The definition of 'happiness' changes with age as for the younger lot, it is 'excitement' that counts, whereas for the older generation, it is 'contentment', a new study has revealed.
According to the scientists, for young people, 60 per cent of happiness is about excitement.
On the other hand, as a person gets older, he associates 80 per cent of happiness with 'contentment'.
Professor Cassie Mogilner, of the University of Pennsylvania, who carried out the research, conducted five studies involving different groups of people - teens, people in their 20s, and others in their 30s, 40s and 50s.
"We are talking about two distinct types of happiness - one associated with peacefulness and one associated with being excited," the Daily Mail quoted Mogilner as saying.
"Whereas younger people are more likely to associate happiness with excitement, as they get older, they become more likely to associate happiness with peacefulness."
The difference apparently comes from the varying degrees of importance placed on the future compared to the present.
Younger people, usually more interested in the future, base their happiness more on excitement. Meanwhile, older people place a higher value on the present.
Prof Mogliner and her team used a complicated computer program to evaluate millions of blogs written by people of each age group.
The software analysed words allied to happiness and other emotions.
The researchers also conducted a survey to gauge participants' definitions of happiness.
In another test, participants listened to a calm or energetic song and then revealed how they felt.
In the fourth part of the study, participants were asked to read a passage focusing on the present or a different passage used as a control tape.
Subsequently, they were given a writing exercise. Younger people were more likely to write about the present if they had heard that tape, but there was no effect in older participants.
Finally, participants were asked what they would spend a gift of money on.
All through the different research tests, the results indicated a fairly consistent shift in types of happiness.
The study has been published in the journal Social Psychological and Personality Science.