The study, authored by psychology professor Joseph Forgas at the University of New South Wales, showed that people in a negative mood were more critical of, and paid more attention to, their surroundings than happier people, who were more likely to believe anything they were told.
"Whereas positive mood seems to promote creativity, flexibility, cooperation, and reliance on mental shortcuts, negative moods trigger more attentive, careful thinking paying greater attention to the external world," Forgas wrote.
"Our research suggests that sadness ... promotes information processing strategies best suited to dealing with more demanding situations."
For the study, Forgas and his team conducted several experiments that started with inducing happy or sad moods in their subjects through watching films and recalling positive or negative events.
In one of the experiments, happy and sad participants were asked to judge the truth of urban myths and rumors and found that people in a negative mood were less likely to believe these statements.
People in a bad mood were also less likely to make snap decisions based on racial or religious prejudices, and they were less likely to make mistakes when asked to recall an event that they witnessed.
The study also found that sad people were better at stating their case through written arguments, which Forgas said showed that a "mildly negative mood may actually promote a more concrete, accommodative and ultimately more successful communication style."
"Positive mood is not universally desirable: people in negative mood are less prone to judgmental errors, are more resistant to eyewitness distortions and are better at producing high-quality, effective persuasive messages," Forgas wrote.
The study was published in the November/December edition of the Australian Science journal.
