Table 5. Programmed delay to reinforcement, number of sessions in each condition, and the mean (SD) rate of key pecking per min during delays to reinforcement for the vary and repeat components for each pigeon in Experiment 4. Other details as in Table 1.

Subject	Delay (s)	Sessions	Pecks/min during delay
			Vary	Repeat
P92	0	21	–	–
	post-15	29	0.17 (0.20)	0.00 (0.00)
	pre-15	30	0.17 (0.15)	0.07 (0.16)
	0	64	–	–
P98	0	20	–	–
	post-15	25	0.93 (0.48)	1.30 (0.69)
	pre-15	22	12.53 (2.52)	15.10 (5.97)
	0	45	–	–
P154	0	17	–	–
	post-30	17	1.60 (1.51)	1.50 (1.21)
	pre-30	20	3.60 (1.34)	2.86 (3.46)
	0	73	–	–