The nature vs. nurture debate in personality development

Nature Nurture

Nature vs. Nurture

For many generations, psychologists, philosophers, and natural scientist have all debated the extent to which our genes and our environments influence our lives. This debate has been referred to as nature vs. nurture. If nature is the dominant force for factors such as intelligence and personality traits, then this has many implications for the way that we live our lives and our ability to change. However, if nurture is the dominant force then this has a different set of implications and things such as intelligence and personality traits might be largely a result of the environments in which we develop. Some physical characteristics in humans are obviously the result of genetics. Examples of this include items such as hair color, eye color, and general appearance. However, in the realm of psychology and personality, the influence of genetics is less than clear.

Nature vs. Nurture Debate

DARWIN AND FREUD WALK INTO A BAR

Two alcoholic mice -- a mother and her son -- sit on two bar stools, lapping gin from two thimbles. The mother mouse looks up and says, "Hey, geniuses tell me how my son got into this sorry state." "Bad inheritance," says Darwin. "Bad mothering," says Freud (Hurley, 2013).

The nature and nurture role in development, or nature vs. nurture, debate has existed for over a century. On one pole of the debate, nature is the dominant force that drives physical and mental development though the passing on of genes from one generation to the next. However, on the other end of the spectrum, many psychologists believe that much of our personality is learned from others as social creatures. We learn from our family, friends, and leaders various tidbits that form into our experience. These two poles have led to a polarized discussion of human development from either a biologically mechanistic or social perspective. Some describe the rhetoric used in the nature/nurture debate without a focus on a 'single, well-de-ned and meaningful question' of "confounding statistics and mechanisms" (Stoltz, 2012).

The physiology and cultural-based research on traits such as intelligence, for example, frequently use experiment designs such as twin studies. One study attempted to further knowledge concerning the nature and nurture of intelligence by scrutinizing how heritability coefficients vary across specific cognitive abilities both theoretically and empirically (Kan, Wicherts, Dolan, & Maas, 2013). In this study, data from 23 twin studies (combined N = 7,852) showed that (a) in adult samples, culture-loaded subtests tend to demonstrate greater heritability coefficients than do culture-reduced subtests; and (b) in samples of both adults and children, a subtest's proportion of variance shared with general intelligence is a function of its cultural load. This research suggests that the most heritable abilities are also the most culture dependent traits.

Even economists have weighed in on the nurture and nature divide by looking at siblings and their ability to participate in the economy. In one study, economists examined the relationship between different kinds of siblings and earnings and find that both nature and nurture matter: full-siblings are equally negatively related to earnings regardless of whether one grew up with them or not (Lampi & Norblom, 2012). The number of step-siblings, on the other hand, also turns out significant if one grew up together. Although earnings might not be the direct path to measuring personality traits, it does provide an interesting perspective on the debate.

Somewhere in the middle of the nature and nurture debate, are new theory has been proposed that merges the two poles. Epigenetics is a relatively new concept that represents one of the most interesting new developments in the nature and nurture debate. In the first half of the twentieth century, developmental biology and genetics were separate disciplines. The word epigenetics was coined by Waddington to link the two fields; epigenetics could be broadly defined as the sum of all those mechanisms necessary for the unfolding of the genetic program for development (Holliday, 2006). Research in this field has discovered that genes are not static in nature, rather there is a selection mechanism that selects different genetic sequences based on the environmental conditions; sometimes several generations back. It is argued that the human genome project will be followed by the epigenome project, which is working to unravel the significance of DNA methylation in the control of the specialized gene functions (Holliday, 2006).

DNA methylation has been associated with age-related disease. An intra-individual change in gene-specific DNA methylation over time in a community-based cohort is just beginning to receive research attention (Madrigano, et al., 2012). One study looked at the change in DNA methylation due to aging for nine genes Seven hundred and eighty four men from the Veterans Administration Normative Aging Study who were living in metropolitan Boston from 1999 -- 2009 who donated a blood sample for DNA methylation analysis at clinical examinations repeated at approximately 3-5-year intervals. The statistical analyses of these genes suggest that DNA methylation may reflect differential biological aging.