Allornone Lawprinciple

Bowditch's law. This principle, discovered by the American physiologist Henry Pickering Bowditch (1840-1911) while he was studying cardiac muscle, states that in any single nerve or muscle fiber the response to a stimulus above threshold level is maximal, independent of the intensity of the stimulus, and dependent only on the condition of the cell at the moment of stimulation. The all-or-none property of the nerve impulse is contained in the fact that its amplitude is always the same where the neural code is determined by frequency rather than size of the nerve response. Stronger stimuli result in more impulses being generated per second, but each stimulus has the same amplitude. The process of nerve conduction has been likened to the burning of a fuse because both processes involve the progressive release of energy by local action. However, it is true that not all fuses or all nerve fibers have the same amount of energy available; thick fuses and thick nerve fibers transmit a larger disturbance and transmit it faster. It is true, also, that the available energy in any nerve fiber varies from time to time with corresponding changes in the magnitude and speed of the impulse. The all-or-none law, however, is still valid because the nerve fiber either reacts with all of its available energy, or else (if the stimulus is too weak), it does not react at all. The top speed of the nerve impulse is estimated to be 100 meters per second and is attained only in the larger fibers of the body. Thin fibers conduct impulses at much slower rates, down to about one meter per sec ond in some animal species. The major difference between the fuse and the nerve fiber in this analogy is that the nerve fiber restores itself after each impulse occurs, whereas the fuse does not. Only a small amount of the stored energy is available momentarily at the surface of the nerve fiber where the local activity takes place. The energy is replaced promptly as soon as this portion is consumed by the single nerve impulse. However, the replacement process takes a short amount of time, and a second impulse cannot follow immediately. At this stage in the process, the fiber is said to be in its absolute refractory phase (these events taken collectively are known as the refractory law). Then, within a millisecond or so, the fiber recovers enough to allow a very strong stimulus to create a very weak impulse. Following this relative refractory phase of firing, there is a gradual buildup of available energy where the stimulus threshold is decreased and the magnitude and speed of the impulse are increased. The American psychologist Charles Osgood (1916-1991) coined the term essential identity law, which is related to the physiological all-or-none law and refers to the fact that nerve impulses are all the same in kind. For example, impulses traveling in optic nerve fibers differ qualitatively in no way from impulses in cutaneous fibers, and activity in the visual areas of the cortex does not appear to differ qualitatively from activity in the som-esthetic, or even in the motor, areas. The all-or-none principle from physiology has been expanded conceptually, also, to the area of the psychology of learning where it refers to associations of learned materials that are either formed completely on a single trial or not formed at all (e.g., one-trial learning). The valid all-or-none law/principle has been consistently well-referenced in psychology textbooks from 1885 through 1996 (cf., Roeckelein, 1996). See also CONTINUITY THEORY; GUTHRIE'S THEORY OF BEHAVIOR; SKINNER'S DESCRIPTIVE BE-HAVIOR/OPERANT CONDITIONING THEORY. REFERENCES

Bowditch, H. P. (1871). [All-or-none law of nerve impulse transmission in heart fiber muscles]. Berichte uber die Verhandlungen der koniglichen sa-

chsischen Gesellschaft der Wissenschaften zu Leipzig, mathematischphysische Classe, 23, 652-689. Adrian, E. (1914). The all-or-none principle in nerves. Journal of Physiology, 47, 450-474.

Osgood, C. (1953). Method and theory in experimental psychology. New York: Oxford University Press. Roeckelein J. E. (1996). Citation of laws and theories in textbooks across 112 years of psychology. Psychological Reports, 79, 979-998.

ALLPORT'S CONFORMITY HYPOTHESIS. The American social psychologist Floyd Henry Allport (1890-1978) proposed that conforming behavior may be recognized by its distinctive distribution, which takes the shape of an inverted J curve. A few people overcon-form (are to the left of the curve's peak), the overwhelming majority are positioned exactly at the peak, which accounts for the spike of the J, and a minority deviate from the norm, which accounts for an elongated, but low-level, tail. Allport validated his conformity hypothesis mainly by observations in field situations involving activities such as reporting to work, using holy water in a Catholic church, and stopping at a stop sign. The friction-conformity model states that a pedestrian's rate of walking is affected by the number of obstacles met and by conformity to the pace set by other nearby pedestrians. Allport's data refer primarily to situations where adherence to standards is enforced ("compliant behavior"). Conformity is viewed as an intermediate stage between superficial compliance and permanent internaliza-tion, and as a conflict between what a person basically is and what group membership requires from the individual (cf., group-relations theory - states that behavior is determined not only by a person's unique pattern of traits, but also by the individual's need to conform to social demands and expectations). See also ASCH CONFORMITY EFFECT; ATTITUDE AND ATTITUDE CHANGE, THEORIES OF; BYSTANDER INTERVENTION EFFECT; COMPLIANCE EFFECTS AND TECHNIQUES; CONFLICT, THEORIES OF; GROUPTHINK PHENOMENON.

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