Figure 8. Relative frequency of IRTs plotted in successive 0.25-s bins. Separate distributions are presented for the VI 20-s and VI 120-s components and for each delay condition. The distributions labeled 0-s represent pooled distributions for repeated exposures to the immediate reinforcement baseline condition. Data also were pooled for each of the replicated delay conditions. The data plotted beyond a value of 10 on the x axis represent the relative frequency of IRTs > 10 s. The x axis is logarithmic.