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When something "new" and "interesting" enters our visual field it can usually happen that our eyes move toward the new target. How "intentional" and "controllable" are these movements? What degree of control do we have over this event? Since the movement is amazingly quick (maybe 0.3 seconds), it seems unlikely that a complex decision has been made, so can it be considered involuntary or beyond our control?

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Short answer
We have a lot of control over our eye movements, including saccades. We can suppress saccades and make an anti-saccade instead. So can monkeys, our close cousins. Children have a lot more difficulty with the anti-saccade task, however.

Background
Saccades are fast eye movements, as opposed to the slower smooth-pursuit responses of the eye (Purves, 2001). Saccades are generally initiated when a visual target appears suddenly in our field of view. They can be made either voluntarily, or involuntarily. Once initiated, a saccade cannot be interrupted (source: Brown University). However, a saccade can be suppressed before it is executed. This can be investigated with the anti-saccade task (Munoz & Everling, 2004). In this task, the subject is instructed to look away from a suddenly appearing target and make an eye movement to the opposite side. This is difficult. However, humans can do it, and even monkeys can be trained on the task, although kids are reported to have a lot of difficulty with it. Anti-saccades have a longer delay than saccades, and have a larger margin of error in terms of the accuracy of putting the 'anti-target' on the fovea of the retina. Many of the anti-saccades are preceded by an (unintentionally initiated) pro-saccade, where the subject focuses on the target first, before making the intended eye movement to the opposite side.

References
- Munoz & Everling, Nature Rev Neurosci (2004); 5: 218–28
- Purves et al. (eds). Neuroscience 2nd ed. Sunderland (MA): Sinauer Associates (2001). Types of Eye Movements and Their Functions

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    $\begingroup$ Respiration is probably a similar example people are familiar with. You can exert a lot of control over your breathing when you want to, but it takes some conscious effort, and ordinarily your breathing rate and depth does all sorts of things entirely on its own without any conscious input. Arguably most motor functions work that way. $\endgroup$ Sep 21 '20 at 22:43
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    $\begingroup$ As far as I understand in this experiment people needed to be told in advance that they would be going to have a certain stimulus, in order to control their reaction, right? $\endgroup$ Sep 23 '20 at 7:09
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    $\begingroup$ @MarcoDisce - yes - they received specific instructions $\endgroup$
    – AliceD
    Sep 23 '20 at 7:12

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