The problem is that it is not at all clear how to reconcile this with the understanding of disparity encoding that has developed since Harris and Parker's 1995 paper was published. Physiologically, stereo correspondence is believed to begin in primary visual cortex (V1). Many V1 neurons are tuned to disparity in random-dot patterns like those shown in
Figure 1. These responses can readily be explained by the binocular energy model (Ohzawa, DeAngelis, & Freeman,
1990) which has since become the canonical description of the early stages of disparity encoding. It has been extensively tested against real V1 neurons and although modifications are certainly required, the basic principle underlying the energy model has been vindicated (Cumming & DeAngelis,
2001; Henriksen, Tanabe, & Cumming,
2016; Ohzawa,
1998; Prince, Cumming, & Parker,
2002; Prince, Pointon, Cumming, & Parker,
2002; Read,
2005); notably, the model has made successful predictions about the response of real neurons to impossible stimuli (Cumming & Parker,
1997). Stereopsis is widely used as a model system to study how perceptual experience relates to early cortical encoding (Parker,
2007; Read,
2014; Roe, Parker, Born, & DeAngelis,
2007).