Abstract
To see if a more natural cage design would alter the reactivity of laboratory mice, 192 mice were reared in cages with (1) no dividers, (2) five vertical dividers, (3) nine vertical dividers, or (4) nine vertical dividers and one horizontal platform. The mice preferred the most complex cages, and on almost all measures they were less emotional when reared in the more complex cages. Results suggest that a more natural housing environment would lead to healthier animals.