Norman, a psychologist, is conducting a study about why memory decreases with age and how the skills of problem solving and decision making change as a person grows older. in this scenario, norman's study fits best into the area of specialization known as psychology.

In this scenario, norman's study fits best into the area of specialization known as: cognitive psychology 

Cognitive psychology is a branch of psychology that study the relation between attention, memory,  logical thinking, , perception, the usage of language, problem solving, and creativity to the decision making process. 

So, Norman's effort to find out the relation between memory and decision-making process could be considered as this branch of psychology