![eli robinson on vimr eli robinson on vimr](https://i.vimeocdn.com/video/616486910.jpg)
Here we investigate whether such intuitive oculomotor responses to optic flow are generalizable to a larger group of human observers, and how eye movements are affected by motion signal strength and task instructions. In small groups of human and non-human primates, optic flow triggers intuitive, uninstructed eye movements to the pattern’s focus of expansion (Knöll, Pillow & Huk, 2018). Even though optic flow is ubiquitous in everyday life, it is not well understood how our eyes naturally respond to it. When we move through our environment, objects in the visual scene create optic flow patterns on the retina. (The lines indicating the direction and velocity of the dot motion were not present during the actual experiments.) The right part of the figure shows what these patterns would look like when gaze was directed to the left of the simulated heading direction. The left part of the figure shows the flow patterns for tunnel vision and a central gap condition as they would look when the gaze is directly on the heading direction (as was the task). The lower part of the figure shows what happens to the flow pattern when simulated field defects are introduced.
![eli robinson on vimr eli robinson on vimr](https://i.ytimg.com/vi/sUvWFR9ER8c/maxresdefault.jpg)
The observers' task was to track the heading direction with their eyes. We simulated linear observer motion with a continuously changing heading direction. The real-time gaze position measured by the eye tracker was used to adapt the projection on the screen to the particular visual field defect that was simulated. The screen was updated 120 times per second. Subjects looked with one eye at the screen on which the projection of a (virtual) cloud of dots was shown. Shown is a case of simulated tunnel vision. Schematic representation of the experimental setup. Our results further point out that the calculations underlying heading detection can be performed very quickly, with processing time strongly dependent upon the speed of the simulated translation and the size of the stimulated visual area. The influence of the defect on processing time was largest when the heading changed smoothly. The reverse was the case for simulated central scotomas. When limiting peripheral view, the influence of the field defect on processing time was larger when the heading changed abruptly than when it changed smoothly.
![eli robinson on vimr eli robinson on vimr](https://64.media.tumblr.com/7b93d30411ee4ed389110413fc2b335f/tumblr_p8y2x43kbq1qhusrfo1_1280.jpg)
While accuracy was the same under these conditions, processing time was differentially affected. Therefore, we examined performance during both of these types of change. Under natural circumstances, optic flow patterns can change both smoothly, such as during pursuit of an object, and more abruptly, such as when making saccades. Limiting the peripheral view, as in tunnel vision, or introducing a central scotoma, as in macular degeneration, affected both the accuracy with which subjects could estimate heading direction as well as the time it took them to do this. The subjects’ task was to direct their gaze at the continuously changing direction of heading. Real-time gaze position was used to generate the appropriate optic flow pattern on the screen.
![eli robinson on vimr eli robinson on vimr](https://qa.thersa.org/globalassets/images/fellowship/events-thumbnails/newcastlefellowevents2.jpg)
We simulated tunnel vision and a central scotoma during ego-translation. We examined how simulated visual field defects influence performance on a heading task to gain insight into the origins of the poorer performance seen in subjects with real visual field defects.