"People don't change," according to the hard won wisdom of many twice-burned people. If someone is dishonest, mean, or flaky once, chances are good that when you meet them again, they'll be exactly the same.

Up to now these pessimists have had science on their side. Multiple studies have found that while people certainly shift around the margins - learning new coping skills and tempering some of the volatility of youth - our core personalities appear remarkably stable. If you're introverted or agreeable one decade, previous research has shown that you'll probably be the same the next.

But now a massive new 62-year long study has thrown a big wrench into the works of our understanding of personality. The research followed more than 600 Scottish people, tracking their personalities across six decades. What did it find? You're pretty much a totally different person at 77 than you were at 14.

77 year old you will barely recognize 14 year old you.

The story starts in 1950, when researchers asked Scottish teachers to rate the personalities of 1,208 of their pupils, weighing in on their self confidence, moods, conscientiousness, and other traits. The data sat quietly in archives for decades until, in 2012, University of Edinburgh neuroscientist Matthew Harris and his team managed to track down more than 600 of the original participants in the 1950 study, then aged 77. The study subjects agreed to a fresh round of personality testing and the contemporary results were compared to the decades' old findings.

Did the results jive with earlier studies that covered a mere decade or two and which found that personality pretty much stays the same? Quite the opposite.

"To the researchers' surprise they found there wasn't a statistically significant correlation between the ratings the participants received when they were aged 14 and the ratings they gave themselves at age 77, or the ratings they received at age 77 from a friend or relative," reports the British Psychological Society Research Digest Blog.

Or to put things more bluntly, over six decades the study subjects had been utterly transformed. The personality of a 77 year old would be barely recognizable to her 14-year-old self.

The bottom line: you can change.

These results are obviously a puzzle for personality researchers. Were previous results simply over too short a time frame to record how much change can accumulate in our personalities? Or is there some flaw in the Scottish research that might undermine its conclusions? (BPS highlights a few contenders.) More research will almost certainly delve into these questions.

In the meantime, the findings are heartening news for those who have sometimes felt burdened by their personalities. As Cambridge psychologist Brian Little points out in the fascinating TED talk below, knowing your personality and believing it to be fixed can hold people back from pursuing their dreams. You might believe you're too introverted for leadership, for instance (a myth), or that you lack of the consciousness to stick with a difficult long-term project.

But Little insists, and this new research supports, that people's personalities can and do change based on circumstances and passion. Just think of a meek and agreeable mother becoming fierce when a hospital bureaucrat gets in the way of care for her sick child, or an introvert moved to protest and organize by some injustice in the world. You are probably capable of much more adaptation than you believe.

So while the jury is still out on the science, and whether to trust in others' change is an open, case-by-case question, you should at least be more optimistic about your own capacity for growth. Chances are excellent that you will be very surprised by who you become a few decades down the line. Use that potential for change to accomplish whatever is important to you in life.