Insight occurs when a person suddenly reinterprets a stimulus, situation, or event to produce a nonobvious, nondominant interpretation. This can take the form of a solution to a problem (an "aha moment"), comprehension of a joke or metaphor, or recognition of an ambiguous percept. Insight research began a century ago, but neuroimaging and electrophysiological techniques have been applied to its study only during the past decade. Recent work has revealed insight-related coarse semantic coding in the right hemisphere and internally focused attention preceding and during problem solving. Individual differences in the tendency to solve problems insightfully rather than in a deliberate, analytic fashion are associated with different patterns of resting-state brain activity. Recent studies have begun to apply direct brain stimulation to facilitate insight. In sum, the cognitive neuroscience of insight is an exciting new area of research with connections to fundamental neurocognitive processes.

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There are now numerous observations of subtle right hemisphere (RH) contributions to language comprehension. It has been suggested that these contributions reflect coarse semantic coding in the RH. That is, the RH weakly activates large semantic fields-including concepts distantly related to the input word-whereas the left hemisphere (LH) strongly activates small semantic fields-limited to concepts closely related to the input (Beeman, 1993a,b). This makes the RH less effective at interpreting single words, but more sensitive to semantic overlap of multiple words. To test this theory, subjects read target words preceded by either "Summation" primes (three words each weakly related to the target) or Unrelated primes (three unrelated words), and target exposure duration was manipulated so that subjects correctly named about half the target words in each hemifield. In Experiment 1, subjects benefited more from Summation primes when naming target words presented to the left visual field-RH (Ivf-RH) than when naming target words presented to the right visual field-LH (rvf-LH), suggesting a RH advantage in coarse semantic coding. In Experiment 2, with a low proportion of related prime-target trials, subjects benefited more from "Direct" primes (one strong associate flanked by two unrelated words) than from Summation primes for rvf-LH target words, indicating that the LH activates closely related information much more strongly than distantly related information. Subjects benefited equally from both prime types for Ivf-RH target words, indicating that the RH activates closely related information only slightly more strongly, at best, than distantly related information. This suggests that the RH processes words with relatively coarser coding than the LH, a conclusion consistent with a recent suggestion that the RH coarsely codes visual input (Kosslyn, Chabris, Mar-solek, & Koenig, 1992).

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How accurate are insights compared to analytical solutions? In four experiments, we investigated how participants’ solving strategies influenced their solution accuracies across different types of problems, including one that was linguistic, one that was visual and two that were mixed visual-linguistic. In each experiment, participants’ self-judged insight solutions were, on average, more accurate than their analytic ones. We hypothesised that insight solutions have superior accuracy because they emerge into consciousness in an all-or-nothing fashion when the unconscious solving process is complete, whereas analytic solutions can be guesses based on conscious, prematurely terminated, processing. This hypothesis is supported by the finding that participants’ analytic solutions included relatively more incorrect responses (i.e., errors of commission) than timeouts (i.e., errors of omission) compared to their insight responses.

Two experiments examined hemispheric differences in information processing that may contribute to solving insight problems. We propose that right-hemisphere (RH) coarse semantic coding is more likely than left-hemisphere (LH) fine semantic coding to activate distantly related information or unusual interpretations of words, and thus more likely to activate solution-relevant information for insight problems. In Experiment 1, after trying to solve insight problems, participants read aloud solution or unrelated target words presented to the left visual field (lvf) or right visual field (rvf). Participants showed greater lvf-RH than rvf-LH priming for solutions for solved problems and priming only in the lvf-RH for unsolved problems. In Experiment 2, participants showed an lvf-RH advantage for recognizing solutions to unsolved problems. These results demonstrate that in a problem-solving context, there was greater activation of solution-relevant information in the RH than in the LH. This activation is useful for recognizing, and perhaps producing, solutions to insight problems.

Creative ideas seem often to appear when we close our eyes, stare at a blank wall, or gaze out of a window-all signs of shutting out distractions and turning attention inward. Prior research has demonstrated that attention-related brain areas are differently active when people solve problems with sudden insight (the Aha! phenomenon), relative to deliberate, analytic solving. We directly investigated the relationship between attention deployment and problem solving by recording eye movements and blinks, which are overt indicators of attention, as people solved short, visually presented problems. In the preparation period, before problems eventually solved by insight, participants blinked more frequently and longer, and made fewer fixations, than before problems eventually solved by analysis. Immediately prior to solutions, participants blinked longer and looked away from the problem more often when solving by insight than when solving analytically. These phenomena extend prior research with a direct demonstration of dynamic differences in attention as people solve problems with sudden insight versus analytically.

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. HHS Public Access Author Manuscript Author ManuscriptAuthor Manuscript 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...