Interactions between spatially tuned mechanisms: converging evidence.

Detection and identification performance is measured for four pairs of sinusoidal gratings that differ in spatial-frequency separation. A modified two-alternative forced-choice procedure (2 X 2) is used to measure performance on both tasks simultaneously. The results provide new evidence for the existence of interactions between tuned mechanisms that respond to widely separated frequencies. A method to compare data obtained in the 2 X 2 method quantitatively with both single- and double-response rating data is developed and used to compare the current data with previous rating results. The magnitudes of interactions isolated by the three procedures agree closely.