• This experiment demonstrated abstract reasoning deficits in depressed patients and detailed some of the components of cognition that may determine such deficits. Subjects were given a discrimination learning problem in which possible solutions had to be formulated and tested against new information. Depressed subjects performed more poorly on the task than controls. Two types of errors—inability to narrow down the set of possible solutions (poor "focusing") and perseveration on disconfirmed hypotheses—hampered the performance of depressed but not control subjects. While logic, memory, and attention were intact at an elementary level, the inability to coordinate these functions in a complex task appeared to be an important feature of the depressive impairment.
Silberman EK, Weingartner H, Post RM. Thinking Disorder in DepressionLogic and Strategy in an Abstract Reasoning Task. Arch Gen Psychiatry. 1983;40(7):775-780. doi:10.1001/archpsyc.1983.01790060073009