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Has anyone succeeded in measuring where the focus is between saccades? Through some kind of nonintrusive brainscan perhaps? I would like to be able to draw with my thought :) (Something similar would be okay, like the position or shape I am thinking of overlayed on what I see)

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  • $\begingroup$ The definition of saccades implies that there is no focus between movements. Are you asking if it is possible to track eye movements during a saccade? $\endgroup$ – Seanny123 Mar 16 '16 at 21:16
  • $\begingroup$ No, I mean the spot it feels like I am looking at. To me it feels like I move my focus as a smooth curve. I think this could be measured with some kind of brainscan and clever machine learning (the human could draw the ground truth of how it felt it moved its eyes). I do not know if there is a term for this. Percieved focus perhaps? $\endgroup$ – Emil Mar 17 '16 at 6:46
  • $\begingroup$ as @Seanny123 indicates, this question does not make sense. While you may "feel" that you move your "focus" as a smooth curve, this does not reflect the reality of (most) eye movements which are not smooth but jerky saccades. If by "focus" you mean the point at which people are looking and taking in information then this point changes too rapidly during saccades and information processing is suppressed. If you mean the fixations in between saccades (where the eye is mostly still), then yes we can measure them. $\endgroup$ – splint Mar 17 '16 at 13:37
  • $\begingroup$ If you mean "covert" attention, then there are some studies showing brain correlates of this, although the resolution is likely to be very poor. $\endgroup$ – splint Mar 17 '16 at 13:38
  • $\begingroup$ The description on wikipedia of covert attention seems similar to what I mean. Did they measure the brain in realtime using nonintrusive methods? If it can be done at home it would be a pretty awesome toy. $\endgroup$ – Emil Mar 17 '16 at 23:02
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Short answer
The retinal image cannot be refocused on an intermediate target during a saccade.

Background
Psychophysical experiments have shown that during a saccade, attention is aimed at the target location. Instructing the subject to make a saccade from location A to C, while focusing on another point B proved impossible.

The authors conclude that:

[A] saccade executed to a peripheral location in the visual field involves the orienting of attention to that location, prior to the actual execution of the saccade. The inability to orient attention to one location and simultaneously execute a saccade to another location suggests that orienting of attention may be an essential component of preparing and/or executing saccades.

In other words, a saccade is meant to shift the point of focus, and attention cannot be paid to another point during a saccade.

Reference
- Hoffman & Baskaran, Perception & Psychophysics (1995); 57(6), 787-95

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  • $\begingroup$ Well, I can clearly think about things in my peripheral vision while moving my eye about in a different region. I am probably too ignorant of the proper terms. $\endgroup$ – Emil Jun 1 '16 at 20:03
  • $\begingroup$ @Emil - with focus I mean visual focus. Of course you can think about something else $\endgroup$ – AliceD Jun 1 '16 at 20:07

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