In three experiments, healthy young participants listened to stories promoting inferences and named inference-related test words presented to the right visual field-Left Hemisphere (rvf-LH) or to the left visual field-Right Hemisphere (lvf-RH). Participants showed priming for predictive inferences only for target words presented to the lvf-RH; in contrast, they showed priming for coherence inferences only for target words presented to the rvf-LH. These results, plus the fact that patients with RH brain damage have difficulty drawing coherence inferences and do not show inference-related priming, suggest that information capable of supporting predictive inferences is more likely to be initially activated in the RH than the LH, but following coherence breaks these concepts (now coherence inferences) are completed in the LH. These results are consistent with the theory that the RH engages in relatively coarse semantic coding, which aids full comprehension of discourse.When people comprehend stories, they often make inferences -they assume that some events occurred in the stories, even though those events were not explicitly described. Consider what happens when people read or hear the premise that "The shuttle sat on the ground in the distance, waiting for the signal to be given." If they later read or hear a sentence with a coherence break, that is a sentence that interrupts the logical chain of a story, such as "After a huge roar and a bright flash, the shuttle disappeared into space leaving clouds of smoke in its wake," most people infer that the shuttle was launched. As established decades ago, once comprehenders make inferences, they include these inferences when recalling stories (Glenn, 1978;Paris & Lindauer, 1976;Baggett, 1975), and they have a difficult time distinguishing inferred information from information explicitly stated (Johnson, Bransford, & Solomon, 1973). This suggests that normal comprehenders incorporate some inferences into their representation of the discourse.
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Author ManuscriptSome RH-damaged (RHD) patients have difficulty drawing inferences, suggesting that the right hemisphere (RH) may play an important role when comprehenders draw such inferences (Beeman, 1993;Brownell, Potter, Bihrle, & Gardner, 1986). The following experiments explore the idea that concepts necessary for supporting inferences are more likely to be initially activated in the RH than in the LH and that at the coherence break inferences are more likely to be selected-activated strongly enough to reach awareness, to be processed further, or to be output, in the sense proposed by Allport (1987) -in the LH for incorporation into the discourse representation (Beeman, 1993).
PREDICTIVE AND COHERENCE INFERENCESIn principle, comprehenders could draw several types of inferences. Comprehenders could make inferences to embellish or elaborate on a story. They could draw inferences to predict upcoming consequences. For example, as soon as people hear tha...