1. Motion in depth cued by chromatic interocular velocity differences and changing disparity
Alex Wade
Jeffrey Jordan
Milena Kaestner
Priyav Shah
Department of Psychology
University of York, UK

3. CD
IOVD
Rushbass, C., & Westheimer, G. (1961).

4. CD IOVD Disparity computed first Disparity computed second
(Nefs, O’Hare & Harris, 2010, Shioiri, S., Saisho, H., & Yaguchi, H. (2000) )

5. Color Isoluminant color not a strong cue to motion or depth.
But pure chromatic signals can drive both motion and depth perception at high contrasts
Does performance on CD and IOVD detection depend on stimulus chromaticity?

6. Stimuli Random dot stereograms, + and – contrasts
Randomized each 6 frames -> CD
Moving, anticorrelated dots -> IOVD/CD
Moving, decorrelated dots -> pure IOVD
Coherence thresholds compared across all experiments
Individual dots at 2x detection threshold.
Isoluminance determined from minimum motion

7. Mirror stereoscope
CRT
Mirror
Participant
Screen
OPL=1m

8. Pure CD (100% coherence)
Dot FWHM: 0.15deg.
Aperture diameter: 4deg

9. Pure IOVD

10. Pure IOVD * * * *

11. Methods OSX Mac / Psykinematix N=12
Thresholds estimated using a Bayesian adaptive paradigm
Contrast detection thresholds and isoluminance from separate experiments (2AFC, minimum motion), same display.
Subjects indicated polarity of stereomotion sine wave over 1s: average disparity=0

12. Methods
IOVD, CD motion amplitude equiv to 19cm around fixation at 100cm *
38cm * *

13. Results
CD vs IOVD coherence thresholds

14. Coherence thresholds **
Points: All types yield real thresholds. aIOVD t’holds higher than CD, not sig diff from dIOVD.

15. Chromatic stimuli
K.R. Dobkins, Neuron, Vol. 25, 15–18, January, 2000

16. Chromatic stimuli

17. Chromatic stimuli

18. Chromatic stimuli

19. Both IOVD and CD are detectable at isoluminance
Achromatic thresholds

21. Interaction between color and stim type: For CD, advantage to L-M
Interaction between color and stim type: For CD, advantage to L-M. For IOVD, advantage to S

22. Cross-channel noise masking
Do CD, IOVD systems treat chromatic channels independently?
…or are signal, noise pooled across channels before detection?

23. Detection thresholds are independent of noise chromaticity

24. Color calibration?
Estimated luminance signal in both S-cone and L-M stimuli <0.5% contrast
Subjects perform at chance at this contrast level for achromatic tasks
Cross-channel masking (S/Lum and L-M/Lum) not significantly different to within-channel masking.

25. Conclusion
IOVD and CD stereomotion systems can be compared using RDK coherence thresholds
Achromatic CD thresholds are 2/3 those of IOVD
Chromatic IOVD and CD thresholds measured reliably
The advantage of CD over IOVD is reduced at isoluminance and for S-cone system.
Both mechanisms appear to pool signals across chromatic and achromatic channels.

26. Thanks
Steve Shevell
Milena Kaestner
Doug Taylor