Perception & Psychophysics

, Volume 38, Issue 4, pp 354-366

First online:

Balanced and unbalanced, complete and partial transparency

  • Fabio MetelliAffiliated withUniversity of Padua
  • , Osvaldo Da PosAffiliated withUniversity of Padua
  • , Adele CavedonAffiliated withUniversity of Padua


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 α = (p−q)/(a−b) does not require further restrictions because the cases cited by Beck et al. concern nonbalanced transparency. Experiment i 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 of transparency was compared with predictions calculated with the α formula gave satisfactory results. Beck et al.’s thesis, according to which α ∈ α′ hinders transparency whereas t ∈ t′ allows it, is confirmed. Experienced subjects and simple instructions appear to yield clearer results.