Nature vs. Nurture
Nature vs. nurture refers to the question of whether an individual's characteristics are determined by innate, biological factors (e.g., genetics) present at birth or by her or his experiences. Some characteristics are largely or entirely innate, such as gender or eye color, both of which are determined by which genes an individual acquires from his or her parents. Other characteristics, however, such as political or religious affiliation are determined by experiences interacting with others in the environment and have no biological basis.
The nature vs. nurture debate generally focuses on a third category of characteristics: those that are determined by interactions between nature (biology) and nurture (experience). For example, intelligence is to some extent inherited, in that more intelligent parents tend to have more intelligent children. But the development of the children's intelligence is also determined by environmental factors, such as education. Similarly, a professional athlete likely inherited a high level of athletic ability from his or her parents, but further developed this ability through many hours of practice. The extent to which characteristics are innate is referred to as heritability. Researchers are able to calculate heritability of a characteristic by measuring how similar it is across different groups who are more or less genetically similar. This is often done by studying identical twins who were raised in different families (i.e., different environments). Because the twins share 100% of their genes, their innate level of the characteristic is identical. Consequently, the extent to which the characteristic differs between identical twins raised apart reveals the effect of the environment on the characteristic.