Probability of shock in the presence and absence of CS in fear conditioning.
01 Aug 1968-Journal of Comparative and Physiological Psychology (J Comp Physiol Psychol)-Vol. 66, Iss: 1, pp 1-5
TL;DR: 2 experiments indicate that CS-US contingency is an important determinant of fear conditioning and that presentation of US in the absence of CS interferes with fear conditioning.
Abstract: 2 experiments indicate that CS-US contingency is an important determinant of fear conditioning and that presentation of US in the absence of CS interferes with fear conditioning. In Experiment 1, equal probability of a shock US in the presence and absence of a tone CS produced no CER suppression to CS; the same probability of US given only during CS produced substantial conditioning. In Experiment 2, which explored 4 different probabilities of US in the presence and absence of CS, amount of conditioning was higher the greater the probability of US during CS and was lower the greater the probability of US in the absence of CS; when the 2 probabilities were equal, no conditioning resulted. Two conceptions of Pavlovian conditioning have been distinguished by Rescorla (1967). The first, and more traditional, notion emphasizes the role of the number of pairings of CS and US in the formation of a CR. The second notion suggests that it is the contingency between CS and US which is important. The notion of contingency differs from that of pairing in that it includes not only what events are paired but also what events are not paired. As used here, contingency refers to the relative probability of occurrence of US in the presence of CS as contrasted with its probability in the absence of CS. The contingency notion suggests that, in fact, conditioning only occurs when these probabilities differ; when the probability of US is higher during CS than at other times, excitatory conditioning occurs; when the probability is lower, inhibitory conditioning results. Notice that the probability of a US can be the same in the absence and presence of CS and yet there can be a fair number of CS-US pairings. It is this that makes it possible to assess the relative importance of pairing and contingency in the development of a CR. Several experiments have pointed to the usefulness of the contingency notion. Rescorla (1966) reported a Pavlovian 1This research was supported by Grants MH13415-01 from the National Institute of Mental Health and GB-6493 from the National Science Foundation, as well as by funds from Yale University.
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TL;DR: Results indicate that a mechanism of classical conditioning of the withdrawal reflex is an elaboration of the mechanism underlying sensitization, and the mechanisms of higher-order features of learning, such as the effect of contingency, may be built from combinations of the molecular mechanisms of these simple forms of learning.
Abstract: The defensive siphon and gill withdrawal of Aplysia is a simple reflex, mediated by a well-defined neural circuit, that exhibits sensitization in response to strong stimulation of the tail. The siphon withdrawal reflex also exhibits classical conditioning when a weak stimulus to the siphon or mantle shelf (the conditioned stimulus or CS) is paired with a shock to the tail (the unconditioned stimulus or US). Cellular studies indicate that the mechanism of this conditioning shares aspects of the mechanism of sensitization of the reflex: presynaptic facilitation due to a cAMP-mediated decrease in K+ current and consequent broadening of action potentials in the sensory neurones. Thus, tail shock (the US) produces greater facilitation of the monosynaptic EPSP from a sensory to a motor neurone if the shock is immediately preceded by spike activity in the sensory neurone than if it occurs without spike activity (sensitization), or if the shock and spike activity are presented in a specifically unpaired pattern. This activity-dependent amplification of facilitation involves a greater broadening of action potentials in paired than in unpaired sensory neurones and appears to be due to a greater depression of the same serotonin- and cAMP-sensitive K+ current involved in sensitization. These results indicate that a mechanism of classical conditioning of the withdrawal reflex is an elaboration of the mechanism underlying sensitization. By analogy, the mechanisms of higher-order features of learning, such as the effect of contingency, may be built from combinations of the molecular mechanisms of these simple forms of learning.
82 citations
TL;DR: It is reported that blocking can occur in spatial learning, using rats trained to search for hidden food near landmarks in an open field arena and performance at asymptote was controlled by the shape of the landmark array rather than the individual landmarks comprising it, indicating that blocking in the spatial domain may represent a failure to alter the encoded geometry of a learned array.
Abstract: A characteristic feature of associative conditioning is that learning a predictive relationship between two events can block later learning about an added event. It is not yet well established whether blocking occurs in the spatial domain or the circumstances in which it does. We now report, using rats trained to search for hidden food near landmarks in an open field arena, that blocking can occur in spatial learning. The animals noticed the added landmark at the start of the blocking phase and explored it, but either failed to incorporate it into their spatial map or developed a representation in which only some landmarks actually control behavior. Additionally, performance at asymptote was controlled by the shape of the landmark array rather than the individual landmarks comprising it, indicating that blocking in the spatial domain may represent a failure to alter the encoded geometry of a learned array.
81 citations
TL;DR: The nucleus accumbens is implicated in aspects of aversive Pavlovian conditioning; the significance of this finding for theories of cortico-striatal function is discussed.
Abstract: The nucleus accumbens (NAcc) is implicated in reward-related processes and in reinforcement learning. However, its precise role in associative processes is unclear and may not be related solely to appetitive learning. In the present study, the differential effects of selective excitotoxic lesions of the NAcc core and shell were studied on the acquisition of an aversive Pavlovian conditioning task that assessed conditioning to both discrete and contextual cues. Rats with selective lesions of the NAcc shell were not impaired on measures of aversive Pavlovian conditioning to either discrete or contextual cues. In contrast, animals with lesions of the NAcc core showed an impairment in conditioning to discrete cues and an enhancement in conditioning to contextual cues. The NAcc is thus implicated in aspects of aversive Pavlovian conditioning; the significance of this finding for theories of cortico-striatal function is discussed.
81 citations
TL;DR: One explanation for why early word learning can appear baffling is suggested: Adult intuitions may be a poor source of insight into how children learn.
Abstract: The question of how children learn the meanings of words has long puzzled philosophers and psychologists. As Quine famously pointed out, simply hearing a word in context reveals next to nothing about its meaning. How then do children learn to understand and use words correctly? Here, we show how learning theory can offer an elegant solution to this seemingly intractable puzzle in language acquisition. From it, we derived formal predictions about word learning in situations of Quinean ambiguity, and subsequently tested our predictions on toddlers, undergraduates, and developmental psychologists. The toddlers’ performance was consistent both with our predictions and with the workings of implicit mechanisms that can facilitate the learning of meaningful lexical systems. Adults adopted a markedly different and likely suboptimal strategy. These results suggest one explanation for why early word learning can appear baffling: Adult intuitions may be a poor source of insight into how children learn.
79 citations
Cites background from "Probability of shock in the presenc..."
...However, if tones that do not lead to expected shocks are added to the tone-shock pairings, the rats’ conditioned responses will weaken in direct proportion to the increased background rate of tones (Rescorla, 1968)....
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TL;DR: A dual-process model is presented that provides a descriptive account of the boundary conditions for belief and evidence interactions in causal reasoning and it is observed that reasoners were relatively accurate in evaluating the degree to which their judgments were sensitive to empirical evidence but were less able to judge how much their judgments was influenced by their prior beliefs.
Abstract: In three experiments, we examined how reasoners’ preexisting beliefs about causal relations constrained their evaluation of covariation-based empirical evidence. Reasoners were presented with causal candidates that were a priorirated to be either believable or unbelievable, as well as information regarding the degree to which the cause and the effect covaried. Several findings supported the conclusion that preexisting beliefs about causal relations reflect knowledge of both causal mechanisms and covariation relations, that these sources of knowledge are represented independently and contribute independently to causal judgments, and that the evaluation of new empirical evidence is influenced differently by mechanism-based and covariation-based beliefs. Finally, we observed that reasoners were relatively accurate in evaluating the degree to which their judgments were sensitive to empirical evidence but were less able to judge how much their judgments were influenced by their prior beliefs. We present a dual-process model that provides a descriptive account of the boundary conditions for belief and evidence interactions in causal reasoning.
79 citations
References
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TL;DR: This "truly random" control procedure leads to a new conception of Pavlovian conditioning postulating that the contingency between CS and US, rather than the pairing of CS andUS, is the important event in conditioning.
Abstract: The traditional control procedures for Pavlovian conditioning are examined and each is found wanting. Some procedures introduce nonassociative factors not present in the experimental procedure while others transform the excitatory, experimental CS-US contingency into an inhibitory contingency. An alternative control procedure is suggested in which there is no contingency whatsoever between CS and US. This \"truly random\" control procedure leads to a new conception of Pavlovian conditioning postulating that the contingency between CS and US, rather than the pairing of CS and US, is the important event in conditioning. The fruitfulness of this new conception of Pavlovian conditioning is illustrated by 2 experimental results.
1,328 citations
301 citations
TL;DR: In this paper, three groups of dogs were trained with different kinds of Pavlovian fear conditioning for three different types of dogs: randomly and independently; for a second group, CSs predicted the occurrence of USs; and for a third group, S predicted the absence of the USs.
Abstract: Three groups of dogs were Sidman avoidance trained They then received different kinds of Pavlovian fear conditioning For one group CSs and USs occurred randomly and independently; for a second group, CSs predicted the occurrence of USs; for a third group, CSs predicted the absence of the USs The CSs were subsequently presented while S performed the avoidance response CSs which had predicted the occurrence or the absence of USs produced, respectively, increases and decreases in avoidance rate For the group with random CSs and USs in conditioning, the CS had no effect upon avoidance
160 citations
64 citations
TL;DR: Rats in an experimental group were given 30 trials of differential CER and then the CS+ and CS− were combined during CER extinction, resulting in less suppression for the experimental group than shown by a control group, interpreted as a demonstration of the active inhibitory properties of CS−.
Abstract: Rats in an experimental group were given 30 trials of differential CER and then the CS+ and CS− were combined during CER extinction. The combination resulted in less suppression for the experimental group than shown by a control group which had a CS+ and a formerly random stimulus combined during extinction. This was interpreted as a demonstration of the active inhibitory properties of CS−.
44 citations
"Probability of shock in the presenc..." refers background in this paper
...Although such an account is plausible for the present data, it fails to explain the active inhibition of fear found by Rescorla and LoLordo (1965), Rescorla (1966), and Hammond (1967)....
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