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At least 307 records · Page 17Linked to original sources
PubMed1994

On the relationship between background EEG and the P300 event-related potential.

Background EEG was recorded from 24 subjects under eyes open/closed conditions for 5 min. The P3(00) event-related brain potential (ERP) was elicited with auditory stimuli when eyes were open/closed in the same subjects. Target stimulus probability was manipulated (0.20, 0.40, 0.60, 0.80) in different blocks under each eyes open/closed condition. Spectral analysis indicated that EEG power between 8 and 12 Hz demonstrated a similar scalp distribution as the P3 component of the ERP for the electrode sites employed. Spectral power and mean frequency were modestly correlated with P3 amplitude and peak latency primarily in the slower EEG bands, with associations observed across probability conditions and often strongest when target stimulus probability was .20. The results suggest that differences between individuals for EEG variation may contribute to P3 component variability, especially at the parietal recording site and under low target stimulus probability conditions when the P3 is largest and most stable.

Adolescent↗
PubMed1990

Pathological gambling treated with cognitive behavior therapy: a case report.

A novel approach to the cognitive behavioral treatment of pathological gambling is described. The approach is based on the hypothesis that biased information may form the basis of the rules governing gambling behavior. The treatment focused on modifying assumptions and beliefs underlying the gambling behavior of a 47-year-old male with a 26-year gambling history. Based on a 6-month follow-up, the intervention successfully reduced the frequency of the client's gambling behavior from 10 times per month in the 3 years prior to treatment to three total times in the 6-month follow-up period.

Alcoholism↗
PubMedDate not supplied

Objectives to direct the training of emergency medicine residents in off-service rotations: plastic surgery.

This is the fourth article in a continuing series on objectives for emergency medicine training; plastic surgery objectives will be presented. Plastic surgery topics overlap many in emergency medicine. Specific behaviorally based objectives for mastery of skills in plastic surgery are outlined. Specific references are provided for additional information and reinforcement in skill mastery. The basic concepts of plastic surgery are probably best learned by observation and supervised performance. Specific objectives provide guidance and direction for the didactic as well as the supervised experiences in skill mastery. These objectives provide a structure for systematically learning and mastering the content presented on a plastic surgical rotation or experience in emergency medicine training.

Education↗
PubMed2000

Taking advice, using information and knowing what you are doing.

Subjective descriptions of judgment policies have been found to be imperfect. This could be because subjective weights are obtained on just a single occasion after all judgments have been completed. It could also be because people have tended to state their perception of an ideal way of responding rather than their perception of how they actually responded. Finally, it could be because they experience difficulty in relating variation in stimulus dimensions to variation in quite different response dimensions. In our task, people made sales forecasts on the basis of four pieces of information. They also stated the weight they placed on each one and the weight they should have placed on it. The means of weights stated on each trial were more appropriate than those stated at the end of all trials. Stated actual weights were very similar to stated ideal weights. Weights were more appropriate when forecasts and cues varied along the same dimension than when they did not. Thus, our results are consistent with the view that all three factors affect people's ability to provide subjective descriptions of their judgment policies.

Adult↗
PubMed2000

Probability ratings in claustrophobic patients and normal controls.

Forty-nine DSM-IV diagnosed claustrophobics and 49 sex- and age-matched community controls, without any current or past psychiatric disorder, were asked to estimate the probability that three types if events would occur if they were in the described situations. The events were claustrophobic, generally negative, and positive in nature. The results showed that claustrophobics significantly overestimated the probability of events they specifically feared, i.e. the claustrophobic events, while there was no difference between the groups regarding generally negative events and positive events. This finding remained when the higher scores for claustrophobics on the Claustrophobia scale and the Anxiety Sensitivity Index were covaried out. The conclusion that can be drawn is that claustrophobics' probability ratings are characterized by distortions that are specifically connected to anxiety-arousing events and not negative events in general. The hypothesis is proposed that this may be explained by an exaggerated use of simplified rules-of-thumb for probability estimations that build on availability in memory, simulation, and representativity.

Adult↗
PubMed2001

Solving probabilistic and statistical problems: a matter of information structure and question form.

Is the human mind inherently unable to reason probabilistically, or is it able to do so only when problems tap into a module for reasoning about natural frequencies? We suggest an alternative possibility: naive individuals are able to reason probabilistically when they can rely on a representation of subsets of chances or frequencies. We predicted that naive individuals solve conditional probability problems if they can infer conditional probabilities from the subset relations in their representation of the problems, and if the question put to them makes it easy to consider the appropriate subsets. The results of seven studies corroborated these predictions: when the form of the question and the structure of the problem were framed so as to activate intuitive principles based on subset relations, naive individuals solved problems, whether they were stated in terms of probabilities or frequencies. Otherwise, they failed with both sorts of information. The results contravene the frequentist hypothesis and the evolutionary account of probabilistic reasoning.

Adult↗
PubMed2000

Gigerenzer's normative critique of Kahneman and Tversky.

Gigerenzer has argued that it may be inappropriate to characterize some of the biases identified by Kahneman and Tversky as "errors" or "fallacies," for three reasons: (a) according to frequentists, no norms are appropriate for single-case judgments because single-case probabilities are meaningless; (b) even if single-case probabilities make sense, they need not be governed by statistical norms because such norms are "content-blind" and can conflict with conversational norms; (c) conflicting statistical norms exist. I try to clear up certain misunderstandings that may have hindered progress in this debate. Gigerenzer's main point turns out to be far less extreme than the position of "normative agnosticism" attributed to him by Kahneman and Tversky: Gigerenzer is not denying that norms appropriate for single-case judgments exist, but is rather complaining that the existence and the nature of such norms have been dogmatically assumed by the heuristics and biases literature. In response to this complaint I argue that single-case probabilities (a) make sense and (b) are governed by probabilistic norms, and that (c) the existence of conflicting statistical norms may be less widespread and less damaging than Gigerenzer thinks.

Bias↗
PubMed2000

Impaired planning but intact decision making in early Huntington's disease: implications for specific fronto-striatal pathology.

Previous neuropsychological data have suggested that deficits in early Huntington's disease (HD) include executive impairments, which often are linked with frontal-lobe dysfunction. This study sought to investigate the profile of cognitive deficits using two computerised tasks whose performance is known to rely on intact functions of separate areas of the prefrontal cortex. Twenty patients with early HD and 20 matched controls were given the one-touch Tower of London, a stringent measure of visuo-spatial planning, and a decision making task, which involved selecting and gambling on outcomes on the basis of their differing probabilities. Patients were significantly less accurate than controls on the planning test, which is sensitive to frontal lobe lesions and is strongly associated with the dorsolateral prefrontal cortex in functional imaging studies. On the decision making task, patients were unimpaired on the quality of their decision making, in contrast to previous reports of impairment on this task in patients with ventromedial prefrontal cortex lesions. This dissociation of performance is discussed in terms of the usual path of progression of HD through the striatum and the resultant pattern of disruption of the functioning of the different cortico-striatal functional loops.

Adult↗
PubMed2000

Drug abusers show impaired performance in a laboratory test of decision making.

A defining feature of drug addiction is persistent drug use despite long-term adverse consequences. This study examined the performance of drug abusers on a neuropsychological test that requires evaluation of long-term outcomes in the presence of a complex set of mixed reward/punishment contingencies (the Gambling Task). In order to control for generalized deficits related to choice and planning, subjects were also administered the Wisconsin Card Sorting Task. Thirty polysubstance abusers were compared to a comparison group of 24 subjects who did not use illicit drugs of abuse. Drug abusers performed much more poorly on the Gambling Task (net score = 10.2 +/- 4.7, mean +/- s.e.m.) than controls (26.0 +/- 5.3), but did not differ from controls on the Wisconsin Card Sorting Task. The results show that drug abusers are more likely to make maladaptive decisions in the Gambling Task that result in long-term losses exceeding short-term gains. These findings indicate that the Gambling Task may be a useful model in laboratory studies of cognitive dysfunctions associated with drug abuse.

Adult↗
PubMed1997

Transynaptic modulation by insulin-like growth factor I of dendritic spines in Purkinje cells.

Purkinje cells synthesize insulin-like growth factor I and express insulin-like growth factor I receptors during their entire life. An additional source of insulin-like growth factor I for these cells is provided by climbing fiber afferents originating in the inferior olive nucleus. Recently we found that insulin-like growth factor I from the inferior olive is necessary for motor learning processes probably involving Purkinje cell synaptic plasticity. We now studied whether inferior olive insulin-like growth factor I influences the synaptic structure of Purkinje cells, because changes in synaptic morphology are related to neuronal plasticity events. We injected an insulin-like growth factor I antisense in the inferior olive of adult rats, a procedure which we previously found to elicit a significant and reversible decrease of insulin-like growth factor I levels in the contralateral cerebellum. Ultrastructural analysis of the cerebellar cortex of these animals showed a significant reduction in the size of dendritic spines on Purkinje cells of antisense-treated rats compared to controls. The decrease in spine size was linked to a diminished numerical density of dendritic spines on Purkinje cells, without affecting the numerical density of synapses in the molecular layer of the cerebellum. This reduction was not due to a change in the thickness of the molecular layer. Climbing or parallel fiber terminals were also unaffected. Taken together with previous findings, these results support a role for insulin-like growth factor I produced in the inferior olive in the maintenance of Purkinje cell synaptic plasticity.

Animals↗
PubMedDate not supplied

A priori expectancy bias in patients with panic disorder.

BACKGROUND: Several studies have indicated that phobic participants tend to overassociate fear-relevant stimuli and aversive outcomes, i.e, they show a covariation bias. Such a bias seems to be a powerful way to confirm danger expectations and enhance fear. Therefore, a covariation bias might be an important factor in the maintenance of fear. METHODS: To investigate a covariation bias in patients with panic disorder, we had 29 patients and 29 healthy control participants rate the a priori probabilities with which they would expect pictures of mushrooms, spiders, erotic scenes, and emergency situations to be paired with a tone, shock, or nothing. RESULTS: This is the first study to show that patients with panic disorder specifically overestimate the association between panic-relevant stimuli and a following negative consequence. This distorted contingency expectancy represents a panic-specific covariation bias, since it was not observable for other stimuli-consequence combinations and only to a significantly lesser degree in control participants. CONCLUSIONS: The underpinning hypothesis is that overestimation of threat plays a casual role in the origins and maintenance of anxiety. Thus anxiety may induce a covariation bias, which in turn may enhance the perceived threat, which in turn may intensify the anxiety etc. This reciprocal relationship between covariation bias and anxiety may have clinical implications for prediction and treatment in patients with panic disorder.

Adult↗
PubMed2000

Learning non-stationary conditional probability distributions.

While sophisticated neural networks and graphical models have been developed for predicting conditional probabilities in a non-stationary environment, major improvements in the training schemes are still required to make these approaches practically viable.

Models, Neurological↗
PubMed1997

Application of autonomous neural network systems to medical pattern classification tasks.

This paper presents a study of the application of autonomously learning multiple neural network systems to medical pattern classification tasks. In our earlier work, a hybrid neural network architecture has been developed for on-line learning and probability estimation tasks. The network has been shown to be capable of asymptotically achieving the Bayes optimal classification rates, on-line, in a number of benchmark classification experiments. In the context of pattern classification, however, the concept of multiple classifier systems has been proposed to improve the performance of a single classifier. Thus, three decision combination algorithms have been implemented to produce a multiple neural network classifier system. Here the applicability of the system is assessed using patient records in two medical domains. The first task is the prognosis of patients admitted to coronary care units; whereas the second is the prediction of survival in trauma patients. The results are compared with those from logistic regression models, and implications of the system as a useful clinical diagnostic tool are discussed.

Artificial Intelligence↗
PubMed1990

Random number generation by normal, alcoholic and schizophrenic subjects.

Controls (N = 45), schizophrenics (N = 20) and alcoholics (N = 23) were asked to choose at random a number between 1 and 10, 100 times. The correlation matrices of five different randomization indices were used to study within group variation; these matrices were similar for the normal and alcoholic groups, but very different for the schizophrenic group. The differences between the three groups were studied by canonical analysis and, in terms of the canonical variables, the mean performance of the normal group is clearly discriminated from that of the alcoholic and schizophrenic subjects.

Adult↗
PubMed1997

Probabilistic reasoning in deluded, depressed and normal subjects: effects of task difficulty and meaningful versus non-meaningful material.

BACKGROUND: Research indicates that deluded patients 'jump to conclusions' on probabilistic reasoning tasks. Two experiments were carried out with patients suffering from persecutory delusions and depressed and normal controls in order to determine whether this response bias is affected by task difficulty and the meaningfulness of the materials. METHODS: Tasks were variants of those employed by Huq et al. (1988) and Garety et al. (1991). In Experiment 1, subjects judged which of two bags a sequence of coloured beads had been taken from. Difficulty was manipulated by varying the ratios of coloured beads in the bags. In experiment 2, a neutral condition required judgements about coloured beads drawn whereas, in meaningful conditions, subjects had to judge whether personality characteristics described one of two individuals. RESULTS: In Experiment 1, estimates of certainty varied with task difficulty, and there was no evidence of 'jumping to conclusions' in the deluded group. In Experiment 2, all groups reached an initial level of certainty and reduced their estimates of certainty following disconfirmatory evidence more quickly in the meaningful conditions. Both clinical groups expressed higher certainty levels in early trials, and a greater magnitude of reduction in certainty following disconfirmatory information. These group differences were more evident in the meaningful conditions than in the neutral conditions. CONCLUSIONS: Probabilistic reasoning is affected by task difficulty and meaningfulness of materials in both deluded and depressed subjects. Observed reasoning abnormalities were not specific to the deluded group.

Adult↗
PubMed1992

The science of choosing the right decision threshold in high-stakes diagnostics.

Many diagnostic tasks require that a threshold be set to convert evidence that is a matter of degree into a positive or negative decision. Although techniques of decision analysis used in psychology help one select the particular threshold that is appropriate to a given situation and purpose, just the concept of adjusting the threshold to the situation is not appreciated in many important practical arenas. Testing for the human immunodeficiency virus (HIV) and for dangerous flaws in aircraft structures are used here as illustrations. This article briefly reviews the relevant techniques and develops those two examples with data. It suggests that use of the decision techniques could substantially benefit individuals and society and asks how that use might be facilitated.

Aircraft↗
PubMed1998

Young children's predictions of illness: failure to recognize probabilistic causation.

In this study preschool-age children made predictions for a set of salient probabilistic causes. Of interest was whether the children viewed outcomes of familiar causes of illness as definite or as probabilistic. In Experiment 1, children judged that a common cause would affect all members of a group in the same way. In Experiment 2, children believed they could definitely predict illness outcomes in a single case. These judgments contrasted with adults' variable and uncertain predictions. Children did recognize uncertainty in outcomes dependent on voluntary choices. Experiment 3 presented both high- and low-potency causes of illness. Children treated all causes of illness as nonprobabilistic. These results are discussed in the context of children's understanding of causal relations and the sources of variability.

Adult↗