The purpose of this study was to investigate the effects of the instruction of evaluation (Experiment1) and the expectation of extrinsic rewards (Experiment2) on children's intrinsic motivation.In Exp.1, subjects were divided into evaluative and non-evaluative instruction groups.The former group was instructed to add the outcome to their academic achievement.After doing tasks in both groups, the method of free task choice (Sakurai, 1984a) was conducted.Four kinds of tasks were constructed in two dimensions: difficulty (easy-difficult) and curiosity (old-new). Evaluative instruction group preferred new tasks while the other group had a tendency to prefer difficult tasks.Between the groups, there was significant preference in curiosity of tasks but no significant preference in difficulty. In Exp.2, subjects were divided into expected and non-expected reward groups. The former group was instructed to give the performance-contingent rewards during doing tasks.In the situations of free task choice, both groups preferred difficult tasks, and only expected reward group preferred new ones.Between the groups, there was significant preference in curiosity of tasks but no significant preference in difficulty.Most of these results supported the Self Evaluative Motivation (SEM) Model proposed by Sakurai (1984a).