Evo Psyc Lecture 3

1. EvoPsyc Lecture 3 Big Question: What is evolutionary psychology? EvoPsyc is the application of Darwinian principles to the understanding of human nature. To understand how Darwinian principles are applied to humans one must first understand a number of concepts and premises upon which evo psych is based.

2. Evolutionary Psychology: Basic assumptions 1. History Matters: Any organism (including humans) are what they are today because of the selection pressures faced in the past

3. Evolutionary Psychology: Basic assumptions 2. The environment of evolutionary adaptedness (EEA). • Context where adaptive traits emerged and to which adaptive traits are best suited. The Pleistocene epic (2mya to about 10,000 ya) Hunter-gatherer lifestyle (kin groups; strict male/female division of labor; egalitarianism, etc.) Combo of selection pressures relevant to an adaptive trait (e.g. language: bipedalism & descended larynx; tools and motor control; increased social complexity and TOM)

4. Evolutionary Psychology: Basic Assumptions 3. Proximate and ultimate explanations Ultimately all creatures are strive to survive and reproduce (i.e. maximize fitness). To achieve this they must engage in immediate or more proximate behaviors that are correlated with higher rates of reproduction Key point: Evolution cannot “design” a creature to have copious offspring. Instead, all it can do is motivate a creature to engage in behaviors that in the past were associated with higher rates of reproduction. Ex: having babies vs. having sex or teenage styles

5. Age? Age? Age=22 Age=16 Beer Coke Drink? Drink? Evolutionary Psychology: Basic assumptions 4. Mind as a “Swiss Army Knife” composed of domain specific mental modules for solving adaptive problems. Ex: “cheater detection module” Encapsulation – inputs – algorithms – outputs Jealousy; TOM; mate detection, etc. :

6. Evolutionary Psychology: Basic assumptions 5. Interactionist approach No nature vs. nurture; nature emerges from interaction with nurture. Rejects both genetic determinism and “blank slate.” Genetics provide “experience expectant” framework within which environment molds development within general constraints. Ex: Language: infant “expects” linguistic stimulation which guides language development down predicable “canalized” pathway.

7. Evolutionary Psychology: Basic Assumptions 6. Unconscious emotional guidance down adaptive pathways • Gut attractions and revulsions, no need to know consciously why, just need to respond appropriately.

8. Evolutionary Psychology: Basic Assumptions 7. Stone age minds in a modern world: “mismatch theory” Our minds were adapted to the hunter-gatherer Pleistocene, not the modern urban world Ex: food cravings; social isolation (depression)

9. Evolutionary Psychology: Cross-disciplinary approach • Testing evolutionary hypothesis often requires seeking converging evidence from different disciplines. • Experimental psychology: Ex: Silverman’s studies on sex differences in spatial abilities – male advantage in mental rotation/wayfinding; female advantage in local landmark memory • Evolutionary hypothesis based on “reverse engineering”: present trait is posited to reflect selection pressures of the past, in this case the sexual division of labor in our ancestral past (males hunting, females gathering) • Cross-cultural: Is the advantage a general one or tied to specific cultural conditions? Evolved traits are thought to be general, species wide traits. • Developmental: Evidence that difference are early emerging? • Neuroscience: Evidence that the are tied to specific brain structures , neurotransmitters, hormonal differences with strong genetic inheritance. • Anthropology: Evidence for division of labor in traditional societies? • Primatology: Division of labor among nonhuman primates? • Archeology: Fossil, artifacts, or other remains supportive of falsifying of division of labor among hominin ancestors?

10. Testing evolutionary hypothesis • Evo hypo: a hypothesis derived from evolutionary theory • Ex: General evolutionary theory – parental investment: any effort or energy expended by parent on current offspring that precludes investment on other, future offspring. In mammals, primates, and especially humans, PI falls more heavily on females than males. • Based on this Galperin* et al., (2012) reason that: • “…the fitnessbenefits of having a variety of sex partners were undoubtedly greater, on average, for men than for women. Each time a man had sex with a fertile sex partner, he could potentially produce a new offspring. In contrast, women in natural fertility conditions could only produce a new offspring after completing a prior pregnancy and weaning their child. Consequently, adding more sex partners could not result in a commensurate increase in offspring production for women as it could for men” • * Galperin et al (2012) Sexual regret: Evidence for evolved sex differences. Archives of Sexual Behavior, DOI 10.1007/s10508-012-0019-3

11. Testing evolutionary hypothesis • Based on PI theory, over the course of our evolutionary history multiple sex partners benefited males far more than females in terms of reproductive success. Thus, emotional regret over sexual behavior should show evidence of evolved sex differences: • Galperin et al hypo 1: “Compared to men, women will have more numerous and stronger sexual action regrets, particularly those involving ‘‘casual’’ sex. • Hypo 2: Compared to women, men will have more numerous and stronger sexual inaction regrets, particularly those involving missed opportunities for casual sex or not leaving a sexually inactive relationship. • Method: use internet surveys; sexual/romantic scenarios, and free responses (“list your top five regrets in life etc.”), question males/females about sexual/romantic regrets.

12. Results In the free-response portion of Study 1, participants were asked about their top five life regrets, top five regrets from the past few years, top five action and inaction regrets, and top five romantic/sexual action and inaction regrets. Participants listed a total of 3,478 regrets, 348 of which were sex-related. Fig. 1 Sex differences in regret intensity in sexual action and inaction scenarios (Study 1). Note. Participants rated the intensity of regret for the actor in the vignette (actor) and their own anticipated regret if they were the actor in the scenario (self). The error bars represent 95 % confidence intervals

13. Methods/Results

14. Results

15. Conclusions: “The three studies revealed that regrets concerning sexual actions and inactions were common for both men and women, but we found striking sex differences in the types of sexual experiences that led to regrets. Consistent with the first hypothesis, women reported more numerous and more intensely felt sexual action regrets than men did, particularly regrets involving ‘‘casual’’ sex. Consistent with the second hypothesis, men reported more numerous and stronger sexual inaction regrets than women did, particularly regrets involving failure to engage in casual sex or the pursuit of a relationship that delayed sexual activity or precluded better sexual opportunities. It is noteworthy that we did not find marked sex differences in other regrets, including romantic nonsexual regrets (Study 1) and various other regrets (Study 2). Likewise, the extant literature on regret has not found sex differences in regretting actions and inactions in general…”

16. Limitations of Evo Psych • EP is ambitious and expects one day to explain everything, but: • Present weaknesses: • 1. Unexplained phenomenon: • Homosexuality: kin selection model presently not well supported. Genetic model more promising but too soon to tell. • KS model: “helpers in the nest” • Genetic model: hyper male or female qualities inherited by “other” sex.

17. Limitations of EP • 2. Incomplete understanding of past selection pressures • EP is historical; some things more certain than others (humans lived in h-g bands; highly dependent offspring, parasites a problem, etc.), but these are quite general. Specifics will always be vague and conjectural (how did they use handaxes? When did pair-bonding happen? Grandmothers?)

18. Limitations of EP • Within species or within groups variability Presently EP is much further along in explaining differences between species (humans vs. chimpanzees) and between groups (males vs. females), than within groups or species variability (why do females differ among themselves?)