The role of environmental familiarization in novel-object preference

The experiments in this report examined the behavioral variables modulating novel-object preference in a widely used 'object recognition' preparation. This preparation takes advantage of the tendency of rats to interact more with a novel than a familiar 'sample' object in a free-choice situation. Experiment 1 examined the interaction between environmental familiarization and the duration of sample-object exposure in the development of a novel-object preference. Interaction with the sample object during sample-object exposure was increased when rats were given time in the environment prior to presentation of the sample object. Also, provided that the sample-object exposure was greater than 2 min, rats given environmental familiarization time prior to sample-object exposure displayed a novel-object preference. Rats that received the same amount of sample-object exposure without prior exposure to the environment alone did not discriminate between the sample and novel object. In Experiments 2 and 3, sample-object exposure occurred in a different environment than the novel-object test. Novel-object preference was not affected regardless of whether that testing environment was familiar or novel. This result differs from previous work that finds that an object recovers some novelty when moved to a new spatial location.