The transparency is in the fused image not the monocular image

The transparency is in the fused image not the monocular image Grove, Brooks, Anderson, and Gillam dispute our claim that metric depth can be produced by images that generate an impression of transparency in the absence of conventional binocular disparity. They replicate our finding that our ÔtransparencyÕ stimulus produces the same depth as that produced by a disparity depth probe over a wider range of disparities than does the depth created by monoc-ular occlusion. So there is no dispute about our basic results. Grove et al. argue that they have disproved our claim that transparency must be present in one of the un-fused monocular images. They obtained similar results when they removed all evidence of transparency in the monocular image. But we do not claim that monocular transparency is required in the monocular image but rather that an impression of transparency is created in the binocular image. We admit that the title of our paper suggests that the effect depends on transparency in the monocular image. We used the term ''monocular transparency'' because it is similar to the term ''monocular occlusion'' that is used to describe depth created when one eye does not see a region that the other eye can see. In a similar way, our depth/transparency effect arises in a real-world stimulus when one eye sees a surface through another surface while the other eye sees two abutting surfaces. In that sense the transparency is monocular. In a similar way, in occlu-sion stereopsis, the occlusion is monocular. But the essential transparency, like the impression of occlusion, occurs after, rather than before, the images are fused. We shaded the inner square in one of our images because we wished to replicate the images that are produced when a real square is displaced in depth relative to a transparent surrounding surface, as shown in our Fig. 5. We did not claim that this is essential for the production of an impression of transparency in the fused image. We are not surprised that transparency and the depth effect is still present when the square is evenly shaded as in Grove et al.Õs Fig. 2B. This is an interesting finding but the important point is that, in the fused image of their figure, part of the rectangle appears through a transparent surrounding surface when it is seen beyond the surround. When it is seen in front of the surround the impression of …