Differentiation of press durations with upper and lower limits on reinforced values.

Rats received food following lever-press durations between t and t+t' sec where t was 2, 4, or 8 sec and t' was 0.25t, 0.50t, or 1.00t sec. Modal press durations were greater than t but less than t+t' in all cases. Distributions of press durations were lower and broader for larger values of t. Lower t'/t ratios produced lower median press durations and relatively narrower press-duration distributions. Median press duration was a power function of t within a t'/t ratio condition, corresponding to previous results for latency, interresponse time, and response durations.