Reinforcement of anticipatory eating by short as well as long fasts

Rats can learn to anticipate the omission of subsequent meals by increasing food intake. Our previous reports have analysed group means at each trial but that does not allow for rats learning at different speeds. This paper presents instead a rat-by-rat analysis of all the raw data from previous experiments. The re-analysis supports the published evidence that the capacity for reinforcement generated by withholding of food is greater after a longer fast than after a shorter fast, but that the learning is quicker after the shorter fast. The individualised analyses also extend the evidence that the pattern of learning, extinction and re-learning with shorter fasts is similar to that with longer fasts. These findings indicate that, contrary to our previous interpretation, a single learning mechanism can explain the effects of both durations of food deprivation.