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PubMed1997

Effects of habenular lesions upon two-way active avoidance conditioning in rats.

To evaluate if habenular nuclei lesions improve, impair, or have no effects on two-way active avoidance acquisition and/or retention, rats in a Lesion group were subjected to bilateral electrolytical lesions of this complex, while control rats were sham-operated (Sham group). Once recovered from the stereotaxic procedures, rats were submitted to 5 training sessions (10 trials each, one session per day) of two-way active avoidance conditioning. Ten days after the last training session, another session was administered in order to test the long-term retention of the task. Results indicated that habenular lesions did not affect the overall performance of the rats during either the acquisition sessions or the retention session of two-way active avoidance. We suggest that habenular lesions can affect the acquisition of several learning tasks, probably through their role in modulating stress responses and/or arousal states. The nature of these effects (whether facilitative, detrimental, or neutral) might depend on the interaction between several factors such as the kind of task, the specific conditioning procedures (which may generate different stress levels), and the specific area destroyed by the lesion.

Animals↗
PubMed1998

Influences of prior knowledge on selective weighting of category members.

Three experiments addressed how prior theories affect categorization, comparing the influence of theory-congruent versus theory-incongruent category members. Subjects observed descriptions of persons, some congruent with prior knowledge and some incongruent, then made transfer judgments. In Experiment 1, subjects were given a relatively long time to study each description, whereas in Experiment 2 study time was manipulated between subjects. In Experiment 3, learning was self-paced by each subject. It was found that, with enough study time, prior knowledge had 2 distinct influences. First, prior knowledge provided an initial representation, subsequently revised in light of new observations. Second, incongruent observations had more impact than congruent observations on categorization. In comparison, when study time was more limited, revision proceeded in a Bayesian manner, in that congruent and incongruent observations had equal impacts.

Adult↗
PubMed1994

[Discrete dynamic systems: the effect of perceptual structuring on composition and transfer of knowledge about operating sequences].

This paper reports two experiments in which we explored the impact of perceptual grouping of elements on the organization and use of knowledge about how to operate a device. Experiment 1 explored the effects of different perceptual display regions on the creation of chunks when sequences of inputs had to be reproduced. The effects of regions were not homogeneous, but rather their influence depended on interactions between different modalities and learning conditions. Experiment 2 investigated the influence of grouping-induced composition of knowledge elements on the transfer of sequential knowledge. Two different learning criteria were used in the acquisition phase to manipulate the degree of composition of knowledge elements. In the transfer phase, subjects could transfer (1) the whole sequence of one region, (2) two partial sequences of adjacent regions, or (3) single components. It was found that regional invariance and immediate succession of components were both important for transfer performance. These results suggests that the temporal order of regions is important for the organization and use of sequential knowledge, and not the grouping of elements by itself.

Adult↗
PubMed1989

On the status of nonconscious processes in human cognition: comment on Reber.

Two issues are discussed. The first one pertains to the generality of the nonconscious learning processes and their somewhat paradoxical status in cognitive psychology. We argue that the ability of the human cognitive system to nonconsciously acquire complex knowledge structures is one of its elementary and indispensable properties. Moreover, the existence of this ability constitutes one of the necessary metatheoretical assumptions of contemporary cognitive psychology. Nevertheless, the contemporary cognitive psychology literature often implies that it is only one of many controversial and unusual phenomena. The second issue pertains to the distinction between the so-called primitive unconscious and the sophisticated unconscious as proposed by Reber (1989).

Concept Formation↗
PubMed2000

Unsupervised learning of binary vectors: a Gaussian scenario.

We study a model of unsupervised learning where the real-valued data vectors are isotropically distributed, except for a single symmetry-breaking binary direction Bin¿-1,+1¿(N), onto which the projections have a Gaussian distribution. We show that a candidate vector J undergoing Gibbs learning in this discrete space, approaches the perfect match J=B exponentially. In addition to the second-order "retarded learning" phase transition for unbiased distributions, we show that first-order transitions can also occur. Extending the known result that the center of mass of the Gibbs ensemble has Bayes-optimal performance, we show that taking the sign of the components of this vector (clipping) leads to the vector with optimal performance in the binary space. These upper bounds are shown generally not to be saturated with the technique of transforming the components of a special continuous vector, except in asymptotic limits and in a special linear case. Simulations are presented which are in excellent agreement with the theoretical results.

Bayes Theorem↗
PubMed1985

Hypothalamic neuropeptides and memory.

Vasopressin and oxytocin exert pronounced effects on behavior by a direct action on the brain. A single injection of vasopressin results in a long-term inhibition of extinction of a conditioned avoidance response suggesting that vasopressin triggers a long-term effect on the maintenance of a learned response, probably by facilitation of memory processes. In addition vasopressin improves passive avoidance behavior, facilitates retention of sexually motivated T-maze choice behavior in male rats, delays extinction of an appetitive discrimination task, affects approach behavior to an imprinting stimulus in ducklings, delays the postcastration decline in copulatory behavior in male rats, prevents or reverses amnesia induced by electroconvulsive shock, CO2 inhalation, pentylenetetrazol or puromycin. The majority of these effects may be explained by stimulatory influences of vasopressin on memory processes. Generally oxytocin exerts effects which are opposite to those of vasopressin and it has been suggested that oxytocin may be an amnesic neuropeptide. Evidence has been obtained that endogenous vasopressin and oxytocin play a physiological role in brain processes related to memory. Various limbic system structures seem to act as the anatomical substrate for the behavioral effects of vasopressin and different neurotransmitter systems seem to be involved. It is postulated that in case vasopressin affects retrieval processes the site of action is located in the amygdala and the dentate gyrus of the hippocampal complex with dopamine and serotonin as the respective neurotransmitter systems involved.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Risk for alcoholism, antisocial behavior, and response perseveration.

Numerous studies have demonstrated the existence of an association between alcoholism and antisocial personality (ASP). The present study tested two hypotheses: First, that nonalcoholic men with a multigenerational familial history (MGH) of alcoholism would play more cards on a card task that has been shown previously to differentiate antisocial populations from normals and, second, that MGH subjects would display more evidence of ASP on two personality questionnaires: The Self-Report Psychopathy scale and the Socialization scale of the California Psychological Inventory. A total of 28 subjects (14 MGH and 14 family history negative for alcoholism [FH-]) were employed in this study. MGH subjects played significantly more cards during the card task than did FH- subjects. However, the two groups did not differ on the ASP questionnaires. The possibility that a subtle frontal-lobe deficit, rather than ASP per se, underlies the poorer performance of the MGH males is discussed.

Adult↗
PubMed2000

Preparatory attention: experiment and theory.

This study investigated attention to a spatial location using a new spatial preparation task. Participants responded to a target dot presented in the center of a display and ignored a distractor dot presented to the right or left of the center. In an attempt to vary the level of preparatory attention directed to the target, the distractor dot was presented prior to the onset time of the target and the relative frequency of distractor dots to target dots within a block of trials was varied. The results from the first three experiments showed that when instructions induce weak preparatory attention to the target location, response times to a target on target-only trials increase substantially as the percentage of trials containing a distractor increases from 0 to 75%. In Experiments 2 and 3, instructions and display saliency were used to induce strong preparatory attention to the target location, resulting in almost constant response times across distractor percentages. Experiment 4 varied percentage of target trials in the absence of distractors, with the result that response times decreased as target trial percentage increased. Accounts of these data by early "activity-based" and late "criterion-based" attention theories are compared, and the early theory is given a more detailed description within the context of a cognitive neuroscience theory of attention.

Adolescent↗
PubMed1998

Categorical inference is not a tree: the myth of inheritance hierarchies.

One enduring principle of rational inference is category inclusion: Categories inherit the properties of their superordinates. In five experiments, I show that people do not consistently apply this principle when evaluating categorical arguments involving natural categories and a single nonexplainable predicate such as all electronic equipment has parts made of germanium, therefore all stereos have parts made of germanium. Participants frequently did not apply the category inclusion rule despite affirming the relevant categorical relation (e.g., stereos are electronic equipment). They failed to apply the rule even when categories were universally quantified unambiguously. Instead, judgments tended to be proportional to the similarity between premise and conclusion categories. Neglect of category inclusion relations was observed using arguments concerning natural kinds, artifacts, and social kinds.

Adult↗
PubMed1996

Reasoning from memory: a lifespan inquiry into the necessity of remembering when reasoning about class inclusion.

In the current experiment, we evaluated the relationship between reasoning and remembering across the lifespan (10-, 13-, 15-, 23-, and 67-year-olds) using color and number class-inclusion tasks. Subjects made judgments when memory load or information load was either high or low. Reading latency, choice latency, and choice accuracy data were collected and analyzed using formal models that partitioned memory and reasoning as well as type of reasoning strategy. The results showed that: (1) study skills, as indexed by reading latency, were sophisticated across the lifespan; (2) the difference between color and number choice latencies increased with age; (3) reasonably consistent effects were obtained as a function of increasing memory load, with the quality of both reasoning and remembering being adversely affected; (4) different effects were obtained at each age as a function of increasing information load; and (5) the major developmental trend across the lifespan was a tradeoff between class-inclusion and subclass-subclass forms of reasoning. A number of extant theoretical approaches were discussed, none of which were able to account for variations in class-inclusion performance across the lifespan. What was clear, however, was that memory-reasoning dependencies must be incorporated into any comprehensive theory of cognitive development across the lifespan.

Adolescent↗
PubMed1989

Mental representation and hypothetico-deductive reasoning: the case of the THOG problem.

This article reports three experiments that deal with the source of the difficulty of Wason's (1977) THOG problem. The solution of this problem demands both the postulation of hypotheses and a combinatorial analysis of their consequences. Experiment 1 showed that the generation of the hypotheses is not in itself sufficient to solve the problem. Experiment 2 showed that a version presenting a plausible context for separating the level of data from that of hypotheses produced a better performance than both the original abstract version and a thematic version lacking the plausible context separating the levels. Experiment 3 gave evidence that this context can produce facilitation even with the geometric material of the classic version. This experiment also showed that a pictorial presentation of data and a verbal presentation of hypotheses affect performance negatively. The results demonstrate the role of problem representation in problem solving, and, in particular, the role of homogeneity in representing data and hypotheses in hypothetico-deductive reasoning.

Adult↗
PubMed1992

Children and chess expertise: the role of calibration.

Three studies of calibration are reported. Calibration refers to the accuracy with which one can predict one's own performance. In the first study child chess players, non-chess playing parents, and statistics students were asked to predict chances of winning chess games against hypothetical opponents. These subjective probabilities were compared to the actual probabilities, based on the Elo rating system. Better players' predictions were better calibrated. Confidence and ratings are negatively correlated, indicating that with lower ratings, players re overconfident. Skilled child players' predictions were better calibrated than any of the adults'. In the second study subjects were asked to estimate chances of winning in conjunctive situations, e.g., winning all the rounds in a tournament. Again, better child players were more accurate in their predictions and more accurate than adults. In the third study, child players were asked to predict their chances of winning in a non-chess domain after hearing a hypothetical win/loss history. Higher-rated players' predictions were again better calibrated, even though the domain was outside their expertise. The motivational and cognitive implications of calibration are discussed.

Achievement↗
PubMed1991

Effects of preliminary information in a Go versus No-go task.

A series of studies using a Go versus No-go task examined the question of whether preliminary information available early in the recognition of a stimulus is made available to later processes before stimulus recognition is finished, a question relevant to the controversy between discrete and continuous models. Experiment 1 showed that a Go response is faster following a cue indicating that the response probably would be required than following a cue indicating it probably would not be required. Experiments 2-7 were conducted to find out whether analogous preparation occurred when probability of the Go response was signalled by easily discriminable features of a single stimulus rather than a separate cue. The effect was observed when the easily discriminable features uniquely determined the name of the stimulus letter, but not when they merely indicated that the stimulus name was one of two visually similar letters. These results are consistent with the Asynchronous Discrete Coding model, in which the perceptual system makes available to later processes only preliminary information corresponding to discretely activated stimulus attributes.

Attention↗
PubMed1994

Treatment of pathological gamblers: an experimental study.

The efficacy of a behavioral treatment for pathological gamblers, including cognitive interventions, problem solving and relapse prevention is examined. Three pathological gamblers meeting DSM-III-R criteria were studied in an experimental multiple baseline design. By the end of treatment the subjects ceased all gambling behaviors, increased their perception of self-control of gambling, and evaluated their problems as less severe. Therapeutic gains were maintained at 6- and 9-month follow-ups. The importance of problem solving and the modification of erroneous perceptions in treatment programs for pathological gambling is discussed.

Adult↗