共查询到20条相似文献，搜索用时 31 毫秒
1.
Geoffrey Hall 《Learning & behavior》1996,24(3):233-255
Pavlovian conditioning is taken to reflect the formation of links between the central representations of stimuli. A link will be formed when presentation of the relevant stimuli is scheduled in a way that ensures that two representations are activated concurrently. Once this has occurred, a representation can be activated not only by the occurrence of the appropriate stimulus but also by way of the link. Evidence is reviewed to suggest that activation produced by this second route is, in some ways, functionally equivalent to direct activation; in particular, an associatively activated representation (animage) appears capable of forming further associative links with other event representations. Learning about associatively activated stimulus representations may play a role in a range of phenomena. Its contribution to the following is discussed: sensory preconditioning, second-order conditioning, acquired equivalence and distinctiveness, equivalence class formation, and the perceptual learning effect. Finally, consideration is given to the way in which existing theories of associative learning might be modified in order to accommodate this process. 相似文献
2.
This paper presents a brief, informal outline followed by a formal statement of an elemental associative learning model first described by McLaren, Kaye, and Mackintosh (1989). The model assumes representation of stimuli by sets of elements (i.e., microfeatures) and a set of associative algorithms that incorporate the following: real-time simulation of learning; an error-correcting learning rule; weight decay that distinguishes between transient and permanent associations; and modulation of associative learning that gives high salience to and, hence, promotes rapid learning with novel, unpredicted stimuli and reduces the salience for a stimulus as its error term declines. The model is applied in outline fashion to some of the basic phenomena of simple conditioning and, in greater detail, to the phenomena of latent inhibition and perceptual learning. A detailed account of generalization and discrimination will be provided in a later paper. 相似文献
3.
Delamater AR 《Learning & behavior》2012,40(1):1-23
A significant problem in the study of Pavlovian conditioning is characterizing the nature of the representations of events
that enter into learning. This issue has been explored extensively with regard to the question of what features of the unconditioned
stimulus enter into learning, but considerably less work has been directed to the question of characterizing the nature of
the conditioned stimulus. This article introduces a multilayered connectionist network approach to understanding how “perceptual”
or “conceptual” representations of the conditioned stimulus might emerge from conditioning and participate in various learning
phenomena. The model is applied to acquired equivalence/distinctiveness of cue effects, as well as a variety of conditional
discrimination learning tasks (patterning, biconditional, ambiguous occasion setting, feature discriminations). In addition,
studies that have examined what aspects of the unconditioned stimulus enter into learning are also reviewed. Ultimately, it
is concluded that adopting a multilayered connectionist network perspective of Pavlovian learning provides us with a richer
way in which to view basic learning processes, but a number of key theoretical problems remain to be solved, particularly
as they relate to the integration of what we know about the nature of the representations of conditioned and unconditioned
stimuli. 相似文献
4.
Harris and Livesey. Learning & Behavior, 38, 1-26, (2010) described an elemental model of associative learning that implements a simple learning rule that produces results equivalent to those proposed by Rescorla and Wagner (1972), and additionally modifies in "real time" the strength of the associative connections between elements. The novel feature of this model is that stimulus elements interact by suppressively normalizing one another's activation. Because of the normalization process, element activity is a nonlinear function of sensory input strength, and the shape of the function changes depending on the number and saliences of all stimuli that are present. The model can solve a range of complex discriminations and account for related empirical findings that have been taken as evidence for configural learning processes. Here we evaluate the model's performance against the host of conditioning phenomena that are outlined in the companion article, and we present a freely available computer program for use by other researchers to simulate the model's behavior in a variety of conditioning paradigms. 相似文献
5.
John M. Pearce 《Learning & behavior》2002,30(2):73-95
A configural theory of associative learning is described that is based on the assumption that conditioning results in associations between the unconditioned stimulus and a representation of the entire pattern of stimulation that was present prior to its delivery. Configural theory was formulated originally to account for generalization and discrimination in Pavlovian conditioning. The first part of the article demonstrates how this theory can be used to explain results from studies of overshadowing, blocking, summation, and discrimination learning. The second part of the article shows how the theory can be developed to explain a broader range of phenomena, including mediated conditioning, reinforcer devaluation effects, the differential outcomes effect, acquired equivalence, sensory preconditioning, and structural discriminations. 相似文献
6.
In a Pavlovian conditioning situation, an initially neutral stimulus may be made excitatory by nonreinforced presentations
in compound with an established conditioned excitor [i.e., second-order conditioning (SOC)]. The established excitor may be
either a punctate cue or the training context. In four conditioned suppression experiments using rats, we investigated whether
SOC phenomena parallel other cue interaction effects. In Experiment 1, we found that the response potential of a target stimulus
was directly related to the intertrial interval when SOC was mediated by a punctate cue, and inversely related to the intertrial
interval when SOC was mediated by the training context. Experiment 2 demonstrated that punctate- and context-mediated SOC
are oppositely affected by posttraining context extinction, and Experiments 3 and 4 demonstrated that context- and punctate-mediated
SOC are differentially affected by conditioned stimulus (Experiment 3) and unconditioned stimulus (Experiment 4) preexposure
treatments. These findings parallel phenomena in conditioned inhibition and cue competition situations. 相似文献
7.
Are humans unique in their ability to interpret exogenous events as causes? We addressed this question by observing the behavior of rats for indications of causal learning. Within an operant motor–sensory preconditioning paradigm, associative surgical techniques revealed that rats attempted to control an outcome (i.e., a potential effect) by manipulating a potential exogenous cause (i.e., an intervention). Rats were able to generate an innocuous auditory stimulus. This stimulus was then paired with an aversive stimulus. The animals subsequently avoided potential generation of the predictive cue, but not if the aversive stimulus was subsequently devalued or the predictive cue was extinguished (Exp. 1). In Experiment 2, we demonstrated that the aversive stimulus we used was in fact aversive, that it was subject to devaluation, that the cue–aversive stimulus pairings did make the cue a conditioned stimulus, and that the cue was subject to extinction. In Experiments 3 and 4, we established that the decrease in leverpressing observed in Experiment 1 was goal-directed instrumental behavior rather than purely a product of Pavlovian conditioning. To the extent that interventions suggest causal reasoning, it appears that causal reasoning can be based on associations between contiguous exogenous events. Thus, contiguity appears capable of establishing causal relationships between exogenous events. Our results challenge the widely held view that causal learning is uniquely human, and suggest that causal learning is explicable in an associative framework. 相似文献
8.
Previous simulations revealed that the sometimes competing retrieval model (SOCR; Stout & Miller, Psychological Review, 114, 759-783, 2007), which assumes local error reduction, can explain many cue interaction phenomena that elude traditional associative theories based on total error reduction. Here, we applied SOCR to a new set of Pavlovian phenomena. Simulations used a single set of fixed parameters to simulate each basic effect (e.g., blocking) and, for specific experiments using different procedures, used fitted parameters discovered through hill climbing. In simulation 1, SOCR was successfully applied to basic acquisition, including the overtraining effect, which is context dependent. In simulation 2, we applied SOCR to basic extinction and renewal. SOCR anticipated these effects with both fixed parameters and best-fitting parameters, although the renewal effects were weaker than those observed in some experiments. In simulation 3a, feature-negative training was simulated, including the often observed transition from second-order conditioning to conditioned inhibition. In simulation 3b, SOCR predicted the observation that conditioned inhibition after feature-negative and differential conditioning depends on intertrial interval. In simulation 3c, SOCR successfully predicted failure of conditioned inhibition to extinguish with presentations of the inhibitor alone under most circumstances. In simulation 4, cue competition, including blocking (4a), recovery from relative validity (4b), and unblocking (4c), was simulated. In simulation 5, SOCR correctly predicted that inhibitors gain more behavioral control than do excitors when they are trained in compound. Simulation 6 demonstrated that SOCR explains the slower acquisition observed following CS-weak shock pairings. 相似文献
9.
Three experiments, using rats, demonstrated the encoding of a food unconditioned stimulus (US) in a simple Pavlovian conditioning paradigm. In all three studies, one stimulus was used to signal the delivery of pellets and a different stimulus was used to signal the delivery of sucrose. In Experiment 1, postconditioning devaluation of one of the food USs selectively reduced the frequency of conditioned magazine-directed behavior during the stimulus trained with that US. In Experiment 2, transfer of the stimuli to instrumental responses resulted in selective depression of the response trained with a different outcome. In Experiment 3, acquisition of stimulus-outcome learning was impaired by unsignaled intertrial presentations of the same outcome but not of a different outcome. These results indicate that a detailed representation of the outcome is encoded in the normal course of Pavlovian conditioning. 相似文献
10.
Dickinson and Burke (1996) proposed a modified version of Wagner’s (1981) SOP associative theory to explain retrospective
revaluation of human causal judgments. In this modified SOP (MSOP), excitatory learning occurs when cue and outcome representations
are either both directly activated or both associatively activated. By contrast, inhibitory learning occurs when one representation
is directly activated while the other is associatively activated. Finite node simulations of MSOP yielded simple acquisition,
overshadowing, blocking, and inhibitory learning under forward contingencies. Importantly, retrospective revaluation was predicted
in the form of unovershadowing and backward inhibitory learning. However, MSOP did not yield backward blocking. These predictions
are evaluated against the relevant empirical evidence and contrasted with the predictions of other associative theories that
have been applied to retrospective revaluation of human causal and predictive learning. 相似文献
11.
Dale Swartzentruber 《Learning & behavior》1995,23(2):123-143
Pavlovian conditioning has traditionally been thought to involve the acquisition of excitatory and inhibitory associations between a conditioned stimulus (CS) and an unconditioned stimulus (US). Recent research, however, has encouraged the view that Pavlovian learning may also encompass a higher order modulatory mechanism, in which animals use information about another stimulus to control responding to the CS. Positive modulators signal a positive relationship between the CS and the US, whereas negative modulators signal that the CS-US relationship is not in force. In both cases, the modulatory control appears to be orthogonal to the modulator’s direct associations with the US. This article reviews and evaluates the literature on this Pavlovian modulatory mechanism. 相似文献
12.
Robert A. Rescorla 《Learning & behavior》1997,25(2):200-209
In five experiments, rats were given Pavlovian pairings of auditory and visual stimuli with delivery of food pellets. Experiment 1 found greater responding to an AB compound after training with the individual A and B stimuli, compared with responding both to the A and B elements and to a separately trained CD compound. Experiment 2 found this enhanced responding to depend on the associative strengths of A and B. In Experiment 3, responding was greater to a CD compound than to the other compounds after an AB-, AD+, BC+ training procedure. In Experiment 4, responding to an AB compound was greater than that to the elements after A was reinforced on a 100% schedule and B on a 50% schedule. In Experiment 5, responding to an AC compound was greater than that to either A or C after an AB+, CD+, A-training procedure. A configural theory, such as that proposed by Pearce (1987), anticipates summation in none of these procedures, unless the conditioned context is assumed to have a salience greater than zero. In order to predict summation in Experiments 3, 4, and 5, a context salience greater than that of the elements must be assumed. However, such an assumption also anticipates that extinction of a 100% stimulus should eliminate responding to a 50% stimulus. The results of Experiment 3 contradicted that prediction. These results conform better to the expectations of elemental models of conditioning. 相似文献
13.
It is said that “absence makes the heart grow fonder.” But, when and why does an absent event become salient to the heart or to the brain? An absent event may become salient when its nonoccurrence is surprising. Van Hamme and Wasserman (1994) found that a nonpresented but expected stimulus can actually change its associative status—and in the opposite direction from a presented stimulus. Associative models like that of Rescorla and Wagner (1972) focus only on presented cues; so, they cannot explain this result. However, absent cues can be permitted to change their value by assigning different learning parameters to present and absent cues. Van Hamme and Wasserman revised the Rescorla-Wagner model so that the α parameter is positive for present cues, but negative for absent cues; now, changes in the associative strength of absent cues move in the opposite direction as presented ones. This revised Rescorla-Wagner model can thus explain such otherwise vexing empirical findings as backward blocking, recovery from overshadowing, and backward conditioned inhibition. Moreover, the revised model predicts new effects. For example, explicit information about the absence of nonpresented cues should increase their salience (that is, their negative α value should be larger), leading to stronger associative changes than when no explicit mention is made of cue absence. Support for this prediction is detailed in a new causal judgment experiment in which participants rated the effectiveness of different foods’ triggering a patient’s allergic reaction. Overall, these and other findings encourage us to view human causal learning from an associative perspective. 相似文献
14.
A rat’s preference for food of a given flavor can be substantially enhanced by allowing it to interact with a conspecificdemonstrator that has recently eaten food of that flavor. The heuristic value of treating such socially induced enhancement of flavor preference as an instance of Pavlovian conditioning was examined in three experiments. Conceiving of the smell of the food as a conditional stimulus and other cues emanating from the demonstrator rat as an unconditional stimulus, we determined whether each of three common Pavlovian phenomena-blocking, overshadowing, and latent inhibition-would occur. Using experimental parameters that readily produce socially induced enhancement of flavor preference, none of the three Pavlovian phenomena were found. 相似文献
15.
In two experiments, two groups of rats were trained in a navigation task according to either a continuous or a partial schedule
of reinforcement. In Experiment 1, animals that were given continuous reinforcement extinguished the spatial response of approaching
the goal location more readily than animals given partial reinforcement—a partial reinforcement extinction effect. In Experiment
2, after partially or continuously reinforced training, animals were trained in a new task that made use of the same reinforcer
according to a continuous reinforcement schedule. Animals initially given partial reinforcement performed better in the novel
task than did rats initially given continuous reinforcement. These results replicate, in the spatial domain, well-known partial
reinforcement phenomena typically observed in the context of Pavlovian and instrumental conditioning, suggesting that similar
principles govern spatial and associative learning. The results reported support the notion that salience modulation processes
play a key role in determining partial reinforcement effects. 相似文献
16.
The ability of visual CSs previously paired with flavored substances to substitute for those substances as conditional discriminative cues was examined in two Pavlovian appetitive conditioning experiments using rat subjects. In Experiment 1, a visual stimulus was first paired with the delivery of a sucrose solution. Then the rats were trained in conditional discrimination tasks in which sucrose delivery alone served as a conditional cue signaling whether or not a subsequent tone would be reinforced with food pellets. Subjects rapidly acquired discriminative performance to the tones, especially in a feature-negative condition in which sucrose delivery signaled when the tone would not be reinforced. In a subsequent test in which neither food nor sucrose was delivered, presentation of the visual CS also controlled discriminative performance to subsequently presented tones. Experiment 2 showed the ability of a visual CS to substitute for a flavored substance as a conditional cue to be highly stimulus specific. Experiment 2 also showed that a flavored substance was less effective as a conditional cue when it was made to be expected by preceding it with a previously associated visual signal than when it was made to be surprising by preceding it with a visual stimulus signaling another flavored liquid. These results indicate that CS-evoked representations of events can substitute for those events themselves in the control of previously established conditional discrimination performance. 相似文献
17.
Two experiments with rabbits investigated the concordance of two measures of conditioning, eyeblink and potentiated startle, during a blocking sequence with paraorbital shock reinforcement. In both, a shift in the locus of shock from one eye to the other between the conditioning of an element and a compound of that element and a new cue had differential effects on the two measures of conditioning to the new cue. When the shock was unchanged, diminished conditioning in relation to controls (i.e., blocking) was observed on both measures. When the shock was changed, little conditioning was observed in startle, but control-equivalent amounts were observed in eyeblink (i.e., blocking occurred on the former but not the latter). The results are interpreted as showing a dissociation of the associative learning involving the emotive features of Pavlovian reinforcers and that involving the remaining sensory-perceptual features, and more compatible with a diminished US-processing, than with a CSprocessing, view of blocking. 相似文献
18.
Robert A. Rescorla 《Learning & behavior》1999,27(1):50-62
In five experiments, a Pavlovian appetitive conditioning preparation was used with rats to explore the interaction of associations with different, but equivalently valued, outcomes. Experiment 1 demonstrated summation in magazine responding when two stimuli previously associated with different outcomes were combined. Experiments 2A and 2B found that pairing that stimulus compound with one of the outcomes led to a decrease in performance (overexpectation) for both of the stimulus elements. Experiments 3A and 3B confirmed that result but demonstrated the continued presence of the original stimulus-outcome associations. The results are consonant with a view in which replacing one outcome with another leads to an associative structure containing both stimulus-outcome associations and an outcome-independent depressive process. 相似文献
19.
In two experiments, rats were presented with a taste conditioned stimulus (CS) alone, an odor CS alone, or an odor-taste compound followed by lithium chloride injection. When tested 1 day following conditioning, there was evidence that the odor cue overshadowed conditioning to the taste; however, there was no indication of overshadowing following a longer (21-day) retention interval, despite undiminished strength of the aversion in animals conditioned with only the single element (taste). The overshadowing observed at the 1-day retention interval was not reciprocal. Rats conditioned with the odor CS alone or with the compound CS expressed odor aversions of comparable strength—that is, no overshadowing. However, in contrast to the taste aversion, overshadowing of conditioning to the odor by taste was evident following a 21-day retention interval. Rather than reflecting a failure of the overshadowed stimulus to acquire associative strength, these data suggest that overshadowing may be expressed, or not expressed, as a result of changes in the relative retrievability of learned associations over time. 相似文献
20.
Tolerance to morphine-induced hypoactivity in hamsters was investigated under conditions designed to test a Pavlovian conditioning model of morphine tolerance. One group of animals received i.p. injections of morphine (50 mg/kg) in the test environment and saline in the home cage; a second group received saline in the test environment and morphine in the home cage; a third group received saline in both environments. A subsequent morphine challenge in the test environment gave evidence of both associative and nonassociative tolerance. Associative tolerance was detectable 1 week later during a second morphine challenge. Compensatory hyperactivity, however, was not observed during a saline challenge in the presence of morphine-associated cues. Following the acquisition of tolerance, nonreinforced exposure to morphine-associated cues produced an attenuation of morphine tolerance (i.e., extinction of tolerance). The results are interpreted as providing partial support for the Pavlovian model and are discussed in terms of alternative associative models of tolerance. 相似文献