Anticipation is differently expressed in rats (Rattus norvegicus) and domestic cats (Felis silvestris catus) in the same Pavlovian conditioning paradigm

In rats (Rattus norvegicus) anticipation to an oncoming food reward in an appetitive Pavlovian conditioning procedure is expressed as an increase of behavioural transitions, i.e. hyperactivity. This behaviour might be related to the spontaneous appetitive behaviour of animals in relation to oncoming food rewards. To deepen our insight into anticipatory behaviour we decided to study anticipation in rats and cats (Felis silvestris catus) using the same paradigm, as they show different types of spontaneous appetitive behaviour in relation to oncoming food rewards: 'search behaviour' and 'sit-and-wait behaviour' respectively. Using exactly the same Pavlovian conditioning paradigm in rats and cats it turned out that individuals of both species learned the association between conditioned stimulus (CS) (a tone) and unconditioned stimulus (US) (a food reward) as judged by their conditioned approach to the food dispenser. However, rats showed an increase in behavioural transitions whereas as cats a decrease during the 3 min interval between the offset of the CS and the onset of the US. Under extinction conditions the number of transitions of the rats decreased towards that of controls, whereas that of cats increased towards that of controls. This suggests that the same internal psychological process-anticipation to a coming reward-leads to different anticipatory behaviour in different species. (C) 2002 Elsevier Science B.V. All rights reserved.