PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 4014429

Illusory differences which are stereoacuity test cues.

W L Larson
View original source ↗Export metadata ↓

Abstract

Some persons perceive an illusion of unequal blackness when viewing two equally black rods in a stereoacuity test. With binocular vision, the blacker rod is usually the nearer of the two. If blackness is used as a cue to nearness, a stereoacuity test can be performed successfully without using stereopsis. Nevertheless, stereoacuity obtained by this means is usually inferior to that obtained with distance judgments. For this reason it is advisable to warn subjects against using a blackness difference as a cue to the nearer rod. Those who saw this illusion binocularly also saw it monocularly. Therefore, it is more than just an artifact of stereopsis. One person observed an illusory difference in rod width as well as blackness.

Explore related subjects

CuesDepth PerceptionFemaleHumansIllusionsOptical IllusionsVisual AcuityJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

W L Larson. 1985. Illusory differences which are stereoacuity test cues.. https://doi.org/10.1097/00006324-198506000-00010

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1992

Does limb proprioception drift?

The hypothesis that proprioceptively perceived limb position drifts during visual occlusion was re-examined by combining some of the protocols used in previous experiments. Sixteen adult subjects made judgements of static limb position during visual occlusion lasting up to 2 min. In addition, the effect of brief 250 ms "glimpses" of the limb, occasional proprioceptive stimulation and directed attention were examined. Despite, conflicting evidence from earlier experiments, there was clear evidence of a drift in perceived limb position, towards the body, during visual occlusion. This drift was halted if brief glimpses of the limb were provided, or minor re-positioning (without vision) was allowed. In neither case, however, did the supplementary cues reset limb position to its originally perceived position. Drift was amplified when subjects attempted to attend to limb position rather than perform a secondary tracking task. The results are not easily accounted for if drift is considered purely as an effect of peripheral sensor adaptation. A notion of central-drift between visual and proprioceptive maps is suggested as an alternative hypothesis.

Cues↗
PubMed1992

Gravity as a monocular cue for perception of absolute distance and/or absolute size.

When the motion of an object is influenced by gravity (eg free fall, pendulum, wave motion), that influence may provide a cue to computing the absolute distance and/or size of the object. Formal analysis supports the claim that the distance and size of moving objects are generally computable with reference to the gravitational component of motion. Informal evidence from judgments of realism in films is consistent with this gravity-cue hypothesis.

Cues↗
PubMed1992

The influence of object familiarity on magnitude estimates of apparent size.

Three magnitude-estimation experiments were used to determine the exponents of the power function relating size judgments and physical size for two-dimensional familiar and unfamiliar stimuli. The exponent of the power function was used to index the effect of familiar size on perceived size under a variety of conditions, from full-cue to reduced-cue viewing conditions. Although the value of the exponents varied across the three experiments, within each experiment the exponent of the familiar stimulus was not significantly different from that of the unfamiliar stimulus, indicating that familiar size does not influence the rate of growth of perceived size. The results of a fourth experiment excluded a possible explanation of the findings of experiments 1-3 in terms of subjects responding to relative angular size as a consequence of the successive presentation of the different-sized representations of the familiar stimulus. Taken together, the present findings are consistent with the hypothesis that the influence of familiar size on estimates of size mainly reflects the intrusion of nonperceptual processes in spatial responses.

Cues↗