Abstract
Image differences between the eyes can cause millisecond-scale interocular differences in processing speed. For moving objects, these differences can cause dramatic misperceptions of distance and 3D direction. Here, we develop a continuous target-tracking paradigm that shows these tiny differences are preserved in the movement dynamics of the hand. Human observers continuously tracked a target undergoing Brownian motion with various luminance differences between the eyes. From this data, we recover the time course of the visuomotor response. The difference in the visuomotor response across luminance conditions reveals temporal differences in visual processing between the eyes. Next, using traditional psychophysical methods, we measure interocular processing speed differences in equivalent conditions using a paradigm developed to study the Pulfrich effect. Target tracking and traditional psychophysics provide estimates of interocular delays that agree to within a fraction of a millisecond. Thus, despite the myriad signal transformations occurring between early visual and motor responses, millisecond-scale visual delays are preserved in the movement of the hand. This paradigm provides the potential for new predictive power, the application of analytical techniques from computational neuroscience, and rapid measurements in populations in which traditional psychophysics might be impractical. Further implications for future research will be discussed.
Funding: This work was supported by NIH grant R01-EY028571 from the National Eye Institute and the Office of Behavioral and Social Science Research to JB