People sometimes solve problems with a unique process called insight, accompanied by an “Aha!” experience. It has long been unclear whether different cognitive and neural processes lead to insight versus noninsight solutions, or if solutions differ only in subsequent subjective feeling. Recent behavioral studies indicate distinct patterns of performance and suggest differential hemispheric involvement for insight and noninsight solutions. Subjects solved verbal problems, and after each correct solution indicated whether they solved with or without insight. We observed two objective neural correlates of insight. Functional magnetic resonance imaging (Experiment 1) revealed increased activity in the right hemisphere anterior superior temporal gyrus for insight relative to noninsight solutions. The same region was active during initial solving efforts. Scalp electroencephalogram recordings (Experiment 2) revealed a sudden burst of high-frequency (gamma-band) neural activity in the same area beginning 0.3 s prior to insight solutions. This right anterior temporal area is associated with making connections across distantly related information during comprehension. Although all problem solving relies on a largely shared cortical network, the sudden flash of insight occurs when solvers engage distinct neural and cognitive processes that allow them to see connections that previously eluded them.

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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Measurements of reaction time have played a major role in developing theories about the menial processes that underlie sensation, perception, memory, cognition, and action. The interpretation of reaction time data requires strong assumptions about how subjects trade accuracy for speed of performance and about whether there is a discrete or continuous transmission of information from one component process to the next. Conventional reaction time and speed-accuracy trade-off procedures are not, by themselves, sufficiently powerful to test these assumptions. However, the deficiency can be remedied in part through a new speed-accuracy decomposition technique. To apply the technique, one uses a hybrid mixture of (a) conventional reaction time trials in which subjects must process a given test stimulus with high accuracy and (b) peremptory response-signal trials in which subjects must make prompted guesses before stimulus processing has been finished. Data from this "titrated reaction time procedure" are then analyzed in terms of a parallel sophisticated-guessing model, under which normal mental processes and guessing processes are assumed to race against each other in producing overt responses. With the model, one may estimate the amount of partial information that subjects have accumulated about a test stimulus at each intermediate moment during a reaction time trial. Such estimates provide deeper insights into the rate at which partial information is accumulated over time and into discrete versus continuous modes of information processing. An application of speed-accuracy decomposition to studies of word recognition illustrates the potential power of the technique. People do not think or act instantaneously. The time required to take action depends systematically on mental and physical processes that precede an overt response. Thus, throughout many areas of psychology, conclusions about the nature of mind and body have been based on measurements of human reaction time.' Past uses of reaction time data extend from studies of elementary sensory mechanisms (e.g., Green & Luce, 1973) to studies of perception (e.g.

Dual-coding theory argues that processing advantages for concrete over abstract (verbal) stimuli result from the operation of 2 systems (i.e., imaginal and verbal) for concrete stimuli, rather than just 1 (for abstract stimuli). These verbal and imaginal systems have been linked with the left and right hemispheres of the brain, respectively. Context-availability theory argues that concreteness effects result from processing differences in a single system. The merits of these theories were investigated by examining the topographic distribution of event-related brain potentials in 2 experiments (lexical decision and concrete-abstract classification). The results were most consistent with dual-coding theory. In particular, different scalp distributions of an N400-like negativity were elicited by concrete and abstract words.