Hubrecht, R. C., Serpell, J. A., Poole, T. B. 1992. Correlates of pen size and housing conditions on the behaviour of kennelled dogs. Applied Animal behaviour Science 34, 365-383.

Behavioral data were collected from solitary and group-housed dogs [of different breeds] from animal shelters and laboratories. Solitary dogs were more inactive and spent more time in non-social repetitive locomotory behaviour categories. Dogs housed in pens with spacious, complex outdoor runs were more active and engaged in more species-typical locomotory behaviors than dogs kept in small and barren standard pens.