Convergence of the Integration Dynamics of the Construction-Integration Model

The connectionist network corresponding to the nonlinear integration dynamical system associated with Kintsch's construction-integration (CI) model is analysed with linear algebra tools. This addresses some theoretical questions raised and left unanswered by Rodenhausen (1992, Psychological Review 99, 547-549). A mathematical characterization for equilibrium points, which allows an a priori enumeration of all possible asymptotic states for the integration dynamical system, given a connectivity matrix, is given. The dynamics of convergence of the integration dynamical system is characterized in some detail as well. This provides a tool for understanding CI simulations and helps in particular to let us know to what extent the outcome will depend on the initial conditions. The criteria also provide a new mathematical analysis which allows for the explicit calculation of asymptotic states of the integration process without requiring computer simulation experiments. The new mathematical analysis should facilitate comparisons of the model's predictions with behavioural data. Copyright 2001 Academic Press.     

Dissociations between categorization and similarity judgments as a result of learning feature distributions

A dissociation between categorization and similarity was found by Rips (1989). In one experiment, Rips found that a stimulus halfway between a pizza and a quarter was categorized as a pizza but was rated as more similar to a quarter. Smith and Sloman (1994) discussed these results in terms of the role of necessary and characteristic features. In two experiments, participants had to learn to categorize novel artificial shapes composed of a nonsalient necessary feature combined with a salient characteristic feature. Participants categorized stimuli on the basis of a necessary feature, whereas their similarity judgments relied on characteristic features. The role of deep (essential) features in dissociations is considered. Results are discussed in terms of the differences between requirements of categorization and similarity judgments.     

Outcome evaluation in brief mother-infant psychotherapies: Report on 75 cases

The effects of brief mother–infant psychotherapies (maximum of 10 sessions) were examined in cases of functional and behavioral disturbances in children less than 30 months old. Seventy-five mother-infant dyads were assessed prior to treatment, at 1 week, and 6 months after therapy ended. The outcome measures were changes in the infant's symptoms, the behavioral interactions between mother and infant, and maternal representations. The effect of two forms of intervention—Psychodynamic Therapy and Interaction Guidance Therapy—were compared. Results indicated a significant symptom reduction; dyadic interactions became more harmonious (mothers became less intrusive and infants more cooperative). Maternal self-esteem grew significantly and negative affects decreased. Improvements lasted as least several months, with some positive improvement detected at the 6-month follow-up. No major difference in outcome was found between the effects of the two forms of intervention. Within the limitations of research in a clinical context, this study suggests that brief mother–infant psychotherapies are a cost-effective method of early intervention.     

Philosophical Foundations of a new Concept of Equilibrium in the Social Sciences: Projected Equilibrium

Philosophical Studies -     

Schizophrenia-like syndrome inducing agent phencyclidine failed to impair memory for temporal order in rats

Although subchronic phencyclidine (PCP) administration is recognized as a probative method to model schizophrenia-like symptoms in animals, only a few sets of data support the hypothesis of a cognitive prefrontal cortex (PFc) dysfunction in PCP-treated monkeys and rodents. Two experiments were here conducted to further test the integrity of prefrontal function in two versions of a memory for temporal order (MTO) task administered to rats. Original versions of this task elaborated by Kesner repeatedly yielded moderate to severe performance deficits in PFc lesioned rats. MTO assessment in an eight-arm radial maze consisted in a recency discrimination between two arms previously explored in the context of sequential forced choices. In Experiment 1, 16 naive Long-Evans rats were pre-trained on a variable version of the MTO task involving randomly re-mixed sequences until they reached a group criterion. Then, rats were treated daily for 21 days with PCP (10mg/kg) or saline vehicle and were tested on the same task approximately 20 h after an injection. The performance of the groups did not differ. In Experiment 2, 16 naive Long-Evans rats untrained prior to treatment received 27 daily injections of either PCP (10mg/kg) or saline vehicle and were tested, 20 h after each injection, on a constant version of the MTO task. This time, a fixed set of four sequences of successive arm entries was repeated within each daily session as well as across days. Again, prolonged PCP exposure failed to impair discrimination of temporal order despite the stability of sequential information over time. These negative results are not consistent with long-lasting hypofrontality, a major landmark of human schizophrenia, in the PCP rat model.     

Exemplar effects in the context of a categorization rule: Featural and holistic influences

Brooks and colleagues (S. W. Allen & L. R. Brooks, 1991; G. Regehr & L. R. Brooks, 1993) have shown that the classification of transfer stimuli is influenced by their similarity to training stimuli, even when a perfect classification rule is available. It is argued that the original effect obtained by Brooks and colleagues might have resulted from two potential confounding variables. Once these confounds were controlled, the current authors did not replicate Brooks and colleagues' results in Experiment 1. Exemplar effects appeared in Experiment 2 when transfer stimuli were perceptually more similar to training stimuli than in Experiment 1. In Experiment 3, the authors obtained exemplar effects with separated stimuli, a finding that was not predicted by Brooks and colleagues' model. The authors suggest that a close perceptual match between training and transfer stimuli is necessary for the effect to occur, for both integrated and separated stimuli. The nature of this perceptual match, holistic or featural, is discussed.     

Perception of elliptic biological motion

We tested the ability of the mature visual system for discrimination between types of elliptic biological motion on the basis of event kinematics. Healthy adult volunteers were presented with point-light displays depicting elliptic motion when only a single dot, a moving point-light arm, or a whole point-light human figure was visible. The displays were created in accordance with the two-thirds power kinematic law (natural motion), whereas the control displays violated this principle (unnatural motion). On each trial, participants judged whether the display represented natural or unnatural motion. The findings indicate that adults are highly sensitive to violation of the two-thirds power kinematic law. Notably, participants can easily discriminate between natural and unnatural motions without recognising the stimuli, which suggests that people implicitly use kinematic information. Most intriguing, event recognition seems to diminish the capacity to judge whether event kinematics is unnatural. We discuss possible ways for a cross-talk between perception and production of biological movement, and the brain mechanisms involved in biological motion processing.     

Does personality disorder co-morbidity impact treatment outcome for patients with major depression? A multi-level analysis

In literature, there exists disagreement regarding the impact of comorbid personality disorder(s) (PD[s]) on treatment outcome for patients with major depressive disorder (MDD). The aim of this paper was to investigate whether statistical heterogeneity and inter-dependency are potential moderators of the effect of co-morbid PDs on outcome for patients with MDD. Clinician-rated MADRS scores and DSM-IV Axis II personality disorder diagnoses were obtained from 562 outpatients with MDD who received 6 months of combined psycho- and pharmacotherapy. Single-level regression showed significantly worse treatment outcome among patients with co-morbid PD, as compared to patients with no PD. After controlling for statistical heterogeneity and interdependency, treatment outcome was no longer significantly worse for patients with co-morbid PD. In conclusion, heteroscedasticity and inter-dependency should be considered as potentially compelling explanations for inconsistencies in findings on treatment outcome for depressed patients with co-morbid PDs.