Abstract

It has been hypothesized that patients with closed head injury (CHI) are limited by a generalized slowing of stimulus processing as well as by slowing in the motor execution of the response. Sternberg's (1969) Additive Factor Method features four stages of processing and allows testing the selectivity of a deficit by partialling out the decoding component of response (reaction times, RT) from the motor component (movement times, MT). The results, based on a sample of 22 patients with severe CHI with good motor recovery and 22 matched controls, showed a clear deficit of the TMs in the CHI group but no generalized slowing of RTs. Out of the four processing stages examined, signal detection and motor adjustment showed a selective impairment in patients with TBI, a finding inconsistent with previous results. It is proposed that the size of the effect probing each stage may play a role in producing this outcome.