Delayed reinforcement and delayed choice in symbolic matching to sample: Effects on stimulus discriminability

Six pigeons were trained to peck a red side key when the brighter of two white lights (S₁) had been presented on the center key, and to peck a green side key when the dimmer of two white lights (S₂) had been presented on the center key. Equal frequencies of reinforcers were provided for the two types of correct choice. Incorrect choices, red side-key pecks following S₂ presentations and green side-key pecks following S₁ presentations, resulted in blackout. With 0-s delay between choice and reinforcement, the delay between sample presentation and choice was varied from 0 to 20 s. Then, with 0-s delay between sample presentation and choice, the delay between choice and reinforcement was varied from 0 to 20 s. Both types of delay resulted in decreased discriminability (defined in terms of a signal-detection analysis) of the center-key stimuli, but delayed choice had more effect on discriminability than did delayed reinforcement. These data are consistent with the view that the two kinds of delay operate differently. The effect of a sample-choice delay may result from a degradation of the conditional discriminative stimuli during the delay; the effect of a choice-reinforcer delay may result from a decrement in control by differential reinforcement.     

Delay-interval illumination changes interfere with pigeon short-term memory.

Pigeons acquired a successive depayed matching-to-sample task at delay intervals ranging from 2.5 to 7 seconds. Test sessions were conducted during which delay-interval illumination conditions were changed from those illumination conditions that prevailed during the baselines. Compared to baseline delayed matching performance, changing delay-interval illumination disrupted matching. This disruption occurred whether the change in delay-interval illumination represented an increase or a decrease, relative to the baseline, and whether there was or was not a change in illumination during the test session. It was concluded that illumination per se introduced during delay intervals of delayed matching tasks does not interfere with pigeon short-term memory. Rather, a change in delay-interval illumination, relative to the baseline, appears to retroactively interfere in pigeon short-term memory.     

Memory for sequences of stimuli and responses

Two experiments sought to determine if pigeons could discriminate and remember recent sequences of stimuli and responses. A variant of Konorski's short-term memory procedure involving successive presentation of sample and test stimuli was used. The samples were stimulus-response pairs of the form, (S-R)₁–(S-R)₂. Differential test responding disclosed memory of the two-item samples, with birds showing earlier and greater control by the second item than the first (Experiment 1). When the retention interval separating the second item of the sample sequence from the test stimulus was lenghtened from .5 to 2.0 or 4.0 sec, a systematic loss of stimulus control resulted; however, when varied over the same temporal range, the interval between the two items of the sample sequence had a much smaller effect, or none at all (Experiment 2). These results support an account of response-sequence differentiation that stresses short-term memory of organized behavior patterns.     

Short-term memory in the rhesus monkey: A behavioral analysis of delayed-response performance

This study obtained quantitative data on the bodily orientations of rhesus monkeys in a delayed-response task and determined whether such orientations mediate the correct response in a choice trial. The basic task was a two-key chain schedule with the key leading to food signaled in the initial component. During the subsequent delay interval, the signal was removed, but it was necessary that one of the keys be pressed to advance the schedule to the terminal choice component. The position of the key pressed thus indicated orientation during the delay interval. When the monkeys had free access to the left and right keys, they tended to press the key leading to food throughout the chain schedule components and received food on more than 85% of the trials, even when the delay was extended to 20 seconds. However, when orientation toward the food key was disrupted by forcing the monkeys to press an extraneous center key during the delay, choice performance deteriorated. Requiring the center key presses early, rather than late, in the delay component had a strong disruptive effect. The relation of the results to the mediating coding-response hypothesis is discussed.     

Short-term remembering of discriminative stimuli in pigeons.

Pigeons learned to peck the left or right of two white keys depending on whether a red or a green stimulus was displayed on a third key. The opportunity to peck the white keys was then dealyed for zero to six seconds after the red or green (to-be-remembered) stimulus. On half the trials, the feeder operated during the delay to interrupt behavior that might mediate discriminated responding. No events were scheduled on the remaining trials. In a later condition, the pigeons had the opportunity to peck the white keys during the delay. In general, accuracy decreased as delay increased in all conditions, but performance was least accurate following feeder operations and most accurate when pecking was allowed during the delay. The procedures may be analogous to varying the opportunity for rehearsal in studies of human short-term memory.     

Exploring the relationship between students’ values and the values of postsecondary institutions

Little is known of how institutional and individual value systems are related among university undergraduates. With three different measures and samples of college students, perceptions of university mission and values (i.e., institutional values, creating pro-social climates, and developing a life-long commitment to values) loaded independently of their personal values systems, and often negatively with social desirability. Perceptions of institutional values were generally independent of personal value systems, using either a rank-order (Sample 1, n = 199) or rating scale method (Sample 2, n = 107), or by focusing on moral behavior structures (Sample 3, n = 208). Together, these results indicate that higher education assessment may reflect institutional values that are independent of student personal value systems.Portions of this paper were presented at the 2004 Institute for College Student Values, Tallahassee, FL     

Brief therapy in the Israeli kibbutz

Analysis of results of therapy in an unselected sample of 211 kibbutz patients seen over a three year period by the author in his capacity as kibbutz member and psychiatrist indicated that over 70% of the identified patients responded very satisfactorily to brief therapy. About one-third of the clients did not need more than a single comprehensive therapy session to achieve continuous improvement. In a minority of the cases more than 10 sessions were required. The results were significantly better in cases treated by brief therapy than in the sample treated by long-term therapy, where the pre-treatment severity was determined to be greater. The paper describes the unique aspects of brief therapy in the kibbutz setting, giving an outline of the author's model of intervention, using all components of the individual, family, and community ecosystem.     

Short-term and long-term effects of reinforcers on choice

The relation between molar and molecular aspects of time allocation was studied in pigeons on concurrent variable-time variable-time schedules of reinforcement. Fifteen-minute reinforcer-free periods were inserted in the middle of every third session. Generalized molar matching of time ratios to reinforcer ratios was observed during concurrent reinforcement. Contrary to melioration theory, preference was unchanged during the reinforcer-free periods as well as in extinction. In addition to this long-term effect of reinforcement, short-term effects were observed: Reinforcers increased the duration of the stays during which they were delivered but had little consistent effect either on the immediately following stay in the same schedule or on the immediately following stay in the alternative schedule. Thus, an orderly effect of reinforcer delivery on molecular aspects of time allocation was observed, but because of its short-term nature, this effect cannot account for the matching observed at the molar level.     

发展机会、乐观和工作投入:任务责任心的调节作用

针对以往研究对工作投入短期波动的影响因素缺乏关注的局限,本研究从个体内部和动态视角采用经验取样法探讨了工作投入短期波动的影响因素。通过对65个研究对象连续测量15个工作日的调查,获得了975份个体内数据。HLM分析结果显示:(1)在个体内水平,每日发展机会和乐观对当天工作投入均有显著正向影响;(2)每日乐观部分中介当天发展机会与工作投入之间的正向关系;(3)个体任务责任心正向调节每日乐观与当天工作投入之间的正向关系,并且还能调节每日乐观的中介效应。最后,我们对研究的理论贡献、实践启示和研究局限进行了讨论。