Fixed-interval matching-to-sample: intermatching time and intermatching error runs

Four pigeons were trained on a matching-to-sample task in which reinforcers followed either the first matching response (fixed interval) or the fifth matching response (tandem fixed-interval fixed-ratio) that occurred 80 seconds or longer after the last reinforcement. Relative frequency distributions of the matching-to-sample responses that concluded intermatching times and runs of mismatches (intermatching error runs) were computed for the final matching responses directly followed by grain access and also for the three matching responses immediately preceding the final match. Comparison of these two distributions showed that the fixed-interval schedule arranged for the preferential reinforcement of matches concluding relatively extended intermatching times and runs of mismatches. Differences in matching accuracy and rate during the fixed interval, compared to the tandem fixed-interval fixed-ratio, suggested that reinforcers following matches concluding various intermatching times and runs of mismatches influenced the rate and accuracy of the last few matches before grain access, but did not control rate and accuracy throughout the entire fixed-interval period.     

Nonacademic Career Counseling for Graduate Students

At the University of Michigan, an innovative career counseling service is offered to graduate students. The Office of Non-Academic Career Counseling and Placement assists graduate students expand career options in response to a tight academic market. The career counseling method promotes self-directed behavior and proceeds through a series of four major job-search stages. A brief statement of the effectiveness of our services is included in the discussion.     

Social Misperception and Its Implications for Counseling

This article explores social misperception, a unique way of viewing the behavior problems of children. While the emotional-disturbance label is usually given to behaviorally disordered youngsters, it inaccurately reflects the social learning problems of children. Explored are the characteristics of social misperception (both verbal and nonverbal), its historical foundations (taken from the psychological and educational literature), and its relation to learning disabilities and to emotional disturbance; a differential diagnostic system is offered. Counselors are given techniques by which they can assist teachers with remediation, a task that helps the counselor to assist classroom teachers to become socially sensitive to the emotional needs of children.     

Alleviation of narcotic withdrawal syndrome by conditional stimuli

We systematically paired auditory, olfactory, and social stimuli with each injection of morphine in rats. We found that, when morphine was kept constant at a low dose, the external stimuli acquired the property of a conditional stimulus (CS) to cause hyperthermia which was antagonized by naloxone. In rats in which morphine doses were regularly increased to cause morphine dependence, the CS presented during withdrawal, caused reduction in withdrawal signs (wet shakes, hypothermia, aggression) and produced hyperglycemia as well as elevation of striatal homovanillic acid. CS-induced alleviation of withdrawal hypothermia was blocked by mecamylamine, phenoxybenzamine, haloperidol, benztropine or naloxone but not by cyproheptadine or propranolol.     

Marginal maximum likelihood estimation of item parameters: Application of an EM algorithm

Maximum likelihood estimation of item parameters in the marginal distribution, integrating over the distribution of ability, becomes practical when computing procedures based on an EM algorithm are used. By characterizing the ability distribution empirically, arbitrary assumptions about its form are avoided. The Em procedure is shown to apply to general item-response models lacking simple sufficient statistics for ability. This includes models with more than one latent dimension.Supported in part by NSF grant BNS 7912417 to the University of Chicago and by SSRC (UK) grant HR6132 to the University of Lancaster.We are indebted to Mark Reiser and Robert Gibbons for computer programming. David Thissen clarified a number of points in an earlier draft.     

Spatial selectivity in visual search

To what extent does successful search for a target letter in a visual display depend on the allocation of attention to the target’s spatial position? To investigate this question, we required subjects to discriminate the orientation of a briefly flashed U-shaped form while searching for a target letter. Performance operating characteristics (POCs) were derived by varying the relative amounts of attention subjects were to devote to each task. Extensive tradeoffs in performance were observed when the orientation form and target letter occurred in nonadjacent display positions. In contrast, the tradeoff was much more restricted when the two targets occurred in adjacent positions. These results suggest that the interference between simultaneous visual discriminations depends critically on their separation in visual space. Both visual search and form discrimination require a common limited-capacity visual resource.     

A direct comparison of four methods for eliminating a response

Thirty-two rats pressed one lever (lever A) on a VI 30-sec schedule of food reinforcement and were then shifted to one of four procedures for eliminating the lever A response: extinction, differential reinforcement of other behavior, reinforcement of a different response (pole pushing), and reinforcement of a similar response (pressing lever B). Effectiveness of a response-elimination procedure was measured by (1) how quickly lever A response rate fell to a low level when the procedure was in effect, (2) how much lever A responding recovered when the procedure was discontinued, and (3) how resistant lever A responding was to reinstatement when the VI reinforcement schedule was reimposed. No one method was superior by all three measures. Extinction produced the most variable behavior, while differential reinforcement of other behavior produced the least. Reinforcing alternative behavior produced the greatest recovery in the original lever A response when the response-elimination procedure was discontinued.     

Encoding strategy and sensory and semantic interference

Studies were designed to compare the effects of encoding strategies on two types of interference, sensory and semantic. Paired-associate lists were learned under instructional sets encouraging interactive imagery or repetitious rehearsal. Sensory interference was created by mispairing rhymes and semantic interference was produced by mispairing associatively related words. In control lists word pairs were unrelated. The results indicated that encoding strategy did not influence amounts of sensory and semantic interference. Mispairing rhymes produced the same amount of confusion as mispairing associates whether pairs were encoded through interaction imagery or through repetitious rehearsal. These effects were found with both short and long encoding intervals. The findings are inconsistent with the idea that encoding operations or strategies applied to word pairs completely determine the type of code activated for those pairs. Both sensory and semantic codes appear to be activated under each kind of encoding strategy.     

Pictorial context and the recall of pronoun sentences

Summary Acting on the assumption that pictures affect the processing of sentences only when providing additional information, the authors used pictures, which in an earlier experiment had failed to influence the retention of noun sentences, as illustrations to semantically undefined pronoun sentences, thus establishing a distinct information gradient between sentence and picture. These pronoun sentences were presented to 48 subjects for recall, in four pictorial conditions: without picture, with unambiguous picture, with subject-ambiguous, and with object-ambiguous picture. As hypothesized, picture-less pronoun sentences were more poorly recalled than picture-enriched pronoun sentences. Moreover, sentences accompanied by subject-ambiguous pictures, in which the grammatical subject could not be clearly identified, scored lower than the same sentences with unambiguous or object-ambiguous pictures. The findings invite a communication-theory analysis of the experimental situation, for which Searle's theory of speech acts is invoked.The authors gratefully acknowledge the assistance of Mr. B. Jankowski in the translation of this paper from an original German version.     

Remarks on the test of significance for the method of paired comparisons

A three-component model for comparative judgment which allows for individual differences in preference is proposed. An implication of the model is that errors in the observed proportions due to sampling individuals in paired comparisons experiments are correlated. By neglecting this correlation, Mosteller's test for the method of paired comparisons tends to accept falsely the goodness of fit of the Case V solution. It is shown that bounds may be set for the correlation effect which make a valid test possible in some cases and provide useful standard errors for the estimated affective values.Preparation of this paper has been supported in part by the Quartermaster Food and Container Institute for the Armed Forces. Views and conclusions expressed herein are those of the author and do not necessarily reflect the views or endorsement of the Department of Defense. Comments of one of the reviewers, which substantially improved an earlier version of this paper, are gratefully acknowledged.