Voluntary visual attention and phenomenal line length

In 1956, Fraisse, et al. reported subjects judged that lines were longer when voluntary attention was focused on the lines than when attention was distracted from the lines. In the many attempts to repeat these results, none has ascertained whether attention on reported line length was a phenomenal effect. In the present study, 46 subjects were shown as stimuli pairs of horizontal or vertical briefly flashed lines with a fixation cross placed equidistant between the lines but far from each one. A change in color of one arm of the cross was used as a cue to focus subjects' voluntary attention on one line. Analysis showed attention increased the judged length of attended lines. Since this effect of attention also occurred when subjects were absolutely certain they saw the stimulus lines differed in length, this effect indicates that attention increased the phenomenal length of the attended lines. This lengthening was quite small: it involved a maximum mean increase of about .15 in the probability of the comparative response that the attended line was longer. This effect occurred in the horizontal dimension and was almost absent in the vertical dimension. In agreement with data indicating that flashed lines expand phenomenally by activating motion detectors and that focused attention makes neural motion responses increase in amplitude, the present results suggest that focused attention makes attended lines look longer because it makes these lines expand phenomenally more rapidly.     

The morinaga misalignment effect: Reduction and reversal by modification of figural extremities

Summary In three experiments straight lines varying in length were added to the physically aligned apexes of asymmetrically arranged angles (Experiment 1) and the ends of similarly arranged parallel lines (Experiments 2 and 3). Compared with the condition without added lines, apparent misalignment of the aligned apexes (Morinaga effect) was markedly reduced by the shorter lines and reversed in direction by the longer ones. Apparent misalignment of the ends of parallels was also reduced but not reversed by collinear and right-angle lines. Reduction was greater with the longer collinear lines and with right-angle lines that crossed the parallels a short distance from their ends. These outcomes are interpreted as implicating processes associated with the extremities of figural elements (apexes, ends, and edges) rather than the configuration formed by the elements.     

Measurement of discrimination of separation in elderly persons using a liquid-crystal display and grating method

This study analyzed psychophysical data from younger and elderly people on the influence of spacing between vertical lines, exposure time, and number of vertical lines in a stimulus for visual performance. A total of 50 elderly people and 31 graduate students participated in the experiment. Nine levels of spacing between lines (3, 6, 9, 12, 15, 18, 21, 24, and 29 points), three exposure times (0.2, 0.6, and 1.0 sec.), and five sets of numbers of lines (4, 5, 6, 7, and 8) were manipulated. Analysis showed enhanced spacing between lines and exposure time improved discrimination of separation. However, although performance on discrimination of separation increased as spacing between lines increased up to 21 points, it was degraded at higher values. A positive effect of number of lines on discrimination of separation was also observed, and performance increased as the number of lines decreased. The effect of age group, i.e., elderly versus younger, on performance was significant. The accuracy of the younger was greater than that for the elderly group. Moreover, three interactive two-way effects were found: group x spacing between lines, number of lines x spacing between lines, and number of lines x exposure time. The present findings could be used as a practical reference in the design of instrument displays in which the operator has to consider the scale and markings on a dial, especially if the display is operated in an emergency or is manipulated by elderly people.     

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.     

Effects of luminance ratio in a liquid-crystal display on discrimination of separation by elderly people

In a 2006 study the influence of spacing between vertical lines, exposure time, and number of vertical lines on visual performance was identified. The present study further explored the effects of luminance ratio on discrimination of separation. Analysis showed the luminance ratio of target vertical lines affected the visual performance of both younger and elderly people. The luminance ratio was greater, as was accuracy; however, accuracy might not become greater when the luminance ratio was too high. Further, the effect of the number of vertical lines on accuracy was significant, as was consistent with the 2006 study. Two interactive two-way effects were found, group x luminance ratio and luminance ratio x number of vertical lines.     

Reduction of the Poggendorff effect by the motion of oblique lines

The magnitude of the Poggendorff illusion was measured when the test lines were moved up or down and tracked by subjects. The difference between test lines and inducing lines caused by motion of the test lines significantly reduced the magnitude of illusion (60%). Supplementary experiments seemed to indicate that location of test lines, perceptual shrinkage of space in the vertical dimension, and effective display time were not the main factors contributing to the reduction in illusion magnitude. Instead, it seems that some reduction in interaction between test and inducing lines was the main cause of the reduction. The rising curve of the reduction was very steep with velocity, and the reduction magnitude was almost constant over most of the range of velocities studied. The current evidence seems to suggest that moving and stationary figures are processed by separate channels and that, therefore, the interaction between them is reduced.     

The oblique line illusion: The poggendorff effect without parallels

The apparent misalignment of two oblique collinear lines was investigated in two experiments. In the first the effect with the lines at 45° to the median plane was compared with that for the same two lines separated by the conventional parallels of the Poggendorff figure. The illusion with the two lines was consistent and significant but about one-third the magnitude of that with the parallels. The two illusions were significantly correlated. In the second experiment the angle of the two oblique, collinear lines was varied in 15° steps. The misalignment illusion was maximal at 45° and smaller but significant at 60 and 75°. There was no significant effect at 15 and 30°.     

An “outside-in” processing strategy in the perception of form

The discriminability of line segments in a number of different geometric forms was examined. The procedure used was to have one of the lines within a given form drawn thinner than the other lines. The location of the thin line varied randomly within the form, and subjects were required to detect its location. Three observations were made. First, outer line elements were discriminated more accurately than inner line elements. Second, the outer line advantage appeared to reflect an attentional strategy: By presenting inner and outer lines independently, and informing subjects in advance as to whether target lines would be in the inner or outer area of the form, the outer line advantage could be eliminated. Third, consonant with a global attentional strategy, and in opposition to any retinally tied, peripheral-to-central scanning process, an outer-line advantage was evident regardless of whether the fixation point was positioned within or outside the forms, or whether outer lines were more peripheral than inner lines.     

Aggregation and unit formation in the perception of moving collinear lines

The degree to which collinear lines are treated as a unit in resolving rotary motion in depth was investigated with the use of parallel projection to make direction of motion ambiguous. The proportion of time that the collinear lines appeared to rotate in the same direction was used as an index of their perceptual coherence. When the gap between the lines was small, there was strong grouping of the lines with respect to direction of motion as well as appearance of rigidity for the configuration. For larger gaps the grouping for direction of motion was maintained, but the lines appeared to have different axes of rotation leading to an appearance of nonrigidity. It is concluded that line elements can be aggregated for the resolution of certain properties without constituting a unit in any general sense.     

Position in the visual field and spatial expansion

Measurements of the tilt illusion by parallelism matches have taken as their baseline data estimates of parallelism between two lines. This is because Carpenter and Blakemore and others found in this situation that parallel lines appeared to diverge at their upper ends. It was hypothesised that this effect was due to inappropriate constancy scaling-the parallel lines being interpreted as being located in a receding plane-and that consequently it was inappropriate to take this effect into account in assessing the degree of the tilt illusion. To test the theory, a horizontal line was compared with other horizontal and vertical lines lower down in the visual field. A tendency to underestimate the length of lines lower down in the visual field was found but this varied inversely with distance from the standard. The findings were accounted for on the assumption that the occurrence of inappropriate constancy scaling depended upon prior organization by contiguity which determined whether the two lines were taken as a group or not.     

The aperture problems in the Pulfrich effect

The Pulfrich effect yields a perceived depth for horizontally moving objects but not for vertically moving ones. In this study the Pulfrich effect was measured by translating oblique lines seen through a circular window, which made motion direction ambiguous. Overlaying random dots that moved horizontally, vertically, or diagonally controlled the perceptual motion direction of the lines. In experiment 1, when the lines were seen to move horizontally, the effect was strongest in spite of the same physical motion of the lines. Experiment 2 was performed to test the above conditions again, excluding the Pulfrich effect of the dots on the depth of the lines. The overlaid dots were presented to one eye only. The result showed that the Pulfrich effect of the lines was persistently strong in spite of the perceptual changes in motion direction. Experiment 3 also showed that the Pulfrich depth was independent of the perceived horizontal speed in a plaid display. The Pulfrich effect was determined by measuring the horizontal disparity component, independently of the perceived motion direction. These results demonstrate that the aperture problems in motion and stereopsis in the Pulfrich effect are solved independently.     

A positional discriminability model of linear-order judgments

The process of judging the relative order of stimuli in a visual array was investigated in three experiments. In the basic paradigm, a linear array of six colored lines was presented briefly, and subject decided which of two target lines was the leftmost or rightmost (Experiment 1). The target lines appeared in all possible combinations of serial positions and reaction time (RT) was measured. Distance and semantic congruity effects were obtained, as well as a bowed serial position function. The RT pattern resembled that observed in comparable studies with memorized linear orderings. The serial position function was flattened when the background lines were homogeneously dissimilar to the target lines (Experiment 2). Both a distance effect and bowed serial position functions were obtained when subjects judged which of two target lines was below a black bar cue (Experiment 3). The results favored and analog positional discriminability model over a serial ends-inward scanning model. The positional discriminability model was proposed as a "core model" for the processes involved in judging relative order or magnitude in the domains of memory and perception.     

Perception and masking of wholes and parts

These exerpiments show that the effects of masking on reports of target lines depend on the context in which the target lines appear. Subjects viewed brief presentations of target lines either alone or in drawings of three-dimensional objects, and each target display was preceded and followed by one of several different mask stimuli. There were two main findings: (a) A mask containing a haphazard array of lines interfered more with single lines than it did with lines in objects. (b) A mask containing drawings of the object displays interfered more with lines in objects than did either of two control masks containing relatively flat, less coherent patterns. In a control condition, the object mask interfered slightly less with reports of single lines than either of the control masks did. The discussion considers how the effects obtained here bear on models of the processing of wholistic stimuli and their component parts.     

Preference for opening lines: Comparing ratings by men and women

Opening lines were conceptualized as a method for expanding one's marketplace for dating and marriage partners. In Study 1, university students and employees rated opening lines used by men for meeting women. Respondents (n=600) in one survey rated opening lines for general situations. Respondents (n=431) in a second survey rated opening lines for specific situations, including bars, restaurants, supermarkets, laundromats, and beaches. In Study 2, university students and employees (n=831) rated opening lines used by women for meeting men in general situations. Factor analyses identified three categories of opening lines: cute-flippant, innocuous, and direct. Overall, respondents agreed that cute-flippant opening lines were the least desirable and that innocuous and direct opening lines were the most desirable. Within this general consensus, there was a consistent tendency for women to dislike cute-flippant opening lines more than men and to prefer innocuous opening lines more than men. These differences were related to sex role socialization. Discussion focused on reasons people persist in using cute-flippant opening lines and on an attributional analysis of responses to opening lines.     

How configurations of binocular disparity determine whether stereoscopic slant or stereoscopic occlusion is seen

A partially occluded contour and a slanted contour may generate identical binocular horizontal disparities. We investigated conditions promoting an occlusion resolution indicated by an illusory contour in depth along the aligned ends of horizontally disparate line sets. For a set of identical oblique lines with a constant width added to one eye's view, strength, depth, and stability of the illusory contour were poor, whereas for oblique lines of alternating orientations the illusory contours were strong, indicating a reliance on vertical size disparities rather than vertical positional disparities in generating perceived occlusion. For horizontal lines, occlusion was seen when the lines were of different lengths and absolute width disparity was invariant across the set. In all line configurations, when the additional length was on the wrong eye to be attributed to differential occlusion, lines appeared slanted consistent with their individual horizontal disparities. This rules out monocular illusory contours as the determining factor.     

Confusable gratings selectively elicit orientation-contingent colour aftereffects

Induction of orientation-selective colour aftereffects (the McCollough effect) was studied with groups of young children who differed in their ability to discriminate an oblique grating from its mirror-image under recognition conditions. If the McCollough effect is generated through associative learning, children who failed to learn simple identifying responses to oblique lines as a function of the direction in which the lines point should also fail to associate colour lablels selectively to these same stimuli. Instead, the ease with which the McCollough effect was induced by alternate exposure to left-oblique lines in green light and right-oblique lines in red light was independent of the ability of the young child to discriminate direction of line under recognition conditions.     

Double fusion does not occur in Panum's limiting case: evidence from orientation disparity.

When two lines of different orientations are combined in regular stereograms, the orientation of the resulting line is different from those of the monocular lines. In this study we investigate the percept elicited by orientation disparity in Panum's limiting case. A variant of Panum's limiting case was designed to include orientation disparity. The single line in one half-image tilted leftwards. One of the double lines in the other half-image was parallel to the single line, while the other one tilted rightwards with obliquity one third that of the single line. In this stimulus configuration, if the single line in one half-image fuses with both lines in the other half-image at the same time, both of the two lines perceived after fusion should tilt leftwards. If double fusion does not happen, the two lines should tilt leftwards and rightwards respectively. The results of this study are in agreement with the latter prediction, which implies that double fusion does not occur in this variant of Panum's limiting case.     

Why do children confuse mirror-image obliques?

Thirty-five children aged from 4.17 to 6.58 years were given a delayed-matching task in which they had to choose on each trial which of two lines was the same as a previously displayed standard line. Their choices were no better than random when the lines differed in degree of slope but not in left-right orientation and were only marginally more accurate when the lines were left-right mirror images. Performance improved significantly when the lines differed both in degree of slope from the vertical and in left-right orientation and improved still further if at least one of the lines was horizontal or vertical. The results suggest that young children have extreme difficulty encoding in memory either the degree of slope or the left-right orientation of an oblique line.     

Adaptation to curvature: Eye movements or neural curvature analyzers?

Three experiments were conducted in an attempt to discriminate between an eye-movement theory and a neural curvature analyzer theory of visual adaptation to curvature. Ninety university students served as subjects and were required to inspect stimulus lines presented as (a) curved line pairs, (b) single curved lines, (c) curved line stereograms portraying curved lines concave up, to the right, or toward the subject, or (d) random-dot stereograms portraying curved lines concave up, to the right, or toward the subject. The results of the first two experiments indicate that subjects can readily adapt to the curvature in pairs of lines of opposite curvature presented in different parts of the same or opposite retinas. These results contradict the eye-movement theory of adaptation to curvature. In the third experiment, adaptation to curvature was recorded for curved lines presented as line stereograms and random-dot stereograms. It was concluded that presently the neural curvature analyzer theory of adaptation to curvature best explains the results of these three experiments.