IB Psychology SL key terms

A chemical messenger released by a neuron into the synapse, where it binds to receptors on the next cell and either excites or inhibits it. Behaviour and mood can change when these signalling chemicals are too high or too low.

The tiny gap between two neurons across which chemical signals pass. Neurotransmitters are released from one side and received on the other, so the synapse is where most communication between brain cells happens.

A substance that increases or mimics the effect of a neurotransmitter by binding to its receptors. For example, an agonist drug might make a normally weak signal stronger and so change mood or behaviour.

A substance that blocks or reduces the effect of a neurotransmitter by occupying its receptors without activating them. Antagonist drugs are used to test whether a specific neurotransmitter causes a behaviour.

The process by which a releasing neuron takes its neurotransmitter back out of the synapse. Blocking reuptake leaves more of the chemical in the gap and prolongs its effect on the next neuron.

The idea that particular mental processes and behaviours are controlled mainly by specific areas of the brain rather than by the brain as a whole. Evidence comes from brain scans and from patients with damage to particular regions.

The outer folded layer of the brain, divided into four lobes, that handles complex thinking, perception, movement and language. Damage to different parts of it produces different patterns of lost ability.

The four main sections of each hemisphere: frontal (planning, movement, speech production), parietal (body senses), temporal (hearing, memory) and occipital (vision). Each lobe is linked to particular functions.

A structure deep in the temporal lobe important for forming new long-term memories and for spatial navigation. Damage here typically leaves old memories intact but makes new ones very hard to store.

An almond-shaped structure in the temporal lobe that helps detect threat and attach emotion, especially fear, to experiences. It is central to explanations of fear learning and emotional memory.

The brain's ability to reorganise its connections and structure in response to experience, learning or injury. It shows that brain anatomy is not fixed and can change across the lifespan.

The growth of new dendrites and connections between neurons as a result of learning or enriched experience. It is one measurable mechanism through which neuroplasticity occurs.

Magnetic resonance imaging: a scan that uses magnetic fields to build detailed pictures of brain structure. It shows anatomy such as volume or lesions but does not directly show activity.

Functional magnetic resonance imaging: a scan that tracks blood oxygen changes to show which brain areas are active during a task. It links behaviour to activity but shows correlation, not proof of cause.

A research design comparing identical twins, who share all their genes, with fraternal twins, who share about half, to estimate how much a trait depends on genes versus environment.

A statistical estimate of how much of the variation in a trait within a population is due to genetic differences. It describes a group, not an individual, and depends on the environment studied.

An inherited tendency to develop a particular trait or disorder, which may appear only if certain environmental conditions are also present. Genes raise or lower risk rather than fixing an outcome.

An account of behaviour that argues it was selected because it helped ancestors survive and reproduce. Such explanations are tested by comparing species or by looking for predicted patterns across groups.

A simplified representation of a mental process, such as memory or attention, used to generate testable predictions. Models are judged by how well their predictions match experimental evidence.

A mental framework built from past experience that organises knowledge and guides what we notice, remember and expect. Schemas can distort memory by filling gaps with what we assume is typical.

An early model describing memory as three separate stores (sensory, short-term and long-term) linked by attention and rehearsal. It explains why unrehearsed information is quickly lost.

A model describing short-term memory as an active workspace with a central controller plus separate verbal and visual components. It explains how people hold and manipulate information at the same time.

A method in which a person performs two tasks at once; if performance drops, the tasks are assumed to compete for the same limited mental resource. It is used to test working memory components.

The process of converting information into a form the memory system can store, such as a sound, image or meaning. Deeper, meaning-based encoding usually produces better later recall.

The view that remembering involves rebuilding an event from stored fragments plus schemas and expectations, rather than replaying a recording. This explains confident but inaccurate eyewitness accounts.

Post-event details, including the wording of questions, that can alter what a witness later reports about an event. Its effect is evidence that memory is reconstructed rather than replayed.

A fast mental shortcut that produces a good-enough judgement without full analysis. Heuristics save effort but create predictable biases in decisions and estimates.

Judging how likely something is by how easily examples come to mind. Vivid or recent events feel more probable than they are, which skews risk judgements.

The tendency for an initial number or piece of information to pull later estimates toward it, even when the anchor is irrelevant. It shows how context shapes numerical judgement.

The tendency to seek, notice and remember information that supports existing beliefs while ignoring contradictory evidence. It helps explain why people resist changing their minds.

The amount of mental effort a task demands from limited working-memory capacity. When load is too high, performance and learning decline, which informs how instruction should be designed.

In Piaget's theory, fitting new experience into an existing schema without changing it. It contrasts with accommodation, where the schema itself must be revised to fit the new information.

In Piaget's theory, altering an existing schema or creating a new one because new information does not fit. It is the counterpart of assimilation in cognitive development.

Tajfel's account of how belonging to groups shapes self-concept and behaviour. People favour their own group and derogate outsiders partly to achieve a positive social identity.

The mental act of sorting people, including oneself, into groups. It simplifies the social world but makes differences between groups and similarities within them seem larger than they are.

The group a person belongs to and identifies with. Members tend to be treated more favourably, and this bias can occur even when groups are formed on trivial grounds.

A group a person does not belong to, often perceived as more homogeneous than one's own group. Negative stereotypes about out-groups can fuel prejudice and discrimination.

A generalised belief about the characteristics of a group and its members. Stereotypes can be activated automatically and influence judgement even when a person rejects them.

A negative attitude toward a group or its members, based on group membership rather than individual qualities. It involves evaluation and feeling, and can exist without discriminatory action.

Unfair behaviour or treatment directed at people because of their group membership. Unlike prejudice, it is an observable act and may be institutional as well as individual.

Changing one's behaviour or stated beliefs to match the norms of a group. It is stronger when the group is unanimous, larger and important to the person, and it may be public only.

Conformity driven by the desire to be liked and accepted by a group. A person may publicly agree while privately disagreeing, which is why the change can disappear afterwards.

Conformity driven by the belief that others have better information, especially in ambiguous situations. Here the person genuinely changes their view, not just their public response.

Following a direct order from an authority figure. Rates of obedience depend on factors such as the authority's legitimacy, proximity of the authority and the presence of disobedient peers.

Whether a person offers help to someone in need when others are present. The likelihood often falls as the number of bystanders rises, partly through diffusion of responsibility.

The reduced sense of personal obligation to act that occurs in groups, because each person assumes someone else will help. It is a key explanation for the bystander effect.

Voluntary action intended to benefit another person, such as helping, sharing or comforting. Explanations include empathy, social norms and the evolutionary benefits of cooperation.

The shared norms, values, beliefs and practices transmitted within a group. Cross-cultural research compares groups to see which behaviours are universal and which are shaped by learning.

A cultural pattern that emphasises personal goals, independence and self-expression over group loyalty. It is often contrasted with collectivism when explaining cultural differences in behaviour.

A cultural pattern that stresses group goals, interdependence and duty to family or community over individual preference. It is often measured in cross-cultural studies of behaviour.

The process by which people learn the norms and values of their own culture, largely through parents, peers and institutions. It helps explain cultural similarities within groups.

The process of adapting to a new culture after migration, which can involve integration, assimilation, separation or marginalisation. The strategy chosen is linked to stress and adjustment outcomes.

Learning by observing and imitating others, especially models who are rewarded. It explains how behaviours such as aggression or helping can spread through a group without direct reinforcement.