Transcript Evo Psyc Lecture 3

Evo Psyc Lecture 3
Big Question: What is evolutionary psychology?
Evo Psyc 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.
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
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)
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
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.
Age?
Age?
Age=22
Age=16
:
Beer
Coke
Drink?
Drink?
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.
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.
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)
Evolutionary Psychology: Cross-disciplinary approach
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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?
Testing evolutionary hypothesis
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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 fitness benefits 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
Testing evolutionary hypothesis
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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.
Results
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
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.
Methods/Results
Results
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…”
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.
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?)
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?)