Contrast and reinforcement in consumption

In three experiments negative contrast in consummatory responding was measured, as well as the preference for the flavor associated with the lesser reinforcer. In all experiments one flavor of saccharin was given on days that chocolate milk occurred and another flavor was given on days with no chocolate milk. For some groups the saccharin preceded chocolate milk, for others the order of chocolate milk and saccharin was random, and for others the saccharin followed the chocolate milk. In all experiments rats suppressed consumption of the lesser reinforcer during training (negative contrast) but preferred the flavor of saccharin that had accompanied chocolate milk to the flavor of saccharin that occurred alone. This suggests that contrast is not a reflection of reduced reward value of the lesser reinforcer. Instead some negative reaction to receiving the lesser reinforcer during training must suppress consumption.