  We study the phenomenon of categorical perception within the quantum
measurement process. The mechanism underlying this phenomenon consists in
dilating stimuli being perceived to belong to different categories and
contracting stimuli being perceived to belong to the same category. We show
that, due to the naturally different way in determining the distance between
pure states compared to the distance between density states, the phenomenon of
categorical perception is rooted in the structure of the quantum measurement
process itself. We apply our findings to the situation of visual perception of
colors and argue that it is possible to consider colors as light quanta for
human visual perception in a similar way as photons are light quanta for
physical measurements of light frequencies. In our approach we see perception
as a complex encounter between the existing physical reality, the stimuli, and
the reality expected by the perciever, resulting in the experience of the
percepts. We investigate what that means for the situation of two colors, which
we call Light and Dark, given our findings on categorical perception within the
quantum measurement process.
