Nature Vs. Nurture
PSC 113
Jeff Schank
Outline
• Emergence and Causation
• Nature vs. Nurture: What is Nature? What is
Nurture?
– The Program/Blueprint Metaphors
– Developmental Programs
– Causal Loops and Levels of Organization
• Reductionism and Holism
Emergence and Causation
• With our modern notion of Aristotelian
causation, we can characterize biological and
other complex systems in terms of the first
three causes
Flocks of Starlings
Schools of Fish
Herds of Mammals
Nest Thermoregulation in Social
Insects
FIG. 12 An Apis dorsata [giant honey bees] colony. Workers are spread out on the
comb to reduce brood nest temperature (Photo by Ben Oldroyd). Julia C. Jones and
Benjamin P. Oldroyd (2007 )Nest Thermoregulation in Social Insects.ADVANCES IN
INSECT PHYSIOLOGY VOL.33, pp. 153-191)
FIG. 10 Apis florea [wild bees] colony (Photo courtesy of Nadine Chapman).
Workers that form the protective curtain covering the comb move closer together
at low ambient temperatures, and further apart at high ambient temperatures.
Julia C. Jones and Benjamin P. Oldroyd (2007)Nest Thermoregulation in Social
Insects. ADVANCES IN INSECT PHYSIOLOGY VOL. 33, pp. 153-191)
Nest Thermoregulation in Social
Insects
Nature vs. Nurture: What is Nature?
What is Nurture?
• A program is “a series of coded instructions which when fed
into a computer will automatically direct its operation in
carrying out a specific task”. (A blueprint is plan, scheme, or
pattern for something, i.e., Aristotle's formal cause.)
Developmental Programs
• Although development does not proceed in a way that is analogous to a
computer program, perhaps if we just consider development as a kind of
“black box” with the environment providing input, we can use the notion
of a program metaphorically
•
•
Closed programs require no specific input (experience) for development to
proceed on its genetically predetermined course.
Open programs, however, require input or experience in order for a
developmental program to work.
Closed
X
Open
Critical and Sensitive Periods
• Critical period: A span or period of time during which
specific environmental input is essential if an ability is to
develop
– Critical period hypothesis for Language: There is a critical
period for language acquisition that ends with the onset of
puberty; if an individual has not received sufficient linguistic
input by then, the individual is incapable of acquiring language
• Sensitive period: A span or period of time during which
specific environmental input is important for the
development of an ability, but at least some aspects of that
ability can be learned or acquired without receiving the
input during a sensitive period
• Question: is the acquisition of language subject to a critical
period, sensitive period, or no period at all?
Distinction between Critical and
Sensitive Periods
Critical
X
Sensitive
X
X
?
Testing the Critical Period Hypothesis
for Language
• The problem with the critical period hypothesis is
that it is not testable in the laboratory
• We cannot take children into a laboratory and
raise them with no language input until they
reach puberty
• However, there have been cases of people who,
out of extreme neglect, mistreatment, or
unfortunate circumstances, did not receive
language input before puberty
Genie
• Genie existed for 10 years in
a closet tied to a potty chair
• She had no discernible
linguistic abilities at the time
she was found (age 13)
• Video
Problems
• What other developmental effects did
isolation have on Genie?
• Was the research adequately conducted?
• Did Genie really fail to acquire syntax and
grammar?
• Has there been scientific misconduct in the
case of Genie?
Peter E. Jones
• Concludes that these claims are false or misleading
–
–
–
–
–
Genie was unable to acquire the morphology of English.
Genie was unable to acquire the syntax of English.
Genie’s utterances remained uninflected and telegraphic
Genie’s utterances remained hierarchically flat.
Genie’s linguistic development leveled off during period 1 (1971-1975).
Causal Loops and Levels of
Organization
Ring dove Reproductive
Cycle
Reductionism
• Definition: Reductionism is the view that explanations of things
and/or their behavior should be in terms of things that are simpler,
more obvious, and/or more easily understood than the things
themselves
• Historical Background
– In the 17th and 18th centuries, the British philosophers Locke,
Berkeley, and Hume, were concerned with how we come to have
knowledge of the world and how the mind works
– For all of the them, the mind was essentially a bundle of ideas
– Twentieth Century Logical Empiricists: Rudolf Carnap was probably
the leading figure of this movement
– The problem concerned the interpretation of the things scientific
theories are about—How can we know a thing in itself?
– Answer: Define all scientific terms in terms of statements about
observations using set theory and logic—It turned out not to be
possible
Reductionism
• Historical Background continued…
– Behaviorism originated from the complete rejection
of anthropomorphism, anecdotalism, and
introspectionism at the turn of the century as typified
in the behaviorism of J. B. Watson and B. F. Skinner
– Behaviorists start from the proposition the behavior
of organisms can be studied as natural events and
they sought to discover laws of association among
behavior and stimuli resulting from learning
– Problems: Oversimplified the environment, ignored
what happens inside the organism, and ignored social
learning and context
Reductionism: Nature vs. Nurture
• Especially in the 20th century to today, many researchers have
assumed that the behavior of organisms can be explained by some
proportion of nature (genes) or nurture (environment, experience).
• What proportion of IQ is determined by genes (nature) and what
proportion by experience (nurture)?
• This question makes it sound as though we can always answer such
• questions by giving some percentage such as 60% of IQ is
determined by the genes and 40% is determined by experience
• Research in animal behavior has revealed the relationship between
genes,
• Experience and development are far from this simple (e.g., consider
the ring dove reproductive cycle)
• Thus, the nature vs. nurture distinction is reductionistic in that it
ignores causal loops up and down levels of organization