. Author manuscript; available in PMC: 2016 Apr 1.

Published in final edited form as: J Exp Psychol Anim Learn Cogn. 2015 Mar 23;41(2):179–192. doi: 10.1037/xan0000061

Table 1.

Experimental Design

Experiment	Group	Phase 1	Phase 2	Phase 3
1	VI 10-s	R1: VI 30	R1: Ext	R1: Ext
		R2: ---	R2: VI 10	R2: Ext
	Reverse Thinning	R1: VI 30	R1: Ext	R1: Ext
		R2: ---	R2: VI 1200…VI 10	R2: Ext
	VI 10-s Yoked	R1: VI 30	R1: Ext	R1: Ext
		R2: ---	R2: Yoked VI 10	R2: Ext
	Reverse Thinning Yoked	R1: VI 30	R1: Ext	R1: Ext
		R2: ---	R2: Yoked VI 1200…VI 10	R2: Ext
2	VI 10-s	R1: VI 30	R1: Ext	R1: Ext
		R2: ---	R2: VI 10	R2: Ext
	Thinning	R1: VI 30	R1: Ext	R1: Ext
		R2: ---	R2: VI 10…VI 1200	R2: Ext
	Reverse Thinning	R1: VI 30	R1: Ext	R1: Ext
		R2: ---	R2: VI 1200…VI 10	R2: Ext
3	VI 10-s	R1: VI 30	R1: Ext	R1: Ext
		R2: ---	R2: VI 10	R2: Ext
	Group Alternating	R1: VI 30	R1: Ext	R1: Ext
		R2: ---	R2: VI 10 (Sessions 1,3,5,7); Ext (Sessions 2,4,6)	R2: Ext
	Group Average	R1: VI 30	R1: Ext	R1: Ext
		R2: ---	R2: VI 17.5	R2: Ext

Note: Reinforcer always consisted of pellet delivery. R1 represents the lever available during Phase 1. R2 represents the source of reinforcement during Phase 2. Two levers were always available during Phases 2 and 3. “Yoked” groups had no response requirements and were delivered a “free” pellet immediately after an animal in the corresponding contingent group had earned one.