Fixed-ratio schedule performance of possum (Trichosurus vulpecula)

The first experiment measured possums' food preferences in order to select a consequence that could be used to maintain their behaviour. Four brushtai l possums (Trichosurus vulpecula) were presented with nine different foods, randomly paired. Their selections were used as indicators of preference. C arob was selected most often on average and this was chosen for use as the consequence. In the second experiment the possums learned to operate a key for 3-s access to carob chips, initially under a fixed-ratio 1 schedule, th en under a fixed ratio 5. The schedule was then increased after every five sessions until a subject had received no reinforcer for two consecutive ses sions. The fixed-ratio cycle was then repeated. Overall response rates init ially increased with fixed-ratio size and then there was either no further trend or a continuing increase as the fixed ratio increased further. Averag e post-reinforcement pauses were generally short across small fixed ratios and increased at larger fixed ratios. Total session running response rate c hanged inconsistently across subjects and cycles. In contrast, analysis of the cumulative records showed response runs remained reasonably constant in rate as fixed ratio increased. These different results are a product of th e within-ratio pausing which is included in the total session response rate s. The results show that possum behaviour can be studied under laboratory c onditions and that the behaviour maintained under fixed-ratio schedules by carob was generally consistent with that found for ether species.