Increment and Decrement Detection across the Mach-Band Stimulus

Abstract

The ability of observers to detect bright and dark horizontally oriented lines was measured using standard 2AFC procedures. The lines to be detected were either increments or decrements in luminance superimposed on a luminance pattern that produced horizontally oriented Mach bands. Measurements were made in the uniform regions of high and low luminance that flank the Mach-band-producing luminance ramp as well as in the vicinity of the bright and dark Mach bands. Detection performance was significantly affected by both dark and bright Mach bands. The reliability of the results makes it reasonable to attempt to infer, following E M Lowry and J J DePalmer (1961 Journal of the Optical Society of America 51 740 – 746), spatial weighting functions for (one-dimensional) pattern vision.