Effects of response type on pigeons' sensitivity to variation in reinforcer amount and reinforcer delay

Twelve pigeons, divided into two groups, responded on concurrent nonindependent variable-interval schedules to obtain access to grain by either pecking keys or pressing treadles. Either the amount of grain or the delay to the receipt of grain was varied in separate conditions to determine the sensitivity of relative responding to variation in reinforcer amount (s(A)), the sensitivity to variation in reinforcer delay (s(D)), and s(A)/s(D), a measure related to self-control. There were no significant differ differences between the two groups in the values of s(A), s(D), and s(A)/s(D). These results suggest that the values of s(A), s(D), and s(A)/s(D) for pigeons may be similar across these two types of responses.