An adjusted measure of achievement motivation for males and females and effects of future orientation on level of performance

An adjusted measure of achievement motivation was devised with the combined use of the Mehrabian Achievement Scale (Educational and Psychological Measurement, 1968, 28, 493–502) and the Mandler and Sarason (Journal of Abnormal and Social Psychology, 1952, 47, 166–173) Test Anxiety Questionnaire. Contingent instructions, in which Ss were told success on a test was necessary to qualify for opportunities to succeed on subsequent tests, were contrasted to performance in equivalent noncontingent situations and relative to adjusted achievement motivation for both male and female subjects. In noncontingent situations Ss were told performance on any one test did not affect their opportunity to take subsequent tests. Support was obtained for the use of the above mentioned scales as a predictor of performance for both sexes but not for the Mehrabian by itself. Both male and female Ss high in achievement motivation consistently scored significantly higher than Ss low in achievement motivation in all conditions. The expected interactions between treatments and motive groups were not found but t tests between extreme motive groups within conditions revealed significant differences in the expected directions. These results do not provide statistically reliable support to the elaborated theory of achievement motivation.     

Responding under positive and negative response contingencies in pigeons and crows

Four crows were trained to key peck for food. Then, they were exposed to a positive response contingency that required them to peck the key when it was illuminated briefly (the trial) in order to receive food. This procedure resulted in consistent within-trial pecking. When the contingency changed so that food was presented at the end of a trial when no response occurred, but the trial terminated immediately and food was omitted when a response occurred (negative response contingency), responding decreased markedly. Eight pigeons were studied under the same change in contingencies. These birds varied in their response histories from naive to having several years' experience. The previously naive pigeons also showed rapid declines in responding under the negative contingency; the responding of the birds with extended training histories declined much more slowly. Eventually, however, six of the eight pigeons showed little or no responding under the negative contingency, while they responded consistently when re-exposed to the positive contingency. These findings question the power and the generality of the negative automaintenance phenomenon.     

Matching-based hedonic scaling in the pigeon

Four slightly hungry pigeons chose between pairs of grains in a Findley concurrent choice procedure. For Condition I, choice involved hemp versus buckwheat; for Condition II, wheat versus buckwheat; and for Condition III, hemp versus wheat. In all conditions, frequency of reinforcement was arranged according to concurrent variable-interval variable-interval schedules. On the assumption that subjects matched their behavior and time distributions to those of reinforcer value, the choice functions obtained in Conditions I and II were transformed to yield estimates of values of hemp and wheat relative to buckwheat. These, in turn, provided predictions about behavior and time allocation in Condition III. In general, the predicted outcomes were close to those actually obtained. The results evidence the effectiveness of matching-based hedonic scales in the prediction of choice between qualitatively different reinforcers.     

Time horizons in rats: the effect of operant control of access to future food.

The primary goal of this experiment was to determine whether the addition of an operant requirement for access to a less costly (continuous reinforcement) patch of future food increased the time horizon over which that future patch decreased intake in a currently available depleting (progressive-ratio) patch. Three groups of 4 rats were tested. Each member of the earned-time group was required to cumulate a fixed-time outside the progressive-ratio patch to obtain access to food in the less costly patch; the fixed-time requirement ranged from 2 to 64 min. Rats in the matched-time group received response-independent access to less costly food at the average delay shown by the earned-time group. Rats in the matched-time no-food group were removed from the chamber at the same average delay without receiving access to less costly food. Two of the earned-time rats showed an increased time horizon relative to that shown by the matched-time rats (approaching 40 min for 1 rat). The other 2 earned-time rats markedly increased instrumental responding but showed suppression of intake only when food was less than 20 min away. The matched-time group showed less suppression of intake over a similar range of delay intervals. Surprisingly, the matched-time no-food animals also showed suppression of intake concentrated at the end of the session, possibly reflecting the receipt of their entire daily ration 30 min after the session. The potential importance of time horizons to the foraging process is clear, but experimenters are still working out paradigms for investigation of these horizons.     

Effects of body weight on discriminative-stimulus control by phencyclidine in the pigeon.

Using a color-tracking procedure with responses reinforced under a second-order schedule, the discriminative-stimulus properties of phencyclidine were studied in pigeons maintained at 70%, 80%, or 90% of their free-feeding weights. The generalization curves for phencyclidine were similar at all three body weights. Generalization curves for pentobarbital, d-amphetamine, and saline were also unrelated to body weight. These data suggest that food deprivation may not influence the discriminative-stimulus properties of drugs in the way that it influences the reinforcing-stimulus properties of drugs. The reason may be that during discrimination training interoceptive stimuli resulting from food deprivation do not become conditioned to the stimulus properties of the drug, because the food-deprivation stimuli are paired equally often with the presence and absence of drug stimuli.     

Positive conditioned suppression: an explanation in terms of multiple and concurrent schedules

Rats performed under a baseline variable-interval schedule of food presentation. A response-independent food schedule was then superimposed on the baseline schedule for different periods of time across different conditions. The response-independent schedule operated for the whole session in some conditions, intermittently for sixty second periods in some, and intermittently for ten-second periods in others. Under these latter two sets of conditions, the response-independent food schedule was stimulus correlated and alternated with the baseline schedule according to a multiple schedule. Response-independent food presentations always suppressed responding. The degree of suppression tended to increase the longer the period of response-independent food. Control conditions, in which the superimposed schedule was response-dependent, rather than response-independent, did not produce response suppression. The results fit an analysis of positive conditioned suppression phenomena in the context of multiple and concurrent schedule effects.     

The effects of sleep disruption on the treatment of a feeding disorder

We evaluated the effects of sleep disruption on the mealtime behavior of a young boy with developmental disabilities. Results showed that bite acceptance was less likely to persist during meals following disrupted sleep, but only when escape extinction was not implemented. Findings are discussed in terms of establishing operations and the effects of sleep disruption on the assessment and treatment of feeding problems.     

Noncontingent reinforcement as treatment for food refusal and associated self-injury

We examined the use of noncontingent reinforcement to decrease self-injury and increase bite acceptance in a child who exhibited food refusal. First, a brief functional analysis suggested that self-injury was maintained by escape from food presentation. Next, we evaluated an intervention that involved noncontingent access to a video during feeding sessions. Results of the intervention showed a decrease in self-injury and an increase in bite acceptance.     

Food and water intake as functions of resource consumption costs in a closed economy.

In two experiments, rats living in a closed economy were offered continuous, concurrent access to four resources: food, water, a nest, and a running wheel. Costs of consuming food and water were imposed with bar-press requirements, and the price of either one or both resources was raised. As the consumption cost increased, less was consumed in each bout of resource use. Bout frequency increased, but not sufficiently to compensate for the fall in bout size, and total intake fell. Food and water tended to be complementary resources, in that as intake of one fell with its price, intake of the other also decreased. This interaction was accounted for by the defense of the ratio of body water to lean body mass. As amount consumed decreased, increases in feed efficiency (weight gain per unit of food ingested) and the use of stored calories compensated for the reduced energy intake. There was evidence of competition between feeding and drinking at the higher costs: When both commodities were expensive, the decline in the intake of each one was greater than when only one commodity was expensive. Although the time spent nesting, running, and in unmonitored activity was adjusted when feeding or drinking took more of the rat's day, there was no particular activity that was sacrificed.     

Within-session changes in the VI response function: separating food density from elapsed session time.

Previous studies examining the relationship between response rate and reinforcement rate on variable-interval schedules (the variable-interval response function) have confounded elapsed session time with within-session changes in food density. The present experiments attempted to manipulate these factors independently and thus isolate their effects on responding. In Experiment 1, 7 rats pressed a bar for food on a series of four variable-interval schedules (7.5 s, 15 s, 30 s, and 480 s). Elapsed session time was held constant while food density was manipulated via a presession feeding. Changes in food density altered the form of the variable-interval response function, independently of elapsed session time. In Experiment 2, 8 rats responded on the same series of variable-interval schedules as in Experiment 1, but food density was held constant and elapsed session time was manipulated via the use of timeout periods. The results revealed no evidence for an effect of elapsed session time independent of food density. The present results extend a recent analysis of the variable-interval response function by Dougan, Kuh, and Vink (1993) by identifying food density as an important factor determining the form of the function. The present results also help clarify the controversy over the correct empirical form of the variable-interval response function by further defining the variables responsible for differences in the form of that function.