Perceptual Experience
(This page last updated 4 October, 2004.)

Perceptual Filling In
- What causes the blind spot?
- Neurons from retinal ganglion cells all leave the eye at
one point.
- No photoreceptors at that point.
- How do you perceive stimuli that cross the blind spot
region?
- Does the visual system actively fill in the blind spot area?
- "Yes!" says Ramachandran
- He claims that examples from assignment demonstrate that
the visual system fills in simple patterns across the blind
spot area before the stimulus is perceived.
- Can fill in lines across blind spot.
- Lines that are not aligned may be perceived as
aligned.
- More complex patterns are not reproduced across blind
spot.
- "No!" says Dennett
- Why should filling-in be necessary? Who would view the
filled in stimulus?
- Once the visual system determines that there is a
continuous line that passes through the blind spot, why
would it need to draw in the missing portion?
- Each level of representation is used to build the next
level. Once a higher level has been constructed, no need to
revise the lower level.
- Patients with scotomas also experience perceptual
filling-in.
Next class: Attention and Consciousness

Psych 391D:
Consciousness
Kyle Cave
Psychology Dept.
U.
Mass.