1 Psychology and human development1.11 Underlying concepts in human development
1.11.4 Genetic influences on development
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Written by Resident Doctor Committee · Published
Genes and heritability
Phenotype is an observable characteristic arising from the genotype acting within an environment.
Most common psychiatric disorders, intelligence and temperament are polygenic: many small-effect variants act alongside environment.
Heritability is the proportion of variation in a trait associated with genetic differences within one population, not a fraction of one person's trait.
Gene-environment interaction
An interaction means an exposure's effect varies with genotype. Both merely being present is not enough.
Model | Susceptible people in a poor environment | Susceptible people in a good environment |
|---|---|---|
Diathesis-stress | Do worse than others | No advantage |
Differential susceptibility | Do worse than others | Do better than others |
Differential susceptibility holds that some people are more plastic and respond to the environment in both directions, so their outcomes cross over those of others (a crossover).
Highly reactive infants show this: they fare worse than others with insensitive care but better with sensitive care.
Caspi and colleagues (Dunedin cohort) reported a monoamine oxidase A by maltreatment interaction, but replication concerns limit conclusions.
Gene-environment correlation
Correlation means genetic differences are associated with exposure to different environments.
Type | How it arises |
|---|---|
Passive | Parents provide both genes and environment |
Evocative | A child's traits shape others' responses |
Active | People seek environments that fit them |
Probabilistic pathways
Multifinality is one vulnerability leading to different outcomes.
Equifinality is different pathways leading to one outcome.