²⁰The sensitivity levels, or thresholds, can also be modified by experience to some extent. For example, if as a child, you saw something that made you really scared, you may lower the threshold a lot—commonly known as a phobia. This leads to another problem, widely recognized in clinical psychology: the payoffs change during an individual’s lifetime as well. In adults, they may be very different from what they were in our childhood environment, while any learning of the payoffs may mainly happen as a child. The best survival strategy for a child in an adverse environment may be to be constantly afraid of other people; this may not be optimal anymore when the child grows up, and is in fact a possible source of psychiatric problems.