Base-rate effects in category learning: a comparison of parallel network and memory storage-retrieval models

Exemplar-memory and adaptive network models were compared in application to category learning data, with special attention to base rate effects on learning and transfer performance. Subjects classified symptom charts of hypothetical patients into disease categories, with informative feedback on learning trials and with the feedback either given or withheld on test trials that followed each fourth of the learning series. The network model proved notably accurate and uniformly superior to the exemplar model in accounting for the detailed course of learning; both the parallel, interactive aspect of the network model and its particular learning algorithm contribute to this superiority. During learning, subjects' performance reflected both category base rates and feature (symptom) probabilities in a nearly optimal manner, a result predicted by both models, though more accurately by the network model. However, under some test conditions, the data showed substantial base-rate neglect, in agreement with Gluck and Bower (1988b).     

Effects of signals preceding and following shock on baseline responding during a conditioned-suppression procedure

Long-Evans rats were exposed to a succession of conditioned-suppression procedures involving pairings of (1) signal-shock, (2) shock-signal, and (3) a signal-shock-signal sequence in which first and second signals were at first physically identical. Traditional suppression of food-reinforced responding was obtained under the signal-shock arrangement, and exposure to the shock-signal sequence resulted in conditioned enhancement of responding during the signal. The signal-shock-signal condition reliably suppressed responding during the first signal, but produced no differential effect on response rate during the second signal. Baseline responding was least changed from preshock rates under the signal-shock-signal procedure, but baseline rate was considerably reduced under the signal-shock and shock-signal arrangements, the latter yielding most substantial reductions. A second experiment indicated that the magnitude and direction of changes in baseline responding reported in Experiment I were not confined to cases in which the first and second signals in the signal-shock-signal arrangement were physically identical. It is suggested that the major effects of the conditioned-suppression procedure on response rate might not be confined to presentations of the signal.     

A tempest, a birth, and death: Freud, Jung, and Shakespeare’sPericles

This essay applies a Freudian psychoanalytic and Jungian archetypal narrative analysis to Shakespeare’s first and oft-criticized romance. The author argues that key structural and thematic elements ofPericles are best illuminated when viewed through a psychological interpretative lens, and that the play is best comprehended when examined in the context of its associative, rather than linear, richness. Masculinity and femininity, central themes of the narrative, are explored both in relation to the Oedipal complex and psychological individuation.Pericles also provides an excellent basis to examine key differences between Freud’s and Jung’s approach, particularly Jung’s widening of the primarily sexual psychoanalytic approach to encompass broader archetypal meaning.     

Response-duration of lever pressing in the rat

Two aspects of the lever-holding behaviour of rats in a Skinner-box have been analysed: firstly, the changes in the duration of the responses during the acquisition and experimental extinction phase, and, secondly, the bunching of responses during the experimental extinction phase. The response-durations on the first few acquisition trials were found to be bimodally distributed, but to become stabilized at 0.42 seconds as practice increased. During experimental extinction response-durations increased. The rate of increase depended on the conditions of secondary reward. Rats who had the source of secondary reward removed, or restricted, yielded a steeper slope than those who responded under the same conditions of secondary reward as during training.

The analysis of the extinction scores revealed that unrewarded responses were emitted in groups. Response-group latencies were shown to progress as a positive function of the number of response-groups, and the average response-duration for consecutive response-groups to increase progressively. The slope of the duration curve plotted for successive response-groups increased, and this was related to an increase in the value of the time-intercept for successive response-groups.     

Periodicity of response in operant extinction

The distribution of responses during experimental extinction trials for a group of 11 rats, trained in the Skinner-box, was examined. Our analysis supports an earlier suggestion that the extinction trial may be separated into respondent and silent periods. Response rates during respondent periods show relatively little decline throughout the extinction period investigated, whereas silent periods increase with positive acceleration. The traditional exponential function used to describe response rates during experimental extinction trials should therefore be regarded as a very rough approximation to the mathematical characteristics of the animal's behaviour. Its use as a basis for quantifying critical intervening variables, such as habit strength or behaviour potentiality, is consequently seriously challenged.     

Response elimination without performance

Hungry rats were taught to press a lever in order to obtain a small quantity of food. It has been shown that the strength of the lever-pressing response can be reduced by allowing the animals to explore the box without finding food. This result conflicts with a simple reactive-inhibition theory of forgetting and response-elimination. Three possible explanations have been considered: (a) that the failure to find food changed the motivational condition of the animal; (b) that a conditioned drive, associated with the food-box, underwent extinction; (c) that a genuine response extinction occurred, and that this could be accounted for in terms of a principle of reaction-chain acquisition and extinction which differs in important respects from Skinner's (1938) and Hull's (1954) principles of conditioning.     

Toward Developing Laboratory-Based Parent–Adolescent Conflict Discussion Tasks that Consistently Elicit Adolescent Conflict-Related Stress Responses: Support from Physiology and Observed Behavior

Parent–adolescent conflict poses risk for youth maladjustment. One potential mechanism of this risk is that stress in the form of increased arousal during conflict interactions results in adolescents’ impaired decision-making. However, eliciting consistent adolescent stress responses within laboratory-based tasks of parent–adolescent conflict (i.e., conflict discussion tasks) is hindered by task design. This limitation may stem from how conflict topics are assessed and selected for discussion. Within a sample of 47 adolescents (ages 14–17) and parents, we investigated whether a modified version of a conflict discussion task could elicit physiological (i.e., arousal) and behavioral (i.e., hostility) displays of adolescents’ conflict-related stress responses. We assessed parent–adolescent conflict via structured interview to identify topics for dyads to discuss during the task. We randomly assigned dyads to complete a 5-min task to discuss either a putatively benign topic (i.e., control condition) or a conflict topic while undergoing direct assessments of continuous arousal. Trained raters coded dyad members’ hostile behavior during the task. Adolescents in the conflict condition exhibited significantly greater levels of arousal than adolescents in the control condition. We observed an interaction between discussion condition and baseline conflict. Specifically, higher baseline conflict predicted greater hostile behavior for adolescents in the conflict condition, yet we observed the inverse relation for adolescents in the control condition. Our modified laboratory discussion task successfully elicited both physiological and behavioral displays of adolescent conflict-related stress. These findings have important implications for leveraging experimental paradigms to understand causal links between parent–adolescent conflict and adolescent psychopathology, and their underlying mechanisms.