When our actions are followed by predictable consequences, we anticipatorily move our eyes towards the location at which the expected effects of our actions will appear in the future. Such anticipatory saccades demonstrate a proactive effect monitoring process that supports a subsequent comparison of the actual and the expected effect. Importantly, the timing of such anticipatory saccades correlates with the timing of effect-generating (e.g., manual) actions. We hypothesized that this is the case, because the processes of action selection and proactive effect monitoring rely on the same cognitive resource. Thus, here we manipulated action complexity (1 choice vs. 2 choice left/right manual actions vs. corresponding steering wheel turns) while keeping target-effect intervals constant and varying the time of the manual response (immediate vs. delayed: wait for go signal).
Anticipatory saccade latencies, like manual reaction times, were longer in the delayed condition and increased with action complexity. Furthermore, anticipatory saccades preceded delayed manual responses for all action complexity levels. Moreover, the frequency of anticipatory saccades decreased with increasing action complexity. The observed pattern of results supports the idea that action selection and proactive effect monitoring rely on the same cognitive resource.