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1.
The acquisition and maintenance of signal-directed pecking was examined in week-old Leg-Horn chicks responding to a keylight stimulus paired with heat. In contrast with previous studies using pigeons with food as the US, both speed of acquisition and asymptotic level of keypecking were a direct function of US duration. Experiment 2 examined responding using a within-subject design to isolate the effects of trial spacing on performance during the immediate trial from the effects on performance during a following trial of fixed length. These comparisons revealed a significant effect of intertriai interval (ITI), with less responding after shorter intervals. The effect of different temporal spacing was apparent in responding on the immediate trial, but not on the following trial. These local ITI effects were better predicted by a recent autoshaping model based on relative waiting time (Jenkins, Barnes, & Barrera, 1981) than by a model based on relative US expectancy (Gibbons & Balsam, 1981). However, neither model predicted the effect of US duration. A reexamination of the US-duration literature suggested that the diversity of previous findings is consistent with the assumption that conditioned responding is an inverted U-shaped function of US duration. 相似文献
2.
In four conditioned suppression experiments with rats (Rattus norvegicus), backward pairings of a shock unconditioned stimulus (US) and a tone conditioned stimulus (CS) eliminated an already established conditioned response (CR), but there was recovery of the CR if the shock was later withheld. In Experiment 1, there was recovery after backward pairings, regardless of whether the period after the US was normally shock free or not. In Experiment 2, the occurrence of recovery depended on the CS’s being presented closely after the US in response elimination. Levels of recovery were positively correlated with the resistance of the response to elimination during backward pairings (Experiments 3 and 4). Taken together, these data support the notion that recovery after backward pairings is a form of renewal (see, e.g., Bouton, 1991) and is not due toprotection from extinction. 相似文献
3.
Lick suppression experiments with rats revealed that the magnitude of both second-order conditioning (Experiment 1) and sensory preconditioning (Experiment 2) was superior when that conditioning was based on backward (US→CS) relative to forward (CS→US) first-order pairings of a CS and US. The superiority of backward relative to forward first-order conditioning on suppression to the higher order cues can be understood by assuming that the magnitude of higher order conditioning was determined by a memory representation of the higher order cues that provided information about the expected temporal location of the US. The results suggest that temporal information such as order between paired CSs and USs was encoded, preserved, and integrated with memory for the higher order stimuli. The relevance of these findings to memory integration in Pavlovian learning, the temporal coding hypothesis (Barnet, Arnold, & Miller, 1991; Matzel, Held, & Miller, 1988), backward excitatory conditioning, and the associative structure that underlies second-order Pavlovian fear conditioning are discussed. 相似文献
4.
A one-trial-a-day procedure was used to investigate the effects of US-CS pairings on extinction of conditioned suppression of licking by rats. Following acquisition trials, response suppression was immediately eliminated when US preceded CS, but it reappeared during subsequent CS-alone presentations. Ss that received backward pairings reached a significant level of extinction one trial before Ss that received conventional extinction trials. 相似文献
5.
Conditioned lick suppression in rats was used to explore the role of timing in trace conditioning. In Experiment 1, two groups of rats were exposed to pairings of a CS (CS1) with a US, under conditions in which the interstimulus interval (ISI) that separated CS1 offset and US onset was either 0 or 5 sec. Two additional groups were also exposed to the same CS1→US pairings with either a 0 or a 5-sec ISI, and then received “backward” second-order conditioning in which CS1 was immediately followed by a novel CS2 (i.e., CS1→CS2). A trace conditioning deficit was observed in that the CS1 conditioned with the 5-sec gap supported less excitatory responding than the CS1 conditioned with the 0-sec gap. However, CS2 elicited more conditioned responding in the group trained with the 5-sec CS1-US gap than in the group trained with the 0-sec CS1-US gap. Thus, the CS1-US interval had inverse effects on first- and second-order conditioned responding. Experiment 2 was conducted as a sensory preconditioning analogue to Experiment 1. In Experiment 2, rats received the CS1?CS2 pairings prior to the CS1→US pairings (in which CS1 was again conditioned with either a 0 or a 5-sec ISI). Experiment 2 showed a dissociation between first- and second-order conditioned responding similar to that observed in Experiment 1. These outcomes are not compatible with the view that differences in responding to CSs conditioned with different ISIs are mediated exclusively by differences in associative value. The results are discussed in the framework of the temporal coding hypothesis, according to which temporal relationships between events are encoded in elementary associations. 相似文献
6.
Paul Craddock Jessica S. Wasserman Cody W. Polack Thierry Kosinski Charlotte Renaux Ralph R. Miller 《Learning & behavior》2018,46(2):171-181
Second-order conditioning (SOC; i.e., conditioned responding to S2 as a result of S1–US pairings followed by S2–S1 pairings) is generally explained by either a direct S2→US association or by an associative chain (i.e., S2→S1→US). Previous research found that differences in responses to S2 after S1 was extinguished often depended on the nature of the S2–S1 pairings (i.e., sequential or simultaneous). In two experiments with human participants, we examined the possibility that such differences result from S1 evoking S2 during extinction of S1 following simultaneous but not sequential S2–S1 pairings. This evocation of S2 by S1 following simultaneous pairings may have paired the evoked representation of S2 with absence of the outcome, thereby facilitating mediated extinction of S2. Using sequential S2-S1 pairings, both Experiments 1 and 2 failed to support this account of how extinction of S1 reduced responding to S2. Experiment 1 found that extinguishing S1 reduced responding to S2, while extinguishing S2 had little effect on responses to S1, although forward evocation of S1 during extinction of S2 paired the evoked representation of S1 with absence of the outcome. In Experiment 2, evocation of S2 during S1 nonreinforced trials was prevented because S2–S1 pairings followed (rather than proceeded) S1-alone exposures. Nevertheless, responding to S2 at test mimicked S1 responding. Responding to S2 was high in the context in which S1 had been reinforced and low in the context in which S1 had been nonreinforced. Collectively, these experiments provide additional support for the associative-chain account of SOC. 相似文献
7.
The associative effects of “backward” US-CS pairings were compared when the pairing occasions were either consistently preceded by a well-trained CS+ or were unannounced. The investigation employed a conditioned emotional response procedure with rats, under conditions in which all subjects received the same schedule of shock USs, some signaled and others not, and the back-ward CS was arranged to follow either the former or the latter, in separate groups. The major finding was that although the backward CS became excitatory when it followed unsignaled USs, it became inhibitory when it followed signaled USs. This outcome, which is in line with prior findings of Wagner and Terry (1975), is in accordance with a “sometimes-opponent-process” model proposed by Wagner (1981). It is contrary to data reported by Fowler, Kleiman, and Lysle (1984) that may have resulted from a confounding of the different circumstances of backward conditioning with differences in the predictability of the US in the experimental context. 相似文献
8.
Rabbits (Oryctolagus cuniculus) were given either a 100% or a 50% reinforcement schedule in classical conditioning. Two groups received an aversive US (shock) and two groups received an appetitive US (water to the oral cavity). With parameter estimates for the two-phase model serving as the dependent variables, it was possible to define more precisely the effect of US omission with the intermittent reinforcement schedule. For the aversive preparation, the major effect of intermittent reinforcement was to increase the duration of Phase 1, a phase during which response likelihood remains constant at its initial value. Only a small proportion of subjects reflected the effect of US omission during Phase 2, the “learning” phase, this being a low operator limit following trials on which neither the CR nor the US occurred. The major effect of US omission for the appetitive preparation was in Phase 2, primarily a result of a minority of subjects having a low operator limit following trials on which neither the CR nor the US occurred. Many subjects required separate operators for trials on which the CR did or did not occur. The results were interpreted to pose difficulties for strength theories of conditioning, and the limitation implied for successful application of the Rescorla-Wagner theory are discussed. The implications of the data for response-contingent interpretations and for individual differences are also discussed. 相似文献
9.
Douglas A. Williams Travis P. Todd Chrissy M. Chubala Elliot A. Ludvig 《Learning & behavior》2017,45(1):49-61
Three experiments assessed how appetitive conditioning in rats changes over the duration of a trace conditioned stimulus (CS) when unsignaled unconditioned stimuli (USs) are introduced into the intertrial interval. In Experiment 1, a target US occurred at a fixed time either shortly before (embedded), shortly after (trace), or at the same time (delay) as the offset of a 120-s CS. During the CS, responding was most suppressed by intertrial USs in the trace group, less so in the delay group, and least in the embedded group. Unreinforced probe trials revealed a bell-shaped curve centered on the normal US arrival time during the trace interval, suggesting that temporally specific learning occurred both with and without intertrial USs. Experiments 2a and 2b confirmed that the bulk of the trace CS became inhibitory when intertrial USs were scheduled, as measured by summation and retardation tests, even though CS offset evoked a temporally precise conditioned response. Thus, an inhibitory CS may give rise to new stimuli specifically linked to its termination, which are excitatory. A modification to the microstimulus temporal difference model is offered to account for the data. 相似文献
10.
Kenneth A. McNish Stephanie L. Betts Susan E. Brandon Allan R. Wagner 《Learning & behavior》1997,25(1):43-52
Two experiments of Pavlovian conditioning with rabbits evaluated the effects of initiating or continuing a conditioned stimulus (CS) after a paraorbital unconditioned stimulus (US). In Experiment 1, backward pairings, in which a CS came on after the US, produced a CS that appeared inhibitory on a measure of eyeblink conditioning but excitatory on a potentiated-startle measure of conditioned fear. In Experiment 2, extending the duration of a CS that came on prior to the US, so that it continued after the US, decreased eyeblink conditioned responses, whereas it increased conditioned fear. The data from the two experiments confirm and extend those of Tait and Saladin (1986), supporting the suppositions of AESOP (Wagner & Brandon, 1989) that conditioned eyeblink and conditioned fear can be dissociated under various temporal relationships between the CS and US. 相似文献
11.
In three experiments, groups of albino rats received one strictly simultaneous pairing of a 4-sec auditory conditioned stimulus (CS) and a 4-sec 1-mA shock unconditioned stimulus (US). Other groups received a backward pairing, in which the US began before the CS, or a forward pairing, in which the CS began before the US. Control groups received only the US or received both the CS and the US but widely separated in time. Later, the CS was presented while the rats licked a drinking tube for water, and CS-elicited suppression of licking was taken as an index of the Pavlovian conditioned response (CR). It was found that groups receiving a single forward or a single simultaneous pairing suppressed more than groups that had received a backward pairing; and the backward groups, in turn, suppressed more than the control groups. It appears, then, that excitatory fear conditioning, as reflected in conditioned suppression of licking in rats, can be produced in a single trial by both backward and simultaneous conditioning procedures. 相似文献
12.
Two experiments used rats in a conditioned lick suppression preparation to investigate how the conditioned stimulus (CS)-duration
and partial-reinforcement effects (i.e., weakened responding due to conditioning with a CS of longer duration and presenting
nonreinforced CSs intermingled with CS—unconditioned stimulus [US] pairings, respectively) interact with overshadowing. Experiment
1 found that when overshadowing treatment was combined with either extended CS duration or partial reinforcement, the response
deficit was weaker than when either of these three treatments was administered alone. In Experiment 2, the generality of the
findings in Experiment 1 was investigated by replicating it with various US—US intervals. This time counteraction was observed
only when both the absolute duration of total CS exposure and the US—US interval were short. The results support neither the
view that the ratio between the total CS exposure and total time in the context determines the CS-duration and the partial-reinforcement
effects nor the view that these two effects arise from a loss of effectiveness of the excitatory CS—US association during
CS-alone exposures in partial reinforcement or early periods of CS exposure with long CSs. 相似文献
13.
Illumination effects during steady-state performance of discrimination tasks in animals have been well documented, whereas research on illumination effects during acquisition has been largely ignored. Exceptions to this rule are Wasserman’s (1973) autoshaping experiments and Maki’s (1979) successive discrimination experiment. The present experiment investigated the effects of illumination changes on acquisition of a conditional discrimination—delayed matching-to-sample (DMTS). Pigeons were used in a between-groups design which factorially varied house-light illumination, on or off, during the presentations of DMTS stimuli, the delay interval, and the intertrial interval (ITI). DMTS performance over five blocks of sessions was the dependent variable. The major result was the three-way interaction of sessions, the intertrial interval, and the DMTS stimuli. Constant illumination resulted in the highest discrimination ratios over the last four blocks of sessions. A constant dark condition did not differ from a condition with dark ITIs and illuminated stimulus presentations or from a condition with illuminated ITIs and dark stimulus presentations. The proffered explanation of these data emphasizes the disruptive effects of stimulus changes and Wasserman’s (1973) cue localization hypothesis. The loci of the stimulus change and cue localization effect are suggested to be either at the beginning of a trial or at the end of a trial. A pretrial account emphasizes the role of stimulus changes on the encoding of the sample stimulus, and a posttrial account emphasizes the role of stimulus changes during consolidation processing. 相似文献
14.
Conditioning trials that are massed in time produce less conditioning than those that are spaced in time. Four experiments
with rat subjects examined whether a recent conditioning trial interferes with conditioning on the next trial by temporarily
“priming” information in short-term memory (e.g., Wagner, 1978, 1981). We used appetitive conditioning procedures in which
priming trials preceded target trials by 60 sec. When the priming trials were nonreinforced presentations of a conditioned
stimulus (CS), the CS had to be the same CS as the one on the target trial to interfere with conditioning. When priming trials
were actual CS-unconditioned stimulus (US) pairings, the CS identity did not matter; the US was the event that interfered
with conditioning on the next trial. Reinforced trials reduced performance in a way that did not depend on context blocking.
The results suggest that CS and US priming effects do contribute to conditioning deficits observed with massed trial procedures.
The results are consistent with Wagner’s (1981) “sometimes opponent process,” or SOP, model, although a result that is paradoxical
for the model suggests that recent USs may have motivational as well as memory effects. 相似文献
15.
The role of temporal factors in the development of conditioned inhibition was investigated in a backward conditioning design. Separate groups of rats received tone CSs either 3 or 30 sec following shock presentations. The CSs predicted the same shock-free interval for both groups. A third group was presented with a random relationship between CS and shock. The CSs were tested by super-imposition on a Sidman avoidance baseline and only the group with a 3-sec UCS-CS interval revealed an inhibitory effect of the CS. These results are in accord with predictions made by the Solomon-Corbit model of acquired motivation and by Denny’s “relaxation” theory of escape and avoidance. 相似文献
16.
Rats received either forward or backward pairings of an auditory CS and shock. They were then tested for conditioned suppression to the CS while barpressing for food, licking a sucrose solution, or being spontaneously active. Behavior was simultaneously observed using a time-sampling method. In each case, forward-conditioned animals exhibited more freezing than controls, and freezing was reliably correlated with suppression of the baseline. These results suggest that the different loss-of-baseline measures of aversive conditioning reflect the amount of defensive behavior evoked by the CS. They also suggest the utility of freezing as an index of conditioning. Freezing assayed by the time-sampling method was comparable to the more conventional indices of conditioning in sensitivity to the effects of conditioning. 相似文献
17.
Two conditioned lick-suppression experiments with rats were conducted in order to replicate and extend findings by Ewing, Larew, and Wagner (1985). Ewing et al. observed that excitatory responding to a CS paired with a footshock US was attenuated when the ITIs thatpreceded each CS-US trial were short (60 sec) relative to when they were long (600 sec). This effect was isolated in the influence of the preceding ITI because the preceding ITI was consistently short for one CS and consistently long for a different CS, while the following ITIs were equally often short and long for both CSs. Ewing et al. interpreted this finding in the framework of Wagner’s (1981) SOP model. Experiment 1 replicated this trial-spacing effect and demonstrated a similar effect under conditions in which thefollowing ITI was consistently short for one CS and consistently long for a different CS, while the durations of preceding ITIs were equally often short and long for both CSs. Experiment 2 revealed that the detrimental effect of a short preceding or a short following ITI could be alleviated by extinguishing the conditioning context after CS-US training. The latter observation indicates that the trial-spacing effect is not mediated by a failure of a CS trained with a short ITI to enter into excitatory associations with the US, a conclusion that is not wholly consistent with the SOP model. Finally, we suggest that short pretrial and short posttrial ITIs may enhance the excitatory value of local context cues that modulate responding to a CS. 相似文献
18.
Prior research has demonstrated renewal, which is the ability of contextual cues to modulate excitatory responding to a Pavlovian conditioned stimulus (CS). In the present research, conditioned lick suppression in rats was used to examine similar contextual modulation of Pavlovian conditioned inhibition. After Pavlovian conditioned inhibition training with a CS in one context, subjects were exposed to pairings of the CS with an unconditioned stimulus (US) either in the same or in a second context. Results indicated that, when the CS was paired with the US in the second context, the CS retained its inhibitory control over behavior, provided that testing occurred in the context used for inhibition training. However, when the CS-US pairings occurred in the inhibition training context, the CS subsequently proved to be excitatory regardless of where testing occurred. These observations indicate that conditioned inhibition is subject to renewal. 相似文献
19.
Ben A. Williams 《Learning & behavior》1989,17(4):418-432
Rats were trained on a series of reversals of a successive discrimination in which the percentage of S+ trials ending in food was varied. Changes in the discrimination index occurred more slowly with 50% reinforcement than with 100% reinforcement when the number of training trials was equated across conditions, but were approximately invariant when the conditions were equated with respect to the number of obtained reinforcements. Presentation of free reinforcement during the intertrial intervals reduced the overall rate of discrimination acquisition, but left this invariance unaffected. Invariance in reinforcements necessary to attain acquisition also occurred when different discriminations correlated with different percentages of reinforcement were intermixed within experimental sessions. The failure of the invariance effect to be disrupted by either manipulation suggests that previous accounts of the invariance effect in terms of “comparator” models of conditioning (e.g., Gibbon & Balsam, 1981) are inadequate. 相似文献
20.
Two lick suppression experiments with rats were conducted in order to determine the nature of the temporal information that is encoded as a result of Pavlovian conditioned inhibition training (conditioned stimulus {CS} A→unconditioned stimulus {US}/AX→noUS). After inhibition training, the conditioned inhibitor (X) was paired with the US in order to measure inhibition, as assessed through retarded behavioral control by CS X. Three temporal relationships were manipulated: the A-US interval, the X-A interval of inhibition training, and the X-US interval of the retardation test pairings. Retardation was greatest when the X-US temporal relationship matched the time at which the US was expected (but not delivered) on the X-A inhibition training trials. Thus, the present experiments provide evidence with retardation tests that, during conditioned inhibition training, subjects encode the temporal location of the omitted US relative to the inhibitory CS. These findings complement those of previous studies using summation tests of conditioned inhibition (Barnet & Miller, 1996; Denniston, Blaisdell, á Miller, 1998; Denniston, Cole, & Miller, 1998). 相似文献