Frequency versus magnitude of reinforcement: New data with a different procedure

Two pigeons, with previous exposure to concurrent schedules, were submitted to 29 sessions of 8 hours each with concurrent variable-interval variable-interval schedules in which reinforcement parameters changed from session to session. In the first nine sessions reinforcement durations were equal in both schedules while reinforcement frequencies varied; in Sessions 10 through 18, both frequency and duration of reinforcement were varied; in Sessions 19 through 29, only reinforcement duration was varied. Results with this different procedure confirm previous findings that behavior is more sensitive to changes in reinforcement frequency than to reinforcement magnitude.     

Estimation of psychometric functions from adaptive tracking procedures

Because adaptive tracking procedures are designed to avoid stimulus levels far from a target threshold value, the psychometric function constructed from the trial-by-trial data in the track may be accurate near the target level but a poor reflection of performance at levels far removed from the target. A series of computer simulations was undertaken to assess the reliability and accuracy of psychometric functions generated from data collected in up-down adaptive tracking procedures. Estimates of psychometric function slopes were obtained from-trial-by-trial data in simulated adaptive tracks and compared with the true characteristics of the functions used to generate the tracks. Simulations were carried out for three psychophysical procedures and two target performance levels, with tracks generated by psychometric functions with three different slopes. The functions reconstructed from the tracking data were, for the most part, accurate reflections of the true generating functions when at least 200 trials were included in the tracks. However, for 50- and 100-trial tracks, slope estimates were biased high for all simulated experimental conditions. Correction factors for slope estimates from these tracks are presented. There was no difference in the accuracy and reliability of slope estimation due to -target-level-for the adaptive track, and only minor differences due to psychophysical procedure. It is recommended that, if both threshold and slope of psychometric functions are to be estimated-from the trial-by-trial tracking data, at least 100 trials should be included in the tracks, and a three- or four-alternative forced-choice procedure should be used. However, good estimates can also be obtained using the two-alternative forced-choice procedure or less than 100 trials if appropriate corrections for bias are applied.     

Dichotic listening pattern in conduction aphasia

This paper reports a finding of hemispheric brain asymmetry for speech in short-gestation infants (mean gestational age = 36 weeks). Using a new measure—degree of reduction in limb tremors following exposure to speech stimuli compared to two control groups, one hearing orchestral music, the other no patterned stimuli—we found that speech disproportionately affected right limb movements. It is not clear whether the effect is due to asymmetries in cortical or subcortical processing. This provides evidence against the notion that brain specialization for language functions necessarily appears over time; rather, specialization for some functions (e.g., speech reception) must be present at birth.     

Videoconferencing-based cognitive-behavioral therapy for obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a prevalent, chronic and disabling anxiety disorder. Despite the efficacy and strength of pharmacologic interventions for OCD, medications are not always well accepted or effective, making an efficacious psychosocial alternative especially attractive. Cognitive-behavioral therapy (CBT) has been established as an effective treatment for adult OCD, yet access to such treatment is limited, especially in rural areas. Technological advances allow for therapy to be provided in a real-time format over a videoconferencing network. This method allows therapists to provide state-of-the-art treatment to patients who would not otherwise have access to it. This paper presents three cases of OCD successfully treated via videoconferencing CBT. The presence of OCD was established via structured clinical interview and clinician-rated outcome measures were completed by evaluators blinded to the method of treatment. A multiple baseline across individuals design was used to support the internal validity of the CBT outcome data. Patient ratings of therapeutic alliance were high across all three cases. Information gathered from qualitative interviews post-treatment confirmed quantitative measures finding high levels of patient satisfaction. This pilot study suggests that videoconferencing-based CBT is a promising method to bring appropriate treatment to thousands who live far distances from well-trained therapists.     

Comparisons and perceived deprivation in ethnic minority settings

Two studies investigated comparison choices among ethnic minorities and majorities. The perceived status of the self vis-á-vis different comparison targets also was assessed. Antecedents and consequences of comparisons and relative deprivation were examined. Predictions were derived from social comparison, stigma, social identity, and relative deprivation research. Two surveys were conducted, one in London with mainly Asian participants (N = 235) and one in Germany with Turkish and Aussiedler participants (N = 166) and German majority members (N = 351). Participants preferred intragroup and temporal comparisons (with other ingroup members and with the self in the past) to various types of cross-group comparisons (with outgroup members). Perceived similarity and contact with a target positively predicted interest in comparing with this target, and perceived higher status of the target was a negative predictor. Some evidence was found that feelings of deprivation depend on comparison choices. Deprivation negatively predicted self-esteem and life satisfaction. Deprivation and group identification were negatively correlated.     

Investment behavior and the negative side of emotion

Can dysfunction in neural systems subserving emotion lead, under certain circumstances, to more advantageous decisions? To answer this question, we investigated how normal participants, patients with stable focal lesions in brain regions related to emotion (target patients), and patients with stable focal lesions in brain regions unrelated to emotion (control patients) made 20 rounds of investment decisions. Target patients made more advantageous decisions and ultimately earned more money from their investments than the normal participants and control patients. When normal participants and control patients either won or lost money on an investment round, they adopted a conservative strategy and became more reluctant to invest on the subsequent round; these results suggest that they were more affected than target patients by the outcomes of decisions made in the previous rounds.     

A new approach to the formulation and testing of learning models

It is argued that current attempts to model human learning behavior commonly fail on one of two counts: either the model assumptions are artificially restricted so as to permit the application of mathematical techniques in deriving their consequences, or else the required complex assumptions are imbedded in computer programs whose technical details obscure the theoretical content of the model. The first failing is characteristic of so-called mathematical models of learning, while the second is characteristic of computer simulation models. An approach to model building which avoids both these failings is presented under the title of a black-box theory of learning. This method permits the statement of assumptions of any desired complexity in a language which clearly exhibits their theoretical content.Section II of the paper is devoted to the problem of testing and comparing alternative learning theories. The policy advocated is to abandon attempts at hypothesis testing. It is argued that, in general, we not only lack sufficient data and sufficiently powerful techniques to test hypotheses, but that the truth of a model is not really the issue of basic interest. A given model may be true in the sense that on the basis of available evidence we cannot statistically reject it, but not interesting in the sense that it provides little information about the processes underlying behavior. Rather, we should accept or reject models on the basis of how much information they provide about the way in which subjects respond to environmental structure. This attitude toward model testing is made precise by introducing a formal measure of the information content of a model. Finally, it is argued that the statistical concept of degrees-of-freedom is misleading when used in the context of model testing and should be replaced by a measure of the information absorbed from the data in estimating parameters.I would like to express my indebtedness to Ernest W. Adams and Julian Feldman for their guidance and encouragement of the research reported here.Much of the research reported here was conducted at the University of California, Berkeley, and incorporated in a Ph.D. dissertation in Logic and the Methodology of Science [15]. The research was supported in part by the Computer Institute for Social Science Research, Michigan State University.