Can Personality Change?

Question: "I took an assessment approximately 10 years ago. If I took it again today, would my new personality profile be similar to my first profile, or would it show significant changes"?

That really depends on the reliability of an assessment. Fortunately, the Trego assessments have very high reliability.

For more than 25 years, I have been accumulating test/retest data for the purpose of answering this question. I now have test/retest data for 129 individuals. The time between test and retest averaged 48 months. Using the Trego TPS the results of this analysis had the personality scores yielding a similarity of almost 90%.

Additional results:

a. The percent test/retest similarity for the Learning/Reasoning Ability scale is 92%.

b. The Endorsement scores changed for four individuals. Two individuals changed from average to below average and two individuals changed from below average to average.


According to William James (1890-1981), regarded by many as one of the fathers of psychology, "In most of us, by the age 30, the character has been set like plaster and will never soften again". The result of this project clearly supports William James. For most of us, our personality is remarkably stable over time and further research indicates it is set by the age of 20.

In the final analysis, although people do grow and change, the results of this project clearly show that they do so on a foundation of enduring basic personality tendencies. Basically, when it comes to your personality - you’re stuck with it.