Temporal proximity and reinforcement sensitivity in multiple schedules

Distributions of reinforcers between two components of multiple variable-interval schedules were varied over a number of conditions. Sensitivity to reinforcement, measured by the exponent of the power function relating ratios of responses in the two components to ratios of reinforcers obtained in the components, did not differ between conditions with 15-s or 60-s component durations. The failure to demonstrate the “short-component effect,” where sensitivity is high for short components, was consistent with reanalysis of previous data. With 60-s components, sensitivity to reinforcement decreased systematically with time since component alternation, and was higher in the first 15-s subinterval of the 60-s component than for the component whose total duration was 15 s. Varying component duration and sampling behavior at different times since component transition may not be equivalent ways of examining the effects of average temporal distance between components.     

Sequential effects in dimensional contrast

Two experiments examined pigeons' response rates during short trials signaled by stimuli closely spaced along a wavelength continuum. In Experiment 1 separate halves of the continuum were correlated with different reinforcement schedules. In Experiment 2, the middle stimulus was accompanied by a lower probability of reinforcement than were the remaining wavelengths. Both procedures resulted in dimensional contrast “shoulders,” seen as relatively enhanced or depressed response rates in the presence of stimuli between the extreme of the continuum and the border separating the positive and negative stimuli. Sequential analyses addressed possible contributions of the following interactions: (a) local contrast, seen when rate during a given schedule depends on the schedule in the just-preceding trial; (b) modification of local contrast by the similarity of the signaling stimuli (P. Blough, 1983); and (c) schedule-independent rate contrast, seen when rate in a given trial depends on the rate controlled by the stimulus that accompanied the just-preceding trial (Malone & Rowe, 1981). Dimensional contrast functions were similar when isolated according to the schedule, to the similarity of the signaling stimulus, and to the response rate of the just-preceding trial. The interactions noted above do not appear to make important contributions to this effect.     

Representation and retention of three-event sequences in pigeons

The present experiments studied a three-event delayed sequence-discrimination (DSD) task: one arrangement (order) of two stimuli (red and yellow overhead lights) taken three in succession (e.g., red, yellow, red) was the positive sequence and the remaining seven arrangements were the negative sequences for responding and reward during the subsequent test stimulus. In Experiment 1, the final stimulus (recency) and the order of stimuli in the positive sequence controlled acquisition of discrimination. In Experiment 2, increasing the duration of memory intervals between stimuli reduced the discriminability of those negative sequences identical to the positive sequence after the delay. Three-event DSD performance in Experiments 1 and 2 was similar to two-event DSD performance in comparable published experiments. Models developed to explain pigeon performance in two-event DSD were extended to the three-event task. Results from both two- and three-event versions of the DSD task falsified a noncumulative model and several cumulative integration models (i.e., adding, averging, and some multiplying models), but corroborated one cumulative, multiplying model.     

A reflection: Howard Scott Liddell, 1895-1962

Howard S. Liddell, Professor of Psychobiology in the Department of Psychology at Cornell University, was one of the earliest American students and developers of I.P. Pavlov's theory of the conditioned reflex and an early researcher on stress. The significance of Liddell's work on stress was fully recognized when he was sent, as a member of a commission, to the battlefront at the height of the Korean War to study stress and self-control in the soldiers. This profound experience convinced Liddell that behavioral research must ultimately be made relevant to the understanding and elevation of human behavior. He spent the remaining ten years of his life in efforts to implement this conviction through research, writing, and lectures before scientific and lay groups.     

Impulsivity and perception: individual differences in the processing of the local and global dimensions of stimuli

There appears to be an association between a "global" mode of perceptual processing and a cluster of personality traits, one of which is impulsivity. The goal of the present study was to clarify this relationship. Subjects differing in impulsivity (as measured by a self-report inventory) performed speeded cardsorting tasks. They sorted stimuli consisting of large letters made up of smaller letters. Highly impulsive subjects had no more difficulty than other subjects in ignoring the large, "global," letters when they tried to attend to the smaller, "local," letters of which they were composed, nor were they more vulnerable than other subjects to Stroop-like response interference produced by the global letters. High impulsives did have particular difficulty when the task required that they integrate the information provided by the local and global letters. This finding can be explained in terms of individual differences in the value placed on speed relative to accuracy in information processing.     

Contributions of elicitation to measures of self-control

Pigeons' not pecking or pecking constituted choice between a delayed, large reinforcer and an immediate, small reinforcer (self-control) and at other times between a delayed reinforcer and no reinforcer (omission). Both a tone and a keylight were tested as choice signals, and the delayed reinforcer was either response independent or response dependent. Pigeons pecked during the choice signals on over 95% of the trials in the self-control procedure, and pecked during the choice signals on over 75% of the trials in the omission procedure. Consistent pecking was observed with either the tone or the keylight as a choice signal, with the exception that a tone paired with a response-independent delayed reinforcer did not maintain pecking in the omission procedure. Pigeons pecked during more choice signals when delayed reinforcers were response dependent than when the delayed reinforcers were response independent. These results indicate that Pavlovian conditioning influences self-control experiments, especially in single-key procedures.     

A survey os school psychologists'' use of behavior modification procedures

A national survey of behavior modification procedures used by school psychologists is reported. Usable questionnaires were received from 148 (49%) of 300 randomly selected members of the 1982 National Association of School Psychologists directory. Each respondent was asked to indicate the type of exposure, use, and inclusion of data collection procedures for each of 18 commonly used behavioral techniques. Conditional probabilities between type of exposure and use found strong relationships between supervision and subsequent use. The implications for the field of school psychology and future directions for training programs are discussed.