P 37. Hemispheric asymmetries in language processing: Evidence from false memories for lists, texts, and ambiguous words

Abstract

Previous research suggests that, whereas the left cerebral hemisphere (LH) is dominant for language processing, the right hemisphere (RH) may play a unique role in the comprehension of natural language, i.e. in processing language in contexts that extend beyond the meanings of individual words or sentences such as stories, conversations, or texts, and thus may contribute uniquely to the processing of lexical ambiguity by activating and maintaining a wide range of meanings, including subordinate. A series of studies used the word-lists false memory paradigm (Roediger and McDermott, 1995) to examine the difference between the two cerebral hemispheres in language processing. Specifically, we tested the susceptibility of the LH and RH to unpresented target words following the presentation of semantically related words appearing in either word lists or short texts (Study 1) and whether these differences between the two cerebral hemispheres in semantic processing also affect memory representations for different meanings of ambiguous words (Study 2). Specifically, we tested the differences between the LH and RH in recollecting unpresented, semantically related, ambiguous words following the presentation of lists of words all related to either the dominant or the subordinate meanings of these ambiguous words. Findings of Study 1 showed that the RH produced more false alarms than the LH for unpresented target words following either word lists or texts. These findings reveal hemispheric differences in memory for semantically related information and suggest that RH advantage in long-term maintenance of a wide range of text-related word meanings may be one aspect of its unique contribution to the construction of a discourse model. Findings of Study 2 indicated that for the unpresented ambiguous words, the LH made more false alarms than the RH for the dominant lists, whereas the opposite pattern emerged for subordinate lists. These results support the RH coarse semantic coding theory (Beeman, 1998) indicating that during word recognition, the RH activates and maintains a broader and less differentiated range of related meanings than the LH, including both dominant and subordinate meanings of ambiguous words. Furthermore, the findings suggest that hemispheric differences in ambiguity resolution during language processing extend also to verbal memory.