Inherited environmental influences on the operant behavior of mice.

BALB/cJ and C57BL/10J mice were reared by foster parents of the same 2 strains in the 4 possible combinations or were unfostered. Operant behavior of offspring subsequently produced by these mice was significantly influenced by within-strain fostering and by strain of foster grandparents. Within-strain fostering raised the response rates of BALE Ss while lowering that of C57BL Ss. Both strains responded more if their parents had been reared by BALE rather than by C57BL foster grandparents. Additional effects of grandparental environment on fertility of parents and neonatal mortality of young suggest that transmitted parental influences may contribute to the evolution of behavior in nonprimates.