Reward Effects of Food Via Stomach Fistula Compared with Those of Food Via Mouth
Motivation and reward are closely related. For example, if an animal is not motivated by the drive of hunger, food is not an effective reward. According to the drive-reduction hypothesis the rewarding effects of food are due to the fact that it reduces the strength of the hunger drive, and the relative ineffectiveness of food as a reward after the animal has become satiated is due to the fact that little if any drive is present to be reduced. The chapter provides information on some experiments that compare the hunger-reducing effects of food via stomach fistula with those of food via mouth. The experimental results show that milk injected directly into the stomach can serve as a reward to produce learning, and that milk taken normally by mouth serves as a stronger reward to produce faster learning. The results confirm the prediction from the drive-reduction hypothesis of reinforcement.