Study leader Margie Lachman, a Brandeis University psychologist, said that the main purpose of the study was to determine whether there were differences in actual and perceived ratings of how satisfied Americans were with their lives over a nine-year period.
She revealed that the research team tested the idea by conducting two surveys, the first in 1995-1996, and the second nine years later, between 2004 and 2006.
In the first survey, people aged 24 to 74 completed a telephone interview and questionnaire. They were asked to rate how satisfied they were with their lives at the time, how satisfied they were with their lives 10 years earlier, and how satisfied they expected to be 10 years later.
In 2004, the participants were asked the same questions again.
With both sets of questionnaires in hand, Lachman and her colleagues were able to compare how subjects felt during the second survey with how they had predicted they would feel at that time.
The researchers found that there were age-related differences in how we view the past and the future.
They observed that Americans aged 65 and older viewed the past and the present as being equally satisfying, but believed that the future would be less satisfying than the present.
The subjects who were younger than 65 viewed the present as more satisfying than the past, and were more optimistic about the future than their older counterparts, believing that they would be more satisfied with life in ten years.
Younger and middle-aged adults showed great illusion. Both groups believed life would be better than it turned out to be.
Older adults, on the other hand, were more realistic, and gave accurate predictions about how satisfied they would be. They were consistent in how they viewed the past compared with how they actually answered at that time.
'The older adults appeared wiser with greater self-knowledge and a more astute sense of their past and future feelings; they may strive for acceptance of present circumstances as a way of regulating emotions,' said Lachman.
The researchers concluded: 'Being realistic about the past and future (across all age groups) was associated with the most adaptive functioning across a broad array of variables including good health, a well-adjusted personality, supportive social relationships, high well-being and perceived control, and the absence of depression.'
According to them, people who were doing well were less likely to imagine that things are going to get even better.
Lachman and her colleagues believe that their research has interesting implications for goal-setting and motivational behavior.
They say that their findings indicate that younger adults' optimism about the future motivates them to try to achieve high levels of satisfaction.
The study shows that older adults are not as sanguine about the future as younger adults, perhaps because they have become aware or have experienced the height of life satisfaction and may realize this is as good as it gets.
The authors suggest that older adults may be satisfied as long as they can maintain the status quo while they prepare themselves for future losses.
'These more negative expectations from older adults may be their way of bracing for an uncertain future, a perspective that can serve a protective function in the face of losses and that can have positive consequences if life circumstances turn out to be better than expected,' says Lachman.