In vision research metacontrast masking is a widely used technique to reduce the visibility of a stimulus. Typically, studies attempt to reveal general principles that apply to a large majority of participants and tend to omit possible individual differences. The neural plasticity of the visual system, however, entails the potential capability for individual differences in the way observers perform perceptual tasks. We report a case of perceptual learning in a metacontrast masking task that leads to the enhancement of two types (...) of adult human observers despite identical learning conditions. In a priming task both types of observers exhibited the same priming effects, which were insensitive to learning. Findings suggest that visual processing of target stimuli in the metacontrast masking task is based on neural levels with sufficient plasticity to enable the development of two types of observers, which do not contribute to processing of target stimuli in the priming task. (shrink)

While the majority of perceptual phenomena based research on consciousness is implicitly nomothetic, some idiographic perspective can be sometimes highly valuable for it. It may turn out that after having had a closer look at individual differences in the expression of psychometric functions a need to revise some nomothetic laws considered as the general ones arises as well. A study of individual differences in metacontrast masking published in this issue superbly illustrates this. A myriad of urgent research objectives emerges out (...) of this study, most of them important both for clearing up the still messy theoretical picture on visual masking and for the beginning of asking whether perceptual awareness mechanisms are so universal at all. In this commentary the problems pertinent to this issue are discussed. (shrink)