Table 2. Average food reinforcers earned from each altenrative across the last five sessions Phases 1–3 in Experiment 2.

	50% vs. 50%		50% vs. 75%		50% vs. 100%
Subject	Disc. alt.	Nondisc. alt.	Disc. alt.	Nondisc. alt.	Disc. alt.	Nondisc. alt.
20	18.0	18.0	18.1	26.8	18.0	36.0
135	22.2	13.8	21.1	22.4	20.7	30.6
245	23.6	12.4	23.7	18.4	16.8	45.6
254	21.9	14.1	22.9	19.6	20.2	31.6
257	23.9	12.1	23.7	18.4	24.0	24.0
1056	17.4	18.6	18.2	26.7	19.4	33.2
4074	20.6	15.4	21.4	21.9	20.8	30.4
19227	20.8	15.2	20.6	23.1	20.8	30.4
19229	24.0	12.0	22.1	20.8	20.8	30.4
22642	24.0	12.0	23.2	19.2	18.3	35.4
Mean	21.64	14.36	21.50	21.75	19.98	32.76
Proportion	0.601	0.399	0.497	0.503	0.379	0.621