Multicomponent theory of perception

Summary In a complete identification experiment the three sides of an equilateral triangle were briefly presented as stimuli either singly or in pairs. The resulting 6×6 confusion matrices obtained with three subjects were analyzed according to Rumelhart's (1970, 1971) multicomponent theory of perception (MCTP) in order to test assumptions about feature extraction and decision processes. In agreement with MCTP the detection of a line segment occurring within a pair was stochastically independent of the detection of the other line segment. Two predictions of MCTP were however not confirmed: different line segments are not detected with equal probability, and the probability of detecting a line segment depends on the presence or absence of others. Several decision assumptions of MCTP were tested. The results are the following: If at most one line segment has been detected, then several responses (the candidate set) are compatible with this sensory state. It was argued that response selection from the candidate set is better described by the choice model (Luce, 1959) than by the matching Bayesian rule assumed by MCTP. For a given sensory state the size of the candidate set appears to vary over trials, whereas MCTP assumes it to be constant. In general, the confusion matrices could be predicted quite accurately by MCTP modified according to the above assumptions. However, more accurate predictions were achieved by assuming holistic perceptual processes as well as single feature extraction.This study was supported by a grant from the Universität Konstanz, Forschungsprojekt 32/72 Visuelle Reize, and the experiment to this study was performed in the laboratory of the Arbeitseinheit Mathematische Psychologie im Fachbereich Psychologie/Soziologie der Universität Konstanz.     

On the rationality of pluralistic ignorance

Pluralistic ignorance is a socio-psychological phenomenon that involves a systematic discrepancy between people’s private beliefs and public behavior in certain social contexts. Recently, pluralistic ignorance has gained increased attention in formal and social epistemology. But to get clear on what precisely a formal and social epistemological account of pluralistic ignorance should look like, we need answers to at least the following two questions: What exactly is the phenomenon of pluralistic ignorance? And can the phenomenon arise among perfectly rational agents? In this paper, we propose answers to both these questions. First, we characterize different versions of pluralistic ignorance and define the version that we claim most adequately captures the examples cited as paradigmatic cases of pluralistic ignorance in the literature. In doing so, we will stress certain key epistemic and social interactive aspects of the phenomenon. Second, given our characterization of pluralistic ignorance, we argue that the phenomenon can indeed arise in groups of perfectly rational agents. This, in turn, ensures that the tools of formal epistemology can be fully utilized to reason about pluralistic ignorance.     

Validation of distinct amnesic and executive type memory deficit in a psychiatric sample based on retrieval performance

Studies of localized brain dysfunctions have revealed connections between patterns of cognitive dysfunction and specific profiles of memory impairment. The amnesic type of memory impairment is defined by deficits in both free recall and recognition memory, whereas the dysexecutive memory impairment is characterized by retrieval deficits, i.e. a disproportional impairment in free recall relative to recognition memory. The present study tests whether classifications of psychiatric patients into recall impaired only (= RO group) and Recall and Recognition impaired (= RR group) correspond to the executive type and amnesic type of memory impairment. The alternative hypothesis is that the two groups merely differ in degree of neuropsychological and psychiatric disturbance. Forty-four subjects impaired on California Verbal Learning Test (CVLT) were selected from a larger database of 103 impaired and non-impaired subjects with schizophrenia or recurrent major depression. Subjects were classified into RO and RR groups and compared on measures of memory strategy (recency effect and interference on CVLT), overall neuropsychological function (Stroop Test and WAIS-R similarity) and psychiatric symptom load (positive and negative symptoms). Repeated measures ANOVA showed no effects of group, i.e. the RR group did not perform consistently below the RO group with regard to memory strategy, neuropsychological function or psychiatric symptom load. Two out of three analyses showed group x test interaction, supporting the dissociation of distinct executive and amnesic profiles among psychiatric patients. The RO group was more susceptible to interference but had better recency score than the RR group. The RO had higher negative symptoms while the RR group had higher positive symptoms.     

Modulation of anxiety circuits by serotonergic systems

Anxiety is a complex emotional state associated with sustained heightened autonomic and behavioral arousal and an increase in avoidance behavior. Anxiety-related behavior is a form of risk assessment behavior that is associated with a level of uncertainty or unpredictability regarding the outcome of emotionally salient events, often when both rewarding and aversive outcomes are possible. In this review, we highlight recent advances in our understanding of the neural circuits regulating anxiety states and anxiety-related behavior with an emphasis on the role of brainstem serotonergic systems in modulating anxiety-related circuits. In particular, we explore the possibility that the regulation of anxiety states and anxiety-related behavior by serotonergic systems is dependent on a specific, topographically organized mesolimbocortical serotonergic system that originates in the mid-rostrocaudal and caudal parts of the dorsal raphe nucleus.     

Roache’s Argument against the Cohabitation View

Rebecca Roache’s recent critique of David Lewis’s “cohabitation” view assumes that a person cannot be properly concerned about something that rules out that she ever exists. In this brief response, I argue against this assumption.