Table 1.

Mean values ± SEM of additional measures activity for both schedule types, as well as the number of rats in each condition that completed the 45-min session without emitting a response for 180 s. Additional motoric measures are of the reward collection latencies, rate of magazine entries (magazine entries per second), and the rate of nontarget (blank) screen responses (nontarget responses/sec) for all experimental conditions. Italic type signifies significant effects

	Reward collection latency		Magazine entries/sec		Nontarget responses/sec		No. of 45-min terminations
	PR4	PREXP	PR4	PREXP	PR4	PREXP	PR4	PREXP
Baseline	1.20 ± 0.04*	1.58 ± 0.11*	0.08 ± 0.01	0.07 ± 0.01	0.03 ± 0.00	0.04 ± 0.01	33	14
Reward magnitude
1 pell	1.11 ± 0.06	1.36 ± 0.09#	0.07 ± 0.01#	0.05 ± 0.00#	0.02 ± 0.00	0.03 ± 0.01	5	2
3 pellets	0.97 ± 0.08	0.94 ± 0.12#	0.10 ± 0.01#	0.08 ± 0.01 #	0.02 ± 0.00	0.03 ± 0.01	8	6
Prefeeding
No feed	1.39 ± 0.09	1.51 ± 0.13	0.06 ± 0.01*	0.05 ± 0.00*	0.02 ± 0.00	0.02 ± 0.00	3	2
Prefeed	1.27 ± 0.05	1.56 ± 0.10	0.06 ± 0.01	0.04 ± 0.00	0.02 ± 0.00	0.03 ± 0.01	1	0
Raclopride
Vehicle	1.23 ± 0.09*	1.63 ± 0.15*	0.08 ± 0.01*	0.06 ± 0.01*	0.02 ± 0.00	0.03 ± 0.01	0	0
0.03 mg/kg	1.28 ± 0.06	1.58 ± 0.14	0.07 ± 0.01	0.05 ± 0.01	0.03 ± 0.01	0.04 ± 0.02	2	2
0.3 mg/kg	1.44 ± 0.19*	2.65 ± 0.72*	0.05 ± 0.01 †	0.04 ± 0.00	0.01 ± 0.00 †	0.02 ± 0.01	1	0
Amphetamine
Vehicle	1.44 ± 0.09*	1.80 ± 0.12*	0.09 ± 0.01	0.06 ± 0.01	0.04 ± 0.01	0.03 ± 0.01	1	0
0.1 mg/kg	1.40 ± 0.08*	1.71 ± 0.16*	0.08 ± 0.01	0.06 ± 0.01	0.03 ± 0.01	0.03 ± 0.01	1	2
1 mg/kg	1.35 ± 0.06	1.56 ± 0.09	0.10 ± 0.01	0.09 ± 0.01 †	0.05 ± 0.01	0.05 ± 0.01	6	8

*A significant group difference between schedule types, p < .05. ^#A significant effect of increasing the reward magnitude, p < .05. ^†A significant effect relative to the vehicle condition p < .05