of sipper access. Consumption volumes (±0.1 ml) were visually read from the tube. The sipper tube was filled with a solution of 0.0316% (w/v) saccharin solution. Levers were mounted 2.5 cm above the floor on either side of the sipper tube opening. Each lever had an LED 2.3 cm above it signaling that the lever was active (that is, reinforcement was available on that lever). Control of the operant boxes and collection of data was performed via the MedPC IV software (MedAssociates, St Albans, VT) and MedPC interface cards on a PC compatible computer. Data were sorted in Microsoft Excel (Redmond, WA) and statistical analyses were performed using SPSS 15.0 (Chicago, IL).
