Emergence of choice strategies in the rat: Shift-stay differentiation precedes win-lose differentiation

The choice strategies of rat pups between 12 and 21 days of age were studied in a two-choice discrimination procedure that used access to a nonlactating anesthetized dam as a reward. After receiving a reward (win) or not receiving a reward (lose), a pup repeated a previous choice (stay) or made an alternative response (shift). At 12 and 15 days of age, pups demonstrated neither a stay nor a shift response strategy; at 18 and 21 days of age, pups had a robust tendency to shift. Winning or losing did not alter behavior until 21 days of age, at which point winning produced a greater tendency to return to the initially visited location for rats in the stay condition.