Simulating amnesic symptoms in normal subjects.

Patients with organic brain damage resulting in anterograde amnesia cannot recall a list of words, but when given the first three letters of each word, they complete these word stems with words from the list. We simulated this phenomenon in normal subjects who examined the list words for vowels while ignoring their semantic component. The subjects produced the list words when completing the word stems although they could not recall the words.

The information that amnesic patients do not forget.

The performance of three kinds of amnesic patients and control subjects was assessed using four methods for testing memory: free recall, recognition, cued recall, and word completion. Whereas amnesic patients were impaired on free recall, recognition, and cued recall, they were normal on word completion. Moreover, performance on the word-completion test declined at a normal rate reaching chance after about 120 min. The word-completion test resembled the cued-recall test in that the initial letters of previously presented words were given as cues. It differed from cued recall only in the instructions, which directed subjects away from the memory aspects of the test and asked them to complete each three-letter cue with the first word that came to mind. The present results offer an explanation of conflicting findings that have been obtained with amnesic patients on tests of the cued-recall type. The results are considered in terms of a process (activation or procedural learning), which is spared in amnesia and not dependent on the integrity of the damaged brain regions.

Implicit and explicit forgetting: when is gist remembered?

Recognition (YES/NO) and stem completion (cued: complete with a word from the list; and uncued: complete with the first word that comes to mind) were tested following either semantic or non-semantic processing of a categorized input list. Item/instance information was tested by contrasting target items from the input list with new items that were categorically related to them; gist/categorical information was tested by comparing target items semantically related to the input items with unrelated new items. For both recognition and stem completion, regardless of initial processing condition, item information decayed rapidly over a period of one week. Gist information was maintained over the same period when initial processing was semantic but only in the cued condition for completion. These results are discussed in terms of dual process theory, which postulates activation/integration of a representation as primarily relevant to implicit item information and elaboration of a representation as mainly relevant to semantic (i.e. categorical) information.

Retrieval processes in recognition.

Retrieval processes in the long-term recognition of well organized material showed the expected organizational effects on "slow" recognition responses. Ss sorted 100 words into two to seven categories until a stable organization was achieved. The data showed the usual correlations between organization (number of categories used) and recall and recognition. Recognition tests a week after the sorting task revealed no differences between Ss using many or few categories for the "fast" recognition responses, defined as the faster 50% of each S's latency distribution. The organizational effect was clearly evident for the "slow" 50% of the responses. The data support the retrieval check hypothesis in recognition under the assumption that retrieval operations take additional time during the recognition process.