Visual illusions
Stream of consciousness, not stream of vision!
Inverse optics: onmogelijk veel oplossingen voor wat je ziet. Maar 1 is meest waarschijnlijk.
Heuristics, most plausible solution. Bottom up of top-down processes.
(Binocular) rivalry: different images are presented to the two eyes. Perception flips the two.
bistable patterns. Diverging experimental results. Higher visual areas but also V1 seem to be
important for rivalry. Both V1 and extrastriate areas might contribute to grouping and
segmentation processes in binocular rivalry, although the precise site(s) of inhibitory
competition remain to be resolved.
color phi:
flickering, but you see movement (isnt there). Experience change color halfway! Even first
time! But you dont know what end color is
flash lag effect:
flash seems lagged, but is at same position as moving one. Not about prediction!.. Perception
at certain moment depends on what happends next.
stopped clock illusion:
we zien tijdens saccade niets. Wat gebeurt er met tijd tijdens saccade? De tijd dat saccade
duurt, wordt opgeteld met tijd die je ziet na saccade.
Unexpected events seems to last longer
, Isomorphic filling-in: low levels of visual system, actively filling in details to complete
picture in brain.
Symbolic filling-in: higher up visual system, more conceptual than picture-like.
Top-down hoeft niet te matchen met bottom-up: bv seeing something that is not there (blind
spot). Brain actively fills in the missing info.
Dennett disagrees with idea of brain actively filling in information: having identified one
portrait, and having no information to suggest that the other blobs are not also marilyns, the
brain jumps to the conclusion that the rest are Marilyns too. The reason you would notica a
moustache or a silly hat is that you have dedicated pop-out mechanims to detect such
anomalies.
Afgebroken figuur afmaken (auto achter hek): amodal perception/conceptual filling-in
Bind spot: filling in with surroundings
Is the brain filling in or ignoring gaps? Not simply ignoring gaps
Vertical lines above and below blind spot seem to line up. This does not work for horizontal
lines!
We are unaware of blind spots, because we have two eyes, and the two blind spots cover
different parts of the visual field. But even with one eye the blind spot is normally
undetectable.
VS Ramachandran: subject saw numbers, couldnt read them. See gap (blind spot) close
(gradually, so moving)
Same with artificial scotomas
Is there respons in blind spot in V1? Gray oval is blind spot. Only when bar is before and
behind blind spot, there is percept of bar. There is activation v1, but no retinal input. Retinul
input in blind spot is always absent, because there are no neurons.
No bottom up activation: top down activation vult het in
Figure-background segregation.
Stream of consciousness, not stream of vision!
Inverse optics: onmogelijk veel oplossingen voor wat je ziet. Maar 1 is meest waarschijnlijk.
Heuristics, most plausible solution. Bottom up of top-down processes.
(Binocular) rivalry: different images are presented to the two eyes. Perception flips the two.
bistable patterns. Diverging experimental results. Higher visual areas but also V1 seem to be
important for rivalry. Both V1 and extrastriate areas might contribute to grouping and
segmentation processes in binocular rivalry, although the precise site(s) of inhibitory
competition remain to be resolved.
color phi:
flickering, but you see movement (isnt there). Experience change color halfway! Even first
time! But you dont know what end color is
flash lag effect:
flash seems lagged, but is at same position as moving one. Not about prediction!.. Perception
at certain moment depends on what happends next.
stopped clock illusion:
we zien tijdens saccade niets. Wat gebeurt er met tijd tijdens saccade? De tijd dat saccade
duurt, wordt opgeteld met tijd die je ziet na saccade.
Unexpected events seems to last longer
, Isomorphic filling-in: low levels of visual system, actively filling in details to complete
picture in brain.
Symbolic filling-in: higher up visual system, more conceptual than picture-like.
Top-down hoeft niet te matchen met bottom-up: bv seeing something that is not there (blind
spot). Brain actively fills in the missing info.
Dennett disagrees with idea of brain actively filling in information: having identified one
portrait, and having no information to suggest that the other blobs are not also marilyns, the
brain jumps to the conclusion that the rest are Marilyns too. The reason you would notica a
moustache or a silly hat is that you have dedicated pop-out mechanims to detect such
anomalies.
Afgebroken figuur afmaken (auto achter hek): amodal perception/conceptual filling-in
Bind spot: filling in with surroundings
Is the brain filling in or ignoring gaps? Not simply ignoring gaps
Vertical lines above and below blind spot seem to line up. This does not work for horizontal
lines!
We are unaware of blind spots, because we have two eyes, and the two blind spots cover
different parts of the visual field. But even with one eye the blind spot is normally
undetectable.
VS Ramachandran: subject saw numbers, couldnt read them. See gap (blind spot) close
(gradually, so moving)
Same with artificial scotomas
Is there respons in blind spot in V1? Gray oval is blind spot. Only when bar is before and
behind blind spot, there is percept of bar. There is activation v1, but no retinal input. Retinul
input in blind spot is always absent, because there are no neurons.
No bottom up activation: top down activation vult het in
Figure-background segregation.
