Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Probability Learning”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1989

Base-rate effects in category learning: a comparison of parallel network and memory storage-retrieval models.

Exemplar-memory and adaptive network models were compared in application to category learning data, with special attention to base rate effects on learning and transfer performance. Subjects classified symptom charts of hypothetical patients into disease categories, with informative feedback on learning trials and with the feedback either given or withheld on test trials that followed each fourth of the learning series. The network model proved notably accurate and uniformly superior to the exemplar model in accounting for the detailed course of learning; both the parallel, interactive aspect of the network model and its particular learning algorithm contribute to this superiority. During learning, subjects' performance reflected both category base rates and feature (symptom) probabilities in a nearly optimal manner, a result predicted by both models, though more accurately by the network model. However, under some test conditions, the data showed substantial base-rate neglect, in agreement with Gluck and Bower (1988b).

Adult↗
PubMed1990

Suboptimal choice in a percentage-reinforcement procedure: effects of signal condition and terminal-link length.

Pigeons' choice between reliable (100%) and unreliable (50%) reinforcement was studied using a concurrent-chains procedure. Initial links were fixed-ratio 1 schedules, and terminal links were equal fixed-time schedules. The duration of the terminal links was varied across conditions. The terminal link on the reliable side always ended in food; the terminal link on the unreliable side ended with food 50% of the time and otherwise with blackout. Different stimuli present during the 50% terminal links signaled food or blackout outcomes under signaled conditions but were uncorrelated with outcomes under unsignaled conditions. In signaled conditions, most pigeons displayed a nearly exclusive preference for the 100% alternative when terminal links were short (5 or 10 s), but with terminal links of 30 s or longer, preference for the 100% alternative was sharply reduced (often to below .5). In unsignaled conditions, most pigeons showed extreme preference for the 100% alternative with either short (5 s) or longer (30 s) terminal links. Thus, pigeons' choice between reliable and unreliable reinforcement is influenced by both the signal conditions on the unreliable alternative and the duration of the terminal-link delay. With a long delay and signaled outcomes, many pigeons display a suboptimal tendency to choose the unreliable side.

Animals↗
PubMed1990

Hierarchical structures: chunking by food type facilitates spatial memory.

Three experiments assessed the ability of male Sprague-Dawley rats to organize the spatial locations of different food types in a hierarchical manner to maximize the efficiency of working memory. Independent groups were exposed, on a 12-arm radial maze, to baiting arrangements varying in the stability of the pattern and type of food used as bait. Training rats with stable, differentiable baiting arrangements produced increased accuracy in choice performance, hierarchically ordered patterns of choice selection, slower growth of proactive interference when trials were massed, and the learning of the geometrical relations among food types independent of other extramaze cues. Such findings are strong evidence of the rat's ability to encode and use local cues for navigation, based on properties of the reinforcer. The application of a chunking strategy may provide for more efficient use of working memory by facilitating information storage, recall, or resetting mechanisms.

Animals↗
PubMed1978

Deficits in visual learning produced by posterior temporal lesions in cats.

Eight cats with lesions in the posterior temporal (PT) cortex, seven cats with lesions in the basolateral amygdala (BLA), and eight intact controls were observed on eight tests of visual discrimination learning and of spontaneous responses to salient visual stimuli. The effects of the two lesions were somewhat dissociable. The PT lesions were accompanied by a severe deficit in pattern discrimination learning but no loss in visual tracking or orientation to the silhouette of a threatening cat. The BLA lesions produced a milder and less consistent loss in pattern discrimination but serious defects in tracking and reponse to the cat silhouette. Both operated groups performed well on the visual cliff. The deficit from PT lesions appeared independent of damage to the geniculocortical system. The parallel of symptoms from PT lesions in cats and inferotemporal lesions in monkeys is discussed.

Amygdala↗
PubMed1986

Regularity, exposure time and perception of numerosity.

Two experiments are described. In Exp. 1, subjects compared the apparent numerosity of two kinds of dot patterns, regular vs irregular, with two different exposures (160 vs 2000 msec.). In Exp. 2, the subjects had to estimate the numerosity of the same patterns, presented one at a time. Analysis showed a relative overestimation of the regular patterns in Exp. 1 but not in Exp. 2. In general an overestimation occurred with an increase in exposure. Such results support our hypothesis of two separate processes as the basis of the two kinds of performance (estimating vs comparison).

Attention↗
PubMed1988

Expectancy and visual-spatial attention: effects on perceptual quality.

When we expect important stimuli at a particular spatial location, how does our perceptual sensitivity change over space? Subjects were cued to expect a target stimulus at one location and then required to perform one of the following tasks at that and three other locations: luminance detection, brightness discrimination, orientation discrimination, or form discrimination. The analysis of subjects' performance according to signal detection theory revealed changes in both sensitivity and bias for each of these tasks. Sensitivity was maximally enhanced at the location where a target stimulus was expected and generally decreased with distance from that location. Factors that influenced the gradient of sensitivity were (a) the type of task performed and (b) the spatial distribution of the stimuli. Sensitivity fell off more steeply over distance for orientation and form discrimination than for luminance detection and brightness discrimination. In addition, it fell off more steeply when stimuli were near each other than when they were farther apart.

Attention↗
PubMed1990

Integrating information from separable psychological dimensions.

This article examines decision processes in the perception and categorization of stimuli composed of the separable psychological dimensions, orientation and size. The randomization technique (Ashby & Gott, 1988) of general recognition theory, which allows accurate estimation of a subject's decision boundary in a categorization task, is used in 4 experiments. Even though the stimulus components are clearly separable, it was found that Ss were not constrained to use separable response strategies, nor were they constrained to attend to distance to the prototypes. Instead, they used decision rules that were nearly optimal, even if this required information integration or for the Ss to attend to higher level category properties such as component correlation.

Adult↗
PubMed1990

The Kamin blocking effect, incidental learning and psychoticism.

The Kamin blocking effect consists in impaired learning of an association between a conditioned stimulus (CS2) and an unconditioned stimulus (UCS) if CS2 is presented simultaneously with a different CS (CS1) already associated with the UCS. It is well established with animal but not human subjects. In the two experiments presented here, the effect was clearly demonstrated with UCS = a computer-presented yellow square, CS1 = a blue square and CS2 = a noise (Expt 1) or two smaller white squares (Expt 2). The Kamin effect has, by some theorists, been attributed to switching of attention away from CS2, which conveys only redundant information. If so, the size of the effect should co-vary with indices of selective attention commonly used with human subjects. As predicted, the blocking effect was found to be smaller in subjects who displayed a high degree of incidental learning in either of two tasks in which intentional vs. incidental learning corresponded to (1) words vs. word position, or (2) a target initial word letter vs. non-target initial letters. We report elsewhere that the blocking effect is absent in acute schizophrenics. In the present experiments, however, there was no systematic relation between any of four measures of psychoticism, or intelligence, and either the blocking effect or incidental learning.

Adult↗
PubMed1990

Equivalence classes generated by sequence training.

In Experiment 1, 3, adult females were taught with verbal instructions and contingencies to select, in sequence, three arbitrary visual stimuli from an array of five stimuli. After four different sequences were taught, match-to-sample tests assessed emergent conditional relations among all stimuli that had been selected in the same order in the sequences. Subjects' performances indicated development of four stimulus classes, three based on ordinal position and one based on nonselection. Next, match-to-sample training established conditional relations between each of four novel figures and one member of each of the ordinal stimulus classes. Tests confirmed that the classes were equivalence classes, each expanded by one new member. In subsequent sequence tests, the new stimuli were selected in a sequence that was consistent with ordinal class membership. Experiment 2 replicated Experiment 1 with 2 different adult females, but the verbal instructions were omitted. Results were similar to Experiment 1, except that extensive review and retesting were required before expansion of the ordinal classes with the novel figures was observed.

Adult↗