Eliminating behavior with omission and extinction after varying amounts of training

After rats were trained to leverpress for 1, 3, 9, or 27 days on a variable interval reinforcement schedule, omission training was compared with extinction in effectiveness of response elimination. Extinction produced faster response elimination than omission, although both procedures eventually led to equal response elimination. Resistance to response elimination increased with length of baseline training, although this effect did not interact with omission vs extinction. A test of the durability of elimination effects followed, using a response-independent variable time reinforcement schedule. After extinction, resumption of responding in the durability test increased with length of baseline training, but there was little response resumption following omission regardless of the length of the baseline training. These results amplify and extend previous findings which show omission to be an effective and durable response elimination method.     

Renewal after overexpectation

Four magazine approach experiments were performed with rats to explore the decrement produced by reinforcing a compound of two previously conditioned stimuli. Compound presentation produced the usual over-expectation decrement in responding to the individual stimuli. However, testing in an alternative, but similarly treated, context allowed renewal of the initial responding to the individual stimuli. This renewal is similar to that seen after a decrement produced by nonreinforcement. It joins other results in suggesting that the decrement produced in extinction and overexpectation may be due to the same mechanism.     

The functional equivalence of operant behavior and foraging

Many researchers have used the controlled procedures of operant methodology to test the predictions of foraging theory on the assumption that foraging is operant behavior and operant behavior is foraging. This experiment tested the assumption that leverpressing is functionally equivalent to search effort. Four rats were exposed to two situations: a naturalistic foraging situation (a “patch”) and a standard operant chamber. Each condition represented a different prey density on the patch and a corresponding change in the probability of reinforcement in the chamber. The average number of presses per pellet was linearly related to the density of pellets on the patch. This result indicates that leverpresses were functionally equivalent to search effort.     

Effects of the amount of acquisition and contextual generalization on the renewal of instrumental behavior after extinction

Four experiments with rat subjects examined the role of context during the extinction of instrumental (free-operant) behavior. In all experiments, leverpressing was first reinforced on a variable-interval 30-s schedule and then extinguished before being tested in the extinction and renewal contexts. The results identified three important variables affecting the renewal effect after instrumental extinction. First, ABA and ABC forms of renewal were strengthened by increasing the amount of acquisition training. This suggests that the strength of the association learned during acquisition, or the final level of performance, influences the degree of renewal after extinction. The effect of the amount of training was modulated by the second factor, the degrees of generalization from the acquisition and extinction contexts to the test context. The third variable was acquisition training in multiple contexts, which was shown to strengthen ABC renewal. Methodological, theoretical, and practical implications are discussed.     

Effects of food primes on the operant behavior of nondeprived rats

After rats had been trained to press a lever for food reward, experimenter-initiated food “primes” increased the likelihood of subsequent responding during periods in which the subjects were nondeprived. No such priming effects were found after presentation of a stimulus that had previously been paired with food. In other experiments, nonreinforced leverpresses, as well as subthreshold components of the leverpress response (e.g., forepaw raising), were also found to be enhanced by food primes. Taken together with other reports in the literature, the present findings are consistent with a “motivational aftereffects” interpretation of priming, and also with the notion that all stimuli which possess reinforcing properties possess priming properties as well.     

Multiple determinants of “blocking” effects on operant behavior

Blocking was investigated in a free-operant procedure by presenting a response-contingent signal prior to reinforcer delivery. At issue was the way in which blocking effects previously reported with this procedure are related to conditioned reinforcement effects, also previously found with similar procedures. Signal presentation decreased response rate when delay of reinforcement was 0 or .5 sec, but the signal increased response rate when the delay of reinforcement was increased to 3 sec. Thus, which effect (blocking or conditioned reinforcement) occurred depended critically on the response-reinforcer interval.     

Extinction of operant behavior: An analysis based on foraging considerations

In two experiments, the frequency of food reinforcement provided by variable interval (VI) schedules prior to extinction was varied. In the first experiment, two-component multiple schedules resulted in a greater number of responses in extinction in the presence of the stimulus previously associated with the richer of the two component schedules than that previously associated with the leaner schedule. In the second experiment, different groups of animals were trained on different VI schedules. Responding in extinction was analyzed into bouts of responding showing that the number of response bouts increased and the number of responses per bout decreased with decreasing frequency of reinforcement during training. These data are compatible with an analysis of operant behavior based on an analogy to processes that presumably-occur-in naturalistic foraging situations. According to this analogy, behavior associated with search for a food source (i.e., number of response bouts) and that of procurement of food from a source (i.e., responses per bout) represent aspects of behavior that are differentially strengthened by different VI schedules. Extinction serves to reveal this differential strengthening.     

The pattern of responding after extensive extinction

Extensive extinction greatly reduces response rate and increases the relative frequency of short interresponse times, but does not affect temporal learning or operant response rate. In each of two experiments, 24 rats were trained in a multiple cued interval procedure with three stimuli (noise, light, and clicker) at three intervals (30, 60, and 120 sec). In Experiment 1, after 50 sessions of extinction, response rate decreased from about 25 to 0.5 responses/min, but temporal discriminations were maintained and the initial response gradients in reacquisition had a pattern that corresponded with the original (rather than current) training conditions. In Experiment 2, these results were replicated and extended by examination of the effect of stimulus duration on response patterns during extinction, but its lack of effect on reacquisition. The similarity of the initial performance in reacquisition to the asymptotic performance in acquisition was presumably due to the similarity of context. The individual subject data may be downloaded from www.psychonomic.org/archive.     

Free operant avoidance behavior in hooded rats: IRTs and response chains

Twenty-five hooded rats were given 50 avoidance training sessions with leverpress IRTs obtained during as well as between sessions. Five qualitatively different shapes to the IRT profiles were found: single- or double-peaked shapes, positively or negatively accelerated shapes, and U-shaped distributions. Both the specific shape of the profile and the stability of that shape during a session were related to the avoidance proficiency of an individual rat. Six rats received two additional training sessions, with the final 30 min of each videotaped to obtain frequency counts of nine behavior categories. The observational data showed that avoidance-proficient rats typically incorporated the leverpress requirement into repetitive response chains.     

Contextual control of operant behavior: evidence for hierarchical associations in instrumental learning

Recent research has suggested that operant responses can be weakened when they are tested in new contexts. The present experiment was therefore designed to test whether animals can learn a context–(R–O) relation. Rats were given training sessions in context A, in which one response (R1; lever pressing or chain pulling) produced one outcome (O1) and another response (R2; chain pulling or lever pressing) produced another outcome (O2) on variable interval reinforcement schedules. These sessions were intermixed with training in context B, where R1 now produced O2 and R2 produced O1. Given the arrangement, it was possible for the animal to learn two distinct R–O associations in each specific context. To test for them, rats were then given aversion conditioning with O2 by pairing its presentation with lithium-chloride-induced illness. Following the aversion conditioning, the rats were given an extinction test with both R1 and R2 available in each context. During testing, rats showed a selective suppression in each context of the response that had been paired with the reinforcer subsequently associated with illness. Rats could not have performed this way without knowledge of the R–O associations in effect in each specific context, lending support to the hypothesis that rats learn context–(R–O) associations. However, despite a complete aversion to O2, responding was not completely suppressed, leaving the possibility open that rats form context–R associations in addition to context–(R–O) associations.     

Pre-exposure enhances recovery of conditioned responding after extinction

Four experiments used a within-subjects design with rats to study the effects of preexposure on the restoration of fear responses (freezing) to an extinguished conditioned stimulus (CS). In each experiment, rats were preexposed to one CS (A), but not to another (B), and then were exposed to pairings of each of these CSs with an aversive unconditioned stimulus (US). In each experiment, there was less freezing to A than to B across extinction, showing a latent inhibitory effect of preexposure. There was no differential recovery to A and B following either a US reexposure (Experiment 1) or a delay interval (Experiment 2). However, when a delay interval included US reexposure, there was greater recovery to the preexposed CS, A, than to the nonpreexposed CS, B (Experiments 1, 3, and 4). These results suggest that the effects of US reexposure and delay combine to affect recovery from the depressive effects of CS-alone exposure. The results are consistent with the view that US reexposure produces better mediated conditioning of CSs that are strongly associated with the context. The results may additionally reflect an effect of preexposure on the learning produced by extinction.     

Effects of retraining following response prevention on extinction of escape behavior

Sixty female hooded rats received a sequence of 40 shock-escape training trials, 20 response prevention (or pseudoprevention) trials, either 0, 5, or 20 shock-escape retraining trials and then nonshock extinction procedures. Results of extinction using escape speed and trials-to-criterion indices showed that, in each retraining condition, response prevention reliably facilitated extinction relative to pseudoprevention controls, the degree of facilitation decreasing as amount of retraining increased. In 5-and 20-trial retraining conditions, prevention procedures also reliably impaired shock-escape performance on early retraining trials, this effect dissipating before the start of extinction.     

Resurgence of behavior during extinction depends on previous rate of response

In two experiments, food-deprived rat subjects leverpressed for food in three successive training phases. In the first phase of both experiments, rats were exposed to a multiple schedule, one component of which produced a high rate of response, and the other of which produced a lower rate of response (multiple random ratio [RR], random interval [RI] in Experiment 1, and multiple differential reinforcement of high rate, differential reinforcement of low rate in Experiment 2). Rats were then transferred to a multiple fixed interval (FI; 60-sec, 60-sec) schedule, until the effects of the first phase on response rate were no longer apparent and their response rates did not differ from those of rats responding on a multiple FI 60-sec, FI 60-sec schedule without previously experiencing a multiple RR, RI schedule. During the third stage oftraining, all rats were placed into extinction. During extinction, rates of responding were higher in the component previously associated with the high rate of responding in Phase 1, and they were lower in the component previously associated with low rates of responding in Phase 1. These results suggest that resurgence effects, like other history effects, are controlled by previous rates of responding.     

Spontaneous recovery after extinction of a conditioned taste aversion

Four experiments examined whether or not spontaneous recovery could occur after extinction in the conditioned taste-aversion paradigm. After three extinction trials, spontaneous recovery was obtained over an 18-day retention interval (Experiments 1, 2, and 3). The effect was not due to changes in the unconditioned preference for saccharin over the retention interval (Experiment 2) or to an increase in a nonextinguished aversion over time, as indicated by tests with both the original, nonextinguished aversion (Experiment 1) and with a weaker one (Experiment 3). Spontaneous recovery was not obtained when extinction was overtrained (eight trials) and a 49-day retention interval was used (Experiment 4). However, saccharin intake at asymptote reached the level of baseline water intake, and not the highly preferred level shown by never-conditioned controls. Results of all four experiments suggest that extinction does not return an averted taste to the status of an unconditioned one.     

Recovery effects after extinction in the Morris swimming pool navigation task

In three experiments in which rats were used as subjects, we developed an extinction procedure using a Morris pool. The animals were trained to find a hidden platform located at a fixed position and were then given extinction trials in which the platform was removed from the pool. When training and extinction were carried out in the same context and time was allowed to elapse between extinction and test, spontaneous recovery of learning was observed. On the other hand, those rats that received extinction in a context different from the one used for training failed to show spontaneous recovery of learning when tested in the extinction context after an interval of 96 h. However, they did show renewal of spatial learning when tested in the training context. These results show that extinction in the spatial domain behaves like extinction in standard conditioning preparations.     

Dissociation of conditioned appetitive and consummatory sexual behavior: Satiation and extinction tests

Sexual responses were conditioned in male Japanese quail using the opportunity to copulate with a female as the unconditioned stimulus (US). The conditioned stimulus (CS) was a 3-D object made of a taxidermically prepared female quail head mounted on a terry-cloth body. Both appetitive conditioned responses (approach and proximity to the CS) and consummatory conditioned responses (mount and cloacal contact directed toward the CS) developed when 2-min presentations of the CS were followed immediately by the US, but not when the CS and US were separated by trace intervals of 10 or 20 min (Experiment 1). Postconditioning sexual satiation suppressed conditioned cloacal contact responses more than conditioned approach to the CS (Experiment 2), and “acute” extinction suppressed both conditioned mounting and conditioned cloacal contact responses more than conditioned approach to the CS (Experiment 3). These results demonstrate a functional dissociation between conditioned appetitive and consummatory responses and imply that the motivational and/or associative mechanisms underlying the two types of behavior are distinct.     

Partial reinforcement delayed extinction effect after regularly alternating reward training

When extinction is delayed very long, the superior resistance to extinction of the random schedule group relative to the alternating schedule group disappears (partial reinforcement delayed extinction effect, PRDE). Two experiments assessed the effects of reinforcement/nonreinforcement on Trial 1 on the PRDE. Following extended partial reinforcement acquisition training in a runway, rats received extinction training after a short (1-day) or long (23-day) retention interval. The schedules used in Experiment 1 were: a single-alternation (SA) schedule beginning each day with a rewarded (r) trial, for Group r-SA; an SA schedule beginning with a nonrewarded (n) trial, for Group n-SA; and a random (Rd) schedule, for Group Rd. The schedules and group names used in Experiment 2 were r-SA, Rd, and r-Rd. The results were that (1) rats given r-SA schedules yielded considerable resistance under delayed extinction, (2) those given Rd and r-Rd schedules showed a decline in resistance to extinction over a long retention interval, (3) those given the n-SA schedule showed relatively low resistance at both retention intervals, although retention deficit was not greater than in the case of the Rd schedule, and thus, (4) the PRDE was found in both experiments, although only weakly in Experiment 1. The results indicated that a regularly alternating reward pattern was a more important determinant than was type of reward on Trial 1 for the PRDE. The PRDE due to differential retention deficits among schedules is discussed on the basis of dual-process associative sequential mechanisms and cognitive rule-encoding mechanisms.     

也谈更新教育观念

更新教育观念的核心是培养什么人、怎样培养人的问题。一要坚持以马克思主义为指导,认真学习“三个代表”的思想;二要抓住人的发展这个根本问题;三要继承古代优良传统,借鉴国外先进理念。四要坚持两点论。