A symbol is defined as a species of sign. The concept of a sign coincides with Skinner's (1938) concept of a discriminative stimulus. Symbols differ from other signs in five respects: (1) They are stimuli which the organism can both respond to and produce, either as a self-directed stimulus (as in thinking) or as a stimulus for another individual with a predictably similar response from the recipient in each case. (2) they act as discriminative stimuli for the (...) same kind of object for all members of the verbal community within which they function as a symbols; (3) they acquire their properties by virtue of arbitrary social convention rather than any natural and intrinsic connection between the sign and what it is a sign of; (4) competent members of the verbal community can both produce the appropriate symbol in response to a naturally occurring sign of the presence of the object or a sample of the kind of object which the symbol stands for and select the appropriate object when presented with the symbol; (5) they form stimulus equivalence classes of the kind demonstrated in the matching-to-sample task (Sidman, 1971; Sidman and Tailby, 1982) both with other symbols having the same meaning and, more important, with the naturally-occurring non-symbolic signs of the presence of the object or kind of object which the symbol stands for. (shrink)

Shors & Matzel propose that hippocampal LTP increases the effective salience of discrete external stimuli and thereby facilitates the induction of memories at distant places. In line with this suggestion, a neural network model of associative learning and hippocampal function assumes that LTP increases hippocampal error signals to the cortex, thereby facilitating stimulus configuration in association cortex. Computer simulations show that under these assumptions the model correctly describes the effect of LTP induction and blockade in classical discriminations and (...) place learning. (shrink)

The current study examined whether pigeons could learn to use abstract concepts as the basis for conditionally switching behavior as a function of time. Using a mid-session reversal task, experienced pigeons were trained to switch from matching-to-sample (MTS) to non-matching-to-sample (NMTS) conditional discriminations within a session. One group had prior training with MTS, while the other had prior training with NMTS. Over training, stimulus set size was progressively doubled from 3 to 6 to 12 stimuli to promote abstract (...) concept development. Prior experience had an effect on the initial learning at each of the set sizes but by the end of training there were no group differences, as both groups showed similar within-session linear matching functions. After acquiring the 12-item set, abstract-concept learning was tested by placing novel stimuli at the beginning and end of a test session. Prior matching and non-matching experience affected transfer behavior. The matching experienced group transferred to novel stimuli in both the matching and non-matching portion of the sessions using a matching rule. The non-matching experienced group transferred to novel stimuli in both portions of the session using a non-matching rule. The representations used as the basis for mid-session reversal of the conditional discrimination behaviors and subsequent transfer behavior appears to have different temporal sources. The implications for the flexibility and organization of complex behaviors are considered. (shrink)

Discrimination in the postmodern society can have many different causes and can affect people of different racial, ethnic, national or social backgrounds, such as communities of Asian or African descent, Roma people, indigenous peoples, Aboriginal people and people of different castes. Discrimination can also refer to people of different cultural, linguistic or religious backgrounds, people with disabilities or the elderly. Moreover, people can be discriminated because of their sexual orientation or preferences. Gender-based discrimination is also common, despite progress in many (...) countries. Women are also particularly prone to violent and abusive practices, and therefore often suffer from a double discrimination, both because of their race or origin and because of their gender, which is why feminist literature in recent years points to new acts or forms of discrimination against women. A major problem in the postmodern world is the discrimination that many people are subjected to, especially women and children, because they live in extreme poverty. These circumstances may force them to migrate and further contribute to a conceptual or social contamination, that may aggravate discriminatory tendencies in the societies where they migrate. The article aims to theoretically analyse the degree of functionality that the principle of non-discrimination based on gender, race, religion and sexual orientation has in the contemporary, postmodern, individualistic society. (shrink)

In the metaphor of behavioral momentum, the rate of a free operant in the presence of a discriminative stimulus is analogous to the velocity of a moving body, and resistance to change measures an aspect of behavior that is analogous to its inertial mass. An extension of the metaphor suggests that preference measures an analog to the gravitational mass of that body. The independent functions relating resistance to change and preference to the conditions of reinforcement may be construed as (...) convergent measures of a single construct, analogous to physical mass, that represents the effects of a history of exposure to the signaled conditions of reinforcement and that unifies the traditionally separate notions of the strength of learning and the value of incentives. Research guided by the momentum metaphor encompasses the effects of reinforcement on response rate, resistance to change, and preference and has implications for clinical interventions, drug addiction, and self-control. In addition, its principles can be seen as a modern, quantitative version of Thorndike's (1911) Law of Effect, providing a new perspective on some of the challenges to his postulation of strengthening by reinforcement. Key Words: behavioral momentum; clinical interventions; drug addiction; preference; reinforcement; resistance to change; response strength; self-control. (shrink)

Abstract“Sign stimuli” elicit specific patterns of behavior when an organism's motivation is appropriate. In the toad, visually released prey-catching involves orienting toward the prey, approaching, fixating, and snapping. For these action patterns to be selected and released, the prey must be recognized and localized in space. Toads discriminate prey from nonprey by certain spatiotemporal stimulus features. The stimulus-response relations are mediated by innate releasing mechanisms (RMs) with recognition properties partly modifiable by experience. Striato-pretecto-tectal connectivity determines the RM's recognition (...) and localization properties, whereas medialpallio-thalamo-tectal circuitry makes the system sensitive to changes in internal state and to prior history of exposure to stimuli. RMs encode the diverse stimulus conditions referring to the same prey object through different combinations of “specialized” tectal neurons, involving cells selectively tuned to prey features. The prey-selective neurons express the outcome of information processing in functional units consisting of interconnected cells. Excitatory and inhibitory interactions among feature-sensitive tectal and pretectal neurons specify the perceptual operations involved in distinguishing the prey from its background, selecting its features, and discriminating it from predators. Other connections indicate stimulus location. The results of these analyses are transmitted by specialized neurons projecting from the tectum to bulbar/spinal motor systems, providing a sensorimotor interface. Specific combinations of such projective neurons – mediating feature- and space-related messages – form “command releasing systems” that activate corresponding motor pattern generators for appropriate prey-catching action patterns. (shrink)