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An introduction to the nature/nurture debate, part 2

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Let us continue with Lehrman's critique of the innate/acquired distinction in psychology. Lehrman rejected the attempt to distinguish between innate vs. acquired characteristics through depriving an animal of the sort of interaction with other animals of its species which would be required should the characteristic be acquired rather than innate on the ground that we cannot say that "a certain trait is "innate simpliciter," since there might be predispositions towards the acquisition of that trait are not nurtured with the interactions required for their expression. Instead, these traits might be a combination of innate and acquired. There might be proto-dispostions that require interaction for their full expression. The distinction is artificial and simplistic. In response to this, Lorenz reformulated his understanding of the innate/acquired distinction:

A trait is innate insofar as its development is guided by ‘inherited information’ rather than ‘environmental information.’ Lorenz defined ‘information’ in terms of adaptation. An adaptive trait ‘fits’ its environment and hence can be said to contain information about that environment just as a key can be said to contain information about the lock it will open. The question is where that information comes from – how does the organism ‘know’ about its environment? If a woman has calluses on her palms rather than on the backs of her hands, this represents information about where her skin gets rubbed most. If she were born with calluses on her palms, as Ostriches are born with calluses that match pressure points on their legs, this would imply advance ‘knowledge’ of where her skin is going to be rubbed most. Such anticipatory information, Lorenz argued, must be in the genome. It is in the genome as a result of natural selection, which can be seen as a form of trial-and-error learning (Griffiths, 2009).

Griffiths uses the example of the water flea. It detects chemical traces of predators and grows armor if it detects their presence. "Thus, a flea's possession or lack of defensive armour reflects environmental information"(Griffiths, 2009). The ability to grow defensive armor is an example of inherited information. Flees that possess this trait were able to adapt to harsh environments, and those that did not possess this inherited trait, died off. Thus, natural selection determined which inherited traits were perpetuated. This inherited trait in the flea by which it grows defensive armor reflects environmental information. As a Darwinist, Lorenz saw the perpetuation of these traits as the effects of natural selection. There is a crucial blind spot in this understanding of biology, however:

Writing in the 1960s Lorenz naturally assumed that genes were the only source of inherited information. It is now known that much information about the environment is transmitted from parent to offspring via epigenetic signals, such as methylation patterns on the DNA or RNAs from the mother included in the egg. For example, if a female water flea detects predators and grows defensive armor, its offspring will develop armor even if they do not detect any evidence of predators themselves. Lorenz's theory would imply that traits produced in this way are also innate, since they reflect inherited information, albeit epigenetically rather than genetically inherited (Griffiths, 2009).

It was after World War II that a reaction against a perceived over-emphasis on environmental factors developed. Chomsky became a leading proponent of emphasizing the impotance of taking account of "species-specific biological endowments if [psychology] was to understand how different species interact with their environment and the distinctive things each species is ab le to learn from thesei nteractions"(Griffiths, 2009). Chomsky's particular emphasis was his anti-behaviorist argument that humans are biologically hardwired to develop language. Chomsky argued that if the behaviorists were right, children could never develop the capacity for language because they are not given enough information to construct a grammatical framework for language. The inference is that human children must be biologically hardwired to use language, since apart from such an innate template of acquisition, they would be unable to develop it (Griffiths, 2009).

Griffiths makes the point in his article on the distinction between innate and acquired characteristics that a trait produced by a gene that codes for it is oftentimes mistakenly referred to as 'innate.'

The development of traits always depends upon a highly complex interaction between genes and environment. On the one hand, it is true that trait expression depends upon regulated expression of specific genes. However, environmental interactions determine whether or not certain genes in specific cells are expressed.

Furthermore, genes do not code for unalterable programs. Rather, they code for amino acid sequences of a protein. Specifically, genes code for 23 amino acids and determine their order. There are also genetic codons for "start" and "stop." These determine where DNA transcription begins and ends.

There are numerous relatively intractable consequences that result from specific codings, but this does not mean that the genes specifically "code" for these consequences, intractable though they may oftentimes be. Instead, to speak of genes as coding for a specific trait is more of a colloquial way of saying that genes "cause" these traits. "Coding," however, should not be understood in a literal sense. Phenotypes are not literally written into genes.

Of course, the phenotypic expressions of many genes are quite intractable. The biological sex of a person can be inferred from their Y chromosome, for example. But this is not universally the case for all species. Some fish, for example, switch sexes based on environmental cues.

The question of whether or not genes store information "in a special sense which distinguishes them from other causes is not the piece of common-sense it is often taken to be," but is quite controversial in the philosophy of biology, however (Griffiths, 2009). Griffiths furnishes us with distinct ways of talking about the relationship between genes and environment.

1) Such and such a "norm of reaction" is genetically determined if the phenotype is the same regardless of the environment of the organism. This is the case with certain genetic diseases.

2) Genes interact in an 'additive' manner with norms of reaction. In this case, environment may influence the degree of expression of genes in individuals, but the difference between individuals is not determined by environment. Griffiths notes that IQ scores are a good example of this.

Genes determine differences among individual IQ scores, but environmental factors like education may enrich the expression of genes responsible for IQ. This would mean that such an enriching environment, he notes, may raise the IQ of all involved, yet there would still be genetically determined differences of IQ between individuals.

Richard Lewontin sees gene expression as non-additive. This means that "Genotype and environment jointly determine the outcome in the straightforward sense that the effect of each factor on the outcome is a function of the particular value taken by the other factor"(Griffiths, 2009).

Griffiths, Paul, "The Distinction Between Innate and Acquired Characteristics", The Stanford Encyclopedia of Philosophy (Fall 2009 Edition), Edward N. Zalta (ed.), URL = <plato.stanford.edu/archives/fall2009/entries/innate-acquired/>.

Griffiths, Paul, "The Distinction Between Innate and Acquired Characteristics", The Stanford Encyclopedia of Philosophy (Fall 2009 Edition), Edward N. Zalta (ed.), URL = <plato.stanford.edu/archives/fall2009/entries/innate-acquired/>.

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