Most adults are owls--people who find it hard to get up in the morning; are most productive late in the afternoon and evening; and enjoy the wee hours for late night activities (they are also more prone to nightmares). "Most", you ask? About 93% of adults are owls, starting in adolescence.

Researchers at the University of Toronto wanted to know if this proportion remained true, no matter how old people were. Testing showed that after age 60 there is a definite shift. Only 7% of older people remained owls; the rest gradually adopt the early morning pattern, becoming larks.

Further, the researchers found that early risers--larks--are more optimistic, happier people, more satisfied with life overall. Other studies have reported that, in general, as people age, their outlook on life improves, even when coping with physical decline.

As the preference for rising early increases, and earlier in the day is more productive, older people become happier and more optimistic. It's also likely that morning people are getting enough sleep, which could account for their self-reporting of feeling more alert and healthier (enough sleep being important for a strong immune system).

Those of us who are larks by nature could have told them that.