Chapter 4: Biological Underpinnings of Personality

Shared environment

The effects of growing up with the same parents; also known as family environment.

Nonshared environment

Experiences not shared by siblings, such as certain friends, personal injuries, or participating in different activities.

Twin study

A study examining twins raised apart and together, usually to explore whether characteristics are caused by genetics or environment.

Monozygotic twins

Identical twins sharing the same genetic profile.

Percentage of variance

Variation explained by genetics or environment; refers to the variation among a group of people and not within one individual.

Contrast effect

When one sibling consciously tries to be different from the other.

Gene-environment interaction

When genetics and environment work together to shape personality.

Genotype

An organism's genetic predisposition.

Phenotype

Observable characteristics of an organism resulting from the interaction of the genotype and the environment.

Epigenetics

The idea that some environments can influence how much genetics will matter.

Gene expression

How much a gene influences traits or outcomes.

Discrepancy detection

Noticing something that is different in the environment.

Neurotransmitters

Chemicals that carry signals over the gap between synapses in the brain.

Morningness-eveningness

Whether an individual is a morning person (a lark) or an evening person (an owl).

Evolutionary psychology

The field of research exploring how evolution shaped human psychology.

Sociosexuality

Individual differences in attitudes toward sex without commitment.