Silberman E K, Weingartner H, Post R M
Arch Gen Psychiatry. 1983 Jul;40(7):775-80. doi: 10.1001/archpsyc.1983.01790060073009.
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.
