| Term | Definition |
| behavior genetics | the study of the relative power and limits of genetic and environmental influences on behavior. (Myers Psychology 8e p. 096) |
| chromosomes | threadlike structures made of DNA molecules that contain the genes. (Myers Psychology 8e p. 096) |
| DNA (deoxyribonucleic acid) | a complex molecule containing the genetic information that makes up the chromosomes. (Myers Psychology 8e p. 096) |
| environment | every nongenetic influence, from prenatal nutrition to the people and things around us. (Myers Psychology 8e p. 096) |
| genes | the biochemical units of heredity that make up the chromosomes; a segment of DNA capable of synthesizing a protein. (Myers Psychology 8e p. 096) |
| genome | the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes. (Myers Psychology 8e p. 096) |
| identical twins | twins who develop from a single fertilized egg that splits in two, creating two genetically identical organisms. (Myers Psychology 8e p. 097) |
| fraternal twins | twins who develop from separate fertilized eggs. They are genetically no closer than brothers and sisters, but they share a fetal environment. (Myers Psychology 8e p. 098) |
| heritability | the proportion of variation among individuals that we can attribute to genes. The heritability of a trait may vary, depending on the range of populations and environments studied. (Myers Psychology 8e p. 102) |
| temperament | a person's characteristic emotional reactivity and intensity. (Myers Psychology 8e p. 102) |
| interaction | the effect of one factor (such as environment) depends on another factor (such as heredity). (Myers Psychology 8e p. 105) |
| molecular genetics | the subfield of biology that studies the molecular structure and function of genes. (Myers Psychology 8e p. 105) |
| evolutionary psychology | the study of the evolution of behavior and the mind, using principles of natural selection. (Myers Psychology 8e p. 107) |
| mutation | a random error in gene replication that leads to a change. (Myers Psychology 8e p. 108) |
| natural selection | the principle that, among the range of inherited trait variations, those that lead to increased reproduction and survival will most likely be passed on to succeeding generations. (Myers Psychology 8e p. 108) |
| gender | in psychology, the biologically and socially influenced characteristics by which people define male and female. (Myers Psychology 8e p. 110) |
| culture | the enduring behaviors, ideas, attitudes, and traditions shared by a large group of people and transmitted from one generation to the next. (Myers Psychology 8e p. 119) |
| norm | an understood rule for accepted and expected behavior. Norms prescribe "proper" behavior. (Myers Psychology 8e p. 120) |
| personal space | the buffer zone we like to maintain around our bodies. (Myers Psychology 8e p. 120) |
| collectivism | giving priority to the goals of one's group (often one's extended family or work group) and defining one's identity accordingly. (Myers Psychology 8e p. 121) |
| individualism | giving priority to one's own goals over group goals, and defining one's identity in terms of personal attributes rather than group identifications. (Myers Psychology 8e p. 121) |
| aggression | any physical or verbal behavior intended to hurt or destroy. (Myers Psychology 8e p. 127) |
| X chromosome | the sex chromosome found in both men and women. Females have two X chromosomes; males have one. An X chromosome from each parent produces a female child. (Myers Psychology 8e p. 129) |
| Y chromosome | the sex chromosome found only in males. When paired with an X chromosome from the mother, it produces a male child. (Myers Psychology 8e p. 129) |
| testosterone | the most important of the male sex hormones. Both males and females have it, but the additional testosterone in males stimulates the growth of the male sex organs in the fetus and the development of the male sex characteristics during puberty. (Myers Psychology 8e p. 130) |
| gender role | a set of expected behaviors for males and for females. (Myers Psychology 8e p. 131) |
| role | a set of expectations (norms) about a social position, defining how those in the position ought to behave. (Myers Psychology 8e p. 131) |
| gender identity | one's sense of being male or female. (Myers Psychology 8e p. 132) |
| gender schema theory | the theory that children learn from their cultures a concept of what it means to be male and female and that they adjust their behavior accordingly. (Myers Psychology 8e p. 132) |
| gender-typing | the acquisition of a traditional masculine or feminine role. (Myers Psychology 8e p. 132) |
| social learning theory | the theory that we learn social behavior by observing and imitating and by being rewarded or punished. (Myers Psychology 8e p. 132) |