Looking back on when you were 14, you may be pleased to know that as the years roll on you become less and less like your former self.

You do not just change when you grow out of a teenage punk phase, finish school and grow a few inches taller — your personality also transforms.

In fact, personalities change so much over the course of a person's lifetime that by the time we reach 77, our personalities no longer resemble who we were at 14.

This was the finding from the longest-running personality study out of Scotland, published in Psychology and Aging.

How'd they find out?

The 63-year-long study began in 1950 and involved 1,208 14-year-old students.

Each were rated by their teachers on a five-point scale assessing six personality characteristics: self-confidence, perseverance, stability of moods, conscientiousness, originality and desire to excel.

Decades later, in 2012, researchers tracked down as many of the original participants as they could.

In the end, only 131 agreed to take part in both a detailed questionnaire and telephone interview, during which they completed a number of cognitive tests based on materials sent via post in advance.

At around 77 years of age, those participants who completed the questionnaire rated themselves on the same six traits using the same rating scale, in relation to other people of roughly their current age.

Participants were also requested to ask another person who knew them well — a spouse, friend or family member — to rate them in the same way.

Did this come as a surprise?

Previous studies have been able to demonstrate a moderate amount of stability in a person's personality from childhood to middle age and from middle age to older age, so researchers were expecting that stability to continue over an even longer period.

But that was not the case.

"The longer the interval between two assessments of personality, the weaker the relationship between the two tends to be," Matthew Harris and his colleagues at the University of Edinburgh wrote.

"Our results suggest that when the interval is increased to as much as 63 years, there is hardly any relationship at all."

Personality theory and testing has changed considerably over the years, and the researchers conceded that the teachers' original assessments could have attracted an inherent bias.

However, despite the limitations, the researchers hope the study will open the door for further investigation into understanding how and why our personalities change over the course of our lives.