Psychology 100 Spring 2001 Evolution and Behavior 01-23-01What can evolutionary psychology explain?Selection, Adaptation, Fitness“Individuals are selected for trait X”  those with X have a survival & reproductive advantage.Sexual Dimorphisms in BehaviorCAVEATSPsychology 100 Spring 2001 Evolution and Behavior 01-23-011. Behavior and Evolution2. Conditioning: Biological Influences3. Ethology & Instinctual BehaviorsContinuum of unlearned-learned Instinctual behaviors4. Evolutionary Psychology: Basic IdeasSelection and adpatationUltimate and proximate causes5. Examples from Non-human AnimalsSexual selectionIntra-species competitionMating systemsAltruistic behavior6. Human Behavior and Evolution NeotanyAttractivenessParental investmentMating systemsSexual dimorphisms7. Thinking About Evolution and BehaviorBehavioral dispositions, preferences, brain/mental capacities evolved by natural selection.Rationalized the same way as evolved structures: in terms of their contribution to survival, reproduction, fitness. Instinct: a pattern of behavior, usually complex in structure, that is found universally among members of a species, occurs without the need for prior learning, is relatively invariant in form, and is reliably elicited by a specific stimulusinstinctual behavior = sign stimulus plus fixed-action pattern.What can evolutionary psychology explain?What characteristics should we expect natural selection to explain? The eye, the kangaroo's pouch, the human chin, the cheetah's sprint,, the chameleon's camouflage? What about the peacock's tail, the bee's suicidal sting, the crimson of blood, the flash of colour on a bird's wing? Should we expect it to explain human altruism, our love of music, feelings of aggression, sexual jealousy? And divorce rates, wars, politics, oppression? What, in short, is the scope of natural selection?" (from Helena Cronin, Theant and the peacock).Selection, Adaptation, Fitness- “Individuals are selected for trait X”  those with X have a survival & reproductive advantage. - “X is an adaptation”  X is a characteristic that came about because of the survival & reproductive advantage it conferred. - “Fitness”: reproductive success of individual or of genetically similar individuals (“inclusive fitness”).Sexual Dimorphisms in Behavior "For thousands of years during which our brain characteristics evolved, humans lived in relatively small groups of hunter-gatherers. The division of labor between the sexes in such as society probably was quite marked. Men were responsible for hunting large game,which often required long-distance travel. They were also responsible for defending the group against predators and enemies and for the shaping and use of weapons. Women most probably gathered food near the camp, tended the home, prepared food and clothing and cared for children. Such specialization would put different selection pressures on menand women." (from Doreen Kimura, Scientific American Sept. 1992.)CAVEATS1. Think of instincts as predispositions. 1. Evolutionary psychology deals largely with ultimate causes (evolved).2. Ultimate causes tend to be “cognitively impenetrable.” We are aware/controlled by the immediate reinforcing experience, but not of the ultimate reason why it’s reinforcing. 3. Adaptations developed in the remote past, in response to conditions (selection pressures) that may no longer exist. Example: aggressive competition. 4. "Just so" stories: too easy to rationalize a behavior as an adaptation Example: is morning sickness an adaptation? 5.There may be large individual differences within a species with respect to the strength / of evolved or instinctual behaviors. 6. Naturalistic fallacy: a biological fact doesn't constitute a justification or establish a moral basis.7. Deterministic fallacy: must take account of evolved cortical control and resultingbehavioral