Chapter Eight
The Evolutionary Approach:
Change Over Time
Evolutionary Psychology
Evolutionary Psychology (EP) describes how our
early environment produced our current mental
abilities.
• This environment was the Pleistocene era,
approximately two million years ago, referred to as
the Environment of Evolutionary Adaptation (EEA).
• Evidence to support evolutionary hypotheses
comes from archeological records, huntergatherer societies, between- and within-species
comparisons, and experimentation.
•
Natural selection
EP relies on Darwin’s (1859) theory of natural
selection. It requires three elements:
• Variation in traits within a species.
• The passing of genetic material from one
generation to the next, called inheritance.
• Selection, which is a change in the environment
that favors one trait over another.
Evolved psychological
mechanisms
•
•
•
•
EP views the mind as a collection of special
purpose devices or a “Swiss army knife.”
Each device evolved under selection
pressures to solve a specific problem.
These mechanisms can be considered as
modules.
This is in contrast to the traditional notion of
mind as a general purpose processor.
Properties of an evolved
psychological mechanism
1.
2.
3.
4.
5.
6.
Solves a specific adaptive problem.
Takes in only a narrow band of information.
Informs the user of the type of problem.
Produces a response through a set of decision
rules.
The response can be a physiological reaction,
information to another mechanism, or a behavior.
The response is intended to provide a solution to
the problem.
Evolution and categorization
We form concepts in a graded, continuous fashion,
not “all or none.”
• Natural categories are also continuous. The mind
mimics this organization.
• This allows us to generalize our knowledge from
one category to another.
• Concepts are organized around representative
members of a class, the typicality effect.
•
Which looks more like a bird?
Evolution and memory
•
•
•
We should have a better memory for
information we are exposed to more often.
This is because it is more relevant to our
survival.
Recall for words is proportional to their
frequency of occurrence (Anderson and
Schooler, 1991).
The Wason selection task - hard
version

You have been hired as a clerk. Your job is to make sure
that a set of documents is marked correctly, according to
the following rule: "If the document has an E rating, then it
must be marked code 4." You have been told that there are
some errors in the coding of the documents, and that you
need to find the errors. Each document has a letter rating
on one side and a numerical code on the other. Here are
four documents. Which document(s) do you need to turn
over to check for errors?
The Wason selection task - easy
version

You have been hired as a bouncer in a bar and you must
enforce the following rule: "If a person is drinking vodka,
then he must be over twenty years old." The cards above
have information about four people in the bar. One side of
each card lists a person's age and the other side shows
what he or she is drinking. Which card(s) do you need to
turn over to be sure no one is breaking the law?
Evolution and logical reasoning
•
•
•
The bouncer problem is easy because it
involves cheater-detection.
In the EEA it was important to detect who
might be cheating because in small groups
with limited resources it might mean less for
you (Cosmides and Tooby, 1992).
The logic module thus works only in this
context, implying logic is not domain
general.
Evolution and judgment under
uncertainty
•
•
•
•
Uncertain judgments occur when we make a
decision without complete information.
Most everyday decisions in life are like this.
In such cases, we often rely on heuristics.
But heuristics can lead us to commit
fallacies, a misunderstanding of statistical
rules.
Fallacies
1.
2.
3.
Base-rate fallacy. Ignoring base rates.
Conjunction fallacy. Ignoring the
conjunction rule.
Gambler’s fallacy. Ignoring independent
outcomes.
Example of Base-Rate Fallicy



100 people: 70 lawyers; 30 engineers
Jack is a 45 year old man. He is married
and has four children. He is generally
conservative, careful, and ambitious. He
shows no interest in political and social
issues and spends most of his free time on
his many hobbies, including home carpentry,
sailing, and mathematical puzzles.
Is Jack a lawyer or an engineer?
Example of Conjunction Fallicy


Linda is 31 years old, single, outspoken, and
very bright. She majored in philosophy. In
college, she was involved in several social
issues, including the environment, the peace
campaign, and the anti-nuclear campaign.
Which is more likely:
 Linda is a bank teller.
 Linda is a bank teller active in the feminist
movement.
Examples of Gambler’s Fallacy

You’ve observed two slot machines.





One hasn’t paid off in a long time.
The other just paid off.
Both are now available.
Which is more likely to pay off soon?
A fair coin has come up “heads” eight times
in a row.
 How likely is it to come up “tails” next time?
Evolution and language
•
•
•
Language may have evolved to promote
social bonding (Dunbar, 1996).
It allows for complex coordinated social
behavior. Examples: improvements in
hunting, foraging, and childcare.
It may also play a role in sexual selection.
Evolution and sex differences
•
•
•
•
Attributed to a sexual division of labor in
which men hunted and women gathered.
Hunting may have fostered increased spatial
ability in men.
Gathering may have promoted increased
verbal abilities in women.
But above distinction is too broad. Women
are better at object location memory.
Evolutionary Computing
•
•
Thinking may utilize evolutionary
principles.
Steps in problem solving:
1.
2.
3.
4.
Generate candidate solutions.
Evaluate their fitness.
Select solutions with high fitness values.
Generate new solution offspring by genetic
combination.
5. Repeat steps 2-4.
Artificial Life
The study of manmade systems that behave in
ways characteristic of natural living systems
(Langton, 1989).
• Computer “creatures” are created through
evolutionary rules. They navigate, seek out prey,
and avoid predators in a virtual environment.
• Complex adaptive behaviors emerge including
parasitism, symbiosis, and flocking.
•
Neural Darwinism
•
•
•
•
Application of evolution to neural learning
(Edelman, 1989).
Initial growth of neural structures during
development.
Interaction with environment causes
differential modification of synaptic
strengths.
Reentrant signaling between neural groups.
Evaluating the evolutionary
approach

Novel biological function need not arise to
service survival or reproduction. Other
mechanisms:
1. Exaptation or neutral drift. Random mutation.
2. Molecular drive. Copies of genes mutate.
3. Idea of a spandrel (Gould, 2000). Byproducts
of adaptations.
Spandrels in architecture