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PubMed2000

Bile duct injury during laparoscopic cholecystectomy: myth or reality of the learning curve?

BACKGROUND: Bile duct injury (BDI) is a severe complication of laparoscopic cholecystectomy (LC) that is probably related to the effects of the learning curve. The aim of this prospective, institutional, and longitudinal study is to compare the incidence of BDI during LC in relation to the progressive experience of surgeons. METHODS: A total of 784 LC were examined during a 6-year period. They were divided into the following three consecutive groups: group A (1993-94), group B (1995-96), and group C (1997-98). Incidence and type of BDI, experience of the surgeon, intra- or postoperative diagnosis, treatment performed to repair the injury, and early and late morbidity and mortality were evaluated. RESULTS: The overall incidence of BDI was 1.4%. There were three cases of transection of the common bile duct, four partial lesions of the bile duct, and four cystic leakages. The number of BDI was maintained over the three different time periods; there were no statistical differences in the proportion of injuries among groups. Most BDI were incurred by experienced surgeons. In all, 36% of BDI were recognized intraoperatively. Hepaticojejunostomy, direct suture over a T-tube, and closure of the cystic stump were done to repair BDI. There was no additional morbidity or mortality in the patients with BDI. CONCLUSIONS: No relation was found between the experience of the surgeon and the number of BDI over the different periods of time. Therefore, BDI during LC cannot be attributed solely to the learning curve.

Adult↗
PubMedDate not supplied

The relationship between serum testosterone level and visuomotor learning in right-handed young men.

The relationship between serum testosterone level and visuomotor of learning of hand skill was studied in right-handed young men. Hand skill was assessed by a peg moving task. Peg moving times for the right and left hands linearly decreased at each successive trial (visuomotor learning). The peg moving times for the right and left hands were found to be negatively linearly related to serum testosterone levels: there was a direct relationship between hand skill and testosterone, which was more prominent for the right than the left hand. The slopes of the learning curves for the right hand were found to be equal in subjects with low, normal, and high testosterone. The intercepts of these curves exhibited a shift toward a better hand skill from low- to high-testosterone subjects. The visuomotor learning for the left hand was found to be better in subjects with normal and high testosterone than those with low testosterone. It was concluded that testosterone would favor the visuomotor development especially of the left cerebral hemisphere, probably at puberty; the motor learning of this hemisphere does not seem to be associated with testosterone. Testosterone seems to be advantageous for the visuomotor performance as well as for the motor learning of the right cerebral hemisphere.

Adolescent↗
PubMed2001

Use of warnings in an attentionally demanding detection task.

The study assessed the use of binary warnings in a detection task with high attentional demands. Participants in the experiment had to decide whether to continue or halt production based on a briefly displayed number that indicated a temperature level. The short time that the number was displayed required that participants focus on the display area. Participants were rewarded for production when the system was intact and were heavily penalized for decisions to produce under dangerous temperature levels. Color-coded warning cues (green for safe, red for danger) were displayed to the participants prior to number presentation. The experimental conditions differed in the validity of the cue and in the probability of red cues. Results showed significant learning for all conditions. Participants tended to ignore the nonvalid and low-validity cues and rely only on highly valid cues. However, the mere existence of cues affected participants' general tendency to take risks. Actual or potential applications of this research include improving systems that require operators to devote attention to complex tasks while receiving and responding to warnings.

Adolescent↗
PubMed2004

Implicit learning of musical timbre sequences: statistical regularities confronted with acoustical (dis)similarities.

The present study investigated the influence of acoustical characteristics on the implicit learning of statistical regularities (transition probabilities) in sequences of musical timbres. The sequences were constructed in such a way that the acoustical dissimilarities between timbres potentially created segmentations that either supported (S1) or contradicted (S2) the statistical regularities or were neutral (S3). In the learning group, participants first listened to the continuous timbre sequence and then had to distinguish statistical units from new units. In comparison to a control group without the exposition phase, no interaction between sequence type and amount of learning was observed: Performance increased by the same amount for the three sequences. In addition, performance reflected an overall preference for acoustically similar timbre units. The present outcome extends previous data from the domain of implicit learning to complex nonverbal auditory material. It further suggests that listeners become sensitive to statistical regularities despite acoustical characteristics in the material that potentially affect grouping.

Acoustics↗
PubMed2006

The consequences of surrendering a degree of freedom to the participant in a contingency assessment task.

Many studies of contingency judgments have used a task in which, on each trial, the participant is free either to respond or not to respond, and an outcome may, or may not, be presented. Typically, the experimenter specifies a nominal value for the contingency between responding and outcome, but the actual values of a variety of variables experienced by a particular participant depend on that participant's frequency of responding. The results of computer simulations of various strategies for implementing the contingency manipulation, and the results of an experiment, indicate that the same nominal contingency value will lead to considerable variability in the actual contingency experienced by participants. Moreover, nominal contingency manipulations are confounded with the probability that the subject experiences an outcome. While researchers might be aware of these issues, not enough attention has been paid to their potential impact.

Adaptation, Psychological↗
PubMed1992

Total amount learned versus learning rate of verbal and nonverbal information, in differentiating left-from right-brain injured patients.

Twenty Left-Brain Damaged (LBD), 20 Right-Brain Damaged (RBD), and 20 control subjects were compared on three different learning tasks: (a) verbal, the Paired Associate Learning subtest of the Wechsler Memory Scale; (b) figural, the Gollin Incomplete Figures task, which can be easily verbalized, and (c) spatial, the Stylus Maze. When learning ability was measured, by assessing the total amount learned (sum of items learned in all trials), the results showed that, on all three tasks, the control group's performance significantly surpassed that of the patient groups. The RBD group performed better than the LBD group on the verbal learning task, while LBD subjects performed better than their RBD counterparts on the spatial learning task. No significant difference between the two patient groups was detected on the figural task, suggesting that a task using visually and verbally codable stimuli is not useful in differentiating between LBD and RBD groups. When the learning rate was measured, similar results were obtained in the verbal and figural task. However, in the spatial task, the learning rates of the three groups did not significantly differ, probably because the specific task used required procedural learning, which is normally preserved in amnesics.

Journal Article↗
PubMed2002

Environmental context and recognition: the role of recollection and familiarity.

Evidence for effects of changed environmental context on recognition has been equivocal. Using 3 experiments, the author investigated the role of environmental context from a dual-processing approach. Experiment 1 showed that testing word recognition in a novel context led to a reliable decrement but only for recognition accompanied by conscious recollection, with familiarity-based recognition judgments being unaffected. This was replicated in Experiment 2 using stimuli that were novel to the participants (nonwords). Experiment 3 showed that the decrement in recollection also occurred when the changed-context condition involved presenting items in a different but familiar context. The results suggest that effects of environmental context will only be found when recognition is accompanied by conscious recollection and that this effect is due to a specific item-context association.

Adult↗
PubMed1974

Olfactory learning-set formation in rats.

Rats trained on 16 two-odor discrimination problems showed rapid acquisition of a learning set and one-trial learning by the end of the problem series. Learning to sample odor cues before responding and adoption of a "win-stay, lose-shift" strategy probably accounts for the virtually errorless learning. Learning-set performance of rats trained with odor stimulus comparable to that reported for primates trained on visual cues.

Animals↗
PubMed1989

The relationship between learning disability and delinquency: a review and reappraisal.

Data are presented on the prevalence of learning disabilities among populations of delinquents. Current hypotheses proposed to explain the relatively high prevalence rate are examined in the context of the research literature pertaining to the psychosocial characteristics of youngsters with learning disabilities and the research literature pertaining to delinquency. A multifactorial explanation is offered, according to which the probability of a youngster with a learning disability becoming delinquent is seen as a consequence of the interaction between specific elements of learning disabilities and specific psychosocial correlates of delinquency.

Causality↗
PubMed2006

A statistical property of multiagent learning based on Markov decision process.

We exhibit an important property called the asymptotic equipartition property (AEP) on empirical sequences in an ergodic multiagent Markov decision process (MDP). Using the AEP which facilitates the analysis of multiagent learning, we give a statistical property of multiagent learning, such as reinforcement learning (RL), near the end of the learning process. We examine the effect of the conditions among the agents on the achievement of a cooperative policy in three different cases: blind, visible, and communicable. Also, we derive a bound on the speed with which the empirical sequence converges to the best sequence in probability, so that the multiagent learning yields the best cooperative result.

Learning↗
PubMed2006

Reasoning with conditionals: a test of formal models of four theories.

The four dominant theories of reasoning from conditionals are translated into formal models: The theory of mental models (Johnson-Laird, P. N., & Byrne, R. M. J. (2002). Conditionals: a theory of meaning, pragmatics, and inference. Psychological Review, 109, 646-678), the suppositional theory (Evans, J. S. B. T., & Over, D. E. (2004). If. Oxford: Oxford University Press), a dual-process variant of the model theory (Verschueren, N., Schaeken, W., & d'Ydewalle, G. (2005). A dual-process specification of causal conditional reasoning. Thinking &Reasoning, 11, 278-293), and the probabilistic theory (Oaksford, M., Chater, N., & Larkin, J. (2000). Probabilities and polarity biases in conditional inference. Journal of Experimental Psychology: Learning, Memory, and Cognition, 26, 883-899). The first three theories are formalized as multinomial models. The models are applied to the frequencies of patterns of acceptance or rejection across the four basic inferences modus ponens, acceptance of the consequent, denial of the antecedent, and modus tollens. Model fits are assessed for two large data sets, one representing reasoning with abstract, basic conditionals, the other reflecting reasoning with pseudo-realistic causal and non-causal conditionals. The best account of the data was provided by a modified version of the mental-model theory, augmented by directionality, and by the dual-process model.

Adolescent↗
PubMed1969

Autoradiographic demonstration of biochemical changes in the limbic system during avoidance training.

After injection of leucine-H(3), members from eight triplets of rats were assigned to one of three treatment groups: avoidance learning, the same handling and shocks without opportunity to learn, or passive control. Autoradiographic grains over all nuclei were counted "blind." In the hippocampus, the number of grains for the learning rats was reliably greater than that for either control. The differences approached statistical significance in the entorhinal cortex and the septal area but not in other brain areas or in the liver. Although the processes responsible for the increased incorporation are not yet defined, these changes probably are the result of learning rather than of stress.

Analysis of Variance↗
PubMed1990

Implicit learning in patients with Alzheimer's disease.

We examined implicit memory using priming and procedural learning tasks in patients with probable Dementia-Alzheimer's Type (DAT) to examine whether priming and procedural processes could be dissociated and whether task specificity was a factor in DAT patient performance. Priming was tested using a word recognition paradigm (perceptual priming) and by repeated administrations of a fragmented objects test (long term priming). Procedural learning was tested using repeated and random sequences on a choice serial reaction time task and by repeated administration of a puzzle map of the United States. DAT patients were compared to hospitalized depressed patients, patients suffering from Progressive Supranuclear Palsy (PSP), and normal controls. We found that DAT patients demonstrated marginal but significant implicit learning on both procedural learning and perceptual priming tasks. DAT patients performed relatively better on the procedural learning task than a perceptual priming task compared to PSP patients, suggesting that priming of meaningful stimuli is subserved by cortical structures whereas procedural motor responses to simple serial visual stimulus patterns can be maintained by subcortical systems. Furthermore, our findings suggest that priming and procedural processes can be dissociated and that task specificity is a factor in interpreting the results of implicit learning paradigms in DAT patients. The implications of these results for models of knowledge representation and memory processes as well as the way they can serve as models for testing nootropic drug effects are discussed.

Aged↗
PubMed2001

Unsupervised statistical learning of higher-order spatial structures from visual scenes.

Three experiments investigated the ability of human observers to extract the joint and conditional probabilities of shape co-occurrences during passive viewing of complex visual scenes. Results indicated that statistical learning of shape conjunctions was both rapid and automatic, as subjects were not instructed to attend to any particularfeatures of the displays. Moreover, in addition to single-shape frequency, subjects acquired in parallel several different higher-order aspects of the statistical structure of the displays, including absolute shape-position relations in an array, shape-pair arrangements independent of position, and conditional probabilities of shape co-occurrences. Unsupervised learning of these higher-order statistics provides support for Barlow's theory of visual recognition, which posits that detecting "suspicious coincidences" of elements during recognition is a necessary prerequisite for efficient learning of new visual features.

Adult↗
PubMed2006

Context switch effects on acquisition and extinction in human predictive learning.

Four experiments tested context switch effects on acquisition and extinction in human predictive learning. A context switch impaired probability judgments about a cue-outcome relationship when the cue was trained in a context in which a different cue underwent extinction. The context switch also impaired judgments about a cue trained in a context different from the extinction context, whenever this training was concurrent with extinction of another cue. After extinction, new cue-outcome relationships learned, even in a different task, became context specific. Moreover, renewal was consistently observed. It is suggested that context switch effects result from a process by which ambiguity leads participants to attend to the contexts.

Adolescent↗