For a lot of people they, outside psychology they think of personality and psychology as almost being synonymous, understanding individual differences.
But as we look into things more deeply we realise that the way that people behave differently from each other is more often to do with the circumstances they’re in. For instance, a type of job they’re doing.
If they’re put in the job that requires them to be extrovert or agreeable then most of would behave in that way. We all change our behaviour between different situations. It would be very bizarre if we didn’t.
So, in that situation, personality has only got a portion of explanatory power in deciding how people are going to behave in any given situation.