Manosevitz, M., Pryor, J. B. 1975. Cage size as a factor in environmental enrichment. Journal of Comparative and Physiological Psychology 89, 648-654.

Cage size significantly affected 38-day gross body weight, open-field activity and defecation, running-wheel activity, exploration, and water consumption. .. Rearing in large cages, either wire or Plexiglas, appears to reduce emotionality... The results of this experiment indicate that cage size is one of the important factors of the enriched-environment-rearing experience.