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Results for “SIZE PERCEPTION”

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At least 649 records · Page 36Linked to original sources
PubMed1976

Stimulus length and orientation variables interact in peripheral motion perception.

To determine the effects of stimulus length and orientation on the perception of motion, 5 experienced subjects responded with a simple reaction to accelerating lines in peripheral vision while fixating on a reference cross at the center of a cathode-ray tube. Three experimental variables were involved: (a) line length, (b) direction of motion, and (c) orientation of the line with respect to the motion. Simple reaction time (RT) was significantly longer for vertical than for horizontal motion and for lines oriented in-line with the direction of motion than for lines oriented perpendicular to the direction of motion. A significant interaction was found between line length and orientation. The results show that the generalization that RT is shorter for small objects than for large objects must be modified in terms of the orientation of the object.

Adult↗
PubMed1977

Subjective and objective symmetry in perception of form.

A new quantitative measure of the physical symmetry of 2-dimensional shapes is proposed which relates it to the proportion of translational and rotational (TR) overlap between a figure and its mirror image. Category ratings of the apparent vertical symmetry of distorted diamond figures correlate highly with this measure while it is also an important contributor in the prediction of the apparent symmetry and geometricity of random polygons.

Choice Behavior↗
PubMed1981

Assimilation and contrast in the parallel lines illusion?

Judgments of 40 undergraduates indicated that the assimilative character of the parallel lines illusion was destroyed at large values of both context line length and separation of context and center line variables. Accommodation of a portion of these results requires a modification of Brigner's (1977) theory of perception of illusory extent.

Discrimination Learning↗
PubMed1983

Effect of orientation on judgments of line length.

This study investigated how the parameters of the power function of line judgments by 68 college undergraduates were affected by orientation of line. Exponents of the power functions did not vary as a function of orientation, but the scaling factors varied substantially. These results suggest that the horizontal-vertical illusion is best described as about a 12% illusion. Also, results are inconsistent with the hypothesis that the horizontal-vertical illusion affects the exponent of power functions for judgments of area and volume.

Adult↗
PubMed2005

Efficient visual search without top-down or bottom-up guidance.

Two types of mechanisms have dominated theoretical accounts of efficient visual search. The first are bottom-up processes related to the characteristics of retinotopic feature maps. The second are top-down mechanisms related to feature selection. To expose the potential involvement of other mechanisms, we introduce a new search paradigm whereby a target is defined only in a context-dependent manner by multiple conjunctions of feature dimensions. Because targets in a multiconjunction task cannot be distinguished from distractors either by bottom-up guidance or top-down guidance, current theories of visual search predict inefficient search. While inefficient search does occur for the multiple conjunctions of orientation with color or luminance, we find efficient search for multiple conjunctions of luminance/size, luminance/shape, and luminance/topology. We also show that repeated presentations of either targets or a set of distractors result in much faster performance and that bottom-up feature extraction and top-down selection cannot account for efficient search on their own. In light of this, we discuss the possible role of perceptual organization in visual search. Furthermore, multiconjunction search could provide a new method for investigating perceptual grouping in visual search.

Form Perception↗
PubMed1989

The temporal distribution of stimulus information in the visual evoked potential.

Research in psychophysics (Bloch's law) and perceptual experiments concerned with the integration of successively presented stimuli suggest that the perception of form is a process that occurs over a period of as much as 200-300 msec. Such results prompted the question of whether the visual evoked potential (VEP) might contain information about the distribution over time of perceptual processing. Subjects viewed lines formed from combinations of three lengths and four angles while the EEG was recorded. Analysis of the VEPs indicated that the length and angle of the lines produced temporal distributions of information in the VEP and that the distributions for length and angle were somewhat different. The major difference was that the processing of angle begins earlier and is completed sooner than the processing of length. A conclusion of the experiment was that an alternative or supplement to analyzing VEPs for specific waveform features is to consider the encoding of stimulus information in the VEP as a density or concentration over time.

Adult↗
PubMed1991

Motion capture by a frame: global or local processing?

The possibility that frames serve to capture lines within them so that they appear on a coplanar surface was investigated, using coherence in direction of rotary motion (Gillam, 1972) as a quantitative measure of the coplanarity of frame and internal lines. It was found that perceptual coherence between a pair of lines was greatly increased by surrounding them with a frame, if the frame was perspectivally consistent with the lines. A second experiment showed that this grouping can be attributed to a global effect of the frame and cannot be accounted for by local grouping of the internal lines with components of the frame.

Form Perception↗