Clarifying signal detection theoretic interpretations of the Muller-Lyer and sound-induced flash illusions

In a recent article, Witt, Taylor, Sugovic, and Wixted (2015) made several claims about the way the Muller-Lyer and sound-induced flash illusions should influence the signal detection theory criterion and sensitivity measures, c and d'. Here, we address some crucial conceptual inconsistencies in their simulation of the Muller-Lyer illusion and clarify a previous analysis of the sound-induced flash illusion from the literature that is misinterpreted in their discussion. Alternative signal detection theoretic interpretations of both illusions are offered.