本研究探討受試者於項目指示遺忘(Item-Method Directed Forgetting)作業中對於實驗刺激材料的記憶登錄及提取歷程。在項目指示遺忘作業中，受試者於學習階段時被要求對每一個出現的實驗刺激加以記住或是忘記。在測試階段的時候受試者被要求回憶或是再認所有在學習階段出現過的實驗刺激，無論該刺激在學習階段出現時是被要求記住或忘記的刺激。實驗結果通常發現，受試者對於在學習階段被要求記住的實驗刺激(TBR項目)相較於在學習階段被要求忘記的實驗刺激(TBF項目)有較佳的記憶表現，此現象稱為項目指示遺忘效果(Item-Method Directed Forgetting Effect)。本研究進行三個實驗檢視受試者提取(retrieve)被要求記住的項目以及被要求忘記的項目之間處理歷程的差異，並藉以推論產生項目指示遺忘效果的機制。實驗一及實驗二的測驗階段中，分別使用了主觀報告式的「記得/知道」判斷(Tulving, 1985)以及客觀量測的歷程分離程序(Process Dissociation Procedure, Jacoby, 1991)兩種方法檢視再認記憶(Recognition Memory)中重拾記憶(Recollection)及熟悉(Familiarity)的記憶歷程對於TBR以及TBF項目的貢獻。兩個實驗得到了一致的結果：被再認出來的TBR項目及TBF項目中有相同比例得力於熟悉歷程；在重拾記憶歷程方面，被再認出來的TBR項目相較於TBF項目有較高的比例得力於此歷程。為了進一步探討提取TBF項目時是否牽涉抑制的歷程，實驗三記錄並比較受試者以TBR或是以TBF項目為記憶提取目標時，所伴隨發生的事件相關腦電位(event-related potentials, ERPs)。實驗結果觀察到無論作業的要求是以TBR或是TBF為記憶提取目標，受試者都傾向於提取TBR項目的訊息以資判斷，受試者提取歷程不會受不同作業情境的影響，顯示受試者不僅在登錄TBR及TBF項目時有不同的處理歷程，在提取階段也涉及不同的歷程。Item-method directed forgetting has been studied by presenting with words followed by an “R” cue or an “F” cue, which instructed the subject to remember or to forget the preceding word. The central issue is whether the R/F cue exerts its influence during the encoding or the retrieval stage. The first two behavioral experiments incorporated item-method directed forgetting paradigm with remember-know paradigm, and process dissociation procedure respectively. The behavioral experiments showed that the cue designation only have effects in remembering, but not knowing. This result suggested that differential rehearsal seems to provide a plausible account of item-method directed forgetting effect. The 3rd experiment used exclusion tasks and event-related potentials (ERPs) to examine the retrieval inhibition hypothesis in directed forgetting. At study, subjects were presented with Chinese two-character words followed by an “R” cue or an “F” cue, which instructed the subject to remember or to forget the preceding word. At test, subjects engaged in two blocks of exclusion tasks. The to-be-remembered (TBR) and to-be-forgotten (TBF) items were designated as targets and nontargets respectively in the first task, and vice versa in the second block. ERPs recorded during the test phase were compared across the response categories of hits to targets, correct rejections to nontargets, and correct rejections to new items in the two exclusion tasks. The hit rate was higher when the TBR items were designated as targets as opposed to when the TBF items were designated as targets. In test phases, the left parietal ERP old/new effect -- the electrophysiological correlate of recollection -- was observed for TBR items, but not reliable for TBF item under both exclusion tasks. These findings lend support to the retrieval inhibition hypothesis, which claimed that items followed by an “F” cue became inhibited and less accessible.
