Reaction time measurement of receptive field properties in the human fovea

A Westheimer-like function has been obtained for simple reaction time (RT) to target luminance increments superimposed upon homogeneous background fields. RT to a constant-luminance target progressively increases as the outer diameter of a constant-luminance background is increased up to approximately 6′–8'. Further increases in background diameter up to approximately 10′–22′ then result in progressive decreases in RT. Beyond this background diameter RT remains relatively constant. The magnitude of this effect diminishes rapidly as target luminance is increased beyond a near-threshold value.