From a passing thought to a false memory in 2 minutes: Confusing real and illusory events.

The frequency with which subjects erroneously included a nonpresented word in their recall of a study list was explored in two experiments. The intrusion error was recalled by as many as 80% of the subjects, and when it was perceived to have been presented early in the study list, it was assigned confidence ratings and phenomenological retrieval characteristics equivalent to those for presented words. As a result, subjects were often unable to discriminate memories of real study words from their memories of a related but nonpresented word. Manipulations of encoding, but not of retrieval, conditions altered both the frequencies of illusory memories and their metamemorial characteristics. The results and paradigm are discussed in terms of their relevance to the "memory-recovery" debate.