poster 019 - Adrien Chopin

stereopsis. Threshold (arcsec). Control group. Dressmakers. Absolute Depth Relative Depth. 0. 1000. 2000 ... Nat Rev Neurosci. 2007;8(5):379–391. 2. McKee ...
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Stereoscopic depth from absolute and relative disparities

Adrien Chopin David Knill Dennis Levi Daphne Bavelier

or

The phenomenon of absolute depth "blindness"

VSS 2014

Corresponding author: [email protected]; download at http://adrien-chopin.weebly.com/publications.html

+ φL

φR

a P = φL - φR

φL

φL

-

Fixation

P2 φL

φR

φR

φR r = φL - φR or r = a P1 - a P2

Are absolute and relative depth systems independent? It is an unresolved question: are relative disparities independently acquired or are they 1 computed as a difference of absolute disparities ? Some believe that the two systems are independent because relative depth performance is better than absolute depth performance. However several concerns need to be addressed. Concern 1: The absolute depth condition always presents a visible reference (fixation or screen border), creating relative disparities.2

Control group Dressmakers

2000

1000

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Fixation

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3000

Absolute Depth

Relative Depth

Stereoblindness and absence of fine stereopsis are more likely for absolute depths than for relative depths. 86% of the control participants lack fine stereopsis for absolute depths. Absolute depth training did not yield benefits after 5 sessions. Completely stereoblind 0.8

Control group Dressmakers

0.6 0.4 0.2 0

N = 21 N = 13

R lute elative D Dept epth h

Abso

Absolute depth training

No fine stereo (>900’’) 0.8 0.6 0.4 0.2 0

3000

1000 N=6 0

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R lute elative D Dept epth h

Abso

Concern 2: Absolute depth performance is typically measured with 2IFC and relative depth with 2AFC giving the advantage to relative depths (because of memory decay).3

Solution: Participants were naive: either students or professional dressmakers, who may particularly benefit from a good stereopsis in their activity.

Solution: We used a single stimulus method, introducing the same memory burden in the two conditions. Relative Depth Absolute Depth

Result: Dressmakers are more precise than the control group (p