Changes in functional response units with briefly delayed reinforcement

In two experiments, key-peck responding of pigeons was compared under variable-interval schedules that arranged immediate reinforcement and ones that arranged unsignaled delays of reinforcement. Responses during the nominal unsignaled delay periods had no effect on the reinforcer presentations. In Experiment 1, the unsignaled delays were studied using variable-interval schedules as baselines. Relative to the immediate reinforcement condition, 0.5-s unsignaled delays decreased the duration of the reinforced interresponse times and increased the overall frequency of short (<0.5-s) interresponse times. Longer, 5.0-s unsignaled delays increased the duration of the reinforced interresponse times and decreased the overall frequency of the short interresponse times. In Experiment 2, similar effects to those of Experiment 1 were obtained when the 0.5-s unsignaled delays were imposed upon a baseline schedule that explicitly arranged reinforcement of short interresponse times and therefore already generated a large number of short interresponse times. The results support earlier suggestions that the unsignaled 0.5-s delays change the functional response unit from a single key peck to a multiple key-peck unit. These findings are discussed in terms of the mechanisms by which contingencies control response structure in the absence of specific structural requirements.     

Effects of alternative reinforcement sources: A reevaluation

The effects of two alternative sources of food delivery on the key-peck responding of pigeons were examined. Pecking was maintained by a variable-interval 3-min schedule. In the presence of this schedule in different conditions, either a variable-time 3-min schedule delivering food independently of responding or an equivalent schedule that required a minimum 2-s pause between a key peck and food delivery (a differential-reinforcement-of-other-behavior schedule) was added. The differential-reinforcement-of-other-behavior schedule reduced response rates more than did the variable-time schedule in most instances. The delay between a key peck and the next reinforcer consistently was longer under the differential-reinforcement-of-other-behavior schedule than under the variable-time schedule. Response rates and median delay between responses and reinforcers were negatively correlated. These results contradict earlier conclusions about the behavioral effects of alternative reinforcement. They suggest that an interpretation in terms of response–reinforcer contiguity is consistent with the data.     

Discrimination learning in a foraging situation

Rats were allowed to forage in a simulated natural environment made up of eight food sources (patches) each containing a fixed number of pellets. Two of the eight contained an extra supply of peanuts. The peanut patches were signaled by an olfactory/visual cue located at the bottom of the ladder leading to the patch. In successive phases the number of sessions per day, height of the patches, and availability of peanuts were manipulated. Subjects showed evidence of discrimination learning under these conditions, although the degree of discriminatory behavior varied as a function of environmental manipulations. Assessment of behavior within foraging sessions showed that subjects systematically changed their patterns of utilization of patches across time. Sampling or exploration, as well as food reinforcement, seem implicated in these results.     

Reconsideration of measurement of error in human motor learning

Human motor learning is often measured by error scores. The convention of using mean absolute error, mean constant error, and variable error shows lack of desirable parsimony and interpretability. This paper provides the background of error measurement and states criticisms of conventional methodology. A parsimonious model of error analysis is provided, along with operationalized interpretations and implications for motor learning. Teaching, interpreting, and using error scores in research may be simplified and facilitated with the model.     

Stability of the Peabody Picture Vocabulary Test--revised for emotionally handicapped middle-school-age children

In this pilot study, 20 middle-school-age children classified as emotionally handicapped were administered Forms L and M of the Peabody Picture Vocabulary Test--Revised in test-retest fashion. Pearson correlations for Form L were .90, for Form M, .69, and these dependent correlations were significantly different from each other. As triennial school psychological evaluations typically contain tests which have been administered previously, e.g., WISC-R, WRAT-R, we suggest that psychologists use caution when using Form M to test or retest the receptive vocabulary of emotionally handicapped or disturbed middle-school-age children.     

SETTING CUTOFF SCORES: LEGAL, PSYCHOMETRIC, AND PROFESSIONAL ISSUES AND GUIDELINES

Cutoff scores are used in a variety of settings to help managers make personnel decisions. Although cutoff scores are used widely, information about their derivation and appropriate use is scattered in the legal, psychometric, and professional literatures. The purpose of this paper is to analyze critically and to integrate these diverse literatures, to summarize what is known and what is unknown about the use and misuse of cutoff scores. Alternative methods are examined in relation to legal precedents set by the courts, to psychometric principles, and to the various sets of professional guidelines. Directions for future research are suggested, and we conclude with a set of recommendations regarding acceptable professional practice in this area.