Abstract: There are two kinds of hypotheses regarding to delayed judgment of learning (JOL) effect, which are memory hypothesis and metamemory hypothesis. Two experiments were conducted to investigate the controversy between memory hypothesis and metamemory hypothesis, and the mechanism of monitoring-dual-memories hypothesis (MDM, Nelson & Dunlosky, 1991), respectively.
Both the memory hypothesis and the metamemory hypothesis acknowledge that the accuracy of JOL increases when in delayed-JOL condition than in immediate-JOL condition. However, the explanation of these two hypotheses on the mechanism of this phenomenon differs substantially. The metamemory hypothesis believes that delayed-JOL effect is duo to improvement in metamemory, while the memory hypothesis supposes that delayed-JOL simply affects memory, not metamemory. We believed that these two hypotheses are not either-or. Namely, delayed-JOL affects memory as well as metamemory.
In the first experiment, we removed the memorial difference between delayed-JOL and immediate-JOL by setting in a preliminary test between JOL and final test. The results showed that the memory scores in immediate-JOL condition and delayed-JOL condition had no significant difference. However, the accuracy of delayed-JOL was substantially high than the accuracy of immediate-JOL in a preliminary test. This result confirmed that the delayed-JOL indeed improved the accuracy of metamemory, it affected memory as well as metamemory.
Now that we have proved that the delayed-JOL improved metamemory in the first experiment, we continued to study the mechanism of this improvement in the second experiment. There are three types of metamemory hypotheses, MDM hypothesis is most influential and controversial. There are many researches supported this hypothesis, but Kelemen and Weaver′s (1997) study challenged it. However, they can only determine the removement of short-term memory (STM) through theoretical speculation in traditional experimental procedure, whether the STM was removed or not and the extent of removement could not be measured. We could observe the score of pre-judgment recall by using PRAM method. The results of experiment showed that the distractive assignment could not remove STM effectively. We found that the accuracy of JOL was related to the removement of STM through correlation analysis. The accuracy improved with the extent of removement of STM. So we believed that the delayed-JOL effect was duo to removement of STM thoroughly. Our study confirmed as well as extended the MDM hypothesis.

Key words: delayed-JOL effect, memory hypothesis, metamemory hypothesis, monitoring-dual-memories hypothesis