EVENT-RELATED POTENTIALS AND THE RECOLLECTION OF LOW AND HIGH-FREQUENCY WORDS

A recognition memory test was conducted in which low and high frequenc y words were initially presented in one of two different study tasks. A word was defined as recollected if, at test, it was both confidently judged 'old', and confidently assigned to its correct study context. Low frequency words were more accurately recognised than high frequenc y items, and were also more likely to be assigned to their correct stu dy context. The results are consistent with the view that low frequenc y words are better recognised because they are more likely to be recol lected, rather than because they engender higher levels of relative fa miliarity. Event-related potentials (ERPs) evoked al test by correctly classified new words were contrasted with those evoked by old, recoll ected words. The ERPs to low frequency words exhibited large and relia ble 'old/new' effects, in that from approx. 300 msec post-stimulus, wa veforms were more positive-going for old than for new items. These eff ects were markedly smaller, and indeed non-significant, in the ERPs ev oked by high frequency items. The results show that the interaction be tween word frequency and old/new differences in ERPs does not arise be cause of a confound between frequency and the probability of recollect ion. Together with other findings, they suggest that recollection is b etter conceived of as a graded, rather than as an all-or-none phenomen on.