Subject
Re: TT-2/mnemoptical trick (fwd)
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Perhaps the mnemoptical trick is in part related to the fact that when you
stare at red for a moment then turn your gaze to a blank surface, the
afterimage is green. The past of red shines through as green.
excerpted from:
http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/
www.illusionworks.com/html/color_aftereffect.html
Once we know about this opponency processing stage, first proposed by the
19th century German psychologist Ewald Hering on the basis of perceptual
experiments, the explanation for the color afterimages seen here is
relatively simple. As in other types of negative afterimages, when you
stare at a red stimulus, the cells signaling the presence of red will
start to fatigue. Thus, when looking at the empty screen these cells will
now fire very little. However, because they normally encode through their
activity the presence of red or the absence of green, reduction in their
activity is interpreted by the brain as the presence of green.
Thus, you see a green afterimage. The same applies to the other colors you
see: the green will be replaced by a red afterimage, the yellow by a blue
and the blue by a yellow afterimage. As you continue to observe the
afterimage carefully, it fades and its color changes slightly. This is
because your different cones (and chromatic mechanisms) recover from
adaptation at different rates.
Complementary color afterimages are explained in terms of the neuronal
processing in the retina; the fact that neurons encode color in terms of
opponency processes. In this manner many of the interesting visual
phenomena and illusions associated with the viewing of colors are
accounted for.
See also:
http://www.psych.ucalgary.ca/PACE/VA-Lab/colourperceptionweb/ theories.htm
---------- End Forwarded Message ----------
D. Barton Johnson
NABOKV-L
Perhaps the mnemoptical trick is in part related to the fact that when you
stare at red for a moment then turn your gaze to a blank surface, the
afterimage is green. The past of red shines through as green.
excerpted from:
http://psylux.psych.tu-dresden.de/i1/kaw/diverses%20Material/
www.illusionworks.com/html/color_aftereffect.html
Once we know about this opponency processing stage, first proposed by the
19th century German psychologist Ewald Hering on the basis of perceptual
experiments, the explanation for the color afterimages seen here is
relatively simple. As in other types of negative afterimages, when you
stare at a red stimulus, the cells signaling the presence of red will
start to fatigue. Thus, when looking at the empty screen these cells will
now fire very little. However, because they normally encode through their
activity the presence of red or the absence of green, reduction in their
activity is interpreted by the brain as the presence of green.
Thus, you see a green afterimage. The same applies to the other colors you
see: the green will be replaced by a red afterimage, the yellow by a blue
and the blue by a yellow afterimage. As you continue to observe the
afterimage carefully, it fades and its color changes slightly. This is
because your different cones (and chromatic mechanisms) recover from
adaptation at different rates.
Complementary color afterimages are explained in terms of the neuronal
processing in the retina; the fact that neurons encode color in terms of
opponency processes. In this manner many of the interesting visual
phenomena and illusions associated with the viewing of colors are
accounted for.
See also:
http://www.psych.ucalgary.ca/PACE/VA-Lab/colourperceptionweb/ theories.htm
---------- End Forwarded Message ----------
D. Barton Johnson
NABOKV-L