The Cognitive Bias Task (CBT) is a multiple-choice response selection
paradigm characterized by inherent ambiguity. All items offer a range from
extremely context-dependent to extremely context-invariant responses.
Lateralized prefrontal lesions produce extreme, and opposite, response
biases on CBT in right-handed males. Healthy control subjects perform in
the middle range. Findings suggest a dynamic balance between two
synergistic decision-making systems in the frontal lobes: context-dependent
in the left hemisphere and context-invariant in the right. The robust
lateralized effects, which are dependent on task ambiguity, are sensitive
and specific to frontal dysfunction. CBT is discussed in comparison with
the Wisconsin Card Sorting Test as a potential cognitive activation task
for functional neuroimaging of the frontal lobes.