Nature Vs. Nurture

PSC 113Jeff 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. 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)

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)

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 Open

X

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 Sensitive

X 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

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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