Focused but fixed: the impact of expectation of external rewards on inhibitory control and flexibility in preschoolers.

Promise of rewards has been widely used in controlling preschoolers' behaviors. The current study investigated how the expectation of receiving an external reward may influence preschoolers' executive function. Four- to 5-year-old Singaporean children were randomly assigned to reward-informed and reward-uninformed conditions. Results showed that compared with those in the reward-uninformed condition, although performing the same on the control tasks and reporting similar motivation and mood states before being told about the reward, the children in the reward-informed condition performed better on the Day/Night Stroop (Experiment 1, N = 41) but worse on the Flexible Item Selection Test (Experiment 2, N = 43). These findings suggest that the expectation of receiving an external reward can influence preschoolers' behavioral control.