The nature versus nurture debates concern the relative importance of an individual's innate qualities ("nature") versus personal experiences ("nurture") in determining or causing individual differences in physical and behavioral traits. The view that humans acquire all or almost all their behavioral traits from "nurture" is known as tabula rasa ("blank slate"). With the development of human genetics, many important human traits have been proven to be partially or mostly genetic.
Nurture - Although "nurture" has historically been referred to as the care given to children by their parents, in particular their mother, it is now widely regarded as any environmental (not genetic) factor in the contemporary nature versus nurture debate. This includes the influences on development arising from prenatal, parental, extended family and peer experiences, extending to influences such as media, marketing and socio-economic status. Indeed, a substantial source of environmental input to human nature may arise from stochastic variations in prenatal development. Additionally, although childhood experience (especially early childhood experience) is often regarded as more influential in who one becomes than post-childhood experience, a liberal interpretation of "nurture" might count all life experience as "nurture".
Nature - Genetic and various inborn biological factors affecting overall development.
Personality is a frequently cited example of a heritable trait that has been studied in twins and adoptions. Identical twins reared apart are far more similar in personality than randomly selected pairs of people. Likewise, identical twins are more similar than fraternal twins. Also, biological siblings are more similar in personality than adoptive siblings. Each observation suggests that personality is heritable to a certain extent. However, these same study designs allow for the examination of environment as well as genes. Typically, two kinds of environmental effects are distinguished: shared family effects (those shared by siblings, making them more similar) and nonshared effects (which uniquely affect individuals, making siblings different). Although they are genetically identical and share the same family environment, identical twins reared together do not have identical personalities. These differences are caused entirely (by definition) by nonshared environmental effects. Adoption studies also directly measure the strength of shared family effects. Adopted siblings share only family environment. Unexpectedly, some adoption studies indicate that by adulthood the personalities of adopted siblings are no more similar than random pairs of strangers. This would mean that shared family effects on personality are zero by adulthood. As is the case with personality, non-shared environmental effects are often found to out-weigh shared environmental effects. That is, environmental effects that are typically thought to be life-shaping (such as family life) may have less of an impact than non-shared effects, which are harder to identify. One possible source of non-shared effects is the environment of pre-natal development. Random variations in the genetic program of development may be a substantial source of non-shared environment. These results suggest that "nurture" may not be the predominant factor in "environment".