Edward A. Wasserman

Conceptual Behavior in Pigeons: Categorization of Both Familiar and Novel Examples From Four Classes of Natural and Artificial Stimuli

Two new procedures—a four-key choice procedure and a four-ply multiple fixed ratio schedule procedure—were used to train pigeons to categorize color slides depicting natural (cat, person, flower) and human-made (car, chair) objects. In Experiments IA, IB, 2A, and 2fl, 16 pigeons trained with 10 slides from each of four categories reliably classified novel examples from these categories. However, performance was more accurate on training than on novel stimuli. In Experiment 3, 8 pigeons learned to classify 2,000 nonrepeating slides. Thus, repetitive training with a limited number of stimuli is not necessary for pigeons to learn a four-category classification task. In Experiment 4, 4 pigeons were trained with a set of repeating slides while concurrently being trained with novel stimuli. As in Experiments IA, IB, 2A, and 2e, performance here was more discriminative on repeatedly seen stimuli than on novel ones. Thus, repetition facilitates categorization, whether or not the pigeons are concurrently exposed to novel stimuli. The implications of these results for models of categorization are discussed. We conclude that the conceptual abilities of pigeons are more advanced than hitherto suspected.

Attribution of Causality to Common and Distinctive Elements of Compound Stimuli

Given the task of diagnosing the source of a patients allergic reaction, college students judged the causal efficacy of common (X) and distinctive (A and B) elements of compound stimuli: AX and BX. As the differential correlation of AX and BX with the occurrence and nonoccurrence of the allergic reaction rose from .00 to 1.00, ratings of the distinctive A and B elements diverged; most importantly, ratings of the common X element fell. These causal judgments of humans closely parallel the conditioned responses of animals in associative learning studies, and clearly disclose that stimuli compete with one another for control over behavior.

Forebrain ischemia induces selective behavioral impairments associated with hippocampal injury in rats.

Two groups of rats were tested on a variety of motor and cognitive tasks after either 10 minutes of two-vessel occlusion forebrain ischemia (n = 8) or sham operative procedures (n = 6). Histological injury was absent in the sham-operated group. In the ischemic group, hippocampal injury was restricted to field CA1, while damage in the neocortex and caudoputamen was sparse. Motor tests performed on postoperative days 18 and 28 revealed no significant differences between the ischemic and sham-operated groups. Retention performance of a radial maze discrimination task was impaired, with a significant but transient increase in both working and reference memory errors. Passive avoidance acquisition and retention were not significantly affected, although conclusions concerning the utility of this task must be reserved because of variability in the behavior of the sham-operated rats. Morris maze spatial navigation (place learning) and open-field activity were insensitive to treatment group. These functional results are consistent with the observed histological injury and what is known about hippocampal injury and behavior, and they provide further guidance for the development of neurological assays appropriate for discriminating outcome from forebrain ischemia in rats.

Entropy detection by pigeons: response to mixed visual displays after same-different discrimination training.

Pigeons were trained to peck 2 different buttons in response to 16-icon Same versus Different arrays. In Same arrays, the icons were identical to one another, whereas in Different arrays, the icons were different from one another. In Experiment 1, pigeons discriminated Same from Different arrays and transferred their discriminative responding to arrays of novel icons. In Experiments 2-4, pigeons exhibited sensitivity to the degree of display variability when shown intermediate Mixture arrays. Entropy, an information theoretic measure, systematically described these results while outperforming rival accounts.

Contributions of specific cell information to judgments of interevent contingency.

College students considered the possible effect of an experimental drug on a skin rash. The information came from a 2 x 2 contingency table involving receipt or nonreceipt of the drug and improvement or nonimprovement of the rash: Cell A = receipt-improvement; Cell B = receipt-nonimprovement; Cell C = nonreceipt-improvement; Cell D = nonreceipt-nonimprovement. Without numerical information. Ss judged cells to be ordered A greater than B greater than C greater than D. The same order held when the contribution of each cell was derived from the contingency judgments of other subjects given numerical information. No such consistency was seen when one group of Ss made both judgments: whether individual Ss equally or unequally assessed the importance of the four cells, their contingency estimates showed cell use to be ordered A greater than B greater than C greater than D. These findings may result from strong biases that Ss harbor in processing contingency information.

Pavlovian Conditioning with Heat Reinforcement Produces Stimulus-Directed Pecking in Chicks

In a cooled chamber, chicks approached and pecked a small disk whose illumination preceded heat lamp activation, even when pecks prevented heat lamp onset. These behaviors did not occur when the disk and heat stimuli were randomly presented. Approach and contact of conditioned stimuli may develop even though these behaviors are not (i) evoked by the reinforcing stimulus, (ii) necessary for reinforcer reception, or (iii) ever followed by the reinforcer.

Detecting Response-Outcome Relations: Toward an Understanding of the Causal Texture of the Environment

Publisher Summary This chapter discusses that experimental psychology is no longer a unified field of scholarship. The most obvious sign of disintegration is the division of the Journal of Experimental Psychology into specialized periodicals. Many forces propel this fractionation. First, the explosion of interest in many small spheres of inquiry has made it extremely difficult for an individual to master more than one. Second, the recent popularity of interdisciplinary research has lured many workers away from the central issues of experimental psychology. Third, there is a growing division between researchers of human and animal behavior; this division has been primarily driven by contemporary cognitive psychologists, who see little reason to refer to the behavior of animals or to inquire into the generality of behavioral principles. The chapter considers the study of causal perception. This area is certainly at the core of experimental psychology. Although recent research in animal cognition has taken the tack of bringing human paradigms into the animal laboratory, the experimental research is described has adopted the reverse strategy of bringing animal paradigms into the human laboratory. A further unfortunate fact is that todays experimental psychologists are receiving little or no training in the history and philosophy of psychology. This neglected aspect means that investigations of a problem area are often undertaken without a full understanding of the analytical issues that would help guide empirical inquiry.

Performance of pigeons on delayed simple and conditional discriminations under equivalent training procedures

Abstract A pair of experiments investigated the short-term memory of pigeons under delayed simple and conditional discriminations. Trial sequences in both discriminations consisted of a color as the sample stimulus, a memory interval, a line orientation as the test stimulus, and a trial outcome, which was either food reinforcement or blackout. Pecking rates during the test stimulus defined discrimination performance. In the simple discrimination, the sample provided the necessary information regarding the subsequent trial outcome. In the conditional discrimination, the sample and test stimuli conjointly provided this information. In Experiment 1, the two procedures were compared with independent groups of pigeons. In Experiment 2, the comparison was made within subjects. The simple discrimination was acquired more quickly and was performed better with a memory requirement. Introduction of long delays disrupted performance even at shorter delays in both discriminations. Postulation of prospective as well as retrospective mediating processes facilitates the interpretation of these results.

PIGEONS SHOW SAME-DIFFERENT CONCEPTUALIZATION AFTER TRAINING WITH COMPLEX VISUAL STIMULI

Eight pigeons were first trained to peck 1 button in the presence of 16 distinct 4 x 4 arrays of identical pictures and to peck a 2nd button in the presence of 16 distinct 4 x 4 arrays of nonidentical pictures. Later, they were tested with 16 other same and 16 other different stimulus arrays involving untrained pictures. Performance to the testing arrays greatly exceeded chance levels, thus suggesting same-different conceptualization by pigeons.

BEHAVIORAL DEFICITS INDUCED BY BINGELIKE EXPOSURE TO ALCOHOL IN NEONATAL RATS : IMPORTANCE OF DEVELOPMENTAL TIMING AND NUMBER OF EPISODES

The importance of the timing and number of episodes of bingelike alcohol exposure in neonatal rats on subsequent behavioral outcomes was evaluated with a parallel bar task and a spatial conditional alternation task. Different groups of Sprague-Dawley rat pups were exposed to alcohol delivered via artificial rearing procedures either on postnatal Days (PD) 4 and 5, on PD 8 and 9, or on both PD 4/5 and 8/9 (Combined), producing daily peak blood alcohol concentrations around 400 mg/dl. Controls included an artificially reared group and a normally reared group. Exposure during PD 4/5 produced significantly more severe motor deficits and significantly more severe reductions in cerebellar and brainstem weights than did exposure on PD 8/9. Combined exposure produced greater deficits on these measures than either of the limited exposures. Significant deficits in the acquisition rates for conditional alternation were found only with the Combined exposure, although both the PD 8/9 and Combined groups committed significantly more within-trial errors. All three alcohol treatments produced significant and comparable reductions in forebrain weight. The type and severity of behavioral and neural deficits induced by neonatal bingelike alcohol exposure depend on the timing and number of exposures.