psychology - biological approach

Neurotransmitter

A chemical that carries signals across the synapse between neurons, rapidly affecting mood, thinking, and behaviour. Ex: Low serotonin is linked to depression; dopamine drives reward and motivation.

Hormone

A chemical released by glands into the bloodstream that travels to target organs and affects behaviour more slowly and broadly than a neurotransmitter. Ex: Cortisol (stress) impairs memory; oxytocin promotes bonding and trust.

Localisation of function

The principle that specific psychological functions are controlled by specific, identifiable brain areas. Ex: The hippocampus is essential for forming new long-term and spatial memories.

Neuroplasticity

The brain's ability to physically change its structure and neural connections in response to experience, learning, or damage. Ex: London taxi drivers grow a larger posterior hippocampus from years of navigating (Maguire, 2000).

Genetic predisposition

An inherited increase in likelihood (not certainty) of a trait or disorder, which often appears only when triggered by the environment. Ex: The short 5-HTT allele raises depression risk, but usually only after life stress (Caspi, 2003).

Concordance rate

The probability that if one twin has a trait, the other does too; used to estimate genetic influence by comparing identical (MZ) and fraternal (DZ) twins. Ex: Higher concordance for depression in MZ than DZ twins indicates a genetic component.

Evolutionary explanation

The idea that a behaviour exists because it boosted ancestors' survival and reproduction and was therefore naturally selected. Ex: Disgust toward rotten food likely evolved to prevent disease.

Animal model

Using animals to study biological processes assumed to be similar in humans, often where human experimentation would be unethical. Ex: Rats in enriched cages grew thicker cortices (Rosenzweig, 1972) — but generalising to humans is a limitation.