- Two experiments investigated temporal bisection in pigeons using a procedure similar to that of Stubbs (1976). This procedure measures the point in time at which the bird switches from the shorter to the longer valued of two fixed-interval reinforcement schedules with a common starting point. The first experiment substantiated previous findings of switching at the geometric mean of the two interval values and strengthened identification of this switching with bisection by eliminating the possibility that the birds simply switched to the longer interval when the shorter one was perceived to have expired. The experiment also extended the range of values for which temporal intervals have been found to be bisected at their geometric mean. A second experiment demonstrated that the usefulness of the present procedure for determining temporal bisection points is limited to cases in which the longer interval is no more than four times the duration of the shorter interval. Greater separation of the two interval durations produced a period of nonresponding during which the location of the switching or bisection point was totally ambiguous.