Generality of learning differences in brain-weight-selected mice.

Eight lines of mice from two independent selection programs for high, medium, and low brain weight were raised in enriched environments and tested on active avoidance, water maze, operant discrimination, and passive avoidance tasks. Although statistically reliable performance differences were found on each task within at least one selection, there was no consistent relation within selections and across tests or within tests and across selections between brain weight and performance. The results emphasize the necessity of eliminating confounded performance variables in behavior genetic research on learning phenotypes and suggest that brain weight-learing corrleations in mice are either small or nonexistent.