Spatial resolution of visual feedback affects variability and structure of isometric force.

The purpose of this study was to examine the effect of spatial resolution of visual feedback on the variability and structure of isometric force. We manipulated spatial resolution of the display by changing the number of possible feedback dot positions. Twelve healthy young adults (5 men, 7 women) attempted to apply a constant level of force normal to a load cell with the index finger using two types of visual displays. One display provided high spatial resolution visual feedback by allowing feedback dot take any position from the 440 pixels along the vertical dimension of the screen. This display provided precise information about the current level of force relative to the target and to a range of allowable force deviation around the target. The other display provided low spatial resolution visual feedback by depicting applied force as taking on only three discrete values--below, within, or above the target range. Participants produced less variable and more complex (higher approximate entropy) force output with the displays that had higher spatial resolution. Recurrence quantification analysis of the force time series revealed that the display with low visual feedback resolution promoted a more intermittent, discontinuous force-production performance.