Micropattern orientation and spatial localization.
A current, popular, theory of spatial localization holds that the visual system represents the location of simple objects by a single positional tag, the accuracy of which is largely independent of the internal properties of the object. We have already presented evidence of the limitations of such a view (Keeble & Hess (1998). Vision Research, 38, 827-840) in that 3-micropattern alignment performance was found to be dependent on the orientation of the micropatterns. We tested whether this was caused by a local anisotropy in positional coding by conducting 3-micropattern bisection experiments with varying patch orientation. No corresponding effect of patch orientation was found, implying a difference in the mechanisms used for the two tasks. In a further experiment we show that alignment task performance is very similar to the otherwise identical 2-patch orientation discrimination task. We conclude that the 3-micropattern alignment task is mediated by orientational mechanisms. We therefore present a 2nd-order orientation model for 3-patch alignment.
Keeble
D R
DR
Human and Information Science Laboratory, NTT Communication Science Laboratories, 3-1, Morinosato-Wakamiya, Atsugi-shi, Kanagawa 243-0198, Japan. d.r.t.keeble@bradford.ac.uk
Nishida
S
S
D016880:Anisotropy; D004192:Discrimination, Psychological; D006801:Humans; D010364:Pattern Recognition, Visual; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D012399:Rotation; D012684:Sensory Thresholds; D013028:Space Perception