You are going to a concert with your friend, who brings along john and Adam two people whom you have never met before, you just know one is a musician and the other is a professor. upon meeting them you notice that john wears glasses and is a bit more shy, whilst Adam is confident and wears ripped jeans. without asking, you assume Adam is the musician and John is the professor. later you find out that you were wrong. which common type of heuristic is this an example of?