Making the sour sweet? Upcoming food-pellet reinforcement produces positive induction when rats press a lever for unsweetened lemon juice

Research has suggested that rats increase their response rate for a low-valued reinforcer when a high-valued reinforcer will soon be available (i.e., positive induction) because the value of the low-valued substance has increased. The present study tested if such a procedure could be used to increase rats’ responding for a non-reinforcing food. Rats pressed a lever for unsweetened lemon juice in the first half of a 50-min session and, in treatment conditions, for food pellets in the second half. Experiment 1 demonstrated that rates of responding for the lemon juice generally varied directly with the upcoming rate of food-pellet reinforcement and that responding in lemon juice-only sessions did not differ significantly from that observed during extinction. Experiment 2 demonstrated that rats consumed more lemon juice following a condition in which they were displaying positive induction than following a condition in which they only responded for lemon juice. The present results are consistent with the increase in value account of positive induction. More importantly, they may indicate that certain environmental conditions can increase food-directed behavior for a non-reinforcing food, a finding which may have implications for our understanding of eating behavior and dysfunctions (e.g., overeating).