Ultradian rhythms: one complete cycle that repeats in less than twenty-four hours, for instance different stages of sleep several times during a single night's sleep.
Unconditional positive regard: complete acceptance and caring of an individual, without imposing conditions.
Unconditioned response: in classical conditioning, a reflexive response elicited by an unconditioned stimulus, such as pupil contraction to bright light, without prior learning.
Unconditioned stimulus: in classical conditioning, a stimulus which elicits a reflexive (unconditioned) response.
Unconscious: in Freud’s theory, portion of the psyche that cannot be directly accessed by the unconscious, repressing urges, impulses and thoughts, which may filter into conscious awareness directly or in symbolic form.
Unconscious motive: a term used to describe that much of (motivated) behaviour is a result of influences outside our conscious awareness, and manifests in defence mechanisms or other symbolic ways.
Understanding: the cognitive condition of someone who understands. It is is the possession of knowledge coupled with the capability of reasoning and making judgements relating to the applicability of the knowledge.
Unfalsifiable: a theory or hypothesis is unfalsifiable if it cannot be disproved by data and thus cannot be used to make predictions.
Unipolar depression: see depression
Universal: any characteristic that can be applied to all members of the species, despite a variety of experiences and development.
Unstructured interview: an interview whereby the interviewer does not have pre-determined questions, but instead asks questions spontaneously as topics arise.
Upper quartile: the data point that is at the 75 per cent point of the data set when the data is ranked in order.
Utilitarianism: states that what is ethically acceptable is that which produces the greatest pleasure and happiness (in comparison to pain and suffering) for the greatest number of people.
Valence: in psychology, especially in discussing emotions, means the intrinsic attractiveness (positive valence) or aversiveness (negative valence) of an event, object, or situation.
Validity: the extent to a test measures what it claims and was intended to measure.
Values: involves one's principles or standards or judgments about what is valuable or important in life.
Variable: in an experimental setting, any measured factor which shows variation across cases or conditions.
Variable interval schedule: in operant conditioning, a schedule of reinforcement determined by the average time interval which must elapse since the last reinforcer before a response will be reinforced.
Variable ratio schedule: in operant conditioning, a schedule of reinforcement determined by the average number of responses required to receive a reinforcer.
Variability: in statistics, the dispersion of scores within a set of data.
Ventro-medial hypothalamus: section of the hypothalamus, that when lesioned in a rat’s brain, the rat will demonstrate abnormal appetitive behaviour.
Vicarious learning: see observational learning.
Vicarious reinforcement: learning behaviour by observing others being rewarded for the behaviour.
Visual agnosia: a general term for disorders which occur as a result of disruption of visual recognition.
Visual cliff: an apparatus used to assess an infant's perception of depth, comprised of a thick pane of glass that covers a shall drop and a deep drop. Surfaces of both are covered with the same chequered pattern; however children of six months and older will not explore the deep side which demonstrates depth perception.
Visual pathways: the routes by which nerve impulses travel from the retina to the visual areas of the brain.
Visual perception: the process by which sensory information from the eyes is transformed to produce an experience of depth, distance, colour, etc.
Volume: an increase in magnitude of vibration in the air (measured in decibels). Sounds increase in volume as the amplitude of the waves increases.
Voluntary response: a response which is controlled by the individual rather than being elicited by specific stimuli as reflexes are.
Volunteer bias: participants who volunteer for a research investigation may differ on particular characteristics from non-volunteers, therefore comprising a non-representative sample.