Position of operant costs affects visits to resources by laboratory mice, Mus musculus

A recently recognized problem in consumer demand studies has been whether subjects should be allowed free exit from a resource cage that they have paid to enter. If decisions related to switches in behaviour are affected by the position of operant costs, then demand studies that offer free return routes from resources may result in different behavioural organization from those that split the same payment between entry to and exit from resources. We aimed to assess the extent of any such differences by comparing results from four operant treatments. The closed economy treatments differed in the position of the operant costs required to allow a mouse to enter a food cage and then return to the home cage. Three of the treatments carried the same overall cost: a full cost to enter the food cage; a full cost to leave the food cage; or with the cost split equally between entering and leaving the food cage. The fourth treatment imposed a half cost to enter the food cage but allowed free exit. The mice spent longer in whichever cage carried an exit cost. The most even distribution of their time was with the split cost. The number of visits undertaken depended on the magnitude of the cost, and on the resource cage for which the mice were paying. Significantly more visits were made when payment was required to enter the home cage. The mice responded to the immediate costs of entry to the cages, rather than the overall costs of a round trip. The lower number of visits made under higher costs was compensated for by the greater duration of those visits. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.