Hetts, S., Clark, J. D., Calpin, J. P. et al. 1992. Influence of housing conditions on beagle behaviour. Applied Animal Behaviour Science 34, 137-155.

Single-housing for prolonged periods is likely to be deleterious to the dog and is associated with an increased incidence of behavioral disorders. Pair-housed dogs barked less, slept more and exhibited less stereotypic behaviour than single-housed animals. The results indicate that spatial area and activity are not likely to be the most important factors to be considered when evaluating psychosocial [emphasis added] well-being of dogs. In assessing the psychosocial well-being of dogs, social isolation may be as harmful or more harmful than spatial restriction.