Additive and multiplicative models for gamma distributed random variables,and their application as psychometric models for response times

A class of models for gamma distributed random variables is presented. These models are shown to be more flexible than the classical linear models with respect to the structure that can be imposed on the expected value. In particular, both additive, multiplicative, and combined additive-multiplicative models can be formulated. As a special case, a class of psychometric models for reaction times is presented, together with their psychological interpretation. By means of a comparison with existing models, this class of models is shown to offer some possibilities that are not available in existing methods. Parameter estimation by means of maximum likelihood (ML) is shown to have some attractive properties, since the models belong to the exponential family. Then, the results of a simulation study of the bias in the ML estimates are presented. Finally, the application of these models is illustrated by an analysis of the data from a mental rotation experiment. This analysis is preceded by an evaluation of the appropriateness of the gamma distribution for these data.     

EQUATING INVERSE PROBABILITIES IN IMPLICIT PERSONALITY JUDGMENTS

Abstract— Meehl and Rosen (1955) observed that their colleagues tended to equate the sensitivity of a sign (its probability given a diagnostic category) with its predictive accuracy (the probability of the diagnostic category given the sign). Such equating of inverse probabilities implies ignoring base rates. Later, many researchers demonstrated such neglect in a number of experimental contexts involving hypothetical judgments; others have found some use of base rates—but only when base rates were supplied by the experimenter, in which case even irrelevant base rates influenced judgment. The present study tested for equating conditional probabilities in a context similar to the contexts involved in the initial observations—that is, subjects strove for accuracy rather than attempted to make good judgments about hypothetical problems, and the base rates were generated by the subjects themselves. Neglect of base rates was revealed by within-individual comparisons showing subjects equated inverse probabilities without equating the corresponding unconditional ones.     

The object-line inferiority effect in pigeons

Eight pigeons (Columba livia) were trained to discriminate between diagonal lines presented alone or embedded in a redundant L-shape right-angle form. The stimuli were white and were presented in an environment that was otherwise totally dark. Numerous experiments done with human observers have shown a strong superiority effect when the diagonal lines are embedded in redundant contexts. However, in Experiment 1 ofthe present study, the pigeons discriminated significantly better between the two diagonal lines when presented alone than when they were embedded in the right-angle context. In order to check on the possibility that these results were restricted to the semi-Ganzfeld condition of Experiment 1, a second experiment was done with black stimuli presented on a white background. Results of Experiment 2 also showed a strong distractor effect. The results of the present experiments confirmed the predictions of the Heinemann and Chase model of pattern recognition by pigeons.     

Semantics and the computational paradigm in cognitive psychology

There is a prevalent notion among cognitive scientists and philosophers of mind that computers are merely formal symbol manipulators, performing the actions they do solely on the basis of the syntactic properties of the symbols they manipulate. This view of computers has allowed some philosophers to divorce semantics from computational explanations. Semantic content, then, becomes something one adds to computational explanations to get psychological explanations. Other philosophers, such as Stephen Stich, have taken a stronger view, advocating doing away with semantics entirely. This paper argues that a correct account of computation requires us to attribute content to computational processes in order to explain which functions are being computed. This entails that computational psychology must countenance mental representations. Since anti-semantic positions are incompatible with computational psychology thus construed, they ought to be rejected. Lastly, I argue that in an important sense, computers are not formal symbol manipulators.     

A Thematic Analysis of Spectator Violence at Sporting Events in North America

This study examines aggravating and mitigating circumstances surrounding spectator fights at stadiums and arenas in North America. Data were collected utilizing a sample of video recordings posted to a popular video-sharing website. A thematic analysis of the data reveals several influences including the role of team allegiances, alcohol use, security presence, and bystander behavior. Potential preventive and reactive interventions to discourage violence in this setting are discussed and evaluated.     

Psychosocial factors in heart surgery: presurgical vulnerability and postsurgical recovery

OBJECTIVE: Distress and low perceived social support were examined as indicators of psychosocial vulnerability in patients about to undergo heart surgery. Design: A total of 550 study patients underwent heart surgeries, including bypass grafting and valve procedures. Psychosocial interviews were conducted about five days before surgery, and biomedical data were obtained from hospital records. MAIN OUTCOME MEASURES: Sociodemographic, personality, religious, and biomedical factors were evaluated as predictors of psychosocial vulnerability, and all five sets of variables were evaluated as contributors to hospital length of stay (LOS). RESULTS: Patients scoring higher on one or more indicator of presurgical psychosocial vulnerability were younger, more likely to be female, less likely to be married, less well educated, lower in dispositional optimism, higher in trait anger, and lower in religiousness. Older age, depression, low support, and low trait anger each showed an independent, prospective association with greater LOS, and several other predictors had prospective relationships with LOS that were statistically mediated by depression or perceived support. CONCLUSION: Evidence that multiple psychosocial factors may influence adaptation to heart surgery has implications for understanding and ameliorating presurgical distress and for improving postsurgical recovery.