Submitted for presentation at 2005 meeting of the Society for Neuroscience

The Trail Making Test (TMT) requires participants to draw a line through randomly-located items on a sheet of paper. A comparison between the two conditions of the test provides a measure of efficiency of executive function. Although TMT is easily administered and scored and widely used in both research and clinical settings there are several deficiencies in the design that limit conclusions as to which frontal lobe functions are actually implicated in deficient TMT performance. Component processes of executive function, specifically task switching, were evaluated with a computer-based variant of the Trial Making Test (TMT).

Both younger and older participants used natural, pointing responses to order series of numbers, letters, or intermixed letters and numbers. This interactive test assesses baseline speed for detecting and responding to individual items, captures the time for each response, and segregates erroneous responses from correct ones. The interresponse times with intermixed letters and numbers showed that participants did not always switch between the two different ordering-tasks, but instead often recall letter-number pairs as single units. An additive factors analysis decomposed test times into functional components, including executive function, which took longer in older participants. With modest practice, both young and older participants sped up their ordering of intermixed numbers and letters, probably reflecting increased automaticity and reduced dependence upon executive function.