Presentation on theme: "Human Behavior: Applying an Evolutionary Perspective."— Presentation transcript:
Human Behavior: Applying an Evolutionary Perspective
The goal of research in evolutionary psychology is to discover and understand the design of the human mind. Evolutionary psychology is an approach to psychology, in which knowledge and principles from evolutionary biology are put to use in research on the structure of the human mind… In this view, the mind is a set of information-processing machines that were designed by natural selection to solve adaptive problems faced by our hunter-gatherer ancestors… An evolutionary approach allows one to recognize … natural competences … it indicates that the mind is a heterogeneous collection of these competences and, most importantly, it provides positive theories of their designs.” Evolutionary Psychology
Darwin (1860): “In the distant future … Psychology will be based on a new foundation”, i.e., evolution. William James (Principles of Psychology, 1890): ‘instincts’ = ~ specialized neural circuits common to all members of the species, a product of the species’ evolutionary history ‘instincts’ taken together = ~ human nature James ‘instincts’ are similar to Haidt’s ‘intuitions’ Darwin and James
The Standard Social Science Model (SSSM) “Both before and after Darwin, a common view among philosophers and scientists has been that the human mind resembles a blank slate, virtually free of content until written on by the hand of experience …
The Standard Social Science Model (SSSM) Over the years, the technological metaphor used to describe the structure of the human mind has been consistently updated, from blank slate to switchboard to general purpose computer, but the central tenet … has remained the same … [and] has become the reigning orthodoxy in mainstream anthropology, sociology, and most areas of psychology… According to this orthodoxy: all of the specific content of the human mind originally derives from the "outside" – from the environment and the social world – and the evolved architecture of the mind consists solely or predominantly of a small number of general purpose mechanisms that are content-independent, and which sail under names such as … 'learning,' 'intelligence,' 'imitation,‘ culture‘…
SSSM versus EP SSSM: Same general-purpose mechanisms govern all psychological tasks (except basic perception, language), e.g., how one learns language learns to recognize emotional expressions thinks about incest acquires ideas and attitudes about friends and reciprocity Mechanisms of reasoning, learning, and memory operate uniformly – they are content-independent or domain-general. EP: All normal human minds reliably develop a collection of domain-specific reasoning and regulatory circuits. “These circuits organize the way we interpret our experiences, inject certain recurrent concepts and motivations into our mental life, and provide universal frames of meaning that allow us to understand the actions and intentions of others”.
Principle 1: The brain is a physical system. It functions as a computer. Its circuits are designed to generate behavior that is appropriate to your environmental circumstances. Principle 2: Our neural circuits were designed by natural selection to solve problems that our ancestors faced during our species' evolutionary history. “The reason we have one set of circuits rather than another is that the circuits that we have were better at solving problems that our ancestors faced during our species' evolutionary history than alternative circuits were”. For example, just as natural selection has shaped dung flies to approach dung, it has shaped us to avoid it. Five Principles
Principle 2: Our neural circuits were designed by natural selection to solve problems that our ancestors faced during our species' evolutionary history. Designed to solve adaptive problems, i.e., problems that cropped up again and again during the evolutionary history of a species whose solution affected the reproduction of individual organisms “Obviously, we are able to solve problems that no hunter- gatherer ever had to solve – we can learn math, drive cars, use computers. Our ability to solve other kinds of problems is a side-effect or by-product of circuits that were designed to solve adaptive problems. For example, the fact that we can surf and skateboard are mere by-products of adaptations designed for balancing while walking on two legs”. Five Principles
Principle 3: Consciousness is just the tip of the iceberg; most of what goes on in your mind is hidden from you. As a result, your conscious experience can mislead you into thinking that our circuitry is simpler that it really is. Most problems that you experience as easy to solve are very difficult to solve – they require very complicated neural circuitry. Principle 4: Different neural circuits are specialized for solving different adaptive problems. “A basic engineering principle is that the same machine is rarely capable of solving two different problems equally well. We have both screw drivers and saws because each solves a particular problem better than the other”. Five Principles
Principle 4: Different neural circuits are specialized for solving different adaptive problems.
Five Principles “Until recently, it was thought that perception and, perhaps, language were the only activities caused by cognitive processes that are specialized. Other cognitive functions – learning, reasoning, decision-making – were thought to be accomplished by circuits that are very general purpose”. "General intelligence" – a hypothetical faculty composed of simple reasoning circuits that are few in number, content- independent, and general purpose “Crib sheets” or privileged hypotheses Babies < 1 yo assume that the self-propelled movement of animate objects is caused by invisible internal states – goals and intentions – whose presence must be inferred, since internal states cannot be seen. Toddlers have a well-developed "mind-reading" system (impaired in autism)
Principle 5: Our modern skulls house a stone age mind. “Natural selection, the process that designed our brain, takes a long time to design a circuit of any complexity. The time it takes to build circuits that are suited to a given environment is so slow it is hard to even imagine – it's like a stone being sculpted by wind-blown sand. Even relatively simple changes can take tens of thousands of years. “ Actually evidence is accumulating in many areas that selection can occur quickly, at least sometimes. The Environment of Evolutionary Adaptedness (EEA): Hunter-gatherer (foraging) societies of the African savanna. Five Principles
Hunter-gatherer (foraging) society: Subsistence gained from hunting animals, fishing, and gathering edible plants in the wild. Small, simple band level of social organization. Hunting and gathering is thought to have been the only subsistence strategy employed by human societies for more than two million years, from the Paleolithic until the end of the Mesolithic period. As recently as 15,000 years ago, everyone in the world lived by foraging. The transition into the subsequent Neolithic period is chiefly defined by the development of agricultural practices (~ 10,000 years ago). Environment of Evolutionary Adaptedness (EEA)
“The environment that humans – and, therefore, human minds – evolved in was very different from our modern environment. Our ancestors spent well over 99% of our species' evolutionary history living in hunter-gatherer societies. That means that our forbearers lived in small, nomadic bands of a few dozen individuals who got all of their food each day by gathering plants or by hunting animals. Each of our ancestors was, in effect, on a camping trip that lasted an entire lifetime, and this way of life endured for most of the last 10 million years.” Cosmides & Toobey: Evolutionary Psychology: A Primer Environment of Evolutionary Adaptedness (EEA)
“Our species lived as hunter-gatherers 1000 times longer than as anything else. The world that seems so familiar to you and me, a world with roads, schools, grocery stores, factories, farms, and nation-states, has lasted for only an eye blink of time when compared to our entire evolutionary history. … Natural selection is a slow process, and there just haven't been enough generations for it to design circuits that are well- adapted to our post-industrial life … In other words, our modern skulls house a stone age mind. The key to understanding how the modern mind works is to realize that its circuits were not designed to solve the day-to- day problems of a modern American – they were designed to solve the day-to-day problems of our hunter-gatherer ancestors.” Cosmides & Toobey: Evolutionary Psychology: A Primer Environment of Evolutionary Adaptedness (EEA)
“Evolutionary psychology is relentlessly past-oriented. Cognitive mechanisms that exist because they solved problems efficiently in the past will not necessarily generate adaptive behavior in the present. Indeed, EPs reject the notion that one has "explained" a behavior pattern by showing that it promotes fitness under modern conditions … Cosmides & Toobey: Evolutionary Psychology: A Primer Environment of Evolutionary Adaptedness (EEA)
Key point: mismatches between modern environments and the EEA will inevitably compromise the effectiveness of human adaptations that evolved in the EEA = adaptive lag. Environment of Evolutionary Adaptedness (EEA) “In practice, the evolutionary part of EP often reduces to rather vague claims about selective conditions in the EEA that may have favoured the evolution of a hypothesized psychological mechanism … To the extent that our knowledge of the EEA remains sketchy, rigorous quantitative testing of precise selectionist hypotheses becomes virtually impossible, and the result can easily degenerate into adaptive storytelling”. Smith et al 2000
“Knowledge of adaptive function is necessary for carving nature at the joints.” (Note: Neuroethology operates on this same principle!) Design evidence. Adaptations are problem-solving machines, and can be identified using the same standards of evidence that one would use to recognize a human-made machine: design evidence. Nature and nurture: An adaptationist perspective Evolutionary psychology is not just another swing of the nature/nurture pendulum. A defining characteristic of the field is the explicit rejection of the usual nature/nurture dichotomies – instinct vs. reasoning, innate vs. learned, biological vs. cultural. Design Features
Reasoning instincts: An example Wason Selection Task: Subject is asked to look for violations of a conditional rule of the form If P then Q. Rule: "If a card has an even number on one face, then its opposite face is red”. Which card(s) must be turned over to see if this rule has been violated. ‘8’ and brown cards – only ~25% of subjects get this right!
Reasoning instincts: An example Wason Selection Task: Subject is asked to look for violations of a conditional rule of the form If P then Q. Rule: "If a Cambridge resident goes into Boston, then that person takes the subway.” Each card represents one person. One side of a card tells where a person went, and the other side of the card tells how that person got there. Indicate only those card(s) you definitely need to turn over to see if any of these people violate this rule. Boston & cab cards – only ~25% of subjects get this right!
Reasoning instincts: An example Wason Selection Task: Subject is asked to look for violations of a conditional rule of the form If P then Q. People who ordinarily cannot detect violations of if-then rules can do so easily and accurately when that violation represents cheating in a situation of social exchange/contract Rule: "If you are drinking alcohol then you must be 21" 1721 Drinking Beer Drinking Coke Indicate only those card(s) you definitely need to turn over to see if any of these people violate this rule. 17 & drinking beer – most people get this right!
Social contract form again… Which of the following cards do you need to turn over to either confirm or falsify the hypothesis that If you charge a purchase on your credit card, you must pay the bill. Person charges purchase Person doesn’t charge Person pays bill Person doesn’t pay bill Most people get the right answer! Reasoning instincts: An example
Summing Up: Tenets of Evolutionary Psychology 1.Psychological mechanisms – not behaviors – have been shaped by natural selection to enhance reproductive success.
Genes Ψ Mechanisms behavior fitness Natural selection s
Tenets of Evolutionary Psychology 1.Psychological mechanisms – not behaviors – have been shaped by natural selection to enhance reproductive success. 2. Mechanisms have many effects (‘side effects’) besides the favorable (selected) effects. And these side effects can be maladaptive. 3. The historical ecological context (EEA) in which human evolution occurred is different from the contemporary context, especially those of “modern” societies. 4. Therefore, a given trait may be: (a) adaptive; (b) a maladaptive side effect of an otherwise adaptive mechanism; or (c) a maladaptive interaction of an out-of-date adaptive mechanism with a new environmental context.
EP HBE Daly & Wilson 1999 vs. Smith, Borgerhoff Mulder & Hill 2000 Evolutionary Psychology vs. Human Behavioral Ecology
Two Contrasting but (I think) Complementary Evolutionary Perspectives on Human Behavior: Evolutionary Psychology (EP) – derived from a synthesis of biology and psychology Human Behavioral Ecology (HEB) – derived from a synthesis of biology and anthropology Note: In my view both of these viewpoints, though non- complementary on some issues, can be combined into a general ‘evolutionary psychology’ (no caps!) Evolutionary Psychology vs. Human Behavioral Ecology
Evolutionary Psychology Human Behavioral Ecology Focus onUniversalsVariation/Diversity Assumed Selective Environment Environment of Evolutionary Adaptedness Present Environment How measure Adaptation? Design Criteria (re EEA) Reproductive Success or ‘Fitness’ Usual study population Modern societiesTraditional societies
Contrast Evolutionary Psychology (EP) and Human Behavioral Ecology (HBE). To considerable extent EP and HBE are complementary, differing in relative emphasis placed on psychological mechanism versus manifest behavior But they diverge in other, controversial ways: 1.Use of formal models and deductive theory ( HBE) 2.Emphasis on domain-specific cognitive algorithms ( EP) 3.Relationship between psychological mechanisms and observed behavior ( EP) 4.Assertions regarding adaptive lag and adaptation to past environments (EP HBE ) 5.Views on the relevance of fitness measures to analyses of contemporary behavior. (EP HBE ) Smith, Borgerhoff-Mulder & Hill (2000) Evolutionary analyses of human behaviour: a commentary on Daly & Wilson. Anim Behav