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DA See dopamine.
data driven A process determined by the input received (often, the sensory information) rather than being determined by pre-existing ideas or expectations.
debriefing A step at the end of a procedure in which participants are told what the procedure involved and why it was designed as it was, and in which any manipulations to the participants' beliefs or state are undone.
decibels The logarithmic units used to describe sound intensity (or amplitude).
declarative knowledge Knowing "that" (e.g., knowing someone's name), as contrasted with procedural knowledge, which is knowing "how" (e.g., knowing how to ride a bicycle).
deductive reasoning Reasoning in which one tries to determine whether some statement follows logically from certain premises, as in the analysis of syllogisms. This is in contrast with inductive reasoning in which one observes a number of particular instances and tries to determine a general rule that covers them all.
deep processing See depth-of-processing hypothesis.
defense mechanism In psychoanalytic theory, a collective term for a number of reactions that try to ward off or lessen anxiety by various unconscious means. See also displacement, projection, rationalization, reaction formation, repression.
definitional theory of word meaning The theory that our mental representation of word meaning is made up of a small number of simpler concepts. The representation of bachelor, for example, is made up of "adult," "unmarried," and "male."
dehumanization of the victim Steps often taken to make a potential victim seem not human (labeling him as vermin, for example, or treating him as a mere number); these steps make aggression toward the victim more likely and less troubling to the aggressor.
deindividuation A weakened sense of personal identity in which self-awareness is diminished and one's own goals are merged in the collective goals of a group.
deinstitutionalization A movement intended to obtain better and less expensive care for chronically mentally ill patients in their own communities rather than at large, centralized hospitals.
delusions Systematized false beliefs, often of grandeur or persecution.
delusions of persecution A delusion in which the person believes that other people are seeking to harm him.
demand characteristics The cues that tell a research participant what the experimenter expects.
dendrites A typically highly branched part of a neuron that receives impulses from receptors or other neurons and conducts them toward the cell body and axon.
dendritic spines Little knobs that are attached to the surface of the dendrites and serve as the "receiving stations" for most synapses.
dependent variable The thing that is measured or recorded in an experiment, called the dependent variable because the experiment seeks to ask whether this variable depends on (is caused by or predicted by) another variable (the independent variable). Typically, experiments are done to find out if the independent variable does have an influence on the dependent variable.
depressants Drugs that have the effect of diminishing activity levels.
depressive stupor An extreme state of depression in which the person may become entirely unresponsive, rock back and forth, urinate or defecate on herself, and mutter incoherently.
depth cues Sources of information that signal the distance from the observer to the distal stimulus. Some depth cues are present in a single retinal image (the pictorial cues), some require a comparison of the information received from the two eyes (binocular cues), some involve the pattern of motion in the retinal image (parallax and optic flow), and some arise from the positions of the eyes in viewing (e.g., convergence angle).
depth-of-processing hypothesis A theory of memory that stresses the nature of encoding at the time of acquisition. It argues that deeper levels of processing (e.g., attending to a word's meaning) lead to better retention and retrieval than shallower levels of processing (e.g., attending to the word's sound). Thus, maintenance rehearsal leads to much poorer retrieval than elaborative rehearsal. See also elaborative rehearsal, maintenance rehearsal.
diagnosis A practitioner's best opinion, based on a patient's signs and symptoms, as to the patient's specific disorder.
Diagnostic and Statistical Manual for Mental Disorders (DSM) See DSM-IV.
dichotic presentation An experimental procedure in which the participant hears two simultaneous messages, one presented to each ear. Typically, one of these is to be attended to and the other ignored.
difference threshold The amount by which a given stimulus must be increased or decreased so that the research participant can perceive a just-noticeable difference (jnd).
diffusion of responsibility See bystander effect.
directed thinking Thinking that is aimed at the solution of a problem.
direction specific Responding to motion in just one direction.
disconfirmed hypothesis A hypothesis that has been tested but for which the data do not conform to the pattern it predicted.
discrimination A process of learning to respond to certain stimuli that are reinforced and not to others that are unreinforced.
discriminative stimuli In instrumental conditioning, the external stimuli that signal a particular relationship between the instrumental response and the reinforcer. For example, a green light is a positive discriminative stimulus when it signals to a pigeon that it will now get food if it hops on a treadle; the reverse is true of a red light, or the negative discriminative stimulus, which indicates that this action will not now lead to a food reward.
disorganized schizophrenia A subtype of schizophrenia in which the predominant symptoms are extreme incoherence of thought and marked inappropriateness of behavior and affect.
displacement In psychoanalytic theory, a redirection of an impulse from a channel that is blocked into another, more available outlet (e.g., displaced aggression, as in a child who hits a sibling when punished by her parents).
dissociation (1) A term used for symptoms when a patient is impaired in one function but relatively unaffected in another. (2) In post-traumatic stress disorder (PTSD), the period of numbness immediately after the trauma in which the sufferer feels estranged, socially unresponsive, and oddly unaffected by the traumatizing event. (3) A defense mechanism in which one seeks to create a sense of physical or psychological distance from the threatening event, person, or stimulus.
dissociative amnesia A form of memory loss in which an individual seems unable to remember some period of her life, or even her entire past, including her own identity. This memory loss is often understood as a means of coping with extraordinarily painful events.
dissociative disorders Disorders in which a whole set of mental events seems to be stored out of ordinary consciousness. These include dissociative amnesia, fugue states, and, very rarely, cases of dissociative identity disorder.
dissociative fugue A state in which the person wanders away from home, and then, days or even months later, suddenly realizes that he is in a strange place and does not know how he got there; this pattern is often understood as a means of coping with (and escaping from) extraordinarily painful events.
dissociative identity disorder Formerly multiple personality disorder. A dissociative disorder that results in a person developing two or more distinct personalities.
distal stimulus An object or event outside (e.g., a tree) as contrasted to the proximal stimulus (e.g., the retinal image of the tree), which is the pattern of physical energies that originates from the distal stimulus and impinges on a sense organ.
distance cues See depth cues.
distributed representations A model of cognitive organization, especially semantic memory, in which each concept is represented, not by a designated node or group of nodes, but by a widespread pattern of activation across the entire network. See also connectionist model, local representations, network model, node.
doctrine of specific nerve energies The law formulated by Johannes Müller which holds that differences in sensory quality are not caused by differences in the stimuli themselves but by the different nervous structures that these stimuli excite. Thus, stimulating the retina will produce sensations of light, whether the retina is stimulated by a beam of light or pressure to the eyeball.
dodo bird verdict An expression often used to summarize the comparison of the effectiveness of different forms of psychotherapy. According to the dodo bird in Alice in Wonderland, "Everyone has won and all must have prizes." Regarding psychotherapy, this statement is understood to mean that all the major forms of psychotherapy are equally effective.
dominance hierarchy A social order developed by animals that live in groups by which certain individuals are understood to have a certain status or rank, and this determines their access to resources and how they exert power over others.
dominant A relationship among genes such that if the gene on one chromosome specifies one developmental path, and the corresponding gene on the other chromosome specifies a different path, a gene that is dominant will govern the outcome. If a gene is recessive, it will govern the outcome only if the corresponding gene on the other chromosome redundantly specifies the same (recessive) trait.
dopamine (DA) A neurotransmitter involved in various brain structures, including those that control motor action.
dopamine hypothesis Asserts that schizophrenics are oversensitive to the neurotransmitter dopamine. Evidence for this view comes from the fact that the classical antipsychotics, which alleviate positive schizophrenic symptoms, block dopamine transmission. See also classical antipsychotics.
dopamine-serotonin interaction hypothesis Asserts that schizophrenics are oversensitive to both dopamine and serotonin. Evidence for this view comes from the fact that atypical antipsychotics, which relieve both positive and negative symptoms, block receptors for both dopamine and serotonin. See also atypical antipsychotics.
double-blind design See double-blind technique.
double-blind technique A technique for evaluating a manipulation independent of the effects produced by the expectations of research participants (placebo effects) or the experimenters. This is done by assigning participants to the experimental group or a placebo group with both the participants and the researchers in ignorance of who is assigned to which group. See also placebo effect.
downward drift The proposed process through which schizophrenics fall to the bottom of the socioeconomic ladder because they cannot hold down a job or sustain a personal relationship.
dream condensation The idea that events in a dream flash by in a very fast sequence, taking much less time than the dreamed-about events would ordinarily require.
drive A term used by Hull (among others) to refer to a state of internal bodily tension, such as hunger or thirst or the need for sleep.
drive-reduction theory A theory that claims that all built-in rewards are at bottom reductions of some noxious bodily state. The theory has difficulty in explaining motives in which one seeks stimulation, such as sex and curiosity.
DSM-IV The current diagnostic manual of the American Psychiatric Association (adopted in 1994), a substantial revision of its predecessor, DSM-III-R.
dual-center theory A hypothesis about the hypothalamic control of eating. One center (in the lateral hypothalamus) was hypothesized as the "on" center, the initiator of eating; another center (in the ventromedial region) was hypothesized as the "off" center, the terminator of eating. Current evidence indicates, however, that these brain regions, while crucial for eating, are only a part of the circuits controlling eating.
duplex theory of vision The theory that rods and cones handle different aspects of vision. The rods are the receptors for night vision; they operate at low light intensities and lead to achromatic (colorless) sensations. The cones are used in day vision; they respond at higher illumination levels, have greater acuity, and are responsible for sensations of color.
dyslexia Any difficulty in reading not associated with obvious problems like bad eyesight.
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