Preference of laboratory rats for potentially enriching stimulus objects.

In an effort to identify suitable stimulus objects which could be placed into standard laboratory cages in order to provide rats with a degree of environmental enrichment, the preference of rats to spend time near 15 diverse objects was measured in a free-choice paradigm. Rats showed no preference for objects such as pipes and partitions which we had reasoned might satisfy a wall-hugging tendency. They also showed no preference for objects which we had reasoned to be potentially interesting as manipulanda. The rats did show reliable preferences for spending time with some, but not all, chewable objects. A block of wood predrilled with holes was the most attractive, and we cautiously recommend that researchers consider providing laboratory rats with such an object to allow them the opportunity to exercise a fundamental, species-typical behaviour-chewing.