Search PubMed⌕ Search
Home/Archive/PubMed

PubMed · 6458648

Mistracking in alignment illusions.

W H Hotopf
View original source ↗Export metadata ↓

Abstract

A number of anomalies have been pointed out in opposition to attempts to account for the Poggendorff illusion in terms of the expansion of small or medium-sized acute angles. A principle under which these anomalies could be subsumed was proposed and subjected to experimental testing using simplified displays. The following theory emerged from these experiments. If a straight line (the pointer) is aligned with a do (the target) situated at the end of a second line (the induction line) and lying in a different orientation from the pointer, then (depending on the angle between pointer and induction line) the pointer will appear to be aligned with a point further along the induction line. The amount of misalignment varies inversely with increase in size, up to about 135 degrees, of the angle formed by the pointer with the induction line, after which there is no displacement attributable to the induction line. The effect appears not to be due to neural interaction. An explanation in terms of eye movement is discussed.

Explore related subjects

Discrimination LearningForm PerceptionHumansIllusionsOptical IllusionsOrientationSize PerceptionJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

W H Hotopf. 1981. Mistracking in alignment illusions.. https://doi.org/10.1037/%2F0096-1523.7.6.1211

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

KEEP EXPLORING

Related citations

PubMed1999

Influence of shape on haptic curvature perception.

Curvature discrimination of hand-sized doubly curved surfaces by means of static touch was investigated. Stimuli consisted of hyperbolical, cylindrical, elliptical and spherical surfaces of various curvatures. In the first experiment subjects had to discriminate the curvature along a specified orientation (the discrimination orientation) of a doubly curved surface from a flat surface. The curvature to be discriminated was oriented either along the middle finger or across the middle finger of the right hand. Independent of the shape of the surface, thresholds were found to be about 1.6 times smaller along the middle finger than across the middle finger. Discrimination biases were found to be strongly influenced by the shape of the surface; subjects judged a curvature to be more convex when the perpendicular curvature was convex than when this curvature was concave. With the results of the second experiment it could be ruled out that the influence of shape on curvature perception was simply due to a systematic error made by the subject regarding the discrimination orientation.

Discrimination Learning↗
PubMed1998

What is learned about nontarget items in simple visual search?

Human sensitivity to correlational structure between nontargets and likelihood of target presence in a visual letter-search task were studied in two experiments. In each of these experiments, the performance of subjects for whom the nontarget information was altered in the final trial block was compared with the performance of subjects for whom the nontarget information did not change. When stimulus strings were presented individually on a computer screen and subjects were required to make a yes-no decision about target presence (Experiment 1), the change in nontarget structure resulted in increased reaction times for target-absent trials. When subjects searched simultaneously for three possible targets (Experiment 2), the change in nontarget structure produced increased error rates and increased reaction times for both target-absent and target-present trials. Correlations between the amount of predictive information in individual stimulus strings and reaction times also showed that both switching and nonswitching subjects were sensitive to the nontarget context. However, neither self-reports of strategy nor postexperiment choices between context-consistent and-inconsistent letter strings indicated any explicit knowledge of the predictive information in the nontarget stimuli. Subjects can thus acquire and benefit from, apparently without awareness, information about subtle correlational structure in nontarget elements in simple visual search.

Discrimination Learning↗
PubMed1998

Discriminating constant from variable angular velocities in structure from motion.

We investigated accuracy in discriminating between constant and variable angular velocities for orthographic projections of three-dimensional rotating objects. The reported judgments of "constant" or "variable" angular velocity were only slightly influenced by the projected angular velocities, but they were greatly affected by the variations of the deformation, a first-order component of the optic flow. When viewing either a rotating ellipsoidal volume or a planar surface that accelerated and decelerated over the course of rotation, observers' tendencies to report a variable angular velocity were increased when the temporal phase of the acceleration pattern increased the range of variation of the median deformation; the tendencies were decreased when the same acceleration pattern was used to decrease the range of variation of the median deformation. These results provide evidence contrary to the hypothesis that the visual system performs a mathematically correct analysis of the optic flow.

Discrimination Learning↗