Three rats were trained on a schedule in which a response on lever B was reinforced only if it was preceded by a minimum number of consecutive responses on lever A. The minimum requirement was 27 A responses for Rat 1, and 20 A responses for Rats 2 and 3. The schedule maintained high rates of responding on lever A, and a slow, spaced pattern of responding on lever B. The mean number of consecutive responses on lever A was slightly greater than the minimum required. The effect of superimposing on this behavior a stimulus that ended with an unavoidable shock was the suppression of responding on both levers during the pre‐shock stimulus. Responses on lever A were more suppressed, and the proportion of relatively short response runs on lever A during the pre‐shock stimulus increased. With all three rats, the mean number of consecutive responses on lever A during the pre‐shock stimulus decreased to a value below the minimum requirement for reinforcement of the subsequent B res