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PubMed2003

Language dynamics in finite populations.

Any mechanism of language acquisition can only learn a restricted set of grammars. The human brain contains a mechanism for language acquisition which can learn a restricted set of grammars. The theory of this restricted set is universal grammar (UG). UG has to be sufficiently specific to induce linguistic coherence in a population. This phenomenon is known as "coherence threshold". Previously, we have calculated the coherence threshold for deterministic dynamics and infinitely large populations. Here, we extend the framework to stochastic processes and finite populations. If there is selection for communicative function (selective language dynamics), then the analytic results for infinite populations are excellent approximations for finite populations; as expected, finite populations need a slightly higher accuracy of language acquisition to maintain coherence. If there is no selection for communicative function (neutral language dynamics), then linguistic coherence is only possible for finite populations.

Humans↗
PubMed1999

Effects of spatial grouping on the functional response of predators.

A unified mechanistic approach is given for the derivation of various forms of functional response in predator-prey models. The derivation is based on the principle of mass action but with the crucial refinement that the nature of the spatial distribution of predators and/or opportunities for predation are taken into account in an implicit way. If the predators are assumed to have a homogeneous spatial distribution, then the derived functional response is prey-dependent. If the predators are assumed to form a dense colony or school in a single (possibly moving) location, or if the region where predators can encounter prey is assumed to be of limited size, then the functional response depends on both predator and prey densities in a manner that reflects feeding interference between predators. Depending on the specific assumptions, the resulting functional response may be of Beddington-DeAngelis type, of Hassell-Varley type, or ratio-dependent.

Animals↗
PubMed1994

Translating stochastic density-dependent individual behavior with sensory constraints to an Eulerian model of animal swarming.

Density-dependent social behaviors such as swarming and schooling determine spatial distribution and patterns of resource use in many species. Lagrangian (individual-based) models have been used to investigate social groups arising from hypothetical algorithms for behavioral interactions, but the Lagrangian approach is limited by computational and analytical constraints to relatively small numbers of individuals and relatively short times. The dynamics of "group properties", such as population density, are often more ecologically useful descriptions of aggregated spatial distributions than individual movements and positions. Eulerian (partial differential equation) models directly predict these group properties; however, such models have been inadequately tied to specific individual behaviors. In this paper, I present an Eulerian model of density-dependent swarming which is derived directly from a Lagrangian model in which individuals with limited sensing distances seek a target density of neighbors. The essential step in the derivation is the interpretation of the density distribution as governing the occurrence of animals as Poisson points; thus the number of individuals observed in any spatial interval is a Poisson-distributed random variable. This interpretation appears to be appropriate whenever a high degree of randomness in individual positions is present. The Eulerian model takes the form of a nonlinear partial integro-differential equation (PIDE); this equation accurately predicts statistically stationary swarm characteristics, such as expected expected density distribution. Stability analysis of the PIDE correctly predicts transients in the stochastic form of the aggregation model. The model is presented in one-dimensional form; however, it illustrates an approach that can be equally well applied in higher dimensions, and for more sophisticated behavioral algorithms.

Algorithms↗
PubMed1990

A note on the statistical properties of animal locations.

A statistical model of the successive locations of an animal in the plane induces a statistical model of the relative positions of successive locations. A common locational model is that the Cartesian coordinates of successive locations in the plane are independent bivariate normal random variables. This note gives the statistical properties of the direction and length of the vector joining successive locations.

Animals↗
PubMed1978

Affiliations with medical care providers.

Two analytical techniques are applied to a household survey of Rhode Island residents to develop the concept of an affiliation with medical care provider. A modification of a deviant case analysis is used to examine those people who are extreme in terms of the numbers of affiliations that they have with medical care providers. Overall, 4.1% of the sample have no affiliations and 7.3% have four or more affiliations. One of the most important variables in distinguishing those people with an unusual number of affiliations is a subjective variable of health status--whether they worry about their health. Nonparticipants rarely worry about their health and are generally in good health, while those with a high number of affiliations worry a great deal, regardless of their actual health status. A multiple regression analysis reveals that the variables of number of health conditions, sex, insurance, worry about health, income, disability days, and family structure are significantly related to mean number of affiliations with an R2 of 19.5%. Discussion includes the study's implications both for greater understanding of how and why people seek care and for application in the further development of a social psychological model of health behavior.

Adolescent↗
PubMed1989

Context-dependent associations in linear distributed memories.

In this article we present a method that allows conditioning of the response of a linear distributed memory to a variable context. This method requires a system of two neural networks. The first net constructs the Kronecker product between the vector input and the vector context, and the second net supports a linear associative memory. This system is easily adaptable for different goals. We analyse here its capacity for the conditional extraction of features from a complex perceptual input, its capacity to perform quasi-logical operations (for instance, of the kind of "exclusive-or"), and its capacity to structurate a memory for temporal sequences which access is conditioned by the context. Finally, we evaluate the potential importance of the capacity to establish arbitrary contexts, for the evolution of biological cognitive systems.

Artificial Intelligence↗
PubMedDate not supplied

Trends in the psychophysiology of individual differences.

Pavlov's typology of higher nervous activity was the first systematic approach to the psychophysiology of individual differences. Pavlov's theory has been further developed by Teplov, Nebylitsyn and their pupils in the Institute of Psychology in Moscow. In particular, Nebylitsyn has delineated a new property of the nervous system and has shown that it is different from strength of nervous system. In the Western research context we can compare the relationship between these two parameters to that between arousal and conditioning level. Eysenck's theory of the physiological bases of extraversion/introversion is discussed in relation to Nebylitsyn's theses and Gray's conception of arousability. Finally, it is suggested that future work in the psychophysiology of individual differences should stress the study of the ontogenetic development of the physiological variables.

Arousal↗
PubMed2006

Instability in self-esteem and paranoia in a general population sample.

BACKGROUND: Research on the association between paranoia and self-esteem has yielded inconsistent findings. Some studies have indicated an association between paranoia and low self-esteem, while other studies have shown an association with high self-esteem. A plausible explanation for these inconsistencies is that self-esteem is unstable in paranoid individuals. METHOD: The association between instability in self-esteem and paranoia was assessed in a general population risk set of 4636 individuals using logistic regression analysis. RESULTS: Self-esteem instability was significantly associated with the presence of paranoid symptoms (OR 1.27 95% CI 1.12-1.45) and not with other positive psychotic symptoms (OR 1.09 95% CI 0.96-1.23), adjusted for a range of a priori selected confounders. CONCLUSION: The finding of a specific association between unstable self-esteem and paranoia is in line with a recent psychological model suggesting that paranoid beliefs arise partly as a consequence of dysfunctional efforts to regulate self-esteem.

Adolescent↗
PubMed2005

Deja vu in neurology.

The significance of deja vu is widely recognised in the context of temporal lobe epilepsy, and enquiry about deja vu is frequently made in the clinical assessment of patients with possible epilepsy. Deja vu has also been associated with several psychiatric disorders. The historical context of current understanding of deja vu is discussed. The literature reveals deja vu to be a common phenomenon consistent with normality. Several authors have suggested the existence of a "pathological" form of deja vu that differs, qualitatively or quantitatively, from "non-pathological" deja vu. The features of deja vu suggesting neurological or psychiatric pathology are discussed. Several neuroanatomical and psychological models of the deja vu experience are highlighted, implicating the perceptual, mnemonic and affective regions of the lateral temporal cortex, hippocampus and amygdala in the genesis of deja vu. A possible genetic basis for a neurochemical model of deja vu is discussed. Clinical approaches to the patient presenting with possible deja vu are proposed.

Amygdala↗
PubMed2002

The value of the Piagetian framework for comparative cognitive studies.

Although the Piagetian framework has been used by numerous researchers to compare cognitive abilities of diverse species, the system is often criticized as implemented. I examine the various criticisms, suggest ways in which the system can be improved, and argue for the need for descriptive systems such as the Piagetian framework to complement programs that look for cellular and molecular bases or mathematical models to explain behavior.

Animals↗
PubMedDate not supplied

Personality assessment based on the five-factor model of personality structure in patients with primary open-angle glaucoma.

PURPOSE: Several characteristic personality types have been reported for glaucoma patients in previous studies. However, none of the previous studies used a common structural theory of personality. In this study, we conducted a multicenter cross-sectional case-control study using the recently established five-factor model of personality structure. METHODS: Personality was evaluated using the Neuroticism Extraversion Openness Five-Factor Inventory (NEO-FFI), which is a questionnaire specifically designed to test the five-factor model of personality: neuroticism (N), extraversion (E), openness (O), agreeableness (A), and conscientiousness (C). Eligible questionnaires were obtained from 196 patients with primary open-angle glaucoma (POAG) (99 men, 97 women) and 223 reference subjects with no ocular disease except cataract (87 men, 136 women). The mean score of each NEO-FFI factor for POAG patients was compared to the scores for the reference subjects. RESULTS: Compared with the reference subjects, the mean N score was significantly higher (P = 0.013), the mean scores for A and C were significantly lower (P = 0.007 and P = 0.001, respectively), and the mean E score tended to be lower (P = 0.055) in male POAG patients. The mean E score was significantly lower (P = 0.023) in female POAG patients. CONCLUSIONS: Characteristic personality traits were noted in POAG patients, and a more significant relationship was found between personality and glaucoma in men than in women.

Aged↗
PubMed2005

Accusations of genital theft: a case from northern Ghana.

Occurrences of panic attacks associated with belief in genital retraction have been described in the anthropological and psychological literature in terms of culture bound reactive syndromes. Similar phenomena occur widely in West Africa, where they are reported as cases of penis snatching. Explanations for these phenomena range from the biomedical emphasis on pathology to the social psychological emphasis on altered perceptual sets. This paper provides a narrative of an accusation of genital theft in a rural West African settlement. Drawing from ethnographic information, it will be argued that the case is best explained in light of social relations, definitions for in-groups and out-groups, and local knowledge concerning witchcraft and divination. Local explanations for the case conform to both biomedical and social psychological models.

Adult↗
PubMed2006

The neuropsychology of mood disorders.

Cognitive dysfunction is central to our understanding of mood disorders in terms of patient experiences, Diagnostic and Statistical Manual of Mental Disorders criteria, and psychological models. In this article, we highlight key findings from studies that have used neuropsychological tests and functional neuroimaging techniques to explore cognitive dysfunction in patients with depression and mania. In particular, we focus on affective processing bias, abnormal response to negative feedback, and decision making. Results are discussed in the context of current conceptualizations of dysfunctional neural circuitry, and in relation to important clinical research implications.

Bipolar Disorder↗
PubMed1989

Explanatory pitfalls and rule-based driver models.

Driver models should refer to either of two levels of explanation, (1) the rational or intentional level that is usually taken to represent the aggregate behavior of the driver population, or (2) the functional level which deals with intra-individual information processing. Frequently the two levels are confounded, which is likely to introduce serious theoretical problems--vicious circles and pernicious homunculi among them. After a conceptual analysis of the confounding problem, arguments in favor of a radical functionalistic (process-level) approach are put forward. Rule-based modeling, using some advanced production system architecture, appears to be the most promising inroad to better theories of driver behavior.

Accident Prevention↗
PubMed1996

Objects, decision considerations and self-image in men's and women's impulse purchases.

Current theories in economics, marketing, and psychology fail to explain underlying reasons for impulse buying and, crucially, why certain goods (e.g., clothes) are bought impulsively more than others (e.g., basic kitchen equipment). We propose and examine a social psychological model, which predicts that people impulse buy to acquire material symbols of personal and social identity. We predict that consumers will differ systematically in the goods they buy on impulse, and in their reasons for doing so, depending on their attitudes towards shopping, and also along important social categories, such as gender. Specifically, our theoretical model-drawing on a social constructionist model of material possessions (e.g., Dittmar, 1992) and symbolic self-completion theory (e.g. Wicklund and Gollwitzer, 1982)-leads to three sets of hypotheses: (i) some consumer durables are more likely to be bought on impulse than others, and there may be gender differences in object choices, (ii) differences will emerge in the buying considerations (e.g., functional, emotional, symbolic) that are used for impulse and planned buying, and (iii) magnitude of self-discrepancies will predict relative impulse buying frequency and the buying considerations used, if the individual uses consumption as a self-completion strategy. These predictions were expected to hold particularly strongly for individuals high in compulsive shopping tendencies. We test our model in a questionnaire study with a sample of British consumers (n = 61). The results lend support to all three sets of hypotheses. The implications of these findings are discussed with respect to economic and consumer theory, and the treatment offered to the increasing number of 'addicted' shoppers.

Adult↗