In the RAT, individuals must think of a word that connects three, seemingly unrelated, words. RAT are often used in experiments, because they can be solved both with and without insight. Two clusters of problems, those solvable by insight and those not requiring insight to solve, have been observed. An individual’s cognitive flexibility, fluency, and vocabulary ability are predictive of performance on insight problems, but not on non-insight problems. In contrast, fluid intelligence is mildly predictive of performance on non-insight problems, but not on insight problems. More recent research suggests that rather than insight versus search, that the subjective feeling of insight varies, with some solutions experienced with a stronger feeling of Aha than others. People in a better mood are more likely to solve problems using insight. Research demonstrated that self-reported positive affect of participants uniquely increased insight before and during the solving of a problem, as indicated by differing brain activity patterns. People experiencing anxiety showed the opposite effect, and solved fewer problems by insight. Emotion can also be considered in terms of the insight experience and whether this is a positive Aha or negative Uh-oh moment. Using a geometric and spatial insight problem, it was found that providing participants with breaks improved their performance as compared to participants who did not receive a break. However, the length of incubation between problems did not matter. Thus, participants' performance on insight problems improved just as much with a short break (4 minutes) as it did with a long break (12 minutes).h  Research has shown sleep to help produce insight. Individuals were initially trained on insight problems. Following training, one group was tested on the insight problems after sleeping for eight hours at night, one group was tested after staying awake all night, and one group was tested after staying awake all day. Those that slept performed twice as well on the insight problems than those who stayed awake. Differences in brain activation in the left and right hemisphere seem to be indicative of insight versus non-insight solutions. Using RAT’s that were either presented to the left or right visual field, it was shown that participants having solved the problem with insight were more likely to have been shown the RAT on the left visual field, indicating right hemisphere processing. This provides evidence that the right hemisphere plays a unique role in insight.  fMRI and EEG scans of participants completing RAT's demonstrated unique brain activity corresponding to problems solved by insight. For one, there is high EEG activity in the alpha- and gamma-band about 300 milliseconds before participants indicated a solution to insight problems, but not to non-insight problems.