Behavioural conflict in two strains of rat: Home cage preference versus dark preference.

When confronted with a novel situation rats show a tendency either to stay in a dark place or to retreat to a familiar place, if available. To produce a conflict between these two tendencies the rat's home cage was connected by a runway to a dark but unfamiliar compartment. Three groups of rats were tested in this apparatus with different levels of illumination in the home cage. Tryon Maze Bright rats showed a strong preference for the home cage which was independent of the illumination level. This preference was also found in Wistar rats. With a very high level of illumination in the home cage, however, Wistar rats showed a preference for the home cage only in the first few trials or a series of repeated trials. In later trials they spent more time in the dark part of the apparatus. The results were regarded as an indication that in a novel situation rats primarily search for a familiar place. When such a place is available they tolerate aversive stimulation present in this place.