International Journal of Comparative Psychology
Immediate and Delayed Flavour-Calorie Learning: Can Rats Do It?
- Author(s): Simbayi, Leickness C.
- et al.
Four experiments which investigated the ability of rats to associate the flavour of a food with the later release of calories are reported. In Experiments 1 and 2, which involved immediate reinforcement, rats were trained to discriminate between two flavours (e.g. cinnamon and wintergreen), one of which was mixed with a solution of glucose which provided many calories on some days and the other with a solution of saccharin which did not yield any calories on other days. In subsequent two-bottle tests between the two flavours mixed with the same type of substrate, all rats displayed large shifts in preferences for the flavour previously paired with glucose compared to the second flavour previously paired with saccharin. Experiment 2 further showed that the conditioned effects extinguished very easily. In Experiments 3 and 4, which involved delayed reinforcement, rats were trained to discriminate between the two flavour cues, both dissolved in saccharin, one of which was reinforced with food after a long delay on some days and the other with nothing on other days. In Experiment 3 glucose was delivered after a 30 min. delay whereas in Experiment 4 various kinds of food were used and the delay was reduced to 20 min. In subsequent preference tests between the flavour cues in Experiment 3, only a small, but significant, increase in preference for the paired flavour was detected. Similarly in Experiment 4 some evidence for discrimination learning was again found with glucose, but there was no evidence that rats could associate a flavour with starch solution or solid chow over the 20 min. delay. Overall these results show that rats can easily form flavour-calorie associations under immediate reinforcement conditions but they do so with great difficulty when long delays are involved.