Feeling grumpy? Don't worry, according to a research, it's good for you.
According to psychologist Joe Forgas at the University of New South Wales in Sydney, Australia, happiness's negative effects stem from a cheery mood's tendency to lull you into feeling secure, thus making you look inwards and behave both more selfishly and more carelessly.
"People in a positive mood generally rely more on their own thoughts and preferences, and pay less attention to the outside world and social norms," says Forgas.
In order to find the effect of happiness on selfishness, Forgas and his colleague Hui Bing Tan put 45 students into good or bad moods by giving them positive or negative feedback on a "cognitive test" that they had taken, reports New Scientist.
The test was a fake and did not measure cognition, while the feedback bore no relation to their performance.
After using a questionnaire to establish that the volunteers really were happy or sad, Forgas and Tan gave each one 10 raffle tickets for a 20-Australian dollar prize. The students could choose between sharing some of their tickets with another, hypothetical student or selfishly keeping them all. On average, those who had been praised kept more raffle tickets.
In another test, Forgas and Tan used film clips to set the mood. Half of a group of 72 students were treated to a 10-minute clip of the British TV comedy Fawlty Towers, whilst the other half endured a passage from the gloomy film Angela's Ashes.
After taking another mood questionnaire, this time the students were shown pictures of a buddy they could share their raffle tickets with - with the intention of making the idea of sharing more vivid than the case of a hypothetical student. Again, the happy students were less likely to share.
Forgas's explanation is that happy people focus more on their own desires. "Positive mood is in a sense an evolutionary signal, subconsciously informing people that the situation they face is safe and non-threatening," he says.
This encourages people to rely more on their own thoughts and preferences, with selfishness the result, the expert added.
On the other hand, grumpiness or sadness produces more vigilant, outward-looking thinkers.
"A negative mood produces a thinking style that is more detailed and attentive, and pays more attention to the demands of the external environment," says Forgas.
The study has been published in the Journal of Experimental Social Psychology.