Maintenance of responding when reinforcement becomes delayed

In four experiments with rats, we examined the persistence of behavior when reinforcement was switched from immediate to delayed. In Experiment 1, lever pressing elicited by instrumental training with immediate reinforcement continued when a 20-sec delay of reinforcement was introduced (easy-to-hard condition), whereas when the delay condition was introduced from the start (hard-to-hard condition), responding remained low throughout. A similar result was obtained in Experiment 2, in which lever pressing was elicited by a classical conditioning (autoshaping) procedure. In Experiment 3, rats initially trained with delayed reinforcement continued to respond at a low rate when switched to immediate reinforcement (hard-to-easy condition). By measuring magazine entry (goal tracking) as well as lever pressing (sign tracking) in Experiment 4, we confirmed that such transfer effects at least partly involve the persistence of whatever type of behavior was initially dominant.     

Rate of reinforcement and session duration as determinants of within-session patterns of responding

Rats pressed levers for Noyes pellets or keys for sweetened condensed milk reinforcers delivered by multiple schedules. Session length and baseline rates of reinforcement were varied in two experiments. Rates of responding increased during the early part of the session and then decreased for both responses and reinforcers, as well as for all subjects and values of the independent variables. Changes in response rates across the session sometimes exceeded 500%. Respoiise rates peaked approximately 20 min after the beginning of the session, regardless of session duration, when subjects responded on a multiple variable interval 1-min variable interval 1-min schedule. The function was flatter for longer sessions than it was for shorter sessions. The function was flatter, more symmetrical, and peaked later for lower rates of reinforcement than for higher rates of reinforcement. The function appeared early in training, and further experience moved and reduced its peak. Variables related to reinforcement exerted more control over some aspects of this function than did variables related to responding. These within-session patterns of responding may have fundamental implications for experimental design and theorizing.     

Conjunctive schedules of reinforcement IV: Effects on the pattern of responding of changes in requirement at reinforcement

The effects of different schedule requirements at reinforcement on patterns of responding by pigeons were assessed under conjunctive schedules with comparable response-number requirements, Under one conjunctive schedule (conjunctive fixed-interval fixed-ratio schedule), a response was reinforced after a 6-min interval had elapsedand a specific minimum number of responses had been emitted, Under a second conjunctive schedule, a response was reinforced after the 6-min fixed interval and upon completion of a tandem schedule requirement (conjunctive fixed-interval tandem schedule), This schedule retained the same required minimum number of responses as the first conjunctive schedule, but responses were never reinforced according to a fixed-ratio schedule; the tandem schedule was comprised of a fixed-ratio and a small (.1 to 10.0 sec) fixed-interval schedule, Under the conjunctive fixed-interval fixed-ratio schedule, responding was characterized by an initial pause, an abrupt transition to a high response rate, and a second transition to a lower rate that prevailed or slightly increased up to reinforcement, Under the conjunctive fixed-interval tandem schedule, pauses were extended, response rates were lower, and the initial high rate of responding was generally absent, The above effects depended upon the size of the fixed interval of the tandem schedule, The distinct pattern of responding generated by conjunctive fixed-interval fixed-ratio schedules depends upon occasional reinforcement of fixed-ratio responding and not merely on the addition of a minimum number of required responses.     

Visual and social determinants of shock-elicited aggressive responding in rats

Light and dark reared, social and isolate housed, male Long-Evans hooded rats were tested in bright and dim light for aggressive response to footshock. Test lighting and socialization main effects were significant, with greater fighting in dim light than in bright light and greater fighting by isolates than by socially housed animals. Test lighting interacted with prior visual experience and socialization interacted with past and present illumination variables. The results suggest an inhibitory effect of test illumination dependent upon prior social and visual experience.     

Acquisition of schedule-induced polydipsia by rats in proximity to upcoming food delivery

Food-deprived rats that receive intermittent delivery of small amounts of food develop excessive drinking--specifically, schedule-induced polydipsia (SIP). A main characteristic of SIP is its occurrence at the beginning of interfood intervals. The purpose of this study was to demonstrate that SIP can be developed toward the end of interfood intervals, in closer proximity to upcoming than to preceding food delivery. In Experiment 1, two groups were exposed to a fixed-time (FT) 30-sec food schedule with water available during the first or the last 15 sec of each interfood interval. Two additional groups, which had access to water throughout, were exposed to FT 30-sec or FT 15-sec schedules of food presentation. The FT 30-sec group with free access to water developed the highest level of intake; similar and intermediate levels were induced in all the remaining groups. In Experiment 2, three groups of rats were exposed to an FT 90-sec food schedule with water available during the first, the second, or the last 30 sec of each interfood interval. One additional group with access to water throughout was exposed to the FT 90-sec schedule of food presentation. The group with free access to water developed a higher level of consumption than did the other groups, but by the end of training none of the four groups showed statistical differences in polydipsic drinking. Results show that adjunctive drinking can be developed in proximity to upcoming food delivery even with long interfood intervals.     

Effect of experience with a preferred food on consummatory responding for a less preferred food in goldfish

In two experiments with goldfish patterned after work with rats, consummatory responding for a less preferred food (adulterated with quinine) was measured in subjects that did or did not have previous experience of a preferred (unadulterated) food. The result in each case was not the negative contrast found in rats, but the opposite—more responding in subjects with experience of both foods. The experiments are in accord with a variety of others that have failed to show control of performance by remembered reward in goldfish.     

Effects of CSs for food and water upon rats barpressing for different magnitudes of food reinforcement

Forty-eight albino rats were first exposed to randomly intermixed, noncontingent presentations of one pellet, six pellets, and water. For each of three groups, a CS+ was paired with one of the reinforcers, while the other two reinforcers and a CS? were presented alone. Then half the subjects experienced a six-pellet reward and half experienced a one-pellet reward for leverpresses during a light S^D. Finally, on test trials, the CS+ or CS? was compounded with the light. Latencies on test trials indicated that responding for the one-pellet reward was significantly more disrupted by a CS+ for six pellets than by the CS+ for one pellet or the CS+ for water. Responding for the six-pellet reward was disrupted by the CS+ for one pellet somewhat more than by the CS+ for six pellets or water, but not significantly so. This pattern of results is partially consistent with an associative model of transfer and appears to contradict a motivational account of such effects.     

Habituation may contribute to within-session decreases in responding under high-rate schedules of reinforcement

Two experiments tested the hypothesis that habituation contributes to within-session decreases in responding. In Experiment 1, rats’ leverpressing was reinforced under a fixed ratio (FR) 4 schedule throughout the baseline sessions. During the dishabituation sessions, the first 21 min and the last 21 min were FR 4; dishabituating events occurred during the middle 3 min. The dishabituating events altered the manner of reinforcer delivery in four different ways. Response rates increased after all dishabituating events. In Experiment 2, rats responded on several FR and variable ratio (VR) schedules. The ratio requirement varied from 3 to 15. Within-session decreases in responding were steeper during FR schedules than during VR schedules. In addition, response rates were well described as linear functions of cumulative number of food pellets eaten within sessions. These results support the habituation hypothesis but do not rule out the possibility that other satiety variables might contribute simultaneously.     

Control of responding by a conditioned reinforcer in the presence of free food

It has been reported that animals will “work” in preference to “freeloading.” However, the variables responsible for this phenomenon are not well understood. Two pigeons were trained to keypeck for food on a fixed-ratio 300 schedule. Next, the food hopper was propped up to permit continuous access to food, and the presence or absence of the hopper light was manipulated. When the hopper light was presented contingent upon the fixed-ratio schedule, keypecking occurred; when it was not presented, keypecking ceased. Thus, responding in the presence of free food was shown to be a function of the conditioned reinforcing properties of the hopper light.     

Rates of responding in the pigeon generated by simple and complex schedules which provide the same rates of reinforcement

Four pigeons pecked for food reinforcement on variable interval 1-min schedules and on the variable-interval 1-min components of multiple, concurrent, and pseudoconcurrent schedules. The pseudoconcurrent schedule provided only one schedule of reinforcement; but, any reinforcer could be collected by responding on either of two keys. The rate of responding generated by the variable interval schedule was not greater than the rates of responding generated by the components of the complex schedules. But, the rate of reinforcement obtained from the variable interval schedule was greater than the rates of reinforcement obtained from the components of the multiple schedule. These results may contradict the equation proposed by Herrnstein (1970). The equation predicts that the rate of responding generated by a schedule of reinforcement will be greater when the schedule appears alone, than when it appears as one component of a complex schedule.     

关于进一步加强高职院校学风建设的探讨

学风建设关系到高职院校的兴衰,进一步加强学风建设是实现高职院校培养目标的根本保证,是学生成人成才的需要,是高职院校自身发展的内在要求。加强高职院校学风建设应从思想政治教育工作、师资队伍建设、政策制度和考风考纪等方面着手。     

Reward sequence and reinforcement level as determinants of S− behavior in differential conditioning

In two differential conditioning experiments, groups of 10 rats each differed with respect to average reward and schedule of reward received in S+. Nonreward (N) occurred on all S? trials. In both experiments, extinction of responding to S? (resistance to discrimination) was extensively regulated by reward sequence and was largely independent of average reward. In Experiment 1, resistance to discrimination was a function of transitions from N to rewarded (R) trials (N-R transitions). In Experiment 2, resistance to discrimination was increased by large reward on the R trial of N-R transitions and decreased by large reward on the R trial of R-N transitions. These schedule effects on resistance to discrimination parallel the effects of comparable schedules on resistance to extinction following partial reinforcement. The results are discussed in terms of sequential theory, reinforcement level theory, and their implications for various schedule manipulations that have previously shown S? behavior to be inversely related to average reward in S+.     

双筋矩形截面梁受压钢筋不屈服时的截面设计探讨与教学

双筋矩形截面梁正截面受弯承载力计算是混凝土结构课程的重要教学内容。当学生进行双筋矩形截面梁正截面受弯承载力计算时,受压钢筋达不到屈服强度是设计中会遇到的情况。如何在此情况下进行结构设计,是学生学习这部分内容的一个难题。本文通过算例分析,将受压钢筋达不到屈服强度时如何进行截面计算的两种方法进行对比,给出了各个方法的控制条件,在此基础上,对如何进行这部分教学内容进行探讨,旨在提高教学质量并锻炼学生思考、解决工程问题的能力。     

The maintenance of matching behavior when contrast occurs in multiple concurrent concurrent schedules of reinforcement

Pigeons were trained on a multiple schedule of reinforcement in which each component was a concurrent schedule. The concurrent schedules were programmed by the changeover-key procedure. The primary purpose was to determine if the relative behavior allocated to two response alternatives is affected when absolute changes in these behaviors occur; i.e., to determine if matching is affected when positive behavioral contrast occurs. Results showed that (1) relative behavior in the unaltered component of the multiple schedule is not disrupted when positive contrast occurs in that component, (2) positive contrast occurred when the overall frequency of reinforcement in the reinforcement-correlated component(s) was high, but not when it was low, (3) changeover behavior was susceptible to positive contrast effects, and (4) changeover contrast and food-key contrast are independent phenomena.     

Recovery of extinction responding in rats following discontinuation of reinforcement of alternative behavior: A test of two explanations

One procedure which has been used to supplement extinction in order to produce faster and more complete response suppression is to provide reinforcement for some alternative response which is incompatible with the response undergoing extinction. When reinforcement for the alternative behavior is discontinued, however, substantial recovery of the original response has often been observed. The present set of experiments demonstrated that such recovery is best accounted for by a “response prevention” hypothesis rather than by a “discriminative cue” hypothesis. High-frequency reinforcement of alternative behavior during the first half of an extinction phase seems similar in effect to procedures which physically prevent rats from emitting the response programmed for extinction.     

中值定理"中间点"当x→+∞时的渐近性态

综述在区间[a，x]上的各中值定理“中间点”当x→＋∞时的渐近性态，给出两个新的渐近估计式。     

Matching when the number of response alternatives is large

Pigeons could choose between five concurrently available response keys, each associated with a different variable-interval schedule of reinforcement. A 2-sec changeover delay was also in effect on each key. In almost all cases, the relative number of responses to a key and the relative time spent at it were nearly equivalent to the relative number of reinforcements it produced. In addition, matching was observed between the relative number of reinforcements at a key and the relative number of changeovers to it.     

见死不救的法律诉求——从新时代荣辱观看道德法律化

有关“见死不救”的报道近段时间频频见诸新闻媒体,并由此引发了社会各界的关注。“见死不救”一直以来是作为一个道德问题被社会所关注的,但当一个问题已经成为一种社会病变,就不得不引起一些法律的思考了。笔者试图从见死不救者是否负有救助义务这一点人手,探析“见死不救”的刑事责任问题,以论道德的法律化来透析“见死不救”的法律诉求,使新时代下的荣辱观得以更好的彰显。     

Runway behavior of Siamese fighting fish,Betta splendens,for aggressive display and food reinforcement

Learning & Behavior - Fish were allowed to choose, in a T-maze, between various combinations of goalboxes containing either food or a mirror, or nothing. Only food and a mirror maintained...