Hemispheric differences in processing the literal interpretations of idioms

The present study examined the role of the left (LH) andright (RH) cerebral hemispheres in processing alternative meanings of idiomaticsentences. We conducted two experiments using ambiguous idioms with plausibleliteral interpretations as stimuli. In thefirst experiment we tested hemispheric differences in accessing either theliteral or the idiomatic meaning of idioms for targets presented to either theleft or the right visual field. In the second experiment, we used functional magnetic resonance imaging (fMRI) to define regionalbrain activation patterns in healthy adults processing either the idiomaticmeaning of idioms or the literal meanings of either idioms or literalsentences. According to the Graded Salience Hypothesis (GSH, Giora, 2003), aselective RH involvement in the processing of nonsalient meanings, such asliteral interpretations of idiomatic expressions, was expected. Results of the two experiments were consistent with the GSH predictions and showthat literal interpretations of idioms are accessed faster than their idiomaticmeanings in the RH. The fMRI data showed that processing the idiomaticinterpretation of idioms and the literal interpretations of literal sentencesinvolved LH regions whereas processing the literal interpretation of idioms wasassociated with increased activity in right brain regions including the rightprecuneus, right middle frontal gyrus (MFG), right posterior middle temporalgyrus (MTG), and right anterior superior temporal gyrus (STG). We suggest thatthese RH areas are involved in semantic ambiguity resolution and in processing nonsalient meanings of conventionalidiomatic expressions.