EFFECTS OF RESPONSE SPACING ON ACQUISITION AND RETENTION OF CONDITIONAL DISCRIMINATIONS

Pigeons were exposed to a repeated acquisition procedure in which no delays were imposed and rate of responding was relatively high. They also were exposed to conditions in which delays were arranged between trials within chains or between completed chains, and rates of responding were lower. Number of trials, rate of reinforcement, difficulty of the discrimination, and motivating operations were held constant. Terminal accuracy was highest under the no‐delay condition, in which rate of responding was highest. Effects of trial spacing on retention were mixed and depended on whether delays were imposed between trials within chains or between completed chains. These findings provide basic‐research support for the rapid presentation of trials in direct instruction and for rate building in precision teaching.     

Solution Strategies and Achievement in Dutch Complex Arithmetic: Latent Variable Modeling of Change

In the Netherlands, national assessments at the end of primary school (Grade 6) show a decline of achievement on problems of complex or written arithmetic over the last two decades. The present study aims at contributing to an explanation of the large achievement decrease on complex division, by investigating the strategies students used in solving the division problems in the two most recent assessments carried out in 1997 and in 2004. The students’ strategies were classified into four categories. A data set resulted with two types of repeated observations within students: the nominal strategies and the dichotomous achievement scores (correct/incorrect) on the items administered.It is argued that latent variable modeling methodology is appropriate to analyze these data. First, latent class analyses with year of assessment as a covariate were carried out on the multivariate nominal strategy variables. Results showed a shift from application of the traditional long division algorithm in 1997, to the less accurate strategy of stating an answer without writing down any notes or calculations in 2004, especially for boys. Second, explanatory IRT analyses showed that the three main strategies were significantly less accurate in 2004 than they were in 1997.     

PROTECTIVE EQUIPMENT: CONTINUOUS AND CONTINGENT APPLICATION IN THE TREATMENT OF SELF-INJURIOUS BEHAVIOR

This study evaluated the use of protective equipment in treating self-injurious behavior (SIB) exhibited by three retarded persons. In Experiment 1, the equipment was first applied continuously during 20-min sessions in individual multiple baseline designs across settings. Results showed substantial reductions in head hitting, eye gouging, and hand biting. Brief periods of time-out with the protective equipment were later made contingent on SIB and combined with a differential reinforcement procedure. Reduced levels of SIB was maintained with all subjects. Additionally, the amount of time during which the equipment was applied decreased as the SIB diminished. Experiment 2 evaluated the use of contingent protective equipment (the final condition in Experiment 1) when applied directly in the subjects' living uints during the day. During Experiment 2, SIB remained at or below the levels found at the termination of Experiment 1. Finally, in an effort to assess the long-term effectiveness of the procedure, responsibility for implementation was given to the staff who were typically assigned to provide therapy to the subjects. Follow-up probe observations conducted up to 104 days after termination of the final experimental condition showed continued low levels of both SIB and equipment usage. Results of these experiments suggest that contingent protective equipment and differential reinforcement may be effective in reducing chronic self-injury.     

Repeated measurements analysis of variance when the correlations have a certain pattern

Consider a repeated measurements study in which a single observation is taken at each oft(t > 2) equally spaced time points for each ofn subjects. This paper uses a result of Box to find the appropriate multiplicative correction term for the degrees of freedom in the analysis of variance table for the case when there is equal variability per time point, and when the correlation between observationsu time units apart is equal to ^u . For large values oft, the multiplicative correction has a lower bound approximately equal to 2.5/(t – 1).Dr. Fleiss is also with the Biometrics Research Unit of the New York State Psychiatric Institute. This work was supported in part by grant DE 04068 from the National Institute of Dental Research.     

Selective antagonism of the rate-decreasing effect of d-amphetamine by chlorpromazine in a repeated-acquisition task.

Pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors. The response chain was maintained by food presentation under a fixed-ratio schedule. When d-amphetamine was administered alone, the overall response rate decreased and the percent errors increased with increasing doses. When a small dose of chlorpromazine, which was ineffective when given alone, was administered in combination with d-amphetamine, the rate-decreasing effect was antagonized. The antagonism was selective, however, in that the error-increasing effect of d-amphetamine was augmented by chlorpromazine. The nature of the joint effect of the two drugs thus depended on the behavioral measure: rate vs. accuracy.     

Some approximate tests for repeated measurement designs

Four approximate tests are considered for repeated measurement designs in which observations are multivariate normal with arbitrary covariance matrices. In these tests traditional within-subject mean square ratios are compared with critical values derived fromF distributions with adjusted degrees of freedom. Two of them—the approximate and the improved general approximate (IGA) tests—behave adequately in terms of Type I error. Generally, the IGA test functions better than the approximate test, however the latter involves less computations. In regards to power, the IGA test may compete with one multivariate procedure when the assumptions of the latter are tenable.The author wishes to thank Garrett K. Mandeville for his careful reading of the final version of the paper.     

SELF-RESTRAINT AS POSITIVE REINFORCEMENT FOR SELF-INJURIOUS BEHAVIOR

Many individuals who engage in self-injurious behavior (SIB) also exhibit self-restraint. We compared rates of SIB exhibited by a 32-year-old woman diagnosed with profound retardation across conditions in which access to restraint was (a) continuously available, (b) presented as a consequence for SIB, or (c) unavailable. Rates of SIB increased when access to restraint was contingent upon SIB and decreased when restraint was unavailable, suggesting that self-restraint functioned as positive reinforcement for SIB.     

Risky choice as a function of amount and variance in food supply.

In Experiment 1, 4 rats earned their daily food ration by choosing on a trials basis between a "risky" and a "riskless" lever. The risky lever produced either 15 45-mg food pellets or no pellets, and on average provided five pellets per choice. The riskless lever always produced three pellets. Across conditions, the number of trials per session was varied. Body weight and choice of the risky lever decreased as the number of trials per session decreased, even though body weight could only be defended by increased choice of the risky lever. In Experiment 2, trials per session were fixed, but the number of pellets delivered by the risky and riskless levers was either at the same level as in Experiment 1 or tripled from those levels. Now choice of the risky lever was inversely related to the size of reinforcement and to body weight. The results of these experiments show that risk aversion covaries with the amount of food available in a session and the daily variance in the amount of food earned.     

The establishment of stimulus control by instructions and by differential reinforcement

A repeated acquisition design was used to study the effects of instructions and differential reinforcement on the performance of complex chains by undergraduates. The chains required responding on a series of keys that corresponded to characters that appeared on a monitor. Each day, subjects performed a new chain in a learning session and later relearned the same chain in a test session. Experiment 1 replicated previous research by showing that instructional stimuli paired with the correct responses in the learning sessions, combined with differential reinforcement in both learning and test sessions, resulted in stimulus control by the characters in each link. Experiment 2 separated the effects of instructional stimuli and differential reinforcement, and showed that stimulus control by the characters could be established solely by differential reinforcement during the test sessions. Experiment 3 showed that when a rule specified the relation between learning and test sessions, some subjects performed accurately in the test sessions without exposure to any differential consequences. This rule apparently altered the stimulus control properties of the characters much as did differential reinforcement during testing. However, compared to differential reinforcement, the rule established stimulus control more quickly.     

Repeated acquisition in the analysis of rule-governed behavior

Five children, ranging in age from 3½ years to 5½ years, were taught various four-response chains using conditioned reinforcement. Experiment 1 investigated the effects of presenting “instruction” stimuli—a sequence of lights over the correct response buttons—to assess their role in facilitating the acquisition of a chain of responses. Without the “instruction” stimuli, children made many errors before responses were brought under the control of the programmed contingencies. When confronted with the same contingencies later in the day, these subjects made fewer errors. In contrast, in the presence of the “instruction” stimuli, subjects made virtually no errors. However, when the “instruction” stimuli were discontinued in the subsequent session, all 5 subjects made errors. In Experiment 2, the subjects were taught to verbalize the contingencies during the phase without the “instruction” stimuli. This resulted in errorless performance during the subsequent exposure to the same procedure, but errors nevertheless occurred again during reexposure to the procedure with the “instruction” stimuli discontinued.