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Evolutionary
Psychology: |
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A Primer
The goal of research in evolutionary psychology is to discover and
understand the design of the human mind. |
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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. |
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It is not an
area of study, like vision, reasoning, or social behavior. |
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It is a way
of thinking about psychology that can be applied to any topic within it. |
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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. |
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This
way of thinking about the brain, mind, and behavior is changing how
scientists approach old topics, and opening up new ones. |
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This chapter
is a primer on the concepts and arguments that animate it. |
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Debauching
the mind: |
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Evolutionary
psychology's past and present
In the final pages of the Origin of Species, after he had presented the
theory of evolution by natural selection, Darwin made a bold prediction: |
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"In the
distant future I see open fields for far more important researches. |
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Psychology
will be based on a new foundation, that of the necessary acquirement of
each mental power and capacity by gradation." Thirty years later,
William James tried to do just that in his seminal book, Principles of
Psychology, one of the founding works of experimental psychology
(James, 1890). |
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In
Principles, James talked a lot of "instincts". |
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This
term was used to refer (roughly) to specialized neural circuits that
are common to every member of a species and are the product of that
species' evolutionary history. |
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Taken
together, such circuits constitute (in our own species) what one can
think of as "human nature". |
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It
was (and is) common to think that other animals are ruled by "instinct"
whereas humans lost their instincts and are ruled by "reason", and that
this is why we are so much more flexibly intelligent than other animals. |
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William
James took the opposite view. |
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He
argued that human behavior is more flexibly intelligent than that of
other animals because we have more instincts than they do, not fewer. |
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We
tend to be blind to the existence of these instincts, however,
precisely because they work so well -- because they process information
so effortlessly and automatically. |
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They
structure our thought so powerfully, he argued, that it can be
difficult to imagine how things could be otherwise. |
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As a result,
we take "normal" behavior for granted. |
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We do not
realize that "normal" behavior needs to be explained at all. |
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This
"instinct blindness" makes the study of psychology difficult. |
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To get past
this problem, James suggested that we try to make the "natural seem
strange": |
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"It
takes...a mind debauched by learning to carry the process of making the
natural seem strange, so far as to ask for the why of any instinctive
human act. |
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To the
metaphysician alone can such questions occur as: |
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Why do we
smile, when pleased, and not scowl? |
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Why are we
unable to talk to a crowd as we talk to a single friend? |
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Why does a
particular maiden turn our wits so upside-down? |
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The
common man can only say, Of course we smile, of course our heart
palpitates at the sight of the crowd, of course we love the maiden,
that beautiful soul clad in that perfect form, so palpably and
flagrantly made for all eternity to be loved! |
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And so,
probably, does each animal feel about the particular things it tends to
do in the presence of particular objects. |
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To the lion
it is the lioness which is made to be loved; |
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to the bear,
the she-bear. |
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To
the broody hen the notion would probably seem monstrous that there
should be a creature in the world to whom a nestful of eggs was not the
utterly fascinating and precious and never-to-be-too-much-sat-upon
object which it is to her. |
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Thus
we may be sure that, however mysterious some animals' instincts may
appear to us, our instincts will appear no less mysterious to them."
(William James, 1890)
In our view, William James was right about evolutionary psychology. |
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Making the
natural seem strange is unnatural -- it requires the twisted outlook
seen, for example, in Gary Larson cartoons. |
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Yet it is a
pivotal part of the enterprise. |
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Many
psychologists avoid the study of natural competences, thinking that
there is nothing there to be explained. |
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As
a result, social psychologists are disappointed unless they find a
phenomenon "that would surprise their grandmothers", and cognitive
psychologists spend more time studying how we solve problems we are bad
at, like learning math or playing chess, than ones we are good at. |
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But
our natural competences -- our abilities to see, to speak, to find
someone beautiful, to reciprocate a favor, to fear disease, to fall in
love, to initiate an attack, to experience moral outrage, to navigate a
landscape, and myriad others -- are possible only because there is a
vast and heterogenous array of complex computational machinery
supporting and regulating these activities. |
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This
machinery works so well that we don't even realize that it exists -- We
all suffer from instinct blindness. |
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As a result,
psychologists have neglected to study some of the most interesting
machinery in the human mind. |
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To show that
an aspect of the phenotype is an adaptation, one needs to demonstrate a
fit between form and function: |
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one needs
design evidence. |
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There
are now a number of experiments comparing performance on Wason
selection tasks in which the conditional rule either did or did not
express a social contract. |
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These
experiments have provided evidence for a series of domain-specific
effects predicted by our analysis of the adaptive problems that arise
in social exchange. |
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Social
contracts activate content-dependent rules of inference that appear to
be complexly specialized for processing information about this domain. |
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Indeed, they
include subroutines that are specialized for solving a particular
problem within that domain: |
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cheater
detection. |
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The
programs involved do not operate so as to detect potential altruists
(individuals who pay costs but do not take benefits), nor are they
activated in social contract situations in which errors would
correspond to innocent mistakes rather than intentional cheating. |
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Nor are they
designed to solve problems drawn from domains other than social
exchange; |
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for
example, they will not allow one to detect bluffs and double crosses in
situations of threat, nor will they allow one to detect when a safety
rule has been violated. |
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The
pattern of results elicited by social exchange content is so
distinctive that we believe reasoning in this domain is governed by
computational units that are domain specific and functionally distinct: |
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what we have
called social contract algorithms (Cosmides, 1985, 1989; |
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Cosmides
& Tooby, 1992). |
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There is, in
other words, design evidence. |
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The
programs that cause reasoning in this domain have many coordinated
features that are complexly specialized in precisely the ways one would
expect if they had been designed by a computer engineer to make
inferences about social exchange reliably and efficiently: |
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configurations
that are unlikely to have arisen by chance alone. |
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Some
of these design features are listed in Table 1, as well as a number of
by-product hypotheses that have been empirically eliminated. |
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(For review,
see Cosmides & Tooby, 1992; |
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also
Cosmides, 1985, 1989; |
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Cosmides
& Tooby, 1989; |
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Fiddick,
Cosmides, & Tooby, 1995; |
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Gigerenzer
& Hug, 1992; |
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Maljkovic,
1987; |
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Platt
& Griggs, 1993.) It may seem strange to study reasoning about a
topic as emotionally charged as cheating -- after all, many people
(starting with Plato) talk about emotions as if they were goo that
clogs the gearwheels of reasoning EPs can address such topics, however,
because most of them see no split between "emotion" and "cognition". |
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There
are probably many ways of conceptualizing emotions from an
adaptationist point of view, many of which would lead to interesting
competing hypotheses. |
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One that we
find useful is as follows: |
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an
emotion is a mode of operation of the entire cognitive system, caused
by programs that structure interactions among different mechanisms so
that they function particularly harmoniously when confronting
cross-generationally recurrent situations -- especially ones in which
adaptive errors are so costly that you have to respond appropriately
the first time you encounter them (see Tooby & Cosmides, 1990a). |
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Their
focus on adaptive problems that arose in our evolutionary past has led
EPs to apply the concepts and methods of the cognitive sciences to many
nontraditional topics: |
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the
cognitive processes that govern cooperation, sexual attraction,
jealousy, parental love, the food aversions and timing of pregnancy
sickness, the aesthetic preferences that govern our appreciation of the
natural environment, coalitional aggression, incest avoidance, disgust,
foraging, and so on (for review, see Barkow, Cosmides, & Tooby,
1992). |
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By
illuminating the programs that give rise to our natural competences,
this research cuts straight to the heart of human nature. |