Consider the following: Proponents of the 'nature' side of the developmental debate argue that human personality is largely determined by genetic heritage. They point to twin studies showing high correlations in traits between identical twins reared apart. Conversely, 'nurture' advocates emphasize the plasticity of the human brain and the profound impact of early childhood environment. The synthesis of these views suggests that genes provide a range of possibilities, while environment determines where within that range an individual falls.