Psych Chapter 4 09/26/2013
Chapter 4: Nature, Nurture, and Human Diversity
People differ in many aspects of psychological functioning. For example, some people possess a “Type A”
personality and are aggressive, ambitious, and controlling, whereas others possess a “Type B” personality
and are passive and easygoing.
Yet, we are also similar in some aspects of our psychological functioning. For example, whether we live in
the Arctic or tropics, we divide the color spectrum into similar colors.
Behavioral Geneticsthe study of effects of environmental and genetic factors, and their interplay, on
differences in psychological traits.
Genesour codes for life. Every cell in your body contains chromosomes23 from mom and 23 from dad.
Each chromosome is made up of two strands of DNA connected in a double helix. Genes are small
segments of DNA molecules. (page 130)
Twin and Adoption Studiesidentical twins develop from a single fertilized egg and are genetically identical,
whereas fraternal twins develop from separate fertilized eggs and share half their genes, just like siblings.
Are adopted children more alike their biological parents, who contributed their genes, or their adoptive
parents, who contribute a home environment?
Surprisingly, in many traits, adoptive children do not closely resemble their adoptive parents and are more
similar to their biological parents.
Heritabilityheritability of a trait is a mathematical estimate of the extent to which variation among individuals
can be attributed to their differing genes; it can range from 0 to 1.
Group Differencesa trait can be found to be substantially heritable, but this does not imply that group
differences, such as those between men and women, are heritable.
Molecular Geneticsthe goal of molecular genetics is to identify specific genes that influence behavior.
APOE4 genehas been linked to Alzheimer’s disease.
Natural Selectionorganisms’ varied offspring compete for survival. Certain behavioral characteristics
increase odds of survival in a particular environment. Offspring that survive reproduce and pass on their
Evolutionary psychologists believe our tendencies as humans have been shaped by evolution.
Parents and Peers
Whether early environment is impoverished or enriched has a major impact on brain development:
Rosenzweig and Krech found that rats raised in an enriched environment developed a larger, and thicker,
cortex than rats raise