"Still, despite all these indications, we have not found final proof for our hypothesis," he said.
Others suggest the evidence isn't there for an intentional creation of a stereoscopic view for paintings.
For instance, the disparities between the two paintings for other areas of the body, not the hands, don't fit with them creating a stereoscopic pair, according to Arguin. "Most in contradiction with this notion is the fact that these disparities are largely oriented vertically, and not horizontally as would be required to replicate the left and right eye views," Arguin said.
He gave an example of Mona Lisa's face: "All the landmark location changes are of the same size. This would not be so in an adequate stereoscopic image since disparities should vary according to relief (i.e. distance from the observer)."
Arguin added of the study: "They are quite accurate in their statements, and their discussion of their findings is sensible and interesting."
Carbon and Hesslinger say they agree with Arguin's comments about the consistency of disparities in certain regions of the "Mona Lisa" paintings and the horizontal or vertical nature of some of the disparities between the two paintings.