“…In Fig. 1a, it is impossible to know whether the illusory sphere (depicted as a gray circle) follows the example dots and reverses its depth, although current evidence strongly suggests that it remains constant (Brouwer & van Ee, 2006;Li & Kingdom, 1999;Pastukhov, Vonau, & Braun, 2012;Petersik, 1979;Stonkute, Braun, & Pastukhov, 2012;Treder & Meulenbroek, 2010;Zivotofsky & Goldstein, 2007). Taking into account that commonly used object shapes such as spheres or cylinders are rotationally symmetric and, thus, depth symmetric, it is easy to see why illusory depth was overlooked.…”