness benefits outweigh the cost E.g.., Fear and opportunity cost Adaptations are often far from optimal due to design constraints. Edison Tan Evolutionary Psychology Singapore Management University  03 Notes about Evolutionary Explanations Edison Tan Evolutionary Psychology Singapore Management University  01 Tinbergen’s Four Question Proximate Analysis Explanations that address the Mechanism Competing Ontogeny immediate causes of a behavior or How is the mental process, as well as how it How did the developed during the individual’s characteristics characteristic structured? lifespan. develop in the Explanations organism? How does the characteristic e.g., Cognitive, Cultural, work? Developmental, and Social Psychology, etc. Does evidence for an adaptation render Level of Analysis socialization, developmental, and cultural Phylogeny Function Ultimate Analysis Explanations that address distant What purpose or explanation unimportant? How did this function did this historical origins of how and why characteristic the psychological structures are characteristic responsible for producing the evolve? serve? behavior or mental process. Not at all. E.g., Evolutionary Psychology Evolutionary explanations often complement Object of Analysis sociocultural and developmental theories rather than contradict them. Edison Tan Evolutionary Psychology Singapore Management University  02 “We evolved to be this way; hence, this is the right way to be and the best way to be.” Naturalistic Fallacy The belief that what is “natural” - how nature is - is therefore Naturalistic “good” and how things should be. e.g., "Warfare must be allowed because human violence is instinctive." and Moralistic Moralistic Fallacy The belief that what is “good” is, therefore, how nature is. The Fallacies belief is that if something is “bad,” it is not “how nature intended it.” e.g., “Warfare is destructive and tragic, and so it is not of human nature." How the world - how nature is – is a statement based on observation. Selection does not have any “intention.” Nature has an “is” but not a “should be.” Use the knowledge about how the world is and an evidence-based what and why to shape the world into the one you want it to be. Edison Tan Evolutionary Psychology Singapore Management University  Discussion Open Floor Discussion Edison Tan Evolutionary Psychology Singapore Management University NEXT WEEK: Core Concepts Additional Readings: Why I Am Not a Sociobiologist, pp. 9 – 10. In Buss, D. M. (1995). Evolutionary Psychology: A New Paradigm for Psychological Science. Psychological Inquiry, 6(1), 1–30. https://doi.org/10.1207/s15327965pli0601_1 Edison Tan Evolutionary Psychology Singapore Management University PSYC205 Evolutionary Psychology Core Concepts Edison Tan Evolutionary Psychology Singapore Management University  01 Products of Evolutionary Processes Edison Tan Evolutionary Psychology Singapore Management University  Products of Evolutionary Processes. Inheritance by genetic transmission Adaptation Most characteristics are coded not by a single gene but by a complex aggregation of many genes Inherited and reliably developing characteristics that came into existence through natural selection Develop reliably to solve adaptive problems. because they helped to solve problems of survival or reproduction better Emerge at appropriate stages of development, not necessarily than alternative designs existing in at birth the population during the period of In a reasonably intact form their evolution Some adaptations are species-typical; others are sex or in subsets of the population. By-products Depending on whether the subgroup faces the recurrent adaptive problem over their evolutionary history Noise Edison Tan Evolutionary Psychology Singapore Management University  Products of Evolutionary Processes Adaptations are functional Function refers to how the adaptation solves adaptive Adaptation problems – the precise solution. Design features of an adaptation refer to the components and Inherited and reliably developing processes of adaptive solutions that contribute to solving the characteristics that came into adaptive problem existence through natural selection Purported adaptations are functional if they are: because they helped to solve problems of survival or reproduction better Adaptation solves than alternative designs existing in Efficient the adaptive problem well the population during the period of their evolution Adaptations are Economic cost-effective By-products Components of adaptation are design to achieve Precise a particular outcome that Noise solves adaptive problems Performs dependably in the specific contexts it Reliable is designed to operate in Edison Tan Evolutionary Psychology Singapore Management University  Products of Evolutionary Processes Adaptations are shaped by natural selection Each adaptation first emerges as a mutation – an error in the Adaptation genetic coding - resulting in a characteristic that deviates from its previous form. Inherited and reliably developing Mutated characteristics that harm the organisms are removed characteristics that came into from the gene pool (sometimes by chance) as they hinder existence through natural selection survival and reproduction. because they helped to solve problems Beneficial mutations are retained and passed down as of survival or reproduction better organisms achieve differential reproductive success. than alternative designs existing in the population during the period of Each adaptation has a unique environment of evolutionary their evolution adaptedness (EEA) Selective forces or adaptive problems responsible for shaping the adaptation over the organism’s evolutionary history By-products Each adaptation has a period of evolution. The timespan natural selection takes to shape the adaptation Noise to its functional form Edison Tan Evolutionary Psychology Singapore Management University Products of Evolutionary Processes Adaptation By-products Characteristics that do not solve adaptive problems and do not have functional design; they are “carried along” with characteristics that do have functional design because they happen to be coupled with those adaptations. Noise Random effects are produced by forces such as chance mutations, sudden and unprecedented changes in the environment, or chance effects during development. It can be harmful or neutral. Edison Tan Evolutionary Psychology Singapore Management University  02 The Evolved Psychological Mechanism Edison Tan Evolutionary Psychology Singapore Management University  The Evolved Psychological Mechanism Decision Algorithm Input Output IF → THEN An evolved psychological mechanism is a set of psychological processes with the following properties: Exist because they solved a recurrent problem of survival or reproduction over our evolutionary history. Their core component (i.e., design features) were shaped in a way they coordinated to overcome specific obstacles to survival or reproduction. An evolved psychological mechanism is designed to take in only a narrow slice of information as inputs. The spectrum of input the psychological mechanisms are sensitive to is relevant for the detection of adaptive problems that are recurring over the EEA – or in modern environments that mimic these inputs The input of an evolved psychological mechanism tells an organism the particular adaptive problem it is facing. Perception can happen consciously or unconsciously. Edison Tan Evolutionary Psychology Singapore Management University  The Evolved Psychological Mechanism Decision Algorithm Input Output IF → THEN An evolved psychological mechanism is a set of psychological processes with the following properties: The input of an evolved psychological mechanism is transformed through an algorithmic decision rule or procedure into outputs. The decision rules are sets of procedures —“if, then” statements—for guiding an organism down one response or another. The output of an evolved psychological mechanism can be a physiological activity, information about other psychological mechanisms, or manifest behavior. Outputs of psychological mechanisms can act as inputs to other psychological mechanisms or as manifest behaviors The output of an evolved psychological mechanism is directed toward the solution to a specific adaptive problem. The output of the mechanisms may not always be successful, but on average, it tends to solve adaptive problems. Edison Tan Evolutionary Psychology Singapore Management University Important Notes about Evolved Psychological Mechanism Evolved Psychological Mechanisms are Problem Specific Adaptations are solutions that need to be specific to addressing the problem faced Generalized solutions, even if they work, they are unreliable and imprecise because they are not designed for a specific problem Every solution, including adaptations, can fail. Errors are more likely to arise from solutions not designed for the problem. ○ When errors occur, they present themselves as a threat to survival and reproduction ○ Organisms evolved to process mechanisms specifically designed for correcting errors (e.g., vomiting) Edison Tan Evolutionary Psychology Singapore Management University Important Notes about Evolved Psychological Mechanism Humans Possess a Complex Array of Evolved Psychology Mechanisms Humans have faced a large number of adaptive problems throughout our evolutionary history. Each adaptive problem requires a specific psychological solution Consequently, we possess just as many evolved psychological mechanisms to address the multitude of adaptive problems. Edison Tan Evolutionary Psychology Singapore Management University Important Notes about Evolved Psychological Mechanism Specificity, Complexity, and Numerousness of Evolved Psychological Mechanism Confers Humans High Level of Behavioral Flexibility Behaviors are not rigid “instinct.” Without environmental stimuli acting as triggers (IF), there will be no behavioral response (THEN) Some mechanisms feed input to another mechanism as outputs The huge number of mechanisms humans possess allows us to generate a huge range of behavioral responses. Response can be altered by changing the input, by changing the environment, or by the operation of a psychological mechanism producing an input as output. Edison Tan Evolutionary Psychology Singapore Management University Important Notes about Evolved Psychological Mechanism Learning, Socialization, Cultural Influence Describe Proximate Operations of Evolved Learning Mechanism Learning requires an environmental input surrounding the individual to generate an output mimicking Learning, socialization, and endorsement of culture require an evolved psychological mechanism to attend to environmental cues to generate functional, socially learned, or culturally influenced behaviors Edison Tan Evolutionary Psychology Singapore Management University  03 Research Methods in Evolutionary Psychology Edison Tan Evolutionary Psychology Singapore Management University  General Evolutionary Theory Levels of Analysis in Evolutionary Middle-Level Evolutionary Psychology Theories Research in Evolutionary Psychology involves (a) Generating hypotheses (b) Empirically testing predictions based on Specific Evolutionary those hypotheses Hypotheses (c) Interpreting study results Evolutionary Psychology does so by organizing evolutionary principles into hierarchical levels of analysis. Specific Prediction Derived from Hypotheses Each level must be consistent with higher levels of analysis without being wholly derived from it. Edison Tan Evolutionary Psychology Singapore Management University  General Evolutionary Theory Levels of Analysis in i.e., Evolution by Natural Selection Evolutionary Middle-Level Evolutionary Psychology Theories General Evolutionary Theory describes the evolutionary principle Specific Evolutionary Hypotheses that natural selection is the core engine of the evolutionary process by which adaptations emerge. Specific Prediction Derived from Hypotheses Edison Tan Evolutionary Psychology Singapore Management University  General Evolutionary Theory Levels of Analysis in i.e., Evolution by Natural Selection Evolutionary Middle-Level Evolutionary For example, genes can increase their own replicative success by Psychology Theories E.g., Kin-Selection Theory promoting the reproduction of other bodies likely to carry copies of themselves. When the core principle of natural selection is applied to specific Specific Evolutionary domains of life, it yields middle- Hypotheses level theories E.g., kin-Selection theory is an extension of natural selection Specific Prediction Derived to the context of altruism from Hypotheses amongst kin. Edison Tan Evolutionary Psychology Singapore Management University  General Evolutionary Theory Levels of Analysis in i.e., Evolution by Natural Selection Evolutionary Middle-Level Evolutionary For example, genes can increase their own replicative success by Psychology Theories E.g., Kin-Selection Theory promoting the reproduction of other bodies likely to carry copies of themselves. Using Middle-level theories, For example, natural researchers can generate specific Specific Evolutionary selection favored the Hypotheses existence of a hypotheses about the operation of psychological e.g., Kin-Recognition hypothesis mechanism that allows evolved psychological mechanisms. individuals to estimate the genetic relatedness between themselves and others. Specific Prediction Derived from Hypotheses Edison Tan Evolutionary Psychology Singapore Management University  General Evolutionary Theory Levels of Analysis in i.e., Evolution by Natural Selection Evolutionary Middle-Level Evolutionary For example, genes can increase their own replicative success by Psychology Theories E.g., Kin-Selection Theory promoting the reproduction of other bodies likely to carry copies of themselves. Researchers can then use For example, natural hypotheses to generate testable Specific Evolutionary selection favored the Hypotheses existence of a empirical predictions. psychological e.g., Kin-Recognition hypothesis mechanism that allows For example, older individuals to estimate siblings will exhibit the genetic relatedness greater altruism between themselves toward younger and others. siblings if they observe Specific Prediction Derived them nursing from from Hypotheses their own mother. Edison Tan Evolutionary Psychology Singapore Management University  General Evolutionary Theory Levels of Analysis in i.e., Evolution by Natural Selection Evolutionary Middle-Level Evolutionary Psychology Theories E.g., Kin-Selection Theory Predictions in Evolutionary Psychology were generated based on specific hypotheses, which in Specific Evolutionary turn were inspired by the middle-level theory of Hypotheses kin selection, which was itself generated based on e.g., Kin-recognition hypothesis evolutionary theory. Applying a simple insight at a broad level, such as that of a middle-level theory like kin selection, can Specific Prediction Derived yield rich and diverse downstream hypotheses from Hypotheses and a priori predictions readily testable in empirical research. Edison Tan Evolutionary Psychology Singapore Management University  Hypothesis Generation Steps Top Down (Theory Drive) Bottoms-Up (Observation Driven) Developing Hypotheses from Existing Developing Hypotheses by Observing Theory Behavioral, Physiological, or Psychological Phenomenon 1 Identify an adaptive problem Observe a phenomenon 2 Hypothesize an adaptation via a task Hypothesize an adaptation via a reverse analysis task analysis – asking if psychological adaptation may be responsible for producing that phenomenon and what adaptive problem that mechanism may be designed to solve. 3 Make predictions regarding the core Make predictions regarding the core design features design features 4 Conduct empirical studies to test Conduct empirical studies to test predictions predictions Edison Tan Evolutionary Psychology Singapore Management University Identifying Adaptive Problems Recurrent adaptive problems must be present to shape adaptations; genes of an individual who solved the adaptive problem are passed down: Useful tools: Existing knowledge about the ancestral environment Using well-established data from disciplines such as anthropology, geology, primatology, and biology, assuming physical laws are unchanging For example, in the Social Brain Hypothesis (Dunbar, 1998), primate seems to have comparatively larger brain sizes than other organisms. Primate, including humans, are known to be social-living organisms Social interactions require neurological infrastructure to support – brain size correlates with group size. Humans likely lived in approximately 150 individuals Edison Tan Evolutionary Psychology Singapore Management University Identifying Adaptive Problems Recurrent adaptive problems must be present to shape adaptations; genes of an individual who solved the adaptive problem are passed down: Useful tools: Applying middle-level theories to the EEA to identify who is most likely to face adaptive problems Sociometer Theory (Leary & Downs, 1995; later Kirkpatrick & Ellis, 2001) – Humans have an innate need to feed included in their group and relationship, and exclusion is detrimental to survival (e.g., predation) and reproduction (e.g., access to mates). Self-esteem is an output of an evolved psychological mechanism that regulates relational investment All humans face the adaptive problem of inclusion given that we are group-living organisms – all humans should possess this mechanism. Edison Tan Evolutionary Psychology Singapore Management University Identifying Adaptive Problems Other useful heuristics to identify adaptive problems: Must-solve vs. Beneficial-to-solve adaptive problems Must-solve Adaptive problems that, if not solved, will singlehandedly result in organisms failing to survive and reproduce. Beneficial-to-solve Problems that did not necessarily have to be solved but whose solution would nonetheless have increased the organism’s fitness improving the performance of an extant adaptive solution increasing the economy of an existing adaptation, such as by decreasing its costs increasing the reliability of the development of an adaptation increasing the number of cues that the adaptation takes as increasing and diversifying the repertoire of outputs that an adaptation can produce to improve the functional match between behavior and the specific cause of the problem Edison Tan Evolutionary Psychology Singapore Management University Identifying Adaptive Problems Other useful heuristics to identify adaptive problems: Must-solve vs. Beneficial-to-solve adaptive problems Aid development of hypotheses that also consider adaptive problems that are less obvious but likely just important in shaping adaptations E.g., Bullying as an adaptation (Volk et al., 2012, 2022) Aggression against peers offers benefits such as access to social and material resources, deterrence from being aggressed against, and some conferences of prestige. People do not NEED TO bully their peers to gain resources, but occasionally, bullying can yield benefits Edison Tan Evolutionary Psychology Singapore Management University Identifying Adaptive Problems Other useful heuristics to identify adaptive problems: Threats vs. Opportunities A threat is a feature or characteristic of the physical, ecological, or social environment with the potential to compromise an individual’s survival or reproduction (see The Hostile Forces of Nature, next week) An opportunity is a previously unexploited situation that could enhance survival or reproduction if taken advantage of. Attending to these “opportunities” and sometimes, their trade-off with “threats” (see “Cost- Benefit Analysis later) can lead to hypotheses, predictions, and findings that might otherwise remain undiscovered. Edison Tan Evolutionary Psychology Singapore Management University  Identifying Adaptive Problems Weak selective Extraordinarily Other useful heuristics to identify pressure but strong selection occurs often pressure adaptive problems: enough to be Often shapes beneficial for complex organism to adaptations Magnitude of impact and Frequency of overcome encounter Low Impact, High Impact, High High Frequency Frequency Adaptive problems that generate strong selective pressures drive the evolution of adaptations. The strength of an adaptive problem depends on: Low Impact, High Impact, Low Low 1. the magnitude of its impact on survival or Frequency Frequency Strong Selective reproduction Pressure Unlikely to shape Adaptation 2. the frequency at which it was faced. adaptation emerges even if an organism did not encounter the adaptive problem in its lifetime. Edison Tan Evolutionary Psychology Singapore Management University Task Analysis Specify the (a) relevant end state—the solution to the adaptive problem— and proceed by (b) detailing the specific design feature of the psychological mechanism capable of producing that end state. “How would an evolved psychological mechanism operate to solve this adaptive problem?” Consider this question at all stages of processing (Inputs → IF-THEN → outputs) What are the inputs? (Identifying the social, cultural, or other environmental inputs that the mechanism is expected to process) What is the IF-THEN rule? (describing the algorithmic processing of these inputs) What are the outputs? (predicting the mechanism’s psychological, physiological, or behavioral outputs) e.g., The Behavioral Immune System Decision Algorithm Input Output IF → THEN Probabilistic cues of IF – Detected (real or Affective: Disgust pathogens (e.g., corpse, perceived) Behavioral: Avoid feces) Then – Manifest Output Physiological: Nausea Edison Tan Evolutionary Psychology Singapore Management University Task Analysis The importance of postulating specific design features: Specification is necessary to confirm that the proposed adaptation could plausibly solve the adaptive problem. Predicting numerous, specific design features enables a researcher to design studies that test for their existence and thereby test for the existence of the adaptation itself. Renders the hypothesized psychological adaptation empirically testable and, consequently, falsifiable. Detailed specification is necessary to submit alternative hypotheses to discriminative tests and adjudicate between them. Edison Tan Evolutionary Psychology Singapore Management University  Cost-Benefit Analysis Context may vary the fitness cost and benefit of manifested output. For example, when e.g., The Behavioral Immune System facing contaminated food: Stress increases pathogen cost (cortisol is an immunosuppressant) Stressed individuals are more Contextual Input: likely to feel disgusted by Stressor contaminated food Hunger indicates potential survival cost due to potential nutritional deficit Hungry individuals are more likely to benefit from eating Input: Decision Algorithm contaminated food Output Contaminated Food IF → THEN Cost and Benefit Analysis allows for a nuanced prediction regarding the operation Stress: ↑ Disgust Hunger: ↓ Disgust of the evolved psychological mechanism – across different cultural contexts, individuals, Contextual Input: and sex. Hunger Al-Shawaf & Lewis (2013) Edison Tan Evolutionary Psychology Singapore Management University Data for Testing Hypothesis and Predictions Paleontological Archeological Records Anthropological Hunter-Gatherer Societies Human Products Sociological/Psychological This is particularly Observation (Field and Lab) important when Self-Report assessing unobservable Public Archives psychological variables! Edison Tan Evolutionary Psychology Singapore Management University The Importance of Triangulation Triangulation in research involves using multiple methods, datasets, and theories (recall Tinbergen's four questions) to increase scientific validity. Multiple data and methods allow researchers to overcome critical limitations associated with specific methods or types of data. Convergence in findings increases our confidence that conclusions are robust, valid, and reliable in the face of a replication crisis in science. Edison Tan Evolutionary Psychology Singapore Management University Interpreting General Evolutionary Theory Research at Different Levels of Middle-Level Evolutionary Theories Analysis A single adaptive problem may have multiple solutions. Hence, a middle-level theory can generate various hypotheses. Specific Hypotheses A Specific Hypotheses B It is possible for a hypothesis about the existence of an adaptation to be falsified without falsifying a middle-level theory. Interpret individual research in the context of other findings within the broader body of research. Science is a cumulative enterprise Specific Prediction Derived Specific Prediction Derived Evaluation of the theory depends on independent from Hypothesis A from Hypothesis B verification and falsification from multiple research Edison Tan Evolutionary Psychology Singapore Management University Interpreting General Evolutionary Theory Research at Different Levels of Middle-Level Evolutionary Theories Analysis All observed findings are open to alternate interpretations, including multiple evolutionary explanations that compete with one another. Specific Hypotheses A Specific Hypotheses B The observed phenomenon might be the output of an adaptation designed to solve a different adaptive problem other than the one proposed or even a non-functional by-product of an adaptation. Consider alternative functions an output may serve and Specific Prediction Derived Specific Prediction Derived make testable predictions about their design feature. from Hypothesis A from Hypothesis B Design studies with robust methods to test competing hypotheses Edison Tan Evolutionary Psychology Singapore Management University  Discussion Edison Tan Evolutionary Psychology Singapore Management University Persistence of Negative Traits “How do evolved psychological mechanisms explain psychological or mental health disorders that appear maladaptive in modern societies?” Edison Tan Evolutionary Psychology Singapore Management University  Why do negative traits and characteristics exist and persist? A trait, cognition, affect, and behavior Natural selection selects for Costly traits may be generally beneficial for are adaptive insofar as fitness characteristics and traits that fitness approaching the extreme but benefits outweigh the cost. enhance reproductive odd, not health maladaptive at the extreme. and well-being. Cost of anxiety, for example, may include: Damage from physiological Costly traits may be adaptive for the genes but distressing for the effects underlying anxiety, individual. e.g., the effect of adrenaline and cortisol. Opportunity cost from Sexual jealousy is an output of a mate-defending mechanism avoidance of potential benefits Motivates attentiveness to potential infidelity Benefits of anxiety include: Ensure offspring belongs to Avoidance of danger that self, aid monopoly of mate’s would have resulted in resource death May cause sleepless nights, anxiety, and interference Benefit of Anxiety > Cost of Anxiety with daily life Edison Tan Evolutionary Psychology Singapore Management University Why does costly traits and characteristic persist? Edison Tan Evolutionary Psychology Singapore Management University Universality Given that evolutionary psychology asserts the universality of psychological mechanisms across cultures, to what extent do these variations suggest that psychological mechanisms are more shaped by specific ecological and social contexts rather than being universally consistent? Edison Tan Evolutionary Psychology Singapore Management University What is Universal? The Psychological Mechanism or the Output? Evolutionary Psychology advances the universality of psychological mechanisms, not the manifest behavior generated by the psychological mechanism. Systematic variability in social and cultural input should lead to systematic variability in psychological output. E.g.., Varying pathogen loads in local ecology predict cultural differences in the importance of physical attractiveness in mate preference Edison Tan Evolutionary Psychology Singapore Management University Domain-Specificity and Flexibility “How do specialized mechanisms enhance behavioral flexibility in humans, and why might having many specialized mechanisms broaden rather than limit the range of possible behaviors, especially in comparison to domain-general mechanisms?” Edison Tan Evolutionary Psychology Singapore Management University Evolved Psychological Mechanisms are Unlikely to be Domain General (Confer et al., 2007) Failure-to-Predict Domain-General explanation typically assumes humans “just figured it out.” Does not explain why humans are so sensitive to specific inputs Does not explain why sex differences exist Combinatorial Explosion Domain-General explanation will require the organism to have a trial-and-error response to the adaptive problem There are potentially exponential numbers of output that can be generated in the face of the adaptive problem Not efficient Not economic Not precise Not reliable Edison Tan Evolutionary Psychology Singapore Management University Evolved Psychological Mechanisms are Unlikely to be Domain General (Confer et al., 2007) Poverty-of-the-Stimulus Domain-General explanation requires an organism to sample a large number of observations to determine the regularity in the occurrence of an adaptive problem E.g., Men need to continuously observe how sexual infidelity leads to paternal uncertainty Unlikely to occur Adaptive Problems are Context-Dependent The most effective solution to an adaptive problem depends on the cost-benefit of output considering the context. Risk-taking during hunting for a childless man vs. risk-taking for a man with mates and offspring There are no “one-size-fits-all” solutions to adaptive problems – what is “rational” in one context may be irrational in another. Edison Tan Evolutionary Psychology Singapore Management University Evolved Psychological Mechanisms are Unlikely to be Domain General (Confer et al., 2007) Purported Domain-General mechanisms are better explained by the existence of a Domain-Specific mechanism. General Intelligence may be an evolved psychological mechanism that solves adaptive problems of novelty – adaptive problems that are not common over the EEA Possibly as low-frequency, high-impact problems Key evidence (Kanazawa, 2004) Intelligence does not seem to boost reproductive success Intelligence does not seem to predict kin-investment or cooperation with non-kin positively Intelligence predicts better performance in an area of life that does not exist in the ancestral past (e.g., standardized education) Edison Tan Evolutionary Psychology Singapore Management University Domain-Specificity Assuming that humans possess domain-general mechanisms would mean that humans would often be completely paralyzed by the ineffective and highly iterative means of generating output. In contrast, having numerous domain-specific evolved psychological mechanisms allows for flexibility of response because: Specialized psychological mechanisms are sensitive to specific inputs, efficiently generating specific output in cognition, affect, and behavior. When multiple psychological mechanisms are engaged, they collectively generate a myriad of outputs that can interact with each other or give feedback to other downstream psychological mechanisms as inputs. Each interaction between psychological mechanisms allows for a wide range of potential outputs that would manifest as a highly flexible range of possible responses to a given situation. Edison Tan Evolutionary Psychology Singapore Management University  Open Floor Discussion Edison Tan Evolutionary Psychology Singapore Management University NEXT WEEK: The Hostile Forces of Nature Additional Readings: Lewis, D. M. G., Al-Shawaf, L., Conroy-Beam, D., Asao, K., & Buss, D. M. (2017). Evolutionary psychology: A how- to guide. American Psychologist, 72(4), 353–373. https://doi.org/10.1037/a0040409 Edison Tan Evolutionary Psychology Singapore Management University PSYC205 Evolutionary Psychology Hostile Forces of Nature Edison Tan Evolutionary Psychology Singapore Management University Anything can kill us Extreme Climates Each of these hostile forces created adaptive problems that have Harsh Weather recurred over generations. Lack of food and food spoilage Act as a filter – those who succumb to these adaptive problems fail Toxin to reproduce. Disease Whoever possesses solutions to these adaptive problems survives Pathogens and reproduces. Predators Other Humans Ourselves Edison Tan Evolutionary Psychology Singapore Management University  01 Food Acquisition and Selection Edison Tan Evolutionary Psychology Singapore Management University Evolved Food Preferences Food preferences aid in solving the adaptive problems of food- seeking Preferences for sweet food – indicative of high caloric value Ranking of food preferences amongst hunter-gatherers positively correlates with caloric values (Berbesque & Marlowe, 2009) Honey is consistently favored over tubers. Preference for salty food – replenishing sodium in the body, which is necessary for neural activities. Sodium-depleted humans rated salty food as more appealing than unsalted food (Neauchamp et al, 1990). Edison Tan Evolutionary Psychology Singapore Management University How Food Drives Human Evolution The Hunting Hypothesis (Tooby & Devore, 1987) Global cooling a few million years ago marked a dramatic decrease in plant-based food sources, making animal hunting the more attractive food source. Physiological evidence The human digestive system appears to be better designed for processing meat in the small intestine (vs. fiber in the colon). Humans are unable to produce vitamins A and B12, found in abundance in meat, despite it being critical to human bodily function Paleontological evidence Not show wear and tear in teeth associated with fibrous plant diet in human fossil Cut marks on collections of bones – indicating early butchering attempts Edison Tan Evolutionary Psychology Singapore Management University How Food Drives Human Evolution The Provisioning Hypothesis Explains: (Tooby & Devore, 1987) Strong Male Coalition Meat from big-game hunting is a highly Large-game hunting requires coordinated action between male economical and concentrated food hunters resource. Reciprocal Altruism and Social Exchange Transporting meat calories is far more Excess perishable food has diminishing fitness returns for sated cost-effective than lower-caloric food individuals and family members. The benefits of sharing food and generating reciprocal debt are high over long distances. Sexual Division of Labor Allow for heavy investment and Men are biologically and physiologically better suited for hunting provisioning of resources to children Ancestral women, often preoccupied with pregnancy and children, supplement food sources by gathering to exchange with returning men Emergence of Stone Tools Edison Tan Evolutionary Psychology Singapore Management University How Food Drives Human Evolution The Show-Off Hypothesis Men who pursue risky hunting strategies would benefit from showing (Hawkes, 1991) off in several ways: Women are more likely to offer benefits Increased sexual access to women, higher odds of fathering more to men who can provide gifts of food, offspring particularly in times of shortage. High odds of offspring survival via better provision of care Siding with them during intragroup Gaining social status within the group conflict Providing care to their children Offering sexual favors Edison Tan Evolutionary Psychology Singapore Management University How Food Drives Human Evolution The Gathering Hypothesis (Tanner, 1983; Tanner & Zihlman, 1976; Zihlman, 1981) A competing hypothesis to the Hunting Hypothesis, which speculates that the emergence of tools was not driven by hunting but by digging and gathering plants – making gathering mode efficient and economical Posit that how much women spend on gathering food depends on how much men bring back from hunting to compensate for a poor provider Does not explain: Strong Male Coalition Sexual Division of Labor Human’s ability to live in an environment with poor plantation Social exchange between men and women Humanity's digestive anatomy seems designed to process meat rather than plants primarily Edison Tan Evolutionary Psychology Singapore Management University How Food Drives Human Evolution Sex Differences in Spatial Ability as Sex-Differentiated Adaptation to Specific Adaptive Problems Faced During Food Acquisition If men and women specialize in different means of acquiring food, we should expect sex differences in ability, wherein each sex is likely to outperform the other on specific skills required for gathering/hunting. Men Women Superior navigational ability Superior recognition and recall of spatial configuration and location of objects Abstract and Euclidian direction orientation Landmark-based direction orientation Aid navigation through unfamiliar terrain during hunting Aid location of plants and fruits during foraging Superior mental rotation Superior object perception and perceptual Facilitate tool and projectile use during memory hunting Facilitate identification of gatherable food (e.g., ripe fruits) Edison Tan Evolutionary Psychology Singapore Management University Evolved Food Preferences Preferences for spices aid in solving the adaptive problems of food contamination Antimicrobial Hypothesis (Billing & Sherman, 1998; Sherman & Flaxman, 2001) Spices are produced as chemicals by plants to deter organisms and pathogens from attacking them. Commonly used spiced in human diets, it often effectively kills foodborne bacteria Garlic, onion, allspice, oregano Sherman & Billing (2009) Climates where food spoils more quickly than to favor a spicier cuisine. Cuisine as an adaptive cultural practice Edison Tan Evolutionary Psychology Singapore Management University Evolved Food Aversion Food aversion aids in solving the adaptive problems of avoiding toxins and contaminated food. Neophobia – aversion to unfamiliar food Humans generally avoid bitterness, which usually indicates toxins (Krebs, 2009) It is possible that ancient human preference–aversion functions for acidic foods evolved to allow ancestral humans to appreciate certain ripe or rotting fruits that contained acids that inhibit harmful microbes Fermentation by lactic acid bacteria better food digestibility, hence increasing food calories In challenging nutritional environments, fruits rotted by yeasts or lactic acid bacteria likely represented a valuable food source that could increase the chances of survival. (Amato et al. 2021) Edison Tan Evolutionary Psychology Singapore Management University Alcohol Consumption Fruits are the mainstay of primate diet, including humans Ethanol plumes cue ripeness In palm fruit (Astrocaryum standleyanum), ripe fruit averages about 0.9% ethanol and up to 4.5% at overripe (Dudley, 2004) Humans have an adaptive preference for ripe fruit – and alcoholism may be a byproduct of this adaptation Edison Tan Evolutionary Psychology Singapore Management University  02 Disease Avoidance Edison Tan Evolutionary Psychology Singapore Management University The Behavioral Immune System A hypothesized set of adaptations that facilitate behavioral avoidance of infectious diseases. Pathogens cannot be detected directly but indirectly via their effect on food and infected organisms, which serve as inputs. Smell (e.g., odor) Look (e.g., pus, mold, slime, sore) Symptoms (e.g., sneeze, cough, lesions) Disgust as an affective output that motivates avoidance and withdrawal of offending stimuli. Edison Tan Evolutionary Psychology Singapore Management University The Behavioral Immune System Some predictions that can be made from the BIS hypothesis: 1. Disgust should be the most strongly evoked by disease-carrying substances Feces and other bodily waste 2. Given that all humans face the adaptive problem of avoiding d