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PubMed2000

The mimetic transition: a simulation study of the evolution of learning by imitation.

Culturally transmitted ideas or memes must have had a large effect on the survival and fecundity of early humans. Those with better techniques of obtaining food and making tools, clothing and shelters would have had a substantial advantage. It has been proposed that memes can explain why our species has an unusually large brain and high cognitive ability: the brain evolved because of selection for the ability to imitate. This article presents an evolutionary model of a population in which culturally transmitted memes can have both positive and negative effects on the fitness of individuals. It is found that genes for increased imitative ability are selectively favoured. The model predicts that imitative ability increases slowly until a mimetic transition occurs where memes become able to spread like an epidemic. At this point there is a dramatic increase in the imitative ability, the number of memes known per individual and the mean fitness of the population. Selection for increased imitative ability is able to overcome substantial selection against increased brain size in some cases.

Adaptation, Psychological↗

PubMed1999

Neural network models of bilateral coordination.

Two mechanisms are described for controlling the movement of a pair of arms. The first is an engineered motion planner that finds solutions to the ill-posed problem of making noncolliding, goal-directed movements. The second uses neural networks that learn to emulate the coordinated behaviors of the motion planner using considerably less computational resources. Analysis of the networks shows in general terms how they work, and allows us to make testable predictions about some of the response properties that might be observed in the brain systems serving bilateral coordination.

Arm↗

PubMed2005

Identification of glyoxalase-I as a protein marker in a mouse model of extremes in trait anxiety.

For >15 generations, CD1 mice have been selectively and bidirectionally bred for either high-anxiety-related behavior (HAB-M) or low-anxiety-related behavior (LAB-M) on the elevated plus-maze. Independent of gender, HAB-M were more anxious than LAB-M animals in a variety of additional tests, including those reflecting risk assessment behaviors and ultrasound vocalization, with unselected CD1 "normal" control (NAB-M) and cross-mated (CM-M) mice displaying intermediate behavioral scores in most cases. Furthermore, in both the forced-swim and tail-suspension tests, LAB-M animals showed lower scores of immobility than did HAB-M and NAB-M animals, indicative of a reduced depression-like behavior. Using proteomic and microarray analyses, glyoxalase-I was identified as a protein marker, which is consistently expressed to a higher extent in LAB-M than in HAB-M mice in several brain areas. The same phenotype-dependent difference was found in red blood cells with NAB-M and CM-M animals showing intermediate expression profiles of glyoxalase-I. Additional studies will examine whether glyoxalase-I has an impact beyond that of a biomarker to predict the genetic predisposition to anxiety- and depression-like behavior.

Analysis of Variance↗

PubMed1990

Psychopharmacological strategies in the search for cognition enhancers.

In order to discover and develop drugs to treat cognitive decline, animal tests are needed which will predict clinical activity. The process of developing such animal models does not differ, in principle, from the approaches used in other areas of psychotropic drug research. One research approach involves attempts to create models homologous with the disorder to be treated. This requires a thorough analysis of the clinical problem and an attempt to reproduce the biological and behavioral aspects of the disorder in animals. Recent studies of the effects of certain brain lesions on learning in monkeys or rats as models of Alzheimer's disease may go some way towards developing an animal model for this disorder. However, it is arguable whether this approach to "modelling" has ever had much success in psychopharmacology. A more pragmatic strategy involves the development of what are sometimes called emperical models, according to which any biological and behavioral test can be used if it provides a reasonable prediction of activity in the clinic. For example, the much used passive avoidance test in rodents does not need to model human cognition if it accurately predicts clinical activity. The extent to which this approach can be used successfully for evaluating cognition-enhancing drugs is discussed in view of the many drugs already marketed as cognition enhancers.

Alzheimer Disease↗

PubMed2006

Electronic momentary assessment in chronic pain II: pain and psychological pain responses as predictors of pain disability.

OBJECTIVES AND METHODS: More than 7,100 electronic diaries from 80 patients with chronic pain (mean: 89.3, range 30-115) entered multilevel analyses to establish the statistical prediction of disability by pain intensity and by psychological functioning (fear avoidance, cognitive, and spousal pain responses). We also tested the differences between pre-chronic, recently chronic, and persistently chronic pain in the prediction of disability (impaired physical and mental capacity, pain interference with activities, immobility due to pain). RESULTS: Pain intensity explained 8% to 19% of the disability variance. Beyond this psychological functioning explained 7% to 16%: particularly fear-avoidance and cognitive pain responses predicted chronic pain disorder disability; spousal responses predicted immobility better than other aspects of disability. Immobility due to actual pain occurred infrequently. When it did, however, it was better predicted by avoidance behavior in the patient and by spousal discouragement of movement than by actual pain intensity. The prediction of immobility due to pain by, respectively, avoidance behavior and catastrophizing was better in chronic pain (>6 months) and that of physical impairment by catastrophizing better in persistently chronic pain (>12 months) than in pain of shorter duration. DISCUSSION: The psychological prediction of chronic pain disorder disability was determined beyond that accounted for by pain intensity. Nonetheless, psychological functioning explained substantial variance in chronic pain disorder disability. The psychological prediction of immobility and physical impairment was stronger with longer pain duration. Patient characteristics and momentary states of disability-and in particular of immobility-should be carefully distinguished and accounted for in chronic pain disorder.

Adult↗

PubMed2003

A theoretical framework for understanding the effects of simultaneous base-rate and payoff manipulations on decision criterion learning in perceptual categorization.

Observers completed perceptual categorization tasks in which base rates and payoffs were manipulated separately or simultaneously across a range of category discriminabilities. Decision criterion estimates from the simultaneous base-rate/payoff conditions were closer to optimal than those predicted from the independence assumption, in line with predictions from the flat-maxima hypothesis. A hybrid model that instantiated the flat-maxima and competition between reward and accuracy maximization hypotheses was applied to the data as well as used in a reanalysis of C. J. Bohil and W.J. Maddox's (2001) study. The hybrid model was superior to a model that incorporated the independence assumption, suggesting that violations of the independence assumption are to be expected and are well captured by the flat-maxima hypothesis, without requiring any additional assumptions.

Decision Making↗

PubMed1986

Corticosterone, choline acetyltransferase and noradrenaline levels in olfactory bulbectomized rats in relation to changes in passive avoidance acquisition and open field activity.

Consequences of olfactory bulbectomy in two behavioural situations, passive avoidance acquisition and activity in a brightly lit open field, were measured in the same animals for which data on four biochemical measures were also obtained. The biochemical measurements were on plasma corticosterone levels, noradrenaline (NA) levels in the midbrain and amygdala + pyriform cortex and the choline acetyltransferase (CAT) levels in the olfactory tubercle. Experimental variation in age groups of rats (7 weeks and 3 months) and in post-bulbectomy periods (1, 2 and 4 weeks) was made. The deficit in passive avoidance as a consequence of olfactory bulbectomy was evident in all groups of young animals and in older animals one and two weeks post-bulbectomy but not in older animals four weeks after bulbectomy. An increase in open field activity was similarly observed in all groups except in the older animals four weeks after bulbectomy. In contrast to reports by other investigators the basal plasma corticosterone levels were not increased in bulbectomized animals nor did we observe any diminution of NA levels in the amygdala (+ pyriform cortex). CAT levels were slightly increased in older animals two weeks after bulbectomy. The absence of a change in the plasma corticosterone level after bulbectomy is discussed in relation to the notion that the olfactory bulbectomized rat is in some way relevant as a test model for predicting efficacy of potential antidepressant drugs.

Animals↗

PubMed2005

Windows.

Some models of performance assume that behavior depends on environmental quantities (for example, rates of reinforcement) that are defined over intervals of fixed duration. Although such window models may serve as useful approximations, they are incompatible with well-known properties of behavior (for instance, sensitivity to delay). Window models with variable window length, however, are more difficult to refute. This article examines some implications of the assumption of random window length. Variable windows are shown to produce continuous forgetting and temporal discounting functions, to display properties analogous to parallel aggregation, and to make reasonable predictions about steady-state relations between reinforcement and responding. Issues of interpretation nonetheless suggest that alternatives to window models should be developed.

Animals↗

PubMed1991

Tests of an exemplar model for relating perceptual classification and recognition memory.

Experiments were conducted in which Ss made classification, recognition, and similarity judgments for 34 schematic faces. A multidimensional scaling (MDS) solution for the faces was derived on the basis of the similarity judgments. This MDS solution was then used in conjunction with an exemplar-similarity model to accurately predict Ss' classification and recognition judgments. Evidence was provided that Ss allocated attention to the psychological dimensions differentially for classification and recognition. The distribution of attention came close to the ideal-observer distribution for classification, and some tendencies in that direction were observed for recognition. Evidence was also provided for interactive effects of individual exemplar frequencies and similarities on classification and recognition, in accord with the predictions of the exemplar model. Unexpectedly, however, the frequency effects appeared to be larger for classification than for recognition.

Adult↗

PubMed1982

Determinants of attention to local and global features of visual forms.

This article deals with the problem of how attention is distributed to different levels of detail (global, local) in visual scenes. Six experiments explore the effect of a previous level of processing on current processing. The contention that processing at a given level of detail biases the distribution of attention so that more is allocated to that level for future processing is supported by the presence in the data of a robust level-readiness effect, whereby processing is faster at a given level if previous processing has been at that level. The level-readiness effect occurs regardless of the conspicuity of features at the various levels. Conflict between levels seems to depend on the imbalance of conspicuity and attention allocation between levels, with the more conspicuous or attended-to-level interfering more. A model of two-state attention switching similar to that of Sperling and Melchnor (1978) is proposed to explain these data. the final experiment confirmed the somewhat unusual prediction of this model that sometimes processing under focusing-attention conditions can be slower than that under divided-attention conditions.

Attention↗

PubMed1990

Understanding face recognition with an interactive activation model.

In this paper we describe how the microstructure of the Bruce & Young (1986) functional model of face recognition may be explored and extended using an interactive activation implementation. A simulation of the recognition of familiarity of individuals is developed which accounts for a range of published findings on the effects of semantic priming, repetition priming and distinctiveness. Finally, we offer some speculative predictions made by the model, and point to an empirical programme of research which it suggests.

Arousal↗

PubMed2000

Research on posttreatment return of claustrophobic fear, arousal, and avoidance using mock diagnostic imaging.

Fear sometimes returns after attenuation via exposure. Return of fear is poorly understood due to conflicting results from diverse experiments. This article reports on two experiments in which claustrophobic fear during mock diagnostic imaging was attenuated and allowed to return so the experiments could be evaluated and return of fear studied. Attentional focus versus distraction during exposure was a between-subjects independent variable. Attempts were made to predict return of fear, return of heart-rate responsivity, and behavioral avoidance using levels of fear and heart-rate during initial mock diagnostic imaging as predictor variables. One third of participants displayed return of fear, heart-rate response, or avoidance 1 week after fear reduction. Heart-rate response during initial mock imaging predicted posttreatment return-of-fear classification; level of fear during initial imaging did not. Neither initial heart rate nor initial fear predicted return of heart-rate reactivity or avoidance. The experiments are offered as models for programmatic research.

Adult↗

PubMed2002

Recursive retrospective revaluation of causal judgments.

Recursive causal evaluation is an iterative process in which the evaluation of a target cause, T, is based on the outcome of the evaluation of another cause, C, the evaluation of which itself depends on the evaluation of a 3rd cause, D. Retrospective revaluation consists of backward processing of information as indicated by the fact that the evaluation of T is influenced by subsequent information that is not concerned with T directly. Two experiments demonstrate recursive retrospective revaluation with contingency information presented in list format as well as with trial-by-trial acquisition. Existing associative models are unable to predict the results. The model of recursive causal disambiguation that conceptualizes the revaluation as a recursive process of disambiguation predicts the pattern of results correctly.

Adult↗

PubMed2003

Staff reactions to self-injurious behaviours in learning disability services: attributions, emotional responses and helping.

OBJECTIVES: The aim of the study was to explore an amended version of Weiner's (e.g. Weiner, 1980) helping behaviour model potentially more specific to the context of care staff working with people with learning disabilities and challenging behaviours. DESIGN: Key elements of the helping model (causal attributions, affective responses, and helping behaviour) were assessed using self-report questionnaires. In contrast to previous research, helping behaviour was conceptualized as behaviour more or less likely to reinforce challenging behaviours rather than as willingness to expend extra effort in helping. Furthermore, dimensions of positive and negative affect associated with challenging behaviour were used. METHOD: A total of 123 care staff in adult services viewed one of two videos depicting a person with learning disabilities engaging in self-injurious behaviour. Information about the behaviour's function was manipulated in order to assess reinforcing staff helping responses. Staff completed self-report scales immediately after viewing the video material. RESULTS: There was very little evidence for the predicted associations between causal attributions and both positive and negative affect, and only one significant association between affect and reinforcing helping responses. Given this lack of association, we did not fully test Weiner's prediction that affect would mediate the impact of causal attributions on helping. CONCLUSIONS: We found no evidence that Weiner's helping model can be amended to account for staff working with challenging behaviour. Close examination of previous studies also reveals very few supportive data of Weiner's original formulation. Therefore, we discuss the potential utility of alternative models in addition to methodological and conceptual issues.

Adult↗

PubMed2001

Gene recognition based on DAG shortest paths.

We describe DAGGER, an ab initio gene recognition program which combines the output of high dimensional signal sensors in an intuitive gene model based on directed acyclic graphs. In the first stage, candidate start, donor, acceptor, and stop sites are scored using the SNoW learning architecture. These sites are then used to generate a directed acyclic graph in which each source-sink path represents a possible gene structure. Training sequences are used to optimize an edge weighting function so that the shortest source-sink path maximizes exon-level prediction accuracy. Experimental evaluation of prediction accuracy on two benchmark data sets demonstrates that DAGGERis competitive with ab initio gene finding programs based on Hidden Markov Models.

Computational Biology↗

PubMed2005

The effect of body mass index on global brain volume in middle-aged adults: a cross sectional study.

BACKGROUND: Obesity causes or exacerbates a host of medical conditions, including cardiovascular, pulmonary, and endocrine diseases. Recently obesity in elderly women was associated with greater risk of dementia, white matter ischemic changes, and greater brain atrophy. The purpose of this study was to determine whether body type affects global brain volume, a marker of atrophy, in middle-aged men and women. METHODS: T1-weighted 3D volumetric magnetic resonance imaging was used to assess global brain volume for 114 individuals 40 to 66 years of age (average = 54.2 years; standard deviation = 6.6 years; 43 men and 71 women). Total cerebrospinal fluid and brain volumes were obtained with an automated tissue segmentation algorithm. A regression model was used to determine the effect of age, body mass index (BMI), and other cardiovascular risk factors on brain volume and cognition. RESULTS: Age and BMI were each associated with decreased brain volume. BMI did not predict cognition in this sample; however elevated diastolic blood pressure was associated with poorer episodic learning performance. CONCLUSION: These findings suggest that middle-aged obese adults may already be experiencing differentially greater brain atrophy, and may potentially be at greater risk for future cognitive decline.

Adult↗

PubMed2006

Policy adjustment in a dynamic economic game.

Making sequential decisions to harvest rewards is a notoriously difficult problem. One difficulty is that the real world is not stationary and the reward expected from a contemplated action may depend in complex ways on the history of an animal's choices. Previous functional neuroimaging work combined with principled models has detected brain responses that correlate with computations thought to guide simple learning and action choice. Those works generally employed instrumental conditioning tasks with fixed action-reward contingencies. For real-world learning problems, the history of reward-harvesting choices can change the likelihood of rewards collected by the same choices in the near-term future. We used functional MRI to probe brain and behavioral responses in a continuous decision-making task where reward contingency is a function of both a subject's immediate choice and his choice history. In these more complex tasks, we demonstrated that a simple actor-critic model can account for both the subjects' behavioral and brain responses, and identified a reward prediction error signal in ventral striatal structures active during these non-stationary decision tasks. However, a sudden introduction of new reward structures engages more complex control circuitry in the prefrontal cortex (inferior frontal gyrus and anterior insula) and is not captured by a simple actor-critic model. Taken together, these results extend our knowledge of reward-learning signals into more complex, history-dependent choice tasks. They also highlight the important interplay between striatum and prefrontal cortex as decision-makers respond to the strategic demands imposed by non-stationary reward environments more reminiscent of real-world tasks.

Adult↗

PubMedDate not supplied

Estimation of the aqueous solubility of organic molecules by the group contribution approach.

Several group contribution methods to estimate the aqueous solubility of organic molecules are proposed and evaluated for their ability to predict the water solubility of new molecules. The learning set consisted of 1168 organic compounds with experimental data taken from the literature after critical evaluation. The best method, based on a new fragment atom scheme, leads to a squared correlation coefficient of 0.95 and an average absolute calculation error of 0.50 log unit, which is superior to other group contribution methods currently available. One of the advantages of this model is that it has upper and lower limits so that the predicted solubilities cannot be unrealistily high or low.

Journal Article↗