Graduation Year

2010

Document Type

Thesis

Degree

M.A.

Degree Granting Department

Psychology

Major Professor

Emanuel Donchin, PhD

Keywords

Word frequency, Event-related potential, P300, Frontal slow wave, Recall memory

Abstract

Words that deviate in their physical characteristics from their surrounding lead to enhanced recall memory, a pattern known as the Von Restorff effect. Furthermore, common (high frequency; HF) words are more likely to be recalled than uncommon (low frequency; LF) words when they occur in pure lists, while this pattern is reversed in mixed lists of both HF and LF words. This study investigated whether the Von Restorff effect and the reversal of word frequency effects in mixed lists, which may both be explained by enhanced perceived distinctiveness, are associated with common underlying brain processes. Event-related potentials (ERPs) were recorded while participants studied and subsequently recalled 70 word lists using rote memorization strategies. The three list types included (1) 14 regular-sized and one larger word, (2) 14 HF words and one LF word, or (3) 14 LF words and one HF word.

The behavioral data showed a typical Von Restorff effect, a word frequency effect, as well as a reversal of the word frequency effect for LF words isolated in HF word lists ("LF isolates"). Larger words and LF isolates elicited a P300, an ERP component associated with subjective distinctiveness, whose amplitude was correlated with subsequent recall for both word types. This indicates that LF isolates were perceived as distinctive, and that this perceived distinctiveness aided subsequent recall in a similar way as for physically deviant words. Both larger words and LF isolates also elicited a left-lateralized slow wave which was larger for subsequently recalled than for not recalled words. This ERP component supposedly reflects item-to-item elaborative processes, indicating that such elaborative processes are enhanced when LF words occur in HF word list. HF words isolated in lists of LF words did not elicit comparable ERP subsequent memory effects.

Rather, for these "HF isolates", the N400 was negatively correlated with subsequent recall, an ERP component that reflects semantic integration processes. We conclude that the reversal of the word frequency effect in mixed lists can be explained by a combination of enhanced subjective distinctiveness and enhanced inter-item elaborative processes for LF words that occur in lists of HF words.

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