Comparison of drug effects on fixed-ratio performance and chain performance maintained under a second-order fixed-ratio schedule.

In one component of a multiple schedule, pigeons were required to complete the same four-response chain each session by responding sequentially on three identically lighted keys in the presence of four successively presented colors (chain performance). Food presentation occurred after five completions of the chain (i.e., after 20 correct responses). Errors, such as responding on the center or right key when the left was designated correct, produced a brief timeout but did not reset the chain. In the other component, responding on a single key (lighted white) was maintained by food presentation under a fixed-ratio 20 schedule. In general, phencyclidine and d-amphetamine produced dose-dependent decreases in the overall response rates in both components. With pentobarbital, overall rate in each component generally increased at intermediate doses and decreased at higher doses. All three drugs produced dose-dependent disruptive effects on chain-performance accuracy. Phencyclidine and pentobarbital increased percent errors at doses that had little or no rate-decreasing effects, whereas d-amphetamine generally increased percent errors only at doses that substantially decreased overall rate. At high doses, all three drugs produced greater disruption of chain performance than of fixed-ratio performance, as indicated by a slower return to control responding, although the effects of d-amphetamine were less selective than those of phencyclidine or pentobarbital.     

Category typicality effects in children's memory performance: Qualitative and quantitative differences in the processing of category information

Kindergarten, third, and sixth graders (6, 9, and 12 years of age, respectively) received a cue-at-input/cue-at-output recall task, using category typical and atypical items that were based on either (1) children's conceptions of item typicality, or (2) adults' conceptions of item typicality. At each grade level, recall was greater with the child-defined lists than with the adult-defined lists, and typical items were recalled to a greater extent than atypical items. Further analyses items were recalled to a greater extent than atypical items. Further analyses revealed that the recall of typical items varied as a function of children's typicality ratings of items, and that the “typicality effect” in the adult-norm condition was due primarily to the childrennot realizing that many of the atypical items were appropriate category exemplars. In contrast, typicality effects in the child-norm condition were attributed to qualitative differences in the judged “goodness of example” of the typical and atypical items. The results were discussed in terms of the appropriateness of typicality as a dimension of children's natural language concepts, the role of age differences in knowledge base in affecting performance on a cognitive task, and of the importance of using child-generated norms in studies of children's processing of category information.     

Presentation of a flashing light following training produces amnesia

Long-Evans rats given exposure to a flashing-light stimulus following one-trial fear conditioning showed amnesia relative to controls not given the flashing-light experience. Together with previous results obtained in this laboratory, it is apparent that the flashing light modulates memory processing.     

Selective antagonism of the error-increasing effect of morphine by naloxone 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. Errors produced a brief timeout but did not reset the chain. When either morphine or naloxone was administered alone, the overall response rate decreased with increasing doses. The rate-decreasing effect was accompanied by an increase in percent errors with morphine but not with naloxone. Both effects of morphine were antagonized by doses of naloxone that were ineffective when given alone. The antagonism was selective in that naloxone (3 mg/kg) completely blocked the error-increasing effect but not the rate-decreasing effect of the higher doses of morphine. The view that naloxone is a specific narcotic antagonist was supported by the finding that naloxone failed to antagonize the rate-decreasing and error-increasing effects of d-amphetamine, pentobarbital, and phencyclidine.     

Assertive training: An adjunct to fluency shaping

“Assertive Training” has been utilized as an adjunct therapy in a six week residential program at Walter Reed Army Medical Center. The speech pathology staff in conjunction with the psychology staff determined that a persistent problem with long term success after patients were dismissed from therapy was largely due to a “behavioral deficit” in their interpersonal verbal confrontations. The anxiety resulting from such communication failure simply chips away at the self confidence needed to maintain a working level of fluency, resulting in a “snowballing” effect back to dysfluency.

Thus, the goals and procedures of assertive training for stutterers are discussed as a means to shape more effective skills in relating to others in difficult situations. Pre, post and six month follow-up data are presented.     

The effects of varied acoustic parameters on performance in dichotic speech perception tasks

Five dichotic speech experiments were conducted with normal adult listeners in which the signal to one or both ears was degraded by manipulation of intensity, signal-to-noise ratio, or bandwidth parameters. Results suggest that: (1) performance of the ear (or ears) receiving the degraded signal can be predicted from the monaural identifiability of the stimuli, and (2) dichotic performance, at least in stop consonant-vowel tests, reflects an additive central process which combines speech information from the two ears.     

Responding maintained by the opportunity to attack during an interval food reinforcement schedule

Pigeons responded in a two-key situation. Responses on the right key (food key) were reinforced with food presentation on a response-initiated fixed-interval schedule, (i.e., first response after a fixed period of time was reinforced); responses on the left key (target key) were reinforced on a fixed-ratio schedule (i.e., every nth response was reinforced) with the presentation of a target bird that could be attacked. When the interval value of the food reinforcement schedule was varied from 1 min to 5 min, both the rate of attack responding on the target bird and the rate of responding on the target key were a function of the interval value. Responding on the target key was not maintained by the stimulus change associated with target availability, and was successively extinguished and reconditioned by removing and returning the target bird to the restraining box. When food was delivered independently of behavior, responding on the target key either remained unchanged or decreased, but was not eliminated. Responding on the target key was not maintained in the absence of an intermittent schedule of food presentation.