The intrinsic constraint model and Fechnerian sensory scaling.

The Intrinsic Constraint (IC) model of depth-cue integration (F. Domini, C. Caudek, & H. Tassinari, 2006) posits a strong link between perceived depth and depth discrimination, much like some Fechnerian theories of sensory scaling. K. J. MacKenzie, R. F. Murray, and L. M. Wilcox (2008) tested the IC model by examining whether two depth-matched pairs of stimuli are separated by equal numbers of Just Noticeable Differences (JNDs) in depth. They concluded that "IC is inconsistent with the psychophysics of depth perception." Here, by using a different methodological approach, we provide empirical findings that are consistent with the predictions of the IC model. We also discuss the relative merits of the IC and Modified Weak Fusion (MWF) models (M. S. Landy, L. T. Maloney, E. B. Johnston, & M. Young, 1995) of depth-cue combination.