Figure 3.

Number of food responses that occurred before the first five ethanol responses were completed expressed as a function of preceding period of food-predominant responding. Points represent the number of responses on the food-associated lever prior to completion of the first five responses on the ethanol-associated lever during a test session following the indicated number of sessions of responding under only 8 kHz, food FR5, ethanol FR5 conditions. More than five food responses prior to completion of five responses on the ethanol lever (points above the horizontal dashed line) would have been reinforced under contingencies in place the previous session (except for the zero-day condition). Some points have been offset for clarity.