Evidence of non-maternally mediated acceleration of eye-opening in 'enriched' artificially reared rat pups.

Rat pups were artificially reared, without their mothers, from postnatal day 5. They were exposed thereafter to impoverished or enriched environmental conditions. The enrichment included gentling, social interaction and homing experience. Enriched rats showed accelerated eye-opening compared with their impoverished littermates (P less than 0.02). This is the first demonstration of stimulation-induced acceleration of development which cannot have been maternally mediated.