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PubMed2005

The power PC theory and causal powers: comment on Cheng (1997) and Novick and Cheng (2004).

It has been claimed that the power PC theory reconciles regularity and power theories of causal judgment by showing how contingency information is used for inferences about unobservable causal powers. Under the causal powers theory causal relations are understood as generative relations in which a causal power of one thing acts on a liability of another thing under some releasing condition. These 3 causal roles are implicit or explicit in all causal interpretations. The power PC theory therefore fails to reconcile power theories and regularity theories because it has a fundamentally different definition of power and does not accommodate the tripartite causal role distinction. Implications of this distinction are drawn out.

Cognition↗
PubMed1990

Learning-forgetting independence, unidimensional memory models, and feature models: comment on Bogartz (1990).

In his recent articles, Bogartz offered a definition of what it means for forgetting rate to be independent of degree of original learning. He showed that, given this definition, independence is confirmed by extant data. Bogartz also criticized Loftus's (1985b) proposed method for testing independence. In this commentary, we counter Bogartz's criticisms and then offer two observations. First, we show that Loftus's horizontal-parallelism test distinguishes between two interesting class of memory models: unidimensional models wherein the memory system's state can be specified by a single number and multidimensional models wherein at least two numbers are required to specify the memory system's state. Independence by Loftus's definition is implied by a unidimensional model. Bogartz's definition, in contrast, is consistent with either model. Second, to better understand the constraints on memory mechanisms dictated by the mathematics of the models under consideration, we develop a simple but general feature model of learning and forgetting. We demonstrate what constraints must be placed on this model to make learning and forgetting rate independent by Loftus's and by Bogartz's definitions.

Humans↗
PubMed2000

Reinforcement learning in continuous time and space.

This article presents a reinforcement learning framework for continuous-time dynamical systems without a priori discretization of time, state, and action. Based on the Hamilton-Jacobi-Bellman (HJB) equation for infinite-horizon, discounted reward problems, we derive algorithms for estimating value functions and improving policies with the use of function approximators. The process of value function estimation is formulated as the minimization of a continuous-time form of the temporal difference (TD) error. Update methods based on backward Euler approximation and exponential eligibility traces are derived, and their correspondences with the conventional residual gradient, TD(0), and TD(lambda) algorithms are shown. For policy improvement, two methods-a continuous actor-critic method and a value-gradient-based greedy policy-are formulated. As a special case of the latter, a nonlinear feedback control law using the value gradient and the model of the input gain is derived. The advantage updating, a model-free algorithm derived previously, is also formulated in the HJB-based framework. The performance of the proposed algorithms is first tested in a nonlinear control task of swinging a pendulum up with limited torque. It is shown in the simulations that (1) the task is accomplished by the continuous actor-critic method in a number of trials several times fewer than by the conventional discrete actor-critic method; (2) among the continuous policy update methods, the value-gradient-based policy with a known or learned dynamic model performs several times better than the actor-critic method; and (3) a value function update using exponential eligibility traces is more efficient and stable than that based on Euler approximation. The algorithms are then tested in a higher-dimensional task: cart-pole swing-up. This task is accomplished in several hundred trials using the value-gradient-based policy with a learned dynamic model.

Algorithms↗
PubMed2003

Scaling techniques for modeling directional knowledge.

A common way for researchers to model or graphically portray spatial knowledge of a large environment is by applying multidimensional scaling (MDS) to a set of pairwise distance estimations. We introduce two MDS-like techniques that incorporate people's knowledge of directions instead of (or in addition to) their knowledge of distances. Maps of a familiar environment derived from these procedures were more accurate and were rated by participants as being more accurate than those derived from nonmetric MDS. By incorporating people's relatively accurate knowledge of directions, these methods offer spatial cognition researchers and behavioral geographers a sharper analytical tool than MDS for studying cognitive maps.

Adult↗
PubMed2002

The power integration diffusion model for production breaks.

The learning curve during repetitive production and the associated forgetting during production breaks are fundamental issues in the understanding of behavior. A model is suggested that combines 3 basic findings, namely, that single memory traces decay according to a power function of the retention interval, that aggregated memory traces can be combined by integration, and that the time to produce a unit can be described by a diffusion process on the memory trace. This power integration diffusion model is validated with empirical data, and the result fits better than 14 other published forgetting models.

Attention↗
PubMed2006

Disordered connectivity in the autistic brain: challenges for the "new psychophysiology".

In 2002, we published a paper [Brock, J., Brown, C., Boucher, J., Rippon, G., 2002. The temporal binding deficit hypothesis of autism. Development and Psychopathology 142, 209-224] highlighting the parallels between the psychological model of 'central coherence' in information processing [Frith, U., 1989. Autism: Explaining the Enigma. Blackwell, Oxford] and the neuroscience model of neural integration or 'temporal binding'. We proposed that autism is associated with abnormalities of information integration that is caused by a reduction in the connectivity between specialised local neural networks in the brain and possible overconnectivity within the isolated individual neural assemblies. The current paper updates this model, providing a summary of theoretical and empirical advances in research implicating disordered connectivity in autism. This is in the context of changes in the approach to the core psychological deficits in autism, of greater emphasis on 'interactive specialisation' and the resultant stress on early and/or low-level deficits and their cascading effects on the developing brain [Johnson, M.H., Halit, H., Grice, S.J., Karmiloff-Smith, A., 2002. Neuroimaging of typical and atypical development: a perspective from multiple levels of analysis. Development and Psychopathology 14, 521-536]. We also highlight recent developments in the measurement and modelling of connectivity, particularly in the emerging ability to track the temporal dynamics of the brain using electroencephalography (EEG) and magnetoencephalography (MEG) and to investigate the signal characteristics of this activity. This advance could be particularly pertinent in testing an emerging model of effective connectivity based on the balance between excitatory and inhibitory cortical activity [Rubenstein, J.L., Merzenich M.M., 2003. Model of autism: increased ratio of excitation/inhibition in key neural systems. Genes, Brain and Behavior 2, 255-267; Brown, C., Gruber, T., Rippon, G., Brock, J., Boucher, J., 2005. Gamma abnormalities during perception of illusory figures in autism. Cortex 41, 364-376]. Finally, we note that the consequence of this convergence of research developments not only enables a greater understanding of autism but also has implications for prevention and remediation.

Autistic Disorder↗
PubMed2003

Where is psychology going? Structural fault lines revealed by psychologists' use of Kuhn.

Psychologists' appropriation of language and ideas from Thomas Kuhn's (1962, 1970b) The Structure of Scientific Revolutions reveals deep and contradictory concerns about truth, science, and the progress of the field. The author argues that psychologists, uncomfortably straddling natural and social science traditions, reference Structure for 2 reasons largely overlooked: first, because it presents an intermediate, naturalistic position in the war between relativist and rationalist views of scientific truth, and second, because it presents a psychologized model of scientific change. The author suggests that the history of this mutual influence--psychologists being influenced by Kuhn and vice versa--may usefully inform current practices of psychological science.

Forecasting↗
PubMed2003

A neurodevelopmental model for anorexia nervosa.

This paper integrates genetic and biological data on aetiological risk for anorexia nervosa (AN) with cognitive and psychosocial explanatory models. We have reviewed clinical and basic science data from each of these domains and then used a developmental perspective to formulate a multifactorial threshold model. By positioning interpersonal stress as a central component of this model, psychological, social and biological conceptualisations of AN can be used to generate a data driven, neurodevelopmental hypothesis for the aetiology of this complex disorder.

Adaptation, Psychological↗
PubMed2003

Psychology brings justice: the science of forensic psychology.

In this paper the focus is on one aspect of forensic psychology: the development of psychological instruments, a social psychological model and assessment procedures for evaluating the credibility of witnesses and police detainees during interviewing. Clinically grounded case work and research has impacted on police interviewing and practice, the admissibility of expert psychological testimony and the outcome of cases of miscarriage of justice. After describing the research that laid the foundations for advancement of scientific knowledge in this area, a brief review is presented of 22 high-profile murder cases where convictions based on confession evidence have been quashed on appeal between 1989 and 2001, often primarily on the basis of psychological evidence. The review of the cases demonstrates that psychological research and expert testimony in cases of disputed confessions have had a profound influence on the practice and ruling of the Court of Appeal for England and Wales and the British House of Lords. The cases presented in this paper show that it is wrong to assume that only persons with learning disability or those who are mentally ill make unreliable or false confessions. Personality factors, such as suggestibility, compliance, high trait anxiety and antisocial personality traits, are often important in rendering a confession unreliable. Future research needs to focus more on the role of personality factors in rendering the evidence of witnesses and suspects potentially unreliable.

Forensic Psychiatry↗
PubMed2006

Hostility and pain are related to inflammation in older adults.

Chronically elevated systemic inflammation has a dramatic impact on health for older individuals. As stress-related responses, both hostility and pain perception may contribute to inflammation which in turn may maintain negative emotion and pain over time. We used structural equation modeling to examine the degree to which trait hostility and pain were uniquely associated with C-reactive protein (CRP) and serum IL-6 levels over a 6-year span in a sample of older adults. The sample included 113 present or former caregivers of a spouse with dementia and 101 non-caregivers. After accounting for depression, health behaviours, and other risk factors, which were also assessed longitudinally, pain and, to a lesser extent, hostility were uniquely associated with plasma levels of CRP but not IL-6. When examined separately, the association between pain and CRP was significant only for caregivers, while the association between hostility and CRP was comparable for the two groups. These findings suggest that hostility may play a role in a cycle of inflammation among older adults, and that pain may be particularly problematic for those under chronic stress. Our results also shed light on inflammation as a mechanism underlying the effects of hostility on cardiovascular disease morbidity and mortality.

Age Factors↗
PubMed1989

A social relations analysis of toddler peer relationships.

We examined whether young children form different relationships with specific peers. Using the social relations model, effects of individuals as either actors or partners were distinguished from effects of relationships. Relationship effects are inferred when behavior within a dyad cannot be predicted from behavior that both partners give and receive in other social contexts. 32 20- or 30-month-old children were each paired with 2 partners (same age and gender) and observed for 18 40-min play sessions. The social relations analysis indicated that children differed consistently in their initiation of interaction (actor effects) and in the conflict contributions they elicited from their peers (partner effects). Relationship effects were found in games and contingent interaction, and were generally reciprocal. Relationship effects emerged gradually; in contrast, neither actor nor partner effects increased over time. Results were discussed in the context of definitions of relationships and peer relationships of young children.

Child, Preschool↗
PubMed2006

Interval estimates of weighted effect sizes in the one-way heteroscedastic ANOVA.

A framework for comparing normal population means in the presence of heteroscedasticity and outliers is provided. A single number called the weighted effect size summarizes the differences in population means after weighting each according to the difficulty of estimating their respective means, whether the difficulty is due to unknown population variances, unequal sample sizes or the presence of outliers. For an ANOVA weighted for unequal variances, we find interval estimates for the weighted effect size. In addition, the weighted effect size is shown to be a monotone function of a suitably defined weighted coefficient of determination, which means that interval estimates of the former are readily transformed into interval estimates of the latter. Extensive simulations demonstrate the accuracy of the nominal 95% coverage of these intervals for a wide range of parameters.

Analysis of Variance↗
PubMed2005

Exact and resampling probability values for weighted kappa.

Permutation procedures to compute exact and resampling probability values for weighted kappa are described. Comparisons with asymptotic probability values demonstrate that exact permutation procedures are advantageous for sparse data sets, whereas resampling permutation procedures are appropriate for both sparse and nonsparse data sets.

Humans↗
PubMed2003

Imince: an unrestricted factor-analysis-based program for assessing measurement invariance.

In this article, a Windows program for analyzing measurement invariance in two different populations is described. Factor analysis is a common way of assessing measurement invariance, and restricted factor analysis is now the most popular method. However, applied researchers have usually found that the theoretical advantages of restricted factor analysis do not always apply in practical situations. For example, when the participant sample is large, as is the case in Internet-based questionnaires, the available software for restricted factor analysis might fail to converge on a solution. Our program is based on unrestricted factor analysis and considers the three parameters that define factor invariance: difficulties, discriminations, and residual variances. The statistical significance of the tests for evaluating invariance is obtained using Bootstrap resampling procedures. A real-life example demonstrates the usefulness of the program.

Adult↗
PubMed1999

Why are residential and school moves associated with poor school performance?

Most research on residential mobility has documented a clear pattern: Residential and school moves are associated with poor academic performance. Explanations for this relationship, however, remain speculative. Some researchers argue that moving affects social relationships that are important to academic achievement. But the association between moving and school performance may be spurious; the negative correlation may be a function of other characteristics of people who move often. We offer several conceptual and analytical refinements to these ideas, allowing us to produce more precise tests than past researchers. Using longitudinal data, we find that differences in achievement between movers and nonmovers are partially a result of declines in social relationships experienced by students who move. Most of the negative effect of moving, however, is due to preexisting differences between the two groups.

Child↗
PubMed1986

Women and mental health. A model for practice.

This article has addressed the need to consider multiple sources of stress in women's lives to assist them in determining those areas over which they can increase their sense of control as well as ways of coping with those aspects over which they have limited control. The continuing need to help women define and explore realistic options is stressed.

Adolescent↗