Table 3. Expected ratios as a trial progresses, Experiment 3.

Condition	Stage at which expected ratio takes effect (if no reinforcement occurs)				Difference between persisting and escapinga
	Start of trial	After response number required by short FR	After response number required by medium FR	After response number required by long FR
5, 50, 100, 220	55	100	110	120	100 − (55 + 1) = 44
10, 40, 80, 160	45	70	80	80	70 − (45 + 1) = 34
20, 50, 100, 200	60	80	100	100	80 − (60 + 1) = 19

^aSee text for explanation