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PubMed2000

Launching the effect: representations of causal movements are influenced by what they lead to.

We investigated whether the representation of an observed causal movement is influenced by its observed effect. Subjects watched displays showing collisions between two objects. In this "launching event" (Michotte, 1946/1963), one of the two objects (Object A) started to move and set a second, initially stationary, object (Object B) into motion, which gave a strong impression of apparent causality. The apparent effectiveness of A's movement was manipulated by varying the velocities of A and B. When the velocity of B was higher than that of A, the effectiveness of the collision was high; when it was smaller it was low. Then, subjects were asked to reproduce the velocity of the causal movement. Reproduced velocity followed the velocity of both Object A and Object B, which supports the hypothesis that the effect of a movement is integrated with its apparent cause. However, when apparent causality was reduced by changing the direction of motion of B or by covering the point of collision, the influence of the effect on the representation of the cause persisted, suggesting that retroactive interference may account for the findings. The interference effect could not be reduced to temporal recency or spatial integration and was not obtained in the reverse temporal order (proactive interference). Rather, the two successive movements were blended in memory.

Adult↗
PubMed2000

Move evaluation as a predictor and moderator of success in solutions to well-structured problems.

This paper presents three studies concerned with the evaluation of moves in solutions to Tower of Hanoi problems and the effect that such evaluation processes have on solution success. The existing literature on problem solving suggests that verbalizing whilst solving a problem can have a positive effect upon performance. However, such verbalization has to be directed toward an explicit evaluation of particular moves. What remains unclear is whether evaluation without verbalization has the same effects or whether some characteristic of the process of verbalization gives rise to improved performance on such tasks. For example, the act of verbalizing per se may simply mean that more processing time is directed toward the problem-solving process. The studies reported in this paper suggest that the process of evaluation may be independent of verbalization processes and that non-verbal evaluation of moves (indicated by a key press) produces the same effects as a verbal evaluation of such moves. Moreover, the process of evaluating moves appears to produce a form of behaviour that is prone to disruption via the administration of secondary tasks, whereas non-evaluated solutions are not. This may suggest that problem solvers who engage in evaluation processes develop an explicit representation of the strategies used to solve the problem.

Adult↗
PubMed2000

The suppression of q card selections: evidence for deductive inference in Wason's selection task.

The results of three experiments investigating the role of deductive inference in Wason's selection task are reported. In Experiment 1, participants received either a standard one-rule problem or a task containing a second rule, which specified an alternative antecedent. Both groups of participants were asked to select those cards that they considered were necessary to test whether the rule common to both problems was true or false. The results showed a significant suppression of q card selections in the two-rule condition. In addition there was weak evidence for both decreased p selection and increased not-q selection. In Experiment 2 we again manipulated number of rules and found suppression of q card selections only. Finally, in Experiment 3 we compared one- and two-rule conditions with a two-rule condition where the second rule specified two alternative antecedents in the form of a disjunction. The q card selections were suppressed in both of the two-rule conditions but there was no effect of whether the second rule contained one or two alternative antecedents. We argue that our results support the claim that people make inferences about the unseen side of the cards when engaging with the indicative selection task.

Choice Behavior↗
PubMed2000

Card Perseveration Task performance and post-task feeling states: relationship to drug use in adolescents.

This study examined whether performance on the Card Perseveration Task (Card Task) and self-report of feeling state after the task are related to self-report of drug use. The evaluation was of 64 adolescents from an adolescent psychiatric outpatient clinic (40 males, aged 15.5 years, SD = 1.6; 24 females aged 16.9 years, SD = 1.5). Drug use histories were obtained using a substance dependence symptom checklist based on DSM-III-R. The Card Task was administered, and after completion, a Post-Task Self-Report (PTSR) was administered. A factor analysis with varimax rotation grouped the 28 items of the PTSR into Distress, Happy, Satisfied, and Wanting to Win subscales. Correlations of drug use with performance on the Card Task and the PTSR subscales were obtained. Cards Played on the Card Task were correlated with alcohol (cc = .31, p < or = .01); marijuana (cc = .35, p < or = .01) and polydrug (cc = .26, p < or = .05) dependence symptoms. Money Won on the Card Task was correlated negatively with nicotine (cc = -.26, p < or = .05) and marijuana (cc = -.27, p < or = .05) dependence symptoms. The PTSR Distress subscale correlated with nicotine (cc = .49, p < or = .001), alcohol (cc = .37, p < or = .01), marijuana (cc = .39, p < or = .01), and polydrug (cc = .49, p < or = .001) dependence symptoms. These findings provide evidence that both the Card Task and feeling states associated with task performance are related to self-reports of drug use.

Adolescent↗
PubMed2006

Dominance in vertebrate broods and litters.

Drawing on the concepts and theory of dominance in adult vertebrates, this article categorizes the relationships of dominance between infant siblings, identifies the behavioral mechanisms that give rise to those relationships, and proposes a model to explain their evolution. Dominance relationships in avian broods can be classified according to the agonistic roles of dominants and subordinates as "aggression-submission," "aggression-resistance," "aggression-aggression," "aggression-avoidance," "rotating dominance," and "flock dominance." These relationships differ mainly in the submissiveness/pugnacity of subordinates, which is pivotal, and in the specificity/generality of the learning processes that underlie them. As in the dominance hierarchies of adult vertebrates, agonistic roles are engendered and maintained by several mechanisms, including differential fighting ability, assessment, trained winning and losing (especially in altricial species), learned individual relationships (especially in precocial species), site-specific learning, and probably group-level effects. An evolutionary framework in which the species-typical dominance relationship is determined by feeding mode, confinement, cost of subordination, and capacity for individual recognition, can be extended to mammalian litters and account for the aggression-submission and aggression-resistance observed in distinct populations of spotted hyenas and the "site-specific dominance" (teat ownership) of some pigs, felids, and hyraxes. Little is known about agonism in the litters of other mammals or broods of poikilotherms, but some species of fish and crocodilians have the potential for dominance among broodmates.

Aggression↗
PubMed2004

Application of influence diagrams to prostate intensity-modulated radiation therapy plan selection.

The purpose is to incorporate clinically relevant factors such as patient-specific and dosimetric information as well as data from clinical trials in the decision-making process for the selection of prostate intensity-modulated radiation therapy (IMRT) plans. The approach is to incorporate the decision theoretic concept of an influence diagram into the solution of the multiobjective optimization inverse planning problem. A set of candidate IMRT plans was obtained by varying the importance factors for the planning target volume (PTV) and the organ-at-risk (OAR) in combination with simulated annealing to explore a large part of the solution space. The Pareto set for the PTV and OAR was analysed to demonstrate how the selection of the weighting factors influenced which part of the solution space was explored. An influence diagram based on a Bayesian network with 18 nodes was designed to model the decision process for plan selection. The model possessed nodes for clinical laboratory results, tumour grading, staging information, patient-specific information, dosimetric information, complications and survival statistics from clinical studies. A utility node was utilized for the decision-making process. The influence diagram successfully ranked the plans based on the available information. Sensitivity analyses were used to judge the reasonableness of the diagram and the results. In conclusion, influence diagrams lend themselves well to modelling the decision processes for IMRT plan selection. They provide an excellent means to incorporate the probabilistic nature of data and beliefs into one model. They also provide a means for introducing evidence-based medicine, in the form of results of clinical trials, into the decision-making process.

Aged↗
PubMed2005

Deficits in decision-making in head injury survivors.

Many survivors of head injury suffer chronic personality changes, such as increased impulsivity and a lack of insight and poor judgment. These changes are well recognized and likely to affect the ability to make decisions. However, systematic investigations into their nature have been limited. This study aims to explore the nature of decision making in head injury survivors using a computerized task. Forty-three head injury survivors and a group of 29 matched controls completed the computerized task. The task required participants to make a probability-based choice and to further qualify this choice with an associated "bet." This betting component allows an assessment of the participant's level of confidence in the decision, via the affective evaluation of its possible consequences in terms of points won or lost. The survivors were found to be slow at making the probability- based choice. Whilst at highly favorable odds, the survivors chose the most likely option in a similar manner to the controls, they chose the most likely option less often than the controls at less favorable odds. Examination of the survivors' betting behavior revealed that they responded impulsively compared to controls. This pattern of prolonged decision making and poor quality of decisions is similar to that found in patients with orbitofrontal cortex lesions, whilst impulsive betting has been associated with abnormalities of the dopamine system. These complex deficits in decision making may contribute to difficulties with poor judgment and inhibition in head injury survivors.

Adolescent↗
PubMed2004

Age-related differences in response preparation: the role of time uncertainty.

This study explored the ability of younger and older participants to use a variable preparatory interval (PI) to enhance reaction time (RT) performance. In Experiment 1, 30 seniors and 15 young adults completed simple and choice RT tasks with short and long variable PIs. RT decreased with increasing PI duration in both younger and older adults, but the PI effect was larger in elderly individuals. The results of Experiment 2 (20 seniors and 20 young adults) showed an equivalent preparatory effect in older and younger adults when the probability of the shortest PI was increased. These findings suggest that older adults do not prepare as well as younger adults for unlikely events and that time uncertainty affects age-related differences in response preparation.

Adult↗
PubMed2006

Effects of biasing the location of stimulus presentation, and the muscarinic cholinergic receptor antagonist scopolamine, on performance of a 5-choice serial reaction time attention task in rats.

A major purpose of the present studies was to determine the effects of varying the relative frequency, or bias, of stimulus presentation at different locations in a five-choice serial reaction time attention task. Training sessions were conducted in which the stimulus duration was held constant at 2 s and, initially, stimuli were presented with equal probability above each of the levers. During testing sessions, however, stimulus duration was either 0.2 or 2 s, and the frequency of presentation was varied among no bias, a middle bias, a left bias or a right bias condition. The training conditions were then changed such that the frequency of presentation was always a left bias, and test sessions were again conducted with no, middle, left or right bias. In the presence of the 0.2-s, but not the 2.0-s, stimulus, the percentage of correct responding on each of the choice levers during test sessions varied directly with the bias conditions in that the percentage of correct responding was highest at the most frequently presented location and lowest at the least frequently presented location. In addition, scopolamine, but not metscopolamine, increased omissions while also increasing anticipatory responses in rats trained under left-bias conditions and tested under right-bias conditions. The present findings suggest that varying the frequency of stimulus location can provide additional measures of attention in the five-choice serial reaction time task.

Animals↗
PubMed1993

Operator error in a level coded myoelectric control channel.

Two forms of error exist in the level coded myoelectric control channel: system error and operator error. Currently in level coded (3-state) myoelectric prosthesis, target and switching level settings are optimized for the presence of system error only. In this study, system error was minimized in order to examine operator error. The magnitude of the operator error was found to exceed the magnitude of the experimental system error as well as the system error associated with a typical prosthesis control unit. These findings suggest that operator error should be considered when optimizing target levels and decision boundaries for level coded myoelectric prosthesis controllers. Since the operator response was estimated to be normally distributed, it is described by its mean and standard deviation. This information can be used to determine the desired optimal settings.

Arm↗
PubMed2004

A negentropy minimization approach to adaptive equalization for digital communication systems.

In this paper, we introduce and investigate a new adaptive equalization method based on minimizing approximate negentropy of the estimation error for a finite-length equalizer. We consider an approximate negentropy using nonpolynomial expansions of the estimation error as a new performance criterion to improve performance of a linear equalizer based on minimizing minimum mean squared error (MMSE). Negentropy includes higher order statistical information and its minimization provides improved converge, performance and accuracy compared to traditional methods such as MMSE in terms of bit error rate (BER). The proposed negentropy minimization (NEGMIN) equalizer has two kinds of solutions, the MMSE solution and the other one, depending on the ratio of the normalization parameters. The NEGMIN equalizer has best BER performance when the ratio of the normalization parameters is properly adjusted to maximize the output power(variance) of the NEGMIN equalizer. Simulation experiments show that BER performance of the NEGMIN equalizer with the other solution than the MMSE one has similar characteristics to the adaptive minimum bit error rate (AMBER) equalizer. The main advantage of the proposed equalizer is that it needs significantly fewer training symbols than the AMBER equalizer. Furthermore, the proposed equalizer is more robust to nonlinear distortions than the MMSE equalizer.

Algorithms↗
PubMed2004

Feature selection in MLPs and SVMs based on maximum output information.

This paper presents feature selection algorithms for multilayer perceptrons (MLPs) and multiclass support vector machines (SVMs), using mutual information between class labels and classifier outputs, as an objective function. This objective function involves inexpensive computation of information measures only on discrete variables; provides immunity to prior class probabilities; and brackets the probability of error of the classifier. The maximum output information (MOI) algorithms employ this function for feature subset selection by greedy elimination and directed search. The output of the MOI algorithms is a feature subset of user-defined size and an associated trained classifier (MLP/SVM). These algorithms compare favorably with a number of other methods in terms of performance on various artificial and real-world data sets.

Algorithms↗
PubMed2005

Statistical shape analysis: clustering, learning, and testing.

Using a differential-geometric treatment of planar shapes, we present tools for: 1) hierarchical clustering of imaged objects according to the shapes of their boundaries, 2) learning of probability models for clusters of shapes, and 3) testing of newly observed shapes under competing probability models. Clustering at any level of hierarchy is performed using a mimimum variance type criterion criterion and a Markov process. Statistical means of clusters provide shapes to be clustered at the next higher level, thus building a hierarchy of shapes. Using finite-dimensional approximations of spaces tangent to the shape space at sample means, we (implicitly) impose probability models on the shape space, and results are illustrated via random sampling and classification (hypothesis testing). Together, hierarchical clustering and hypothesis testing provide an efficient framework for shape retrieval. Examples are presented using shapes and images from ETH, Surrey, and AMCOM databases.

Algorithms↗
PubMedDate not supplied

Children's probability intuitions: understanding the expected value of complex gambles.

Two experiments used Information Integration Theory to study how children judge expected value of complex gambles in which alternative outcomes have different prizes. Six-year-olds, 9-year-olds and adults (N = 73 in Study 1, N = 28 in Study 2) saw chance games that involved shaking a marble in a bicolored tube. One prize was won if the marble stopped on blue, another if it stopped on yellow. Children judged how happy a puppet playing the game would be, with the prizes and probability of the blue and yellow outcomes varied factorially. Three main results appeared in both studies: First, participants in all age groups used the normatively prescribed multiplication rule for integrating probability and value of each individual outcome--a striking finding because multiplicative reasoning does not usually appear before 8 years of age in other domains. Second, all age groups based judgment of overall expected value meaningfully on both alternative outcomes, but there were individual differences--many participants deviated from the normative addition rule, showing risk seeking and risk averse patterns of judgment similar to the risk attitudes often found with adults. Third, even the youngest children took probability to be an abstract rather than physical property of the game. Overall, in contrast to the traditional view, the present results demonstrate functional understanding of probability and expected value in children as young as 5 or 6. These results contribute to the growing evidence on children's intuitive reasoning competence. This intuition can, on the one hand, support surprisingly precocious performance in young children, but it may also contribute to the biases evident in adults' judgment and decision.

Adolescent↗
PubMedDate not supplied

Analytic and heuristic processing influences on adolescent reasoning and decision-making.

The normative/descriptive gap is the discrepancy between actual reasoning and traditional standards for reasoning. The relationship between age and the normative/descriptive gap was examined by presenting adolescents with a battery of reasoning and decision-making tasks. Middle adolescents (N = 76) performed closer to normative ideals than early adolescents (N = 66), although the normative/descriptive gap was large for both groups. Correlational analyses revealed that (1) normative responses correlated positively with each other, (2) nonnormative responses were positively interrelated, and (3) normative and nonnormative responses were largely independent. Factor analyses suggested that performance was based on two processing systems. The "analytic" system operates on "decontextualized" task representations and underlies conscious, computational reasoning. The "heuristic" system operates on "contextualized," content-laden representations and produces "cognitively cheap" responses that sometimes conflict with traditional norms. Analytic processing was more clearly linked to age and to intelligence than heuristic processing. Implications for cognitive development, the competence/performance issue, and rationality are discussed.

Adolescent↗
PubMed2001

Predicting the effects of actions: interactions of perception and action.

Many theories in cognitive psychology assume that perception and action systems are clearly separated from the cognitive system. Other theories suggest that important cognitive functions reside in the interactions between these systems. One consequence of the latter claim is that the action system may contribute to predicting the future consequences of currently perceived actions. In particular such predictions might be more accurate when one observes one's own actions than when one observes another person's actions, because in the former case the system that plans the action is the same system that contributes to predicting the action's effects. In the present study participants (N = 104) watched video clips displaying either themselves or somebody' else throwing a dart at a target board and predicted the dart's landing position. The predictions were more accurate when participants watched themselves acting. This result provides evidence for the claim that perceptual input can be linked with the action system to predict future outcomes of actions.

Adult↗
PubMed2003

Partition priming in judgment under uncertainty.

We show that likelihood judgments are biased toward an ignorance-prior probability that assigns equal credence to each mutually exclusive event considered by the judge. The value of the ignorance prior depends crucially on how the set of possibilities (i.e., the state space) is subjectively partitioned by the judge. For instance, asking "what is the probability that Sunday will be hotter than any other day next week?" facilitates a two-fold case partition, [Sunday hotter, Sunday not hotter], thus priming an ignorance prior of 1/2. In contrast, asking "what is the probability that the hottest day of the week will be Sunday?" facilitates a seven-fold class partition, [Sunday hottest, Monday hottest, etc.], priming an ignorance prior of 1/7. In four studies, we observed systematic partition dependence: Judgments made by participants presented with either case or class formulations of the same query were biased toward the corresponding ignorance prior.

Bias↗