The effect of attention allocation on smooth pursuit
eye movements (SPEM) was investigated. Eye movements were
electrooculographically recorded in 27 healthy subjects
who tracked a visual target that moved horizontally with
constant or unpredictably varying velocity. In some trials,
subjects performed additional auditory discrimination tasks
varying in difficulty. Pursuit error decreased when attention
was divided between both tasks. The pattern of results
is incompatible with the assumption made in previous research
that attention enhancement improves SPEM accuracy. Rather,
ocular smooth pursuit appears to be executed in the automatic
mode, although intentional and selective processes must
contribute. Moreover, controlled attention directed to
the tracking task interfered with smooth pursuit. A reinterpretation
of earlier studies in which visual monitoring tasks were
used to improve eye tracking is needed.