Single housing is believed to be chronically stressful and to have a negative impact on welfare and cognition in rats (Rattus norvegicus). However, single housing does not consistently evoke stress-like responses nor does it consistently impair cognitive performance. In an experiment
in which all cages were separated by an opaque barrier, single- and pair-housed pigmented (dark-eyed) rats performed equally in a cognitive test and displayed similar levels of anxiety during testing. Additionally, bar biting in the home cage did not differ between the two groups. Stress levels
both during cognitive testing and in the home cage were higher than those we have previously reported when rats were housed without opaque barriers between the cages. We conclude that visual interactions between rats in different cages may be of sufficient significance that single housing
in a cage with a view to neighbouring rats and to the rest of the laboratory holding room may be preferable to pair housing in a cage without this view.