Momentary maximizing in concurrent schedules with a minimum interchangeover interval

Eight pigeons were trained on concurrent variable-interval variable-interval schedules with a minimum interchangeover time programmed as a consequence of changeovers. In Experiment 1 the reinforcement schedules remained constant while the minimum interchangeover time varied from 0 to 200 s. Relative response rates and relative time deviated from relative reinforcement rates toward indifference with long minimum interchangeover times. In Experiment 2 different reinforcement ratios were scheduled in successive experimental conditions with the minimum interchangeover time constant at 0, 2, 10, or 120 s. The exponent of the generalized matching equation was close to 1.0 when the minimum interchangeover time was 0 s (the typical procedure for concurrent schedules without a changeover delay) and decreased as that duration was increased. The data support the momentary maximizing theory and contradict molar maximizing theories and the melioration theory.     

IMPROVED CURVEBALL HITTING THROUGH THE ENHANCEMENT OF VISUAL CUES

This study investigated the effectiveness of using visual cues to highlight the seams of baseballs to improve the hitting of curveballs. Five undergraduate varsity baseball team candidates served as subjects. Behavior change was assessed through an alternating treatments design involving unmarked balls and two treatment conditions that included baseballs with 1/4-in. and 1/8-in. orange stripes marking the seams of the baseballs. Results indicated that subjects hit a greater percentage of marked than unmarked balls. These results suggest that the addition of visual cues may be a significant and beneficial technique to enhance hitting performance. Further research is suggested regarding the training procedures, effect of feedback, rate of fading cues, generalization to live pitching, and generalization to other types of pitches.     

Category discrimination by pigeons using five polymorphous features

Eight pigeons were trained to discriminate between sets of color photographs of natural scenes. The scenes differed along five two-valued dimensions (site, weather, camera distance, camera orientation, and camera height), and all combinations of the feature values were used. One value of each dimension was designated as positive, and slides containing three or more positive feature values were members of the positive stimulus set. Thus, each feature had an equal, low, correlation with reinforcement, and all features had zero correlations with each other. Seven of the 8 pigeons learned this discrimination, and their responding came under the control of all five features. Within the positive and negative stimulus sets, response rates were higher to stimuli that contained more positive feature values. Once discrimination had been achieved, reversal training was given using a subset of the slides. In this subset, only a single feature was correlated with reinforcement. All pigeons learned this reversal successfully and generalized it to additional photographs with the same feature content. After reversal, the original reinforcement contingencies were reinstated, and training was continued using all the slides except those that had been used in reversal. Reversal generalized to these slides to some extent. Analysis of the response rates to individual slides showed that, compared with prereversal training, only the feature that had been subjected to reversal contingencies showed a reversed correlation with response rate. The remaining features showed the same correlation with response rate as they had before reversal training. Thus, reversal on some members of a category following category discrimination training led to generalization to stimuli within the category that were not involved in the reversal, but not to features that were not reversed. It is therefore inappropriate to refer to the pigeons as learning a concept.     

Additional-delay schedules: A continuum of temporal contingencies by varying food delay

Pigeons performed on discrete-trial, temporally defined schedules in which the food delay (D) was adjusted according to the latency of the key peck (X) and two schedule parameters (t and A). The schedule function was D = A(t − X), where D is the experienced delay between a response and a reinforcer. The schedule parameter t is the maximum value below which the present contingencies occur. A is the additional delay to reinforcement for each second the response latency is shorter than the t value. When A = 0 s, the schedule is a continuous reinforcement schedule with immediate reinforcement. When A = 1 s, the schedule is a conjunctive fixed-ratio 1 fixed-time t-s schedule. When A approaches infinity, the schedule becomes a differential reinforcement of long latency schedule. The latencies for subjects with t = 10 s and t = 30 s were observed with the present schedules having seven values for A between 0 s and 11 s. In addition, the latencies for subjects for which t = 30 s were observed at an A value of 31 s to 41 s. As the A value increased, the latencies approached the t value for subjects for which t = 10 s. The latencies for 30-s-t subjects did not approach t, even when the A value was 41 s. The latencies for 10-s-t subjects at 11-s A value were longer than those under yoked conditions having exactly the same delays/interreinforcement intervals. These results demonstrated a continuum of latency related to the schedule continuum (value of A) at a small t value.     

Tempo discrimination in infants

An habituation/dishabituation paradigm demonstrates that 2- and 4-month-old infants are able to discriminate auditory sequences that vary slightly in tempo. Discriminations were only observed for intermediate tempi (600 ms but not 100, 300, 1500 ms IOI), suggesting that infants have the same optimal tempo range as adults.     

A NOTE ON TRANSFER OF STIMULUS CONTROL IN THE DELAYED-CUE PROCEDURE: FACILITATION BY AN OVERT DIFFERENTIAL RESPONSE

This case study describes initially unsuccessful attempts to use the delayed-cue procedure to teach conditional discriminations to an individual with moderate mental retardation. The task was matching printed-word comparison stimuli to dictated-name sample stimuli. In three experiments, the subject typically waited for the delayed cue unless differential responses to the dictated samples (repeating the sample names) were required. Hence, the study provides an example of a way to make the delayed-cue method more effective. The stimulus control bases for the results are discussed.     

汉字内隐记忆的实验研究（Ⅱ）：任务分离和反应倾向

在实验Ｉ的基础上,操纵学习时的呈现时间（２５０ｍｓ,５００ｍｓ,７５０ｍｓ）和注意变量（目标和非目标字）,运用任务分离方法及间接证明逻辑,比较了再认测验和整字偏好测验在不同条件下的辨别力（Ａ′）和反应倾向（Ｂ″）。结果：（１）双向功能分离的出现表明再认测验和偏好测验存在本质差异。根据“过程纯净”假设,可以推证内隐记忆存在于偏好测验中。此时,匹配比较法的标准未满足。（２）偏好测验中,５００ｍｓ呈现目标字时,有显著正向启动效应：７５０ｍｓ呈现非目标字时,有显著负向启动效应。（３）内隐记忆和外显记忆发生时,都具有稳定的心理状态。但是前者的报告标准较松宽,而后者的较严格。     

Biasing the pacemaker in the behavioral theory of timing

In the behavioral theory of timing, pacemaker rate is determined by overall rate of reinforcement. A two-alternative free-operant psychophysical procedure was employed to investigate whether pacemaker period was also sensitive to the differential rate of reinforcement. Responding on a left key during the first 25 s and on a right key during the second 25 s of a 50-s trial was reinforced at variable intervals, and variable-interval schedule values during the two halves of the trials were varied systematically. Responding on the right key during the first 25 s and on the left key during the second 25 s was not reinforced. Estimates of pacemaker period were derived from fits of a function predicted by the behavioral theory of timing to right-key response proportions in consecutive 5-s bins of the 50-s trial. Estimates of pacemaker period were shortest when the differential reinforcer rate most strongly favored right-key responses, and were longest when the differential reinforcer rate most strongly favored left-key responses. The results were consistent with the conclusion that pacemaker rate is influenced by relative reinforcer rate.     

Formation of transitivity in conditional matching to sample by pigeons

Four homing pigeons were trained over 5 months in a zero-delay, “arbitrary” matching-to-sample procedure with sample and comparison stimuli presented on any of three response keys. Birds were also required to complete a fixed-ratio 10 requirement on both sample and comparison stimuli to terminate their presentation. The procedure resulted in the establishment of relations that were not specifically trained and that can be characterized by the property of transitivity in a stimulus equivalence context. This result was in contrast with the findings obtained from most previous research with nonhuman subjects.     

Human d-amphetamine drug discrimination: methamphetamine and hydromorphone.

Standard measures of subjective and discriminative effects of drugs were compared in 5 human volunteers. Subjects responded on a second-order color-tracking procedure, where 30 mg of d-amphetamine served as a discriminative stimulus for one response and its absence as the discriminative stimulus for another response. Self-reported subjective effects were assessed concurrently using the single-dose questionnaire, subscales of the Addiction Research Center Inventory, and several analogue rating scales. On different days following discrimination acquisition, varying doses of d-amphetamine, methamphetamine, and hydromorphone were administered. In these test sessions, either response was reinforced. Methamphetamine and d-amphetamine occasioned dose-related increases in d-amphetamine appropriate responding; hydromorphone did not. Methamphetamine and d-amphetamine occasioned dose-related increases in reports of the drug received being most like "speed"; hydromorphone occasioned dose-related increases in reports of the drug received being most like "dope." All three drugs occasioned dose-related increases in reports of drug liking, and increases in the morphine-benzedrine group, amphetamine, and benzedrine group scales of the Addiction Research Center Inventory. This experiment demonstrated that although explicit discriminative control of behavior by a drug may covary with drug identification, it does not necessarily covary with other self-reported subjective effects. Thus, the complementary nature of the data provided by drug discrimination and standard subjective-effects measures provides quantitative and qualitative data useful in studying both relatively novel compounds and the behavioral biology of psychoactive drugs in general.