There are thus multiple routes to successful comprehension, and studies combining ERP measures with visual half-field presentation methods, used to bias processing toward the contralateral hemisphere, have made clear that it would be an error to conceive of comprehension as unfolding along a single processing stream, even within a given individual of a particular age (for reviews, see Federmeier 2007; Federmeier et al 2008). Such data reveal both important contributions to meaning comprehension from RH processing as well as important hemispheric differences, including the extent to which processing in each hemisphere is sensitive to prediction-based influences. Federmeier (2007) has hypothesized that an important source for such asymmetries may be more efficacious top-down connections in the LH, supported by LH-dominant language production mechanisms. Regardless of the precise nature and source of the differences, however, ERP data make clear than any complete theory of language processing will have to acknowledge the separate contributions of these two processing streams and explain how they are integrated to serve comprehension goals.
