共查询到20条相似文献，搜索用时 31 毫秒
1.
John E. Kelsey 《Learning & behavior》1977,5(1):83-92
Male rats which had received approximately 21 min of pulsed, inescapable tail shock during a 6-h session in a wheel-turn chamber were markedly deficient in acquisition of an FR 2 crossing escape response in a shuttlebox when first tested 22 or 70 h later (Experiments 1 and 2). Rats which had received identical amounts and patterns of escapable/avoidable shock, however, were not deficient (Experiment 1). Preventing wheel-turn responses during the inescapable shocks prevented the occurrence of the subsequent escape deficit, whereas reducing the feedback provided for the first crossing response of the FR 2 requirement enhanced the deficit (Experiment 3). These data can be best explained by the learned helplessness hypothesis and indicate that the types of responses available and made during the inescapable shocks are more important than previously indicated. 相似文献
2.
The effect upon subsequent escape acquisition of control over shock intensity in the absence of control over other shock characteristics was examined. Pretreatment involved random shocks of 1.6 and .75 mA at a density of about 10/min. The experimental group could avoid the higher shock intensity if they leverpressed at least once every 15 sec. Yoked and no-shock rats completed the triadic design. Experimental and yoked animals received all scheduled shocks. Triads were later tested for FR 2 shuttlebox escape at either the .75 mA (low) or 1.6 mA (high) intensity. During testing, avoidance rats performed as well as no-shock rats at the low intensity and escaped even more rapidly at the high intensity. Yoked rats showed interference at both intensities, with interference very marked, including many failures to escape, at the low intensity. These findings indicate that control over shock intensity, by itself, is sufficient to prevent learned helplessness and suggest that control over any salient characteristic of shock may be sufficient for immunization. 相似文献
3.
Five groups of pigeons were studied in an auto-shaping procedure which programmed two types of trials represented by hues on the response key. Each signal was separated by a brief intertriai interval. Three groups were studied with a positive correlation between one of the signals and food (contingent groups). They differed with respect to the frequency with which the positive signal appeared. Two noncontingent groups were studied in which the correlation between the signals and food was eliminated by programming food with the same probability following either signal. One noncontingent group had a high density of reinforcement produced by adding reinforcement in the other signal, at the same rate as programmed in the positive signal for the contingent groups. The other noncontingent group experienced the same number of reinforcements in the session as the contingent group with the least frequent positive trial, but these reinforcements were distributed with equal probability across the signals. Birds in the contingent groups with intermediate or infrequent positive signals all acquired reliable pecking, with acquisition most rapid for the infrequent signal. Maintained responding covaried with the speed of acquisition. No birds in the noncontingent groups showed reliable responding. Birds in the contingent group with a frequent positive signal (approximately 3/4 of the session), also showed no reliable pecking. This result suggests that more than one noncontingent group is informative for assessing the role of differential reinforcement probability in the acquisition of auto-shaped keypecking. In particular, a noncontingent group which controls for the frequency of reinforced trials is an appropriate reference group.
相似文献4.
In three experiments, rats received presentations of a diffuse 30-sec stimulus (a light) and of food, and their tendency to enter the food tray was monitored. Experiment 1 showed that when the light was made to signal the delivery of food, the response of entering the food tray increased in frequency during the stimulus. The acquisition of this conditioned response to the light was retarded in subjects that had received preexposure to the stimulus. In Experiments 2 and 3, subjects received preexposure to the stimulus, some in the same context as that subsequently used for stimulus-food pairings and some in a different context. Those experiencing the change of context acquired the response more readily. It is argued that these results demonstrate a latent inhibition effect that is attenuated by contextual change. 相似文献
5.
After escape training in an alley, rats received either nonpunished (NP) or punished (P) extinction, During extinction, NP and P groups received (a) a novel tone in the startbox, (b) a tone in the start- and goalboxes (the tone had been presented in the goalbox to these subgroups during acquisition—safety signal condition), or (c) no tone. Punishment produced greater resistance to extinction than nonpunishment (self-punitive effect) only under no-tone conditions. The elimination of self-punitive behavior with novel tone and safety signal treatment is consistent with the hypothesis that self-punitive running is motivated by excessive fear. 相似文献
6.
In four experiments utilizing an appetitive conditioning preparation, reacquisition of conditioned responding was found to occur both rapidly and slowly following extinction. In Experiment 1, acquisition of responding to a tone that had been conditioned and extinguished occurred more rapidly than acquisition in either a group that received equivalent exposure to the food unconditioned stimulus or a “rest” control group that received only exposure to the apparatus in the first two phases. However, reacquisition was impaired relative to acquisition in a “learning-experienced” group that had previously received conditioning and extinction with a different stimulus. Experiments 2 and 3 produced similar results, but also found that high responding during reacquisition was confined to trials that followed reinforced, rather than nonreinforced, trials. Experiment 4, in which very few initial conditioning trials were used, produced reacquisition that was slow compared with both learning-experienced and rest controls. The results are consistent with a role for sequential learning: Reacquisition is rapid when animals have learned that reinforced trials signal other reinforced trials. 相似文献
7.
The present experiments investigated the sunk cost error, an apparently irrational tendency to persist with an initial investment, in rats. This issue is of interest because some have argued that nonhuman animals do not commit this error. Two or three fixed-ratio (FR) response requirements were arranged on one lever, and an escape option was arranged on a second lever. The FRs were of different sizes, and escaping was the behavior of interest. Several variables that might influence the decision to persist versus escape were manipulated: the number of trials with different FR schedules in an experimental session (Exps. 1 and 2), effort to escape (Exp. 2), and the size of the larger FR (Exp. 3). The sunk cost error would result in never escaping, and the optimal strategy would be to escape from the larger FR. The main variable that determined persisting versus escaping was the size of the large FR. Rats that escaped from the large FR-apparently optimal behavior-did so at a suboptimal point, and hence committed the sunk cost error. 相似文献
8.
The acquisition and extinction of locomotor responses of rats in a straight alley were examined for groups trained under escape, partial-avoidance, and avoidance procedures. During acquisition, one group (escape) received a 0-sec delay between being dropped into the alley and the onset of shock; two groups (partial avoidance) had 0.5- and 1-sec delays; and two groups (avoidance) had delays of 2 and 4 sec. On the final day of acquisition, the partial-avoidance rats displayed higher running speeds than either the escape- or avoidance-trained animals. The 4-sec avoidance group was consistently slower than all other groups. Speeds for all groups decreased during extinction, with rate of decline showing some relation to terminal acquisition level. Relative group performance levels proved to be consistent with a simple arithmetic model based on the assumption that changes in running speeds affect the aversiveness of the situation by altering US duration, CS duration, and effective US length. 相似文献
9.
Male rats were tested as intruders for 25 consecutive days in colonies that had either aggressive (i.e., alpha) or nonaggressive conspecific residents. Alpha-defeated intruders, in contrast to nondefeated rats, showed more defensive behavior, less gain in body weight, and received more bites during the course of these sessions. Tail-flick tests, using a heat source, revealed that both groups of intruders showed comparable sensitivity/reactivity to pain, and there was no evidence of analgesia as a function of resident encounters. Immediately after the last intruder session, all subjects were tested for exploratory activity in an open-field apparatus with the odors (i.e., soiled bedding) from the alpha colonies present. Defeated intruders showed significantly less locomotion, in terms of the number of grid crossings, than nondefeated rats. Twenty-four hours later, randomly selected subgroups of defeated and nondefeated subjects were briefly exposed, without being defeated, to aggressive colonies, and all rats were then retested for activity with alpha odors present. Previously defeated intruders were again less active, and the colony-exposure treatment suppressed the activity of defeated, but not nondefeated, subjects. Finally, 24 h after another resident-intruder session, both groups of intruders showed comparable FR 1 escape performance in a shuttlebox with alpha odors present, but the defeated rats failed to learn a subsequent FR 2 escape task. The findings of this experiment are discussed in terms of the concept of “learned helplessness,” the effects of ethological stressors, and the authors’ stress-coping-fear-defense (SCFD) theory. 相似文献
10.
Charles I. Brooks 《Learning & behavior》1975,3(1):67-72
In Experiment I, rats which had received six partially reinforced runway acquisition trials, with a reward magnitude of 60 sec access to wet mash on rewarded trials, showed less persistent responding over highly massed extinction trials than subjects which had received the same acquisition schedule but reward magnitudes of either 1 or 10 45-mg pellets. In Experiment II, rats which had received six partially reinforced placements into one compartment of a two-compartment box, with 60 sec access to mash on rewarded placements, jumped a hurdle faster to escape nonreward than subjects which had received the same reward schedule but 10 45-mg pellets on rewarded trials. The data supported a primary frustration analysis for reward-magnitude manipulations within brief partial-reinforcement schedules. 相似文献
11.
Rats were trained on fixed ratio (FR) schedules requiring either 5 or 10 leverpresses to produce reinforcement and an intertrial interval (ITI). Half of the Ss at each ratio requirement were extinguished on an FR 5 and half on an FR 10 schedule of ITI presentation. Fewer foodcup approaches were made on the FR 10 than on the FR 5 extinction schedule, regardless of acquisition FR. Leverpresses per approach were fewer on the FR 5 than on the FR 10 extinction schedule and were fewer following FR 5 than following FR 10 acquisition. Data suggested the existence of interoceptive as well as exteroceptive stimulus control of foodcup approach and were discussed in terms of their implications for a response-unit account of extinction. 相似文献
12.
A series of four experiments investigated a number of parameters reported to produce “helplessness” in rats. Consistent differences in escape behavior were not found between inescapably shocked and restrained rats when a FR 1 shuttling response was used. Escape latencies also did not differ between groups when a reduced shock intensity was employed during escape training in FR 2 procedure or when an increased FR 3 response was employed during escape training. Findings are discussed in terms of the robustness of the failure-to-escape phenomenon from which “helplessness” in the rat is inferred. 相似文献
13.
Random presentations of keylights and food retarded acquisition and suppressed asymptotic rates of keypecking in autoshaping. Sequences of 10 sessions of random training alternated with 10 sessions of autoshaping resulted in poor performance (in terms of both the acquisition and asymptotic indices) relative to a group that received sequences of CS-only (rather than random) training alternating with autoshaping. When the birds that previously were trained with the random sequence were exposed to CS-alone extinction, retardation of acquisition was alleviated but the asymptotic suppression was not (Experiment 1). Pigeons with a history of autoshaping without prior random training showed no asymptotic suppression when exposed to the random procedure. These birds, when switched between two-session sequences of random training alternating with two-session sequences of autoshaping, were able to (1) surpass pigeons that received CS-only rather than random treatment in terms of asymptotic levels of responding in autoshaping, and (2) showed improvement in extinction performance with repeated random/autoshaping sequences (Experiment 2). Detailed observations of pigeons in random training showed that stereotypic activity behaviors were acquired, and these generally persisted in autoshaping; the degree of change in these behaviors was related to asymptotic rates of keypecking in autoshaping (Experiment 3). The same kinds of behaviors were observed when pigeons initially were autoshaped, and these persisted in subsequent random and fixed-interval 10-sec training. We suggest that the suppression effect is reflected in activity, conditioned in random training, which persists in autoshaping (especially if the activity is compatible with the kinds of behaviors elicited by the autoshaping contingency itself), and that the effect may be a deficit due to performance factors rather than to associative learning. 相似文献
14.
Nigel W. Bond 《Learning & behavior》1984,12(3):323-331
Rats of the Australian High Avoider (AHA) and Australian Low Avoider (ALA) strains and their reciprocal crosses were exposed to 50 trials of one of three shuttlebox procedures. The avoidance group received pairings of a tone and shock. If the animals shuttled during the tone, they avoided the shock. If they waited until the shock came on, they could then escape it. The classical group received pairings of the tone and a brief inescapable shock. If they shuttled during the tone, the tone ceased and they immediately received the shock. If they did not shuttle, they received the brief shock at the termination of the tone. The pseudoconditioning group received the tone and the shock explicitly unpaired. If they shuttled during either the tone or the shock, the stimulus was terminated. There was no acquisition of anticipatory responding under the pseudoconditioning procedure. All groups evidenced an increase in anticipatory responding over trials under the classical procedure. The AHAs acquired the response faster and reached a higher asymptote than did the ALAs. Performance of the two reciprocal crosses fell in between. A similar pattern was observed under the avoidance procedure, albeit at slightly higher response levels. Subsequent studies established that the AHAs acquired a one-way avoidance response quickly, but were impaired on a passive avoidance task, whereas the reverse was the case for the ALAs. The reciprocal crosses were proficient at both tasks. These results suggest that shuttlebox avoidance is largely accounted for by classical conditioning of the predominant defensive response. When that response is compatible with performance on the task, acquisition is rapid (AHAs), and when it is not, acquisition is slow (ALAs). 相似文献
15.
Two groups of albino rats were trained on a simultaneous pattern discrimination task, one with a classical procedure in which the discriminanda remained invariant throughout training, and the other with a fading procedure in which the final task was approached through a series of graduated steps. In a subsequent reversal stage, during which the initial positive stimulus became negative and vice versa, each group was subdivided so that half of the subjects in each original group received reversal training with the same procedure as during acquisition and the other half with the other method. Fading procedures yielded a more proficient performance on every occasion, independently of experimental stage or previous learning history. Results are analyzed in terms of favorable conditions offered by the procedure itself and of beneficial influences exerted over subsequent learning. 相似文献
16.
Information was sought on how the strength of fear, acquired and extinguished in a classical conditioning paradigm, might be affected by certain of the circumstances that normally are associated with the course of avoidance learning. Following preconditioning exposures to the conditioned stimulus, one group of rats (Group PRF) was given continuous conditioned stimulus-unconditioned stimulus (CS-US) acquisition trials followed by stepwise reductions in US probability (given the CS) over three phases to about 11% for the final phase. Another group, Group US(lo), was given continuous CS-US pairings throughout, but, following acquisition, received stepwise reductions in US intensity (to permit evaluation of a progressively changing feature of the US over a wide range without having to employ excessive shock) over the same phases. A third group, Group US(hi), received unchanging (from acquisition) CS-US pairings over these phases, and an explicitly unpaired control group (Group RU) was included. Although outcomes differed somewhat depending upon whether suppression ratios or absolute measures of responding were considered, the major findings were that suppression to the CS was complete by the end of acquisition and persisted thereafter throughout the three phases for all but control subjects. In contrast to Group US(lo), which showed relatively little resistance to extinction of suppression to subsequent CS-only exposures, Groups US(hi) and PRF displayed marked resistance over two separate, extended sets of extinction sessions. Suppression to context cues was pronounced only for Groups US(hi) and RU, and varied as a function of US parameters and not whether the shocks were or were not signaled. Theoretical reconciliation of these findings was most difficult for Groun PRF. 相似文献
17.
Four experiments test the hypothesis that escape learning in response to shock will transfer to a similar food-reinforced response and affect resistance to appetitive extinction. In the first two experiments, subjects were given escape training in a straight alley followed by continuous food reinforcement and then extinction. Prior escape training resulted in greater resistance to extinction of the food-reinforced response as compared to several control procedures. In the third experiment, the escape response was manipulated to be compatible or incompatible with the subsequent food-reinforced response. Greater resistance to extinction was shown when the two responses were compatible. The fourth experiment confirmed and extended this finding. The relationship of the present results to Amsel’s theory of persistence was discussed. 相似文献
18.
The availability of an effective coping response has been shown to attenuate the deleterious behavioral and physiological consequences of inescapable electric shock. In the current study, two groups of rats could escape tailshock by turning a wheel. When short-latency responses that appeared to be elicited by shock onset were permitted to terminate shock, rats subsequently failed to learn to escape in a shuttlebox and did not differ from rats which received an equivalent amount of inescapable shock. However, when a relatively long-latency response was required and short-latency responses were not allowed to affect shock, rats subsequently readily learned to escape in the shuttlebox. The implications of these results for explanations of the manner in which prior exposure to shock influences subsequent escape learning were discussed. 相似文献
19.
The effect of food deprivation level at the time of initial exposure to a subsequent food reinforcer was investigated in two experiments. In Experiment 1, deprivation at the time of initial exposure influenced the subsequent acquisition and extinction of an instrumental response. In Experiment 2, the residual deprivation effect associated with a reduction in deprivation level occurred only when rats initially experienced the reinforcer at a high, as compared with a low, deprivation level. Results were discussed in terms of the assumption that the limits of incentive generated by a reinforcer are influenced by the deprivation state at the time of first exposure to that reinforcer. 相似文献
20.
Pigeon subjects received training of a diffuse stimulus as either a conditioned inhibitor or a conditioned facilitator of a keylight signal for food. The ability of these diffuse stimuli to modulate responding was then assessed with two other keylights that were undergoing discrimination reversal. At a point where responding was equivalent for the two targets, the modulators had a greater impact on the target undergoing extinction than on the target undergoing acquisition. These results have implications for the nature of modulation and extinction. 相似文献