Happy mood improves problem solving (and intellectual flexibility).

Researchers were interested in the influence of positive affect (good mood) on clinical reasoning in physicians. One group was primed positively and the other neutral. Physicians then thought aloud as they solved a liver disease case. Two expert listeners rated the physician’s thinking and reasoning to determine how quickly they got to the liver disease insight and how much they anchored to incorrect ideas. The positive affect group considered the correct diagnosis significantly earlier (50% of the time) and showed far less anchoring (so more clarity of thought) with 3X more intellectual flexibility.

REFERENCES

Estrada, C. A., Isen, A. M., & Young, M. J. (1997). Positive affect facilitates integration of information and decreases anchoring in reasoning among physicians. Organizational Behavior and Human Decision Processes, 72(1), 117–135. https://doi.org/10.1006/obhd.1997.2734