International Journal of Comparative Psychology

A series of experiments was carried out in order to explore further the possibility that hungry rats, both mature and weanling, might learn to associate flavours with different sizes of meals made from the same diet. The general procedure used involved providing rats with either a large meal (e.g. 5 gm). usually consisting of wet mash with an added flavour such as anise, or a small meal (e.g. 1 gm) of the same diet with a second flavour such as vanilla added, on alternate days. Following a number of such discrimination training days, subjects were given a two-jar extinction choice test to assess their relative preferences for the two flavours. It was originally anticipated that rats would come to prefer the flavour associated with the larger meal (i.e., conditioned appetite), because the larger meal provided more calories. However, this result was never obtained. When a significant preference was acquired, this was for the flavour of the small meal instead, (i.e. conditioned satiety). The conditioned effects not only extinguished very rapidly but were also rather elusive at times. It is thought that the observed conditioned satiety effects were probably due to flavour-calorie rather than flavour-flavour associations.