Does McCollough effect provide evidence for implicit change perception?

The possibility of implicit change detection in the visual scene is one of the central issues of a change detection process. The present work was aimed at studying the possibility of implicit perception of color changes. With this end, we have acquired the McCollough effect (MCE) with no possibility of explicit perception of the inducing stimulus color. The experiments were conducted on 40 male and female subjects with normal color vision. The MCE acquisition occurred using only one inducing stimulus - a vertical black-green grating. In the adaptation period the grating was presented as short expositions, with an instant substitution of the stimulus by so-called "deleting" image, whose presentation played simultaneously a role of an interstimulus interval. Owing to the fact that the time of exposition was selected so as to allow for the subjects perceive explicitly but the form of an inducing stimulus (in this case the grating's orientation) and not the color of chromatic stripes between the black ones, the subjects couldn't, in the adaptation period, perceive explicitly either the color per se or its appearance-disappearance. In spite of this, in a definite part of subjects (approximately in 20%) the effect was acquired indicating that in the adaptation period perception of not only color but also of its appearance-disappearance did occur, i.e. there took place implicit perception of color change. This result can be viewed as a confirmation of the visual system's ability of implicit change perception.