Capacity: quantifies the amount of information that can be held in memory, e.g. Short-term memory has a limited capacity of 7 +/- 2 items.
Capacity models / resource allocation models (of divided attention): those models proposing that we have a pool of processing resources that we can allocate according to the demands of the task and environmental factors.
Cardiovascular system: consists of two parts, the heart and the blood vessels. It is a system for distributing oxygen and nutrients to the organs in the body. Heart rate, blood pressure and local blood volume are three measures of cardiovascular activity commonly used in research by psychophysiologists.
Case study: a detailed description of a single individual, typically used to provide information on the person's history and to aid in interpreting the person's behaviour.
Castration anxiety: the anxiety that boys suffer during the oedipus complex that their rivalrous father may castrate them.
CAT (computed axial tomography) scans: a non-invasive, multiple x-ray procedure for creating images of the brain.
Cataplexy: sudden paralysis of some or all muscles brought on by laughter, anger, or strong emotions; a hallmark of narcolepsy.
Catatonic schizophrenia: a form of schizophrenia, characterised by a patient who displays motor abnormalities, for instance, changing between a state of complete immobility to energised excitement.
Categorisation: a short cut used when processing information. A category is a set of items perceived to have at least one feature in common. In interpersonal perception, categories such as young-old and male-female are used.
Catharsis: a term used in psychodynamic psychology to mean the release of emotion. An example is crying to release sadness.
Cause and effect: establishing that the independent variable has had a clear effect upon the dependent variable.
Central core: this exists in all vertebrates. The central core regulates the basic life processes such as breathing, pulse, arousal, movement, balance, sleep and also the early stages of processing sensory information. The central core includes the thalamus, pons, cerebellum, reticular formation and medulla.
Central nervous system (CNS): the brain, together with the nerve pathways of the spinal cord.
Central tendency: a single value which is representative of a set of numbers by indicating the most typical value. Three measures of central tendency are the mean, median and mode.
Centration: a characteristic of the preoperational stage of cognitive development. Children centre on one aspect of a problem and overlook other perceptual factors.
Cerebellum: ('little brain' in Latin) two small hemispheres located beneath the cortical hemispheres, at the back of the head; the cerebellum plays an important role in directing movements and balance.
Cerebral cortex: an area of the brain resembling a folded sheet of grey tissue that covers the rest of the brain. The cerebral cortex directs the brains higher cognitive and emotional functions. It is divided into two almost symmetrical halves called the cerebral hemispheres. Each hemisphere contains four lobes. Areas within these lobes regulate all forms of conscious experience such as emotion, perception, thought and planning as well as unconscious cognitive and emotional processes. The cerebral cortex includes the frontal lobe, occipital lobe, parietal lobe and temporal lobe.
Cerebral dominance: the tendency for one hemisphere to be superior for particular functions.
Cerebral hemispheres: two half spheres, made up of the cortex and underlying structures, which comprise the major portion of the brain.
Chaos theory: a branch of mathematics dealing with non-linear functions which has been applied to the modelling of situations such as the weather and stock markets; non-linear systems are not predictable, because very small changes in initial conditions can result in radical differences at a later point.
Charisma: a personal attractiveness or interestingness that enables you to influence others.
Checklist: a simple list of all the behaviours being recorded. On every occurrence of a behaviour on the list, a single tally is recorded. At the end of the observation period, the observer has a record of the number of occurrences of each of the behaviours being investigated.
Child psychology: (developmental psychology) the branch of psychology that studies the social and mental development of children.
Child rearing styles: varying style of parenting classified according to the extent parents are demanding of their child and/or responsive to the child’s needs, including authoritative and authoritarian parenting.
Chi-squared (x2) test of association: a nonparametric inferential statistical test. Used when you have nominal data, the research is independent groups and you are looking for an association between the independent variable and the dependent variable.
Chromosomes: thread-like genetic structures composed of double strands of dna and proteins, containing the genes; in humans, there are twenty-three pairs of chromosomes.
Chromosome abnormalities: typically occur when a chromosome is missing or there is an extra chromosome, e.g. Down’s syndrome.
Chronic schizophrenia: used to diagnose schizophrenics who show no significant improvement after therapy or treatment over a long period of time.
Chunk: the basic measure of short-term memory capacity, representing a meaningful unit, such as random letters, numbers or words.
Chunking: combining individual letters or numbers into larger meaningful units
Circadian rhythm: a roughly 24-hour cycle which is determined by an internal body clock, e.g. The sleep-wake cycle.
Classical conditioning: a basic form of learning, whereby a neutral stimulus is repeatedly paired with an unconditioned stimulus (UCS) that naturally produces an unconditioned response (UCR). After several trials, the neutral stimulus is now a conditioned stimulus (CS) and thus produces a conditioned response (CR).
Claustrophobia: an intense fear of confined spaces such as lifts.
Client-centred therapy: an humanistic approach to therapy developed by Carl Rogers, in which the person seeking treatment (termed a client), not the therapist, is seen as directing the process of therapy; later called person-centred therapy.
Clinical interview: a flexible research method that uses open-ended questions to obtain a lot of information from a participant.
Clinical psychologist: a psychologist who has possesses a doctorate in psychology and has been trained to assess and treat psychological problems.
Clinical psychology: focuses on the assessment and treatment of abnormal or maladaptive behaviour.
Closed questions: questions that have set answers for participants to choose from.
Closure: a term used in gestalt therapy to mean the emotional experience of moving on from a past trauma.
CNS: see central nervous system
Cocktail party effect: refers to (a) a person's ability to concentrate on just one conversation although others are going on all around and (b) the way a person engaged in (attending to) one conversation will nevertheless hear their own name if it is mentioned in a nearby conversation.
Codes of practice: ethical guidelines produced by psychological organisations such as the BPS and the APA, containing advice on research and practice.
Confidence: is generally described as a state of being certain, either that a hypothesis or prediction is correct, or that a chosen course of action is the best or most effective given the circumstances at the time.
Cognition: the processes of reasoning, thoughts, attitudes and memories.
Cognitive: a process of information storage and retrieval, which can be utilised flexibly in behaviour. In humans, cognitive relates to mental operations sometimes termed thought processes, eg. reasoning, calculation and planning.
Cognitive ability: the psychological concept that refers to such processes as perceiving, knowing, recognising, conceptualising, judging, and reasoning.
Cognitive appraisal theory: devised by Lazarus, stating that our cognitive appraisal of a situation in crucial in experiencing emotions.
Cognitive behavioural programmes: programmes designed to modify behaviour by changing attitudes and thoughts.
Cognitive behavioural therapies: techniques that involve helping clients to identify their negative, irrational thoughts and to replace these with more positive, rational ways of thinking.
Cognitive development: the growth of cognitive (thinking) abilities. This may be studied by examining changes in the form and structure of children's thinking as they get older, or by looking at individual differences in the power of children's thinking as measured, e.g. By iq tests.
Cognitive dissonance: in Festinger's theory, a state of tension created when there are conflicts between an individual's behaviour and beliefs, or between two beliefs.
Cognitive interview: an interview technique designed to be used by police investigators to help elicit accurate information from eyewitnesses.
Cognitive labelling theory: Schachter and Singer's theory that it is the combination of physiological arousal and cognitive appraisal that leads to the experience of emotion.
Cognitive map: Tolman's term for the mental representation of learned relationships among stimuli.
Cognitive model of abnormality: the view that stresses the role of cognitive problems (such as illogical thought processes) in abnormal functioning.
Cognitive neo-association theory: Berkowitz's theory that thoughts, memories and behaviour may be triggered by affective states and/or priming.
Cognitive neuroscience: a hybrid discipline aimed at identifying the biological bases of cognitive processes by combining techniques for the study of cognitive processes with measures of physiological processes.
Cognitive pathology: a phenomenon whereby researchers selectively ignore simplifying assumptions and other limitations which are part of the foundations of their theories and methods.
Cognitive processes: aspects of mental 'behaviour' that focus on the acquisition, storage, retrieval and use of knowledge, for instance in memory and perception.
Cognitive psychology: research field in psychology that focuses on mental processes used to acquire, store, retrieve and use knowledge.
Cognitive restructuring: in Ellis's rational-emotive therapy, a process for modifying faulty beliefs and the negative emotions they produce, in order to develop realistic beliefs and self acceptance.
Cognitive science: the study of human intelligence and of the symbol-processing nature of cognition.
Cognitive therapy: a form of therapy which focuses on the role of faulty beliefs and thought patterns in abnormal behaviour; because it also encourages testing beliefs via behavioural strategies, it is sometimes called' cognitive behavioural therapy'. See also rational-emotive therapy.
Cohort: a group of individuals who were born during the same time interval, i.e. 'generation'.
Collective unconscious: in Jung's theory, a biologically based portion of the unconscious which reflects universal themes and ideas, not individual experience.
Collectivism: an orientation which emphasises a person's connections and obligations to a social group (family, tribe, etc.); when applied to describe a culture, typically contrasted to individualism.
Collectivist society: a society characterised by a high level of mutual interdependence between individuals.
Collectivistic cultures: cultures that value group loyalty, prefer group to individual decisions and where the needs of the group outweigh the concerns of the individual.
Colour processing/vision: refers to the ability to see chromatic colours (hues) such as yellow, green and blue. Two theories have been proposed trichromatic and opponent process - but no satisfactory complete explanation exists.
Comfortable interpersonal distance scale: a non-invasive method used to measure people's personal space.
Community environmental design: differs from urban renewal because these projects allow the current residents in the area to have an input in the redesign of the area.
Companionate love: the emotional state that combines feelings of affection and attachment characterised by mutual concern for each other - less intense than romantic love.
Compensation: in Adler's theory, a process of engaging in activities intended to produce a feeling of superiority over others, in order to overcome feelings of inferiority.
Competitive altruism: (also called 'costly signalling theory') the concept that individuals will make large public sacrifices if they believe there is a long-term personal benefit.
Complementarity: a concept developed by physicists to deal with the existence of two models which are both useful, but not directly reconcilable.
Compliance: a form of social influence, whereby an individual seeks to influence another to comply with a demand.
Compulsion: an irresistible impulse to act, regardless of the rationality of the motivation.
Computerised axial tomograms (CAT): see computed tomography.
Computerised imaging techniques: for studying brain function which use computers to convert information into a three-dimensional model of the brain which can be viewed on a television monitor.
Computed tomography (CT): imaging technique using x-rays.
Concordance: a technique for studying inheritance by examining characteristics of individuals whose genetic relationship is known.
Concrete operational period: in Piaget's stages of cognitive development, a period between ages seven and eleven during which children gain a better understanding of mental operations. Children begin thinking logically about concrete events, but have difficulty understanding abstract or hypothetical concepts.
Concurrent validity: an indicator of validity, which compares measures of the same phenomenon to determine whether they produce similar results in the same circumstances.
Conditional positive regard: acceptance and caring given to a person only for meeting certain standards of behaviour.
Conditioned emotional response: an emotional response such as fear which is established through classical conditioning.
Conditioned reinforcer: stimuli which act as reinforcers but are not based on biological survival, such as attention, praise or money.
Conditioned response: in classical conditioning, a response to a previously neutral stimulus which has become a conditioned stimulus by repeated pairing with an unconditioned stimulus.
Conditioned stimulus: a stimulus which by repeated pairings with an unconditioned stimulus comes to elicit a conditioned response.
Conditions for growth: the conditions under which healthy development of personality occurs; defined by Rogers as unconditional positive regard, openness and empathy.
Conditions of worth: restrictions imposed on self-expression in order to earn positive regard.
Conditioning: see classical and operant conditioning.
Conduct disorder: used to describe a pattern of repetitive behaviour of children where the rights of others or the current social norms are violated. Symptoms include verbal and physical aggression, cruel behaviour toward people and pets, destructive behaviour, lying, truancy, vandalism, and stealing.
Cones: photoreceptor cells located in the centre of the retina that allow us to see colour.
Confederates: individuals who pose as participants in empirical research, in order to produce responses from real participants in the study.
Confidentiality: the ethical concern that information gathered during psychological research or therapy should not be divulged to others unless otherwise agreed in advance or unless there is a legal requirement to disclose it.
Confirmation: in research, the process of determining that observations are consistent with the hypothesis being true.
Confirmation bias: a form of cognitive error based on the tendency to seek out information which supports one's beliefs, and ignores contradictory information.
Conformity: a type of social influence expressed through exposure to the views of a majority and our submission to those views.
Confound: in experimental research, a situation where two variables change simultaneously, making it impossible to determine their relative influence.
Confounding variable: uncontrolled variable that produces an unwanted effect on the dependent variable. It obscures the effect of the independent variable.
Congruence: in Rogers's theory, a feeling of integration experienced when the self and ideal self match.
Conscience: a person's moral sense of right and wrong, chiefly as it affects their own behaviour.
Conscious: in Freud's theory, that aspect of the mind which contains those thoughts and feelings of which we are immediately aware at a given moment.
Consciousness: is regarded to comprise qualities such as subjectivity, self-awareness, sentience, and the ability to perceive the relationship between oneself and one's environment. It is a subject of much research in philosophy of mind, psychology, neuroscience, and cognitive science.
Consent: an ethical necessity, whereby participants agree to procedures that will take place and are given the right to withdraw at any time in the study.
Conservation: understanding that physical characteristics of number or quantity do not change, even though the appearance may change, and is demonstrated by children in the pre-operational stage of Piaget’s theory of development.
Consequent control: a behavioural measure in which the intervention follows the behaviour to be changed. Consequent procedures can affect behaviours by using pleasant or unpleasant consequences (positive or negative reinforcement or punishment) to make their performance more or less likely or through the use of feedback.
Constant errors: uncontrolled variables that act on only one level of the independent variable. Their action may either be in the same direction as a predicted difference, exaggerating the apparent effect of the independent variable or in the opposite direction, obscuring the effect of the independent variable.
Constructive theories of perception: top-down (or concept driven) theories that emphasise the need for several sources of information in order to construct our perception of the world. In addition to information available in the sensory stimulus, we need to use higher cognitive processes, according to this theory, to interpret the information appropriately.
Construct validity: an indicator of validity, which aims to demonstrate that the phenomenon being measured actually exists, for example, by justifying it in relation to a model or theory.
Contact hypothesis: suggestion that prejudice can be reduced if members of different groups are brought into contact with each other.
Content analysis: examination of certain types of media (e.g. Books, TV; magazines, the internet) to see what effect they may be having on our perceptions and/or behaviour. It involves the analysis of language, certain words or certain activities that appear in the chosen media.,
Context-dependent forgetting: failure to retrieve information from long-term memory due to the absence of appropriate contextual cues.
Contiguity: in behaviourism, the principle that a reinforcer must occur immediately after a response in order for learning to occur.
Contextual reinstatement: in the context of criminal psychology, a way of improving memory for an event by returning to the place where it happened or asking the witness to imagine themselves back in that place and in the same emotional state.
Contingency of reinforcement: in operant conditioning, a description of the relationship between a response and a reinforcer.
Continuity: in developmental theory, the view that changes occur through a continuous gradual process, rather than as a series of discrete stages; continuity is an assertion about the processes that underlie development, as well as the changes observed in behaviour.
Continuous reinforcement: a reinforcement schedule in which every response is followed by a reinforcer; equivalent to a fixed ratio 1 schedule.
Contrast processing: term used in the study of visual perception to describe the ability to differentiate between brightness levels in adjoining areas.
Control (psychological): the sense that one can anticipate events that occur in one's environment - a feeling that one can accomplish things and is not at the mercy of forces beyond one's control. Types of control include: informational, decisional, behavioural, cognitive and retrospective.
Control group: in an experimental design, group used as a baseline to compare the effect of the independent variable in the experimental group.
Controlled (attentional) processing: a mental operation that is conscious, relatively slow and easily interrupted.
Controls: the steps taken to limit factors that could distort the collection of valid and reliable data.
Convenience sample: a quasi-random sampling procedure in which the potential sample pool actually differs from the population - for example, selecting university students instead of people in general; the impact on representativeness (if any) often depends on what behaviour is being studied.
Convergent problem: a problem which has a single solution, and all elements lead towards that solution; also called closed-end or well-defined problems.
Coping: a person's efforts to minimise, control or tolerate environmental demands that are judged to exceed their resources to fight or avoid.
Coprolalia: an uncontrollable use of obscene language; often accompanied by mental disorders.
Corpus callosum: a wide band of nerve fibres which connect the two hemispheres of the brain.
Correlation: the degree of relatedness between two sets of scores. If two sets of scores are correlated, it enables researchers to predict (with varying degrees of certainty) the approximate value of one score if they know the value of the other. A positive correlation exists when high values on one variable are associated with high values on another variable. A negative correlation exists when high values on one variable are associated with low values on another variable.
Correlational analysis: a type of analysis used to measure the extent of relationship between variables that are thought likely to co-vary.
Correlation coefficient: a descriptive statistic measuring the degree of relationship between two variables; for positive correlations, it is a number which varies between 0.0 and + 1.0, and for negative correlations between 0.0 and -1.0; in both cases, the closer the value is to i, the stronger the relationship between the two variables.
Cortex: the outer layer of the brain which controls many of our higher functions like speech and perception.
Cortical activity: neural activity in the cortex of the brain.
Corticosteroids: drugs that mimic the action of a group of hormones produced by adrenal glands; they are anti-inflammatory and act as bronchodilators.
Counter balancing: the systematic variation of the order of presentation of the levels of the independent variable (eg. Half of the participants first undergo condition a followed by condition b, whilst the other half do vice versa), in a repeated measures design, to avoid order and fatigue effects.
Counter factual thinking: thinking about events that did not actually take place, such as winning when we in fact lost.
Counter transference: as part of psychoanalytic therapy, the therapist may transfer feelings or conflicts they may have about their own life, or significant others in it, onto the client. It is imperative that the therapist recognises this possibility and guards against it.
Co-variation model of attribution: Kelley's theory that people decide on the cause of behaviour by weighing up how consistent and distinctive the behaviour is and how much consensus there is about it.
Covariation principle: proposes that individuals attribute behaviour to a causal factor if it existed whilst the behaviour took place, but was not there when it did not occur.
Creativity: the capacity to produce something which is both unique and useful.
Criminal psychology: is the study of the wills, thoughts, intentions and reactions of criminals.
Crisis: a psychological conflict which needs to be resolved if the individual is to move on to the next stage of development.
Criterion: a standard or test by which individual things or people may be compared and judged.
Critical period: a crucial period in a person's or animal's development when certain experiences must happen for normal development to proceed. Today it is more common to use the term sensitive period to describe the optimum period for certain experiences to happen.
Critical value: the value that is compared with the observed (calculated) value in an inferential statistical test. Each inferential statistical test has a table or tables of critical values. The comparison with the observed (calculated) allows you to conclude if you have found a significant result.
Cross cultural study: a study conducted across two or more cultures in order to make comparisons between them.
Cross sectional sample: a sample which is deliberately selected in such a way that the sample matches the population for particular characteristics, such as age and income.
Cross sectional study: a research design based on selecting representative groups who vary on a particular characteristic; when the characteristic is age, this design provides a means of making developmental comparisons.
Cross tolerance: this phenomenon arises in some drug categories, such as the opiates (heroin, morphine etc) and tryptamines (LSD, mescaline and psilocybin) when the prolonged use of one drug in the group results in the development of tolerance to the others opioids.
Crowd: may refer to a large, cohesive gathering of individuals or to the act of coming together to form a tightly-spaced group. In addition, crowding is used to refer to the psychological perceptions associated with this increase in density.
Crowding: the feeling that is induced if our expectations about the use of space are violated by the presence of others.
Crystallised intelligence: knowledge and skills already acquired by a person, e.g. arithmetic.
Cue-arousal theory: suggests that the presence of specific cues in the environment triggers aggressive behaviour.
Cue-dependent coding: the concept that all information is stored in memory as a set of relationships called the context; remembering is seen as dependent on restoring the cues which formed the original context.
Cue-dependent forgetting: failure to recall memory due to a lack of cues that were present at the time of memory encoding.
Cultural bias: a tendency in psychological theory and research to ignore the differences between cultures and impose understanding based on the study of one culture alone.
Cultural identity: the influence of one's culture on the development of identity. Individualist cultures stress the importance of personal achievement and independence, while collectivist cultures stress the importance of collective achievement and dependence.
Cultural relativism: in the context of atypical psychology, the acknowledgement that symptoms may differ across cultures.
Culture: a system of values, beliefs and practices that characterise a particular group, for example a national or ethnic group.
Culture-bound syndrome: a mental disorder that appears to be confined to the members of a particular cultural group.
Custom: a practice from the past that people continue to observe.
Dark adaptation: the gradual process through which the eyes adjust from a change in illumination from light to low light intensity.
Daydream: a visionary fantasy experienced while awake, especially one of happy, pleasant thoughts, hopes, or ambitions.
Debriefing: an ethical procedure that occurs at the end of a study, whereby participants are given as much information as possible about the study, are given the option to discuss their experience of the study, to ensure that participants leave the experiment in the same emotional state as they entered.
Decay: the loss of information in memory over a long period of time.
Deception: in research, the intentional misleading and misinforming of participants with regard to the aim of the study.
Decibels (DB): a measure of volume (sound intensity) .decision-making: reasoning that involves considering and choosing different options.
Declarative knowledge: memory for facts (semantic knowledge) and events (episodic knowledge).
Deduction/deductive reasoning: the logical process of drawing a particular conclusion from a set of general principles.
Defence mechanism: psychological strategies as part of Freudian psychoanalytic theory, that are used to distort or deny reality, in order to cope with anxiety and/or a situation which an individual feels is difficult to cope with.
Deindividuation: a process through which group members cease to view themselves as individuals. Individual identity is replaced with identification with a group.
Delinquency: criminal/antisocial activity.
Delusion: unfounded and irrational beliefs held despite contrary evidence. Characteristic of mental disorders such as schizophrenia, can be manifested in delusions of grandeur (believing that one is famous or powerful) or delusions of persecution (believing that one is being chased or followed).
Demand characteristic: cues in an experiment that reveal information to participants about the aim and expected outcome, thereby influencing their behaviour and subsequently confounding the results.
Dementia: disorder characterised by considerable deterioration in cognitive function, for instance in loss of memory. Different types of dementia include corticial dementias (e.g. Alzheimers disease) and sub-cortical dementias (e.g. Huntingtons disease).
Demographic: a socioeconomic or similar factor that defines a certain group or area.
Dendrites: branched fibres at the end of the cell body of a neuron that receive incoming impulses
Denial: a defence mechanism, whereby an individual may denies or rejects some aspect of reality.
Deoxyribonucleic acid (DNA): the molecule which forms basis of heredity. DNA holds all genetic information on the chromosomes.
Dependent personality disorder: a form of personality disorder, whereby an individual is heavily reliant upon others and demonstrates feelings of inadequacy and helplessness when alone.
Dependent variable (DV): in an experiment, the values of the variable that change as a result of manipulation of the independent variable.
Depression (unipolar disorder): a type of mood disorder, characterised by persistent feelings of great sadness, hopelessness, worthlessness, guilt and a loss of interest in activities.
Deprivation: a condition of having too little of something.
Depth/distance (visual) perception: the capability to view the world three-dimensionally, utilising monocular and binocular cues to appraise depth and distance between objects.
Descriptive statistics: the description and summation of sets of scores in statistics.
Determinism: the assumption that all behaviour has specific causes.
Developmental psychology: also known as human development. It is the scientific study of the processes which underlie and control growth and change in behaviour over time.
Deviant behaviour: behaviour that is a recognised violation of social norms.
Diagnosis: the identification and classification of a psychological disorder.
Diagnostic and statistical manual (DSM): a multi-axial manual used for the classification, definition and description of mental health disorders.
Diathesis-stress model: an explanation of mental disorders based on a combination of genetic vulnerability (diathesis) and environmental influences.
Dichotic listening: utilised in attention research, whereby a different auditory message is simultaneously presented to each ear. Participants are required to repeat one of the messages whilst ignoring the other.
Diencephalon: a part of the forebrain, containing the thalamus and the hypothalamus.
Diffusion of responsibility: occurs in groups when an individual feels less responsibility because accountability is diffused amongst the group. Evident in emergency situations, whereby the larger the number of bystanders, the less responsibility each bystander feels.
Digit span: a test of short-term memory, whereby participants are presented with a series of digits and asked to repeat them. Average digit span is 7 +/- 2.
Directional hypothesis: states which of the two condition means will be larger, most often used, one tailed t-test.
Discovery learning: a Piagetian belief that children learn through self-discovery, aided by a teacher providing suitable materials, thereby stimulating intrinsic satisfaction.
Discrete variable: measurement using of a discrete category (eg. gender) as opposed to a continuous score (e.g. height, weight, intelligence).
Discrimination: unequal and unlawful treatment based upon race, colour, creed, religion, sex, national origin, age, disability, veteran status, or sexual orientation.
Disengagement theory: mutual process of disengagement in activities expected by the individual and by society.
Disorganised speech: one of the positive symptoms of schizophrenia, a disturbance whereby speech is disjointed and incoherent.
Displacement: forgetting in short-term memory, as a result of to new incoming information replacing the previous contents
Dispositional attribution: when behaviour is attributed to internal factors that are directly controllable by a person, e.g. an individuals effort or ability, as opposed to external factors (situational attributions), such as the weather or bad luck.
Dissociative disorder: is a condition, often caused by trauma, in which a person disconnects from a full awareness of self, time, or external circumstances as a defence against unpleasant realities or memories.
Distal cause: a factor which has an indirect effect on behaviour, such as previous experiences in similar situations.
Divided attention: the ability to divide our attentional processing between more than one task.
Dizygotic twins (non-identical twins): twins that develop from different zygotes (eggs) and only share about fifty percent of their DNA.
Door-in-the-face technique: a technique used to induce compliance, whereby individuals are first asked a large favour, followed by a smaller favour, which is more likely to be followed.
Dopamine: a chemical neurotransmitter in the brain, important for learning and the experience of pleasure and reward.
Dopamine hypothesis: argues that schizophrenia is based on over-activity of synapses that depend on dopamine.
Double-bind theory: a theory of schizophrenia proposed by Bateson, which argues that faulty communication patterns within the family contribute to the onset of schizophrenia.
Double-blind design: a form of experimental control, whereby both the subject and experimenter are kept uninformed about the purpose of the experiment, to reduce any forms of bias (in particular, experimenter bias).
Down's syndrome: a chromosomal disorder that is characterised by low iq levels.
Dreaming: a stage of sleep typified by the experience of visual imagery and rapid eye movements (REM).
Drive reduction theory (of motivation): hull's proposal that all behaviour is motivated and that motivation stems from the satisfaction of homeostatic drives (e.g. hunger and thirst). Stimuli (e.g. food and water) that decrease the drives subsequently reinforce the behaviour that led to them.
Drug treatments: treatment of psychological disorders that are based on biological explanations of abnormal behaviour. Treatment includes anti-anxiety drugs, anti-depressant drugs and anti-bipolar drugs.
Dysfunctional: functioning incorrectly or abnormally.
Dyslexia: 'developmental dyslexia' is used to explain difficulties with written and spoken language (across differing levels of intellect) that occurs as a result of development, whilst acquired dyslexia occurs as a result of a stroke or similar injury, whereby language skills are impaired.