1998 volume 27(1) pages 7 – 20
doi:10.1068/p270007

Cite as:
Liu L, Stevenson S B, Schor C M, 1998, "Vergence eye movements elicited by stimuli without corresponding features" Perception 27(1) 7 – 20
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Vergence eye movements elicited by stimuli without corresponding features

Lei Liu, Scott B Stevenson, Clifton M Schor

Received 7 July 1997, in revised form 22 October 1997

Abstract. We have observed quantitative depth perception with a dichoptic stimulus whichpossessed no contrast-defined binocular corresponding features (phantom stereogram). The depth perception can be the result of appreciation of a partial-occlusion situation depicted by the stimulus, or the result of activities of low-level disparity detectors which are capable of combining dissimilar local features in the stimulus. Although both mechanisms predict similar depth perception, they predict different vergence eye-movement outputs, especially in the vertical dimension. To identify the underlying mechanisms of the phantom stereopsis, we recorded vergence tracking eyemovements to four typesof dichoptic stimuli: (a) conventional stereogram with horizontal disparity (HD); (b) horizontal phantom stereogram (HP); (c) conventional stereogram with vertical disparity (VD); and (d) vertical phantom stereogram (VP). We found that HD, HP, and VD stimuli could elicit robust vergence tracking eye movements but VP stimulus could not. While the success of HP stimulus in eliciting vergence tracking may be explained by proximal vergence, the failure of VP stimulus in eliciting vergence tracking clearly indicates that phantom stereogram could not elicit coherent responses among low-level disparity detectors. Partial occlusion, therefore, has to play an important role in the depth perception from the phantom stereogram.

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