Probability of shock in the presence and absence of CS in fear conditioning
Rescorla compared two conceptions of Pavlovian conditioning, one based on the number of signal and event pairings and one based on contingency, meaning the probability of the event with the signal compared with its probability without it. In the first experiment an equal probability of a brief shock with and without a tone produced no suppression to the tone, while the same probability given only during the tone produced substantial conditioning. In the second experiment four probabilities with and without the signal were tried: conditioning was greater the higher the probability of the event during the signal, lower the higher its probability without the signal, and absent when the two were equal.
Rescorla compared two conceptions of Pavlovian conditioning, one based on the number of signal and event pairings and one based on contingency, meaning the probability of the event with the signal compared with its probability without it. In the first experiment an equal probability of a brief shock with and without a tone produced no suppression to the tone, while the same probability given only during the tone produced substantial conditioning. In the second experiment four probabilities with and without the signal were tried: conditioning was greater the higher the probability of the event during the signal, lower the higher its probability without the signal, and absent when the two were equal.
Written from the abstract, OpenAlex record, 2026-11-11.
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Rescorla, R. A. (1968). Probability of shock in the presence and absence of CS in fear conditioning. Journal of Comparative and Physiological Psychology, 66(1), 1-5. doi:10.1037/h0025984 https://doi.org/10.1037/h0025984