Differential autoshaping to common and distinctive elements of positive and negative discriminative stimuli

The learning by hungry pigeons of a discrimination between two successively presented compound visual stimuli was investigated using a two-key autoshaping procedure. Common and distinctive stimulus elements were simultaneously presented on separate keys and either followed by food delivery, S+, or not, S−. The subjects acquired both between-trial and within-trial discriminations. On S+ trials, pigeons pecked the distinctive stimulus more than the common stimulus; before responding ceased on S− trials, they pecked the common stimulus more than the distinctive one. Mastery of the within-display discrimination during S+ trials preceded mastery of the between-trials discrimination. These findings extend the Jenkins-Sainsbury analysis of discriminations based upon a single distinguishing feature to discriminations in which common and distinctive elements are associated with both the positive and negative discriminative stimuli. The similarity of these findings to other effects found in autoshaping—approach to signals that forecast reinforcement and withdrawal from signals that forecast nonreinforcement—is also discussed.     

Temporal factors influencing the pigeon's successive matching-to-sample performance: sample duration, intertrial interval, and retention interval

A successive matching-to-sample procedure that entails the sequential presentation of sample and test stimuli and the monitoring of response rates in a go/no-go discrimination of matching and nonmatching stimuli was studied as an alternative to the familiar delayed-matching paradigm of animal short-term memory. Three within-subject experiments studied the effects of sample duration (1 to 12 seconds), intertrial interval (5 to 50 seconds), and retention interval (1 to 50 seconds) on the pigeon's successive-matching performance. The results revealed that retention was (a) an increasing function of sample duration and intertrial interval, and (b) a decreasing function of retention interval. These results were in accord with those of more traditional short-term memory paradigms, and reveal the suitability of the successive-matching procedure for studying memory processes.     

The relationship between motor and secretory behaviors in classical appetitive conditioning

Three hungry dogs received pairings of food with an accessible, illuminated panel. This resulted in the dogs’ approaching the lighted panel and salivating. Despite the similarity of these conditioning procedures to those used in a large body of research primarily with avians, however, the dogs did not physically contact the lighted stimulus panel. These results bear on several issues concerning the form and direction of classically conditioned behaviors.     

Body image and dieting failure in college men and women: Examining links between depression and eating problems

The noted co-occurrence between depression and eating problems in women may be due to their common association with negative body image. Specifically, the western cultural ideal that equates feminine beauty with thinness leads a large number of women to be dissatisfied with their bodies. A recent model [M. McCarthy (1990) The Thin Ideal, Depression, and Eating Disorders in Women, Behavioral Research and Therapy, Vol. 28, pp. 205–215] suggests that this dissatisfaction, coupled with high importance placed on appearance, leads most women to engage in dieting to obtain this level of thinness. As dieting is typically unsuccessful as a means of long-term weight control, depression will result from the sense of failure and helplessness associated with dieting failure. This depression then leads to increasingly maladaptive eating behaviors that serve to assuage negative affect and regain control over body appearance. In a sample of 234 male and female, predominantly white, 17–22-year-old college students, we examined several components of this model, including the specificity of these relations for women. In accordance with the model, depressive symptoms and eating problems were predicted to be an interactive function of body image and body image importance, with negative body image/high importance subjects showing the greatest disturbance. In addition, we examined several components of the model to determine (a) the relation between failed dieting and depression, and (b) the extent to which depression could account for eating problems. Regardless of gender, eating problems were indeed highest among those with both negative body image and high body image importance. Depression, however, was higher in subjects with negative body image, regardless of body image importance. For both men and women, failed dieting was significantly related to depression, but only for women did depression account for significant variability in eating problems. Validity of the model is considered. Gender differences in the nature of these relations, and the need to consider possible alternative effects of the cultural standard for masculine attractiveness, are discussed.This research is based in part on an undergraduate honor's thesis submitted by the second author to the Emory University Department of Psychology under the direction of the first author. Funding was provided by a grant from Emory University to the first author. The authors would like to thank Robyn Fivush, Steven Nowicki, Irwin Waldman, Carol Worthman, and two anonymous reviewers for helpful comments on earlier drafts.     

Amodal completion of moving objects by pigeons

In a series of four experiments, we explored whether pigeons complete partially occluded moving shapes. Four pigeons were trained to discriminate between a complete moving shape and an incomplete moving shape in a two-alternative forced-choice task. In testing, the birds were presented with a partially occluded moving shape. In experiment 1, none of the pigeons appeared to complete the testing stimulus; instead, they appeared to perceive the testing stimulus as incomplete fragments. However, in experiments 2, 3, and 4, three of the birds appeared to complete the partially occluded moving shapes. These rare positive results suggest that motion may facilitate amodal completion by pigeons, perhaps by enhancing the figure - ground segregation process.