| Helmholtz theory of colour vision | A theory that there are three colour-perceiving elements in the retina: red, green, and blue. Perception of other colours arises from the combined stimulation of these elements; deficiency or absence of any one of these elements results in inability to perceive that colour and a misperception of any other colour of which it forms a part. Synonym: Helmholtz theory of colour vision. (05 Mar 2000) |
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| Helmholtz theory of hearing | That the basilar membrane of the cochlea acts as a resonating structure, recording low tones from its apical turns and high tones from its basal turns. Synonym: Helmholtz theory of hearing. (05 Mar 2000) |
| Hering's theory of colour vision | That there are three opponent visual processes: blue-yellow, red-green, and white-black. (05 Mar 2000) |
| psychoanalytic theory | Conceptual system developed by freud and his followers in which unconscious motivations are considered to shape normal and abnormal personality development and behaviour. (12 Dec 1998) |
| psychological theory | Principles applied to the analysis and explanation of psychological or behavioural phenomena. (12 Dec 1998) |
| Semon-Hering theory | The theory that stimuli or irritants leave definite traces (engrams) on the protoplasm of the animal or plant, and when these stimuli are regularly repeated they induce a habit which persists after the stimuli cease; assuming that the germ cells share with the nerve cells in the possession of engrams, acquired habits may thus be transmitted to the descendants. Synonym: mnaemic theory, mnemism, Semon-Hering theory. (05 Mar 2000) |
| sensorimotor theory | In the developmental theory of Piaget, the postulation that during the first 18 months of life there occurs a transformation of action into thought; at first there is a gradual shift from inborn to acquired behaviour, then from body-centreed to object-centreed activity, ultimately permitting intentional behaviour and inventive thinking. (05 Mar 2000) |
| humoral theory | The ancient Greek theory of the four body humors (blood, yellow and black bile, and phlegm) that determined health and disease. The humors were associated with the four elements (air, fire, earth, and water), which in turn corresponded to a pair of the qualities (hot, cold, dry, and moist). A proper and evenly balanced mixture of the humors was characteristic of health of body and mind; an imperfect balance resulted in disease. Temperament of body or mind also was supposed to be determined, e.g., sanguine (blood), choleric (yellow bile), melancholic (black bile), or phlegmatic (phlegm). Synonym: fluidism, humoralism, humorism. (05 Mar 2000) |
| hydrate microcrystal theory of anaesthesia | A theory of narcosis pertaining to nonhydrogen-bonding agents; postulates the interaction of the molecules of the anaesthetic drug with water molecules in the brain. Synonym: Pauling's theory. (05 Mar 2000) |
| side-chain theory | Ehrlich postulated that cells contained surface extensions or side chains (haptophores) that bind to the antigenic determinants of a toxin (toxophores); after a cell is stimulated, the haptophores are released into the circulation and become the antibodies. See: receptor. Synonym: Ehrlich's postulate. (05 Mar 2000) |
| somatic mutation theory of cancer | That cancer is caused by a mutation or mutations in the body cells (as opposed to germ cells), especially nonlethal mutations associated with increased proliferation of the mutant cells. (05 Mar 2000) |
| Spitzer's theory | An interpretation of the partitioning of the heart of mammalian embryos primarily on the basis of recapitulations of the adult structural pattern of lower forms; most frequently cited in relation to the partitioning of the truncus arteriosus to form ascending aorta and pulmonary trunk, which is achieved by the phylogenetic development of the lungs. (05 Mar 2000) |
| Nernst's theory | That the passage of an electric current through the tissues causes a dissociation of the ions, with consequent concentration of salts in the solution bathing the cell membranes, the electric stimulus being thereby effected. (05 Mar 2000) |
| neurochronaxic theory | Theory stating that variations in pitch of the human voice are produced by active muscular contractions synchronised with cycles per second of pitch, no longer believed to be true. (05 Mar 2000) |
| stringed instrument theory | A no longer tenable theory stating that in human voice production the vocal cords function in a manner similar to the strings in a stringed musical instrument. (05 Mar 2000) |