The nature-nurture dichotomy
Two major strands of explanations exist to explain sex differences (i.e., differences between men and women). The first set of explanations is usually referred to as "nature" and contains that biological factors underlie alleged sex differences. Conversely, explanations that are usually referred to as "nurture" contain that sex differences in (social) behavior arise from the distribution of men and women in different social roles within society.
BIOLOGICAL AND SOCIAL ESSENTIALISM
Although these approaches stand in sharp contrast to each other with respect to their ideas about the origins of behavioral differences between men and women (biological versus social, respectively). These different positions do, however, share the same ontological viewpoint, namely they are essentialistic. Essentialistic accounts on gender construe gender as consisting of a constellation of internal attributes that are associated with one's sex and that shape one's personality, cognitive processes, moral judgment, and so forth (Bohan, 1993). Gender, in this understanding, is a shared trait, common to all members of a particular sex-category. Clearly, the "traditional" social science explanation that ascribes differences between the sexes to socialization is no less essentialististic than the "nature" explanation (according to which the differences start in the genes, trigger the hormones, shape the brain, and direct behavior). In both models, men and women are seen as markedly different from each other; that is, truly and deeply different.
BIOLOGICAL AND SOCIAL DETERMINISM
Furthermore, both these models are essentially deterministic. In the socialization model gender is conceived as "achieved" (rather than ascribed), but around the age of 5 it is much like sex (i.e., fixed, unvarying, and static). In the biological model sex differences in behavior are said to be determined by the genes (and, in more popular accounts, they are conceived to be "innate", "essential", or "hard-wired") [For more information, see Note 1]. Whatever one's position on determinism may be, clearly there is no reason to expect that genetic influences are any more irreversible than environmental ones (Dawkins, 1981; Mullen, 2006).
BEYOND ESSENTIALISM AND DETERMINISM: NATURE AND NURTURE
While these essentialistic and deterministic accounts perpetuate the so-called "nature-nurture" debate, it is quite widely acknowledged that it concerns a false dichotomy (e.g., Corr, 2006; de Waal, 1999; Fausto-Sterling, 2005; Freese, 2008; Halpern, 2000; Jordan-Young, 2010; Keller, 2010; Li, 2003; McClearn, 2004, 2005; Turkheimer, 2000). Thinking in terms of nature versus nurture, rather than nature and nurture, is unhelpful in understanding the interplay of both sets of factors in all complex psychological traits. There simply can be no nature without nurture, and vice versa. It is simply not possible to determine how much of a particular trait is due to either biological or social factors (Freese, 2008; Money, 1987) because their products are the result of a two-way causal interplay (i.e., the same variables are cause and effect). In a related vein, "developmental systems theorists" argue that there simply exists no distinction between the sources of influence (such as nature and nurture) on a system (Oyama, 1985 , 2005).
So nature and nurture are inextricably entwined. Like the famous metaphor put forward by Richard Lewontin (1974, p. 401) goes: 'If two men lay bricks to build a wall, we may quite fairly measure their contributions by counting the number laid by each; but if one mixes the mortar and the other lays the bricks, it would be absurd to measure their relative contributions by measuring the volume of bricks and mortar.' Hence, there are not just some constant amounts of nature and nurture that contribute to the development of a particular trait. The way nature works is dependent upon nurture, and vice versa. For example, it is a general feature of development that the same genotype can produce different phenotypes under different developmental conditions (Núñez-Farfán and Schlichting, 2001; see also the figure below). So as noted by Boyd et al. (2011, p. 10924), 'it does not make sense to ask, does culture overcome biology? The right question to ask is, how do genetic and cultural inheritance interact to produce the observed patterns of human psychology and behavior?' It simply does not make any sense to ask questions about genetic influences apart from specific environments, or vice versa—which is the tallest plant?
- Underpinning the influence of genes is not the same as saying that our behavior is determined—Dawkins (1981) called this the "myth of genetic determinism"; our genes do not determine our behavior (see also Damasio, 1994; Dawkins, 1976; Stanovich, 2004). All human behavioral traits are of course heritable (see, e.g., Bouchard, 2004; Plomin et al., 2001; Rutter et al., 1997; Turkheimer, 2000), but 'the concept of heritability applies not to individuals but, rather, to differences among many individuals. Stated in statistical terms, heritability applies to the variance of a set of observations rather than to a single specific observation' (Krueger, 2008, p. 1478; see also Rutter, 2006). Also note that genes in fact encode for protein, not function. That is, genes do not specify behavior directly but rather encode molecular products that build and govern the functioning of the brain through which behavior is expressed (Robinson et al., 2008). Equally important, the expressions of genes are also probabilistic.
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