Component Analysis of Orientation Illusions

Perception ◽  
1977 ◽  
Vol 6 (1) ◽  
pp. 57-75 ◽  
Author(s):  
Peter Wenderoth ◽  
Helen Beh
Keyword(s):  
Spatial Frequency ◽  
Indirect Effects ◽  
Component Analysis ◽  
Angular Function ◽  
Local Component ◽  
Tilt Illusion ◽  
Global Orientation ◽  
Positive Direct ◽  
Rod And Frame

Orientation illusions occur when the inducing figure is a line or grating (the tilt illusion) or a square outline frame (the rod-and-frame illusion). In the range of inducing figure tilts between vertical and horizontal, the tilt illusion describes one cycle of positive (direct) and negative (indirect) effects but the rod-and-frame illusion describes two such cycles. In two experiments, angular functions of illusions were measured with the six possible inducing figures which result when two of the four sides of a square inducing frame are deleted. As expected, the parallel-sided frame amputations induced angular functions similar to the tilt illusion and these functions differed from those induced by the orthogonal-sided amputations. In agreement with previous findings on the nonadditivity of tilt illusions, the sum of angular functions induced by frame amputations, which together form a complete frame, were not always equivalent to the angular function induced by a complete frame, and there were asymmetries in the data for which neither of two simple hypotheses could adequately account. The discussion focuses upon properties of inducing figures which psychophysical hypotheses might need to consider in order to account for the shapes of angular functions of orientation illusions and, in particular, a distinction is drawn between the global orientation of the inducing figure and the orientations of its (local) component features. It is suggested that it might be fruitful if the tilt illusion and the rod-and-frame illusion were conceived of as illusions resulting from inducing figures composed of all or part of n gratings of spatial frequency fn intersecting at angles of 180°/ n.

Exposure-Time and Spatial-Frequency Effects in the Tilt Illusion

Perception ◽  
1979 ◽  
Vol 8 (5) ◽  
pp. 557-564 ◽  
Author(s):  
Brian I O'Toole
Keyword(s):  
Spatial Frequency ◽  
Indirect Effects ◽  
Time Course ◽  
Test Line ◽  
Acute Angle ◽  
Direct Effects ◽  
Time Constants ◽  
Frequency Effects ◽  
Tilt Illusion ◽  
Vertical Test

The exposure durations of a vertical test line and a tilted inducing grating were varied and the tilt illusion thus generated was found to change as a function of this variation. Significant direct effects (acute-angle expansion) and indirect effects (acute-angle contraction) were found to occur at times consistent with Andrews's estimate of the time course of inhibition in the visual system when the inducing grating had a spatial frequency of 10 cycles deg−1. However, a 2 · 71 cycles deg−1 grating gave significant effects at exposure durations of 10 as well as 1000 ms, while in a further experiment a 10 · 91 cycles deg−1 grating gave significant effects at 1000 ms only. These results seem to suggest that orientation interactions thought to be due to inhibition (direct effect) and disinhibition (indirect effect) may occur within both sustained and transient channels with concomitant differences in time constants.

Two-Dimensional Tilt Illusions Induced by Orthogonal Plaid Patterns: Effects of Plaid Motion, Orientation, Spatial Separation, and Spatial Frequency

Perception ◽  
1989 ◽  
Vol 18 (1) ◽  
pp. 25-38 ◽  
Author(s):  
Peter Wenderoth ◽  
Syren Johnstone ◽  
Rick Van der Zwan
Keyword(s):  
Spatial Frequency ◽  
Real Line ◽  
Repeated Measures ◽  
Spatial Separation ◽  
Frequency Condition ◽  
Angular Function ◽  
Frame Effect ◽  
Tilt Illusion ◽  
Plaid Motion ◽  
Axes Of Symmetry

Tilt illusions occur when a drifting vertical test grating is surrounded by a drifting plaid pattern composed of orthogonal moving gratings. The angular function of this illusion was measured as the plaid orientation (and therefore its drift direction) varied over a 180° range, This was done when the test and inducing stimuli abutted and had the same spatial frequency, and when the test and inducing stimuli either differed in frequency by an octave, or were spatially separated by a 2 deg blank annulus, or both differed in frequency and were also separated by the annulus (experiments 1–4). The obtained angular function was virtually identical to that obtained previously with the rod and frame effect and other cases involving orthogonal inducing components, with evidence for illusions induced both by real-line components and by virtual axes of symmetry. Although the magnitude of the illusion was very similar in all four experiments, there was evidence to suggest that largest real-line effects occurred in the abutting same-frequency condition, with a pattern of results similar to that obtained previously with the simple one-dimensional tilt illusion. On the other hand, virtual-axis effects were more prominent with gaps between test and inducing stimuli. A fifth, repeated-measures, experiment confirmed this pattern of results. It is suggested that this pattern-induced tilt effect reflects both striate and extrastriate mechanisms and that the apparent influence of spatially distal virtual axes of symmetry upon perceived orientation implies the existence of AND-gate mechanisms, or conjunction detectors, in the orientation domain.

The Distinction between the Rod-and-Frame Illusion and the Rod-and-Frame Test

Perception ◽  
1974 ◽  
Vol 3 (2) ◽  
pp. 205-212 ◽  
Author(s):  
P M Wenderoth
Keyword(s):  
Angular Function ◽  
Frame Effect ◽  
Tilt Illusion ◽  
Single Frame ◽  
Frame Tilt ◽  
Attraction Effects ◽  
Gravitational Vertical ◽  
Rod And Frame Test ◽  
Rod And Frame

Errors in vertical settings of a test rod occur when the rod is enclosed in a laterally-tilted square-outline frame. The majority of previous experiments which have investigated this rod-and-frame effect have used a single frame tilt, usually 28°, and have tabulated errors as average unsigned deviations from gravitational vertical. Evidence is presented that, when the illusion is measured by taking algebraic differences between constant (signed) errors made with and without the frame being present, illusions occur in the direction of frame tilt for frame tilts up to about 25° from vertical (repulsion effects) but that directionally opposite illusions (attraction effects) occur for frame tilts between 25° and 45°. At the frame tilts used most frequently in previous studies (25° to 30°) little or no illusion occurs. A distinction is drawn between the rod-and-frame illusion (RFI), which has an angular function similar to the simple tilt illusion and aftereffect, and the rod-and-frame test (RFT), which uses unsigned deviations from vertical as its measure of error and which probably bears little or no relationship to the RFI.

Obliquity Integration: Variations on a Theme of Delbœuf

Perception ◽  
1993 ◽  
Vol 22 (6) ◽  
pp. 705-712
Author(s):  
Giovanni B Vicario ◽  
Giulio Vidotto ◽  
Elena Zambianchi
Keyword(s):  
Frame Of Reference ◽  
The Other ◽  
Geometrical Illusion ◽  
Tilt Illusion ◽  
Variations On A Theme ◽  
Rod And Frame

An optical—geometrical illusion, described by Delbœuf and not familiar to specialists, is investigated. The results of two experiments show that the divergence between a bar filled with parallel slanting lines and a line drawn above it is clearly related to this angle of the lines which fill the bar. The illusion is already present when this angle is 10°, reaches its maximum at 20°, decreases at 30°, and almost disappears at 40°. These results are similar to those found for the tilt illusion, are slightly different from those found for the rod-and-frame illusion, and differ greatly from those found for the Zöllner illusion. The other variables considered—the distance between the slanting lines filling up the bar, the distance between the upper line and the bar, and the width of the bar—do not influence the illusion as much. Since either the line appears as diverging from the bar, or the bar seems inclined in relation to the line, the illusion should be considered a complex one. The small oblique lines inside the bar induce obliquity in the opposite sense in the display, but which of the elements is seen as diverging from the other depends on which of the two is established as the frame of reference.

scholarly journals Consequentialism, Indirect Effects and Fair Trade

Utilitas ◽  
2012 ◽  
Vol 24 (1) ◽  
pp. 126-138 ◽  
Author(s):  
ANDREW WALTON
Keyword(s):  
Fair Trade ◽  
Indirect Effects ◽  
Poverty Reduction ◽  
Direct Effects ◽  
Positive Direct ◽  
The Impact

In this article I consider two consequentialist positions on whether individuals in affluent countries ought to purchase Fair Trade goods. One is a narrow argument, which asserts that individuals should purchase Fair Trade goods because this will have positive direct effects on poverty reduction, by, for example, channelling money into development. I argue that this justification is insufficient to show that individuals should purchase Fair Trade goods because individuals could achieve similar results by donating money to charity and, therefore, without purchasing Fair Trade goods. The second position has a wider focus. It notes both the direct effects of purchasing Fair Trade goods and possible indirect effects, such as the impact this might have on other individuals. I argue that certain actions, of which Fair Trade is one example, will be more likely to encourage individuals who would not otherwise contribute to poverty reduction to contribute and that this may produce additional positive value. Although space prohibits specific conclusions about Fair Trade, I note that considerations of this kind could give us reason to purchase such goods beyond those that issue from the direct effects of doing so and that, as such, they are crucial for determining whether individuals should purchase Fair Trade goods.

scholarly journals The Role of the Academic and Political Empowerment of Women in Economic, Social and Managerial Empowerment: The Case of Saudi Arabia

Economies ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 45 ◽  
Author(s):  
Maleeha Mohammed Zaaf Al-Qahtani ◽  
Tarek Tawfik Yousef Alkhateeb ◽  
Haider Mahmood ◽  
Manal Abdalla Zahed Abdalla ◽  
Thikkryat Jebril Obaid Talalah Qaralleh
Keyword(s):  
Sustainable Development ◽  
Saudi Arabia ◽  
Direct Effect ◽  
Indirect Effects ◽  
Equation Modeling ◽  
Female Empowerment ◽  
The Political ◽  
Political Empowerment ◽  
Positive Effects ◽  
Positive Direct

Women may be considered to have hidden, unutilized potential for the economy and society, if not utilized at their full capacity, i.e., with effective educational, social and political policies. Allowing women to participate fully in an economy may contribute to the sustainable development of the country in question. The empowerment of women may be accelerated if women are educated for this purpose; as a result, the political authorities in Saudi Arabia have proposed a comprehensive framework to empower women. The empowerment of women is essential in the academic sector to develop educational policies for women’s capacity-building. The empowerment of women in the political process is also very important, so they can suggest appropriate policies, rules and laws that favor the empowerment of women in all sectors of the economy and society. The present research aims at testing the effects of academic and political empowerment on the economic, social and managerial empowerment of women, and opens a new horizon of debate in the practical and theoretical domain of female empowerment in Saudi Arabia. To this end, we utilized structural equation modeling due to the endogenous nature of relationships among the hypothesized variables. Perception-based data were collected on the political, academic, economic, social and managerial empowerment of women through a well-structured questionnaire. The data were collected during the period from October 2019 to January 2020 through a simple random sampling method. Then, we tested the direct effect of political empowerment, and its indirect effects through academic empowerment, on the economic, social and managerial empowerment of women. We found that political empowerment has a positive direct effect on economic and managerial empowerment, but an insignificant effect on social empowerment. Further, political empowerment has a positive direct effect on academic empowerment, which, in turn, has positive effects on economic, social and managerial female empowerment. Moreover, these indirect effects are found to be magnitudes larger than the direct effects of political empowerment. This study recommends improving the economic, social and political status of women through political and academic policies, to accelerate sustainable development.

Large Errors in the Perception of Verticality are Generated by Luminance Borders (Integrated across Space) Not by Subjective Borders

Perception ◽  
10.1068/p3070 ◽  
2001 ◽  
Vol 30 (2) ◽  
pp. 177-184
Author(s):  
Donatella Spinelli ◽  
Gabriella Antonucci ◽  
Maria Luisa Martelli ◽  
Pierluigi Zoccolotti
Keyword(s):  
Opposite Direction ◽  
Subjective Contour ◽  
Standard Condition ◽  
Global Orientation ◽  
Tilted Frame ◽  
Frame Tilt ◽  
Visual Vertical ◽  
Perception Of Verticality ◽  
Rod And Frame

The rod-and-frame illusion shows large errors in the judgment of visual vertical in the dark if the frame is large and there are no other visible cues (Witkin and Asch, 1948 Journal of Experimental Psychology38 762–782). Three experiments were performed to investigate other characteristics of the frame critical for generating these large errors. In the first experiment, the illusion produced by an 11° tilted frame made by luminance borders (standard condition) was considerably larger than that produced by a subjective-contour frame. In the second experiment, with a 33° frame tilt, the illusion was in the direction of frame tilt with a luminance-border frame but in the opposite direction in the subjective-contour condition. In the third experiment, to contrast the role of local and global orientation, the sides of the frame were made of short separate luminous segments. The segments could be oriented in the same direction as the frame sides, in the opposite direction, or could be vertical. The orientation of the global frame dominated the illusion while local orientation produced much smaller effects. Overall, to generate a large rod-and-frame illusion in the dark, the tilted frame must have luminance, not subjective, contours. Luminance borders do not need to be continuous: a frame made of sparse segments is also effective. The mechanism responsible for the large orientation illusion is driven by integrators of orientation across large areas, not by figural operators extracting shape orientation in the absence of oriented contours.

Respective Contribution of Orientation Contrast and Illusion of Self-Tilt to the Rod-And-Frame Effect

Perception ◽  
1995 ◽  
Vol 24 (6) ◽  
pp. 623-630 ◽  
Author(s):  
Corinne Cian ◽  
Dominique Esquivié ◽  
Pierre Alain Barraud ◽  
Christian Raphel
Keyword(s):  
Contrast Effect ◽  
Visual Angle ◽  
Angular Size ◽  
The Other ◽  
Frame Effect ◽  
Tilt Illusion ◽  
Orientation Contrast ◽  
Respective Contribution ◽  
Adjustment Test ◽  
Rod And Frame

The visual angle subtended by the frame seems to be an important determinant of the contribution of orientation contrast and illusion of self-tilt (ie vection) to the rod-and-frame effect. Indeed, the visuovestibular factor (which produces vection) seems to be predominant in large displays and the contrast effect in small displays. To determine how these two phenomena are combined to account for the rod-and-frame effect, independent estimates of the magnitude of each component in relation to the angular size subtended by the display were examined. Thirty-five observers were exposed to three sets of experimental situations: body-adjustment test (illusion of self-tilt only), the tilt illusion (contrast only) and the rod-and-frame test, each display subtending 7, 12, 28, and 45 deg of visual angle. Results showed that errors recorded in the three situations increased linearly with the angular size. Whatever the size of the frame, both mechanisms, contrast effect (tilt illusion) and illusory effect on self-orientation (body-adjustment test), are always present. However, rod-and-frame errors became greater at a faster rate than the other two effects as the size of the stimuli became larger. Neither one nor the other independent phenomen, nor the combined effect could fully account for the rod-and-frame effect whatever the angular size of the apparatus.

scholarly journals Path analysis of iron and zinc contents and others traits in cowpea

2012 ◽  
Vol 12 (4) ◽  
pp. 245-252 ◽  
Author(s):  
Jeane de Oliveira Moura ◽  
Maurisrael de Moura Rocha ◽  
Regina Lúcia Ferreira Gomes ◽  
Francisco Rodrigues Freire Filho ◽  
Kaesel Jackson Damasceno e Silva ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Yield ◽  
Path Analysis ◽  
Protein Content ◽  
Indirect Effects ◽  
Zinc Content ◽  
Direct Selection ◽  
Direct And Indirect Effects ◽  
Iron And Zinc ◽  
Positive Direct

The objective of this study was to estimate the direct and indirect effects of agronomic and culinary traits on iron and zinc contents in 11 cowpea populations. Correlations between traits were estimated and decomposed into direct and indirect effects using path analysis. For the study populations, breeding for larger grain size, higher number of grains per pod, grain yield, reduced cooking time, and number of days to flowering can lead to decreases in the levels of iron and zinc in the grain. Genetic gains for the iron content can be obtained by direct selection for protein content by indirect effects on the number of grains per pod, 100-grain weight and grain yield. The positive direct effect of grain size and protein content on the zinc content indicates the possibility of simultaneous gain by combined selection of these traits.

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