Illusions & Aftereffects Flashcards
Size illusions
Distance related changes in image
CONSTANCY SAMPLING helps is to compensate. Eye knows that when image on the retina shrinks, perceived as maintaining its size as it recedes into the distance
Bistable figures and illusory contours
Give visual system two possible percepts to CHOSE from
ACTIVE rather than passive process
Shape and orientation illusions
Illusory curvature of lines
example of misapplied Constance sampling
When lines with a similar orientation are presented in close proximity to eachother, we overestimate the difference in orientation = OVERESTIMATION OF ACUTE ANGLES
Troxler effect/ Troxler fading
As we focus on the fixation point we ADAPT the cells that had been responding where the intensity changes.
Eye movement prevents adaptation
Everyday life… Eye movement so objects don’t rapidly fade from view
Colour after effects
During prolonged exposure, after a whole their response rate would be reduced as they became ADAPTED
Other cells respond in opposite ways, why we see other colours = OPPONENT PROCESSING = antagonism
Motion after effects
Motion detectors arranged in pairs seeing motion in opposite directions
Cell firing most vigorously corresponds to the direction of motion
Size after effects
Particular cells for certain stimuli. Tunning
Overall pattern of firing = population coding. Depicts size
Prolonged exposure to fat lines makes medium stripes look thin ADAPTATION
Tilt after effects
Prolonged exposure to tilted bars makes subsequently seen vertical lines appear tilted in opposite direction
ADAPTATION
+ orientation selective cells
