Fechnerian sensory scaling: a test of the intrinsic constraint model

In a recent paper, MacKenzie et al (2008) matched the perceived depth of half-cylinders defined by disparity to half-cylinders defined by motion information for two simulated depths and attributed to the IC model (Domini et al, 2006 Vision Research 46 1707 - 1723) the following prediction: The JND count, defined as the difference between two simulated depths divided by the (constant) JND, should be equal for both motion-only and disparity-only stimuli. They conclude that their findings do not conform to the predictions of the IC model. Such conclusion is flawed. In the present study we show that, if the JND count is correct, then the empirical data is compatible with the hypothesis that two depth-matched pairs of stimuli are separated by equal numbers of JNDs. These results are consistent with the predictions of the IC model and support the hypothesis that there is a strong link between perceived depth and depth discrimination. We will also discuss the implications of these results for the MWF theory of depth-cue integration.