Table 2.

Apparatus and Experimental Conditions

Condition	Monitor 1 Left Half	Monitor 1 Right Half	Monitor 2 Right Half	Monitor 3 Left Half
Phase I Baseline	Game A White keyboard VI 32 s	Black screen No trackball	Game B Gray keyboard VI 32 s	No monitor or mouse
Phase II Treatment	Game A White keyboard EXT	Game C Trackball VI 8* s	Game B Gray keyboard EXT	Black screen Mouse If Game B DRO, then 15 s Game D VI 8 s
Phase III Extinction	Game A White keyboard EXT	Black screen No trackball	Game B Gray keyboard EXT	No monitor or mouse

^*The VI schedule for Game C was adjusted across sessions to approximately equate obtained reinforcement for Games C and D.