Beck, Prazdny, and Ivry's (1984) interpretation of Metelli's theory of phenomenal transparency is reexamined here. There are no constraints, because the theory considers only balanced transparency and nothing is asserted against the existence of forms of unbalanced transparency. Experiment 4 of the present study proves that conditions of intensity are primary for complete balanced transparency and cannot be overcome if figural conditions strongly suggest transparency.The equation ex = (p-q)/(a-b) does not require further restrictions because the cases cited by Beck et al. concern nonbalanced transparency. Experiment 1 proves that figural conditions cannot be considered primary and thus be the cause of the perception of transparency. The present paper reports that, contrary to the results Beck et al. obtained in their Experiment 4, a series of experiments in which experienced subjects were used and in which estimation oftransparency was compared with predictions calculated with the ex formula gave satisfactory results. Beck et al.'s thesis, according to which ex *ex' hinders transparency whereas t*t' allows it, is confirmed. Experienced subjects and simple instructions appear to yield clearer results.However, one must keep in mind-a thing Beck et al. failed to do-that the deduction of Equations 3 and 4 is valid only in the case of the episcotister, where the as and the ts are the same in Equations I and 2. 4 where a, b, p, and q are the reflectances of the respective regions (Figure la), t is the virtual reflectance of the transparent layer T, and a and (I-a) are the proportions into which the p and q colors split in giving rise to the color of that part of region A (or B) seen through transparency, and to the transparent layer T. 3 From the system of two equations with two unknowns, the values of a and t can be obtained; that is, speed before a bicolored ground, the perceptual result is a gray transparent disk, through which the colors of the background are visible (Figure 1). Figure la indicates the symbols of the four resulting regions; that is, A and B are parts of the bicolored ground that are directly visible, and P and Q are regions where a transparent disk, T, and parts of the underlying background are perceived. But if part of one of the regions where scission is perceived is isolated with a pierced screen, scission disappears and a single fusion color, p, in the P region, or q, in the Q region, is perceived through the hole."The situation can be described by the following two equations.(1) (2) p = aa+(1-a)t q = ab+(l-a)t, Beck, Pradzny, and Ivry's (1984) paper, "The perception of transparency with achromatic colors, " starts with an exposition of the theory of transparency proposed by the senior author of this paper, which however lacks an essential part.The theory, based on Heider's (1933) theory and, restated by Koffka (1935), is that transparency is a phenomenal scission, in which a stimulation-which, if isolated, gives rise to a single color-gives rise, with scission, to the perception of two co...
