Abstract: Two experiments were designed to investigate the function of Metamemory and its influential factors. In experiment 1, 2x2 within-group design was used to study the influential factors, the independent variables were levels of material difficulty (Chinese word-word pairs vs. number-word pairs) and times of the materials presented to the subjects (once vs. fourth). In experiment 2, subjects were assigned to two levels of rewards and punishment groups to study the probability response criterion (Prc) in the process of output controlling. The materials were presented to the subjects in random order by computer. After the materials were presented, subjects were asked to make Feeling-of-knowing (FOK) judgement on 10 degree scale and to make free recall, then Quasi-signal detection method was used to state and analyze the results of free recall, judgements of FOK, compute the Fit Ratio and the criterion of out-put control. The result of experiment 1 showed that accuracy of recall performance and FOK judgement magnitude were influenced significantly by material difficult and times that items were presented, easier memory materials, more times presented items brought out better objective level memory performance and higher FOK magnitude. The criterion of out-put control and the sensitivity of metamemory control to monitoring (Fit Ratio) were not influenced by the difficulty of material, and the times items were presented to the subjects. The results of experiment 2 showed that under the high and low reward conditions, the Prc were significantly different, under the low reward condition it was higher than under the high reward condition

Key words: metamemory, feeling-of-knowing judgement, response criterion probability, Quasi-signal detection theory