Extended Metaphor and Right Hemisphere Flexibility: What's the right (hemisphere) way to think about metaphor?

Metaphor is ubiquitous in natural human language, and metaphor comprehension is\ud consequently integral to communication. Previous literature (Arzouan et al., 2007; Mashal &\ud Faust, 2009) has suggested that the right hemisphere (RH) and left hemisphere (LH) of the brain\ud perform different functions in metaphor processing, and this lateralization of function may be\ud attributable to the dominance of the RH in coarse semantic coding and the dominance of the LH\ud in finer semantic computation (Jung-Beeman, 2005). The goal of the present study is to test the\ud generality of the findings of Chettih et al. (2012) by exploring the flexibility and contextsensitivity\ud of the RH in comparison to the LH during novel metaphor processing. It was\ud hypothesized that the RH would demonstrate a processing advantage for metaphor vehicle\ud meaning, absent in the LH, when a matched metaphoric mapping, as opposed to an alternative\ud metaphoric mapping or literal description, preceded the presentation of the metaphor vehicle.\ud Participants made "yes" /"no" comprehensibility judgments of target sentences, in which the\ud metaphor vehicle was presented in sentence-terminal position. A divided visual hemifield\ud paradigm was used to separate processing of the metaphor vehicle by hemisphere (left visual\ud field (LVF)/ RH and right visual field (RVF)/ LH). Ratings of Comprehensibility,\ud Conventionality, Surprisingness, and Metaphoricity were collected from other participants for\ud metaphor vehicles in the experimental stimuli. Principal Components Analysis (PCA) of these\ud ratings revealed that Conventionality and Metaphoricity mapped onto the first and second\ud principal components, respectively, accounting for the majority of the variance in the data. In the\ud main experiment, it was found that the previous relationship between Conventionality and\ud response latency was wiped out by a supportive context in the RH, but not the LH, which\ud supports the hypothesis that the RH is more flexibly sensitive to context. Furthermore, if an\ud associated semantic space is modified, the integration of a specific word (metaphor vehicle) is\ud unaffected when that space is irrelevant, but completely altered when the aligned space is\ud relevant. These findings convey the broader ideas that a) words take on different meanings in\ud context versus in isolation, and b) that left-right hemisphere brain processes play different roles\ud in semantic comprehension. Future directions include testing for RH flexibility in the processing\ud of ambiguous items or other forms of abstract language