Illusory Contours from Pictorially Three-Dimensional Inducing Elements: Counterevidence for Parks and Rock's Example

Perception ◽  
1993 ◽  
Vol 22 (7) ◽  
pp. 809-818 ◽  
Author(s):  
Franco Purghé
Keyword(s):  
Three Dimensional ◽  
Illusory Figure ◽  
Illusory Contours ◽  
Line Elements

In 1990 Parks and Rock claimed that, in pictorially three-dimensional (3-D) inducing patterns, an illusory figure does not emerge if a clear occlusion event is not present. A new pictorially 3-D pattern is presented which contradicts this claim. Two experiments were carried out. The first was aimed at ascertaining the presence of an illusory figure in the new 3-D pattern; the second was aimed at offering evidence that in Parks and Rock's pattern the disappearance of the illusory figure could be due to local interferences caused by the line elements in contact with the inducing borders. The results tend to contradict Parks and Rock's conclusions.

Spectral Sensitivity of Photoreceptors and Colour Vision in the Solitary Bee, Osmia Rufa

1988 ◽  
Vol 136 (1) ◽  
pp. 35-52
Author(s):  
R. MENZEL ◽  
E. STEINMANN ◽  
J. DE SOUZA ◽  
W. BACKHAUS
Keyword(s):  
Spectral Sensitivity ◽  
Colour Vision ◽  
Three Dimensional ◽  
Just Noticeable Difference ◽  
Species Discrimination ◽  
Colour Space ◽  
Absorption Function ◽  
Perceptual Distance ◽  
Line Elements ◽  
Colour Signals

The spectral sensitivity of single photoreceptors of Osmia rufa was determined by a fast voltage-clamp technique. Three receptor types were found whose spectral sensitivity functions followed a rhodopsin-like photopigment absorption function with λmax values at 348nm (ultraviolet receptor), 436nm (blue receptor) and 572nm (green receptor). The λmax of the green receptor in Osmia rufa is shifted to much longer wavelengths compared with other insect species. Discrimination of colour signals was tested after training a bee at the entrance to its nest. The colour signals were filter discs (70 mm in diameter) with a hole (10 mm in diameter) in the centre and the bees quickly learned to use the coloured disc as a marker of the nest entrance. Tests were dual forced-choice tests with two coloured discs closely positioned next to each other. 94 different tests were each repeated 5–15 times and were performed after training to 12 different colour signals. A photoreceptor model was used to calculate the loci of the colour signals in a three-dimensional colour space and in a chromaticity diagram. The perceptual distance between the colour loci was calculated as line elements (minimum number of just noticeable difference, jnd-steps), which were based on the noiseproperties of the photoreceptors. The discrimination determined by the behavioural tests correlated very well with the jnd-steps. The correlation was better for the line elements in the colour plane than in the colour space. Osmia rufa was compared with the honeybee Apis mellifera and the stingless bee Melipona quadrifasciata. There is no difference in colour selection between Osmia and Apis, whereas Melipona discriminates less well in the violet-blue region. The model calculation was used to compare the chromaticity diagrams and the spectral discrimination functions of the three species. It is concluded that the receptor model used in this study predicts the discrimination behaviour of the three bee species very well. Therefore, comparative studies on colour vision in flowervisiting insects may be based on spectral measurements of the photoreceptors, and in many cases this reduces the extent of laborious behavioural studies.

Infants Perceive Three-Dimensional Subjective Contours

Perception ◽  
2018 ◽  
Vol 47 (12) ◽  
pp. 1153-1165 ◽  
Author(s):  
Michael Kavšek ◽  
Stephanie Braun
Keyword(s):  
Three Dimensional ◽  
Two Dimensional ◽  
Illusory Effect ◽  
Horizontal Disparity ◽  
Illusory Contours ◽  
Kanizsa Figure

The addition of crossed horizontal disparity enhances the clarity of illusory contours compared to pictorial illusory contours and illusory contours with uncrossed horizontal disparity. Two infant-controlled habituation–dishabituation experiments explored the presence of this effect in infants 5 months of age. Experiment 1 examined whether infants are able to distinguish between a Kanizsa figure with crossed horizontal disparity and a Kanizsa figure with uncrossed horizontal disparity. Experiment 2 tested infants for their ability to differentiate between a Kanizsa figure with crossed horizontal disparity and a two-dimensional Kanizsa figure. The results provided evidence that the participants perceived the two- and the three-dimensional illusory Kanizsa contour, the illusory effect in which was strengthened by the addition of crossed horizontal disparity.

ANALYSIS ON ATTITUDE POSITION OF EARTH CENTERED INERTIAL (ECI) BASED ON RAZAKSAT DATA

2015 ◽  
Vol 76 (12) ◽  
Author(s):  
Mohd Zamri Hasan ◽  
Sazali Yaacob ◽  
Amran Ahmed ◽  
Nor Hazadura Hamzah ◽  
Shamshul Bahar Yaakob ◽  
...  
Keyword(s):  
Coordinate System ◽  
Reference Frame ◽  
Earth Rotation ◽  
Attitude Determination ◽  
Three Dimensional ◽  
Measurement Data ◽  
Inertial Reference Frame ◽  
Determination System ◽  
Line Elements

Attitude determination system (ADS) is a process to control the orientation of satellite to make sure that the orientation of satellite is relative to inertial reference frame such as Earth. Earth Centered Inertial (ECI) is one of reference frame for satellite that determines the attitude in three dimensional spacecraft. Since RazakSAT orbits on earth, ECI coordinate system will be used for satellite relative to earth rotation. This paper is about the analysis on attitude position of ECI and velocity at X, Y and Z axis based on RazakSAT data. Satellite Tools Kit (STK) is used to estimate the attitude and velocity based on Two Line Elements (TLE) of RazakSAT. The result is compared with RazakSAT measurement data to observe the accuracy of estimation by using STK.

On the Microgenesis of Illusory Figures: A Failure to Replicate

Perception ◽  
1994 ◽  
Vol 23 (7) ◽  
pp. 857-862 ◽  
Author(s):  
Theodore E Parks
Keyword(s):  
Problem Solving ◽  
Viewing Time ◽  
Illusory Figure ◽  
Illusory Contours ◽  
Do So

Reynolds found in 1981 that with increased viewing time of a pattern which may or may not produce illusory contours there were: first, reports of the pattern without an illusory figure; then, at longer exposures, an increase in the frequency with which illusory figures were reported; and then, with still longer exposures, a decrease in such reports if the pattern contained elements which tended to contradict the possibility of such a figure. Unfortunately, however, three attempts to replicate these potentially very important findings—with the aid of substantially improved methodology—consistently failed to do so. It is suggested that this failure, although it is disappointing to those who subscribe to a ‘problem solving’ explanation of illusory contours, may not constitute a strong refutation of such a theory. Regardless, the purpose in the report is to clarify and rectify the published record concerning this part of the evidential underpinnings of that theory.

Amodal Completion versus Induced Inhomogeneities in the Organization of Illusory Figures

Perception ◽  
1992 ◽  
Vol 21 (5) ◽  
pp. 627-636 ◽  
Author(s):  
Marco Davi ◽  
Baingio Pinna ◽  
Marco Sambin
Keyword(s):  
Phenomenological Model ◽  
Control Experiment ◽  
Amodal Completion ◽  
Brightness Contrast ◽  
Primary Factor ◽  
Paired Comparisons ◽  
Illusory Figure ◽  
Illusory Contours ◽  
Energetic Model ◽  
Method Of Paired Comparisons

An analysis is presented of a phenomenological model of illusory contours. The model is based on amodal completion as the primary factor giving rise to the illusory figure. In the experiment, conducted by the method of paired comparisons, the same parameter was manipulated in two series of equivalent configurations. The first series yielded examples of amodal completion, the second examples of illusory figures. Three groups of subjects evaluated the magnitude of completion, the brightness contrast of the illusory figure, and the contour clarity of the illusory figure. A control experiment was conducted, which demonstrated that in these configurations amodal completion and amodal continuation behave in the same way. Line displacement did not influence the brightness or the contour clarity of the illusory figures, though it influenced the magnitude of amodal completion. These results are in agreement with the energetic model developed by Sambin.

Banishing Illusory Contours: A New Possibility

Perception ◽  
1997 ◽  
Vol 26 (6) ◽  
pp. 753-754 ◽  
Author(s):  
Theodore E Parks
Keyword(s):  
Harmful Effect ◽  
Illusory Figure ◽  
Illusory Contours

As an alternative to an earlier hypothesis, it may be that the harmful effect of certain modifications to a pattern which would otherwise produce an illusory figure may be due to excessive coincidences that would be present if an illusory figure were to be seen.

THEORETICAL TRANSFORMS OF THE GRAVITY ANOMALIES OF TWO IDEALIZED BODIES

Geophysics ◽  
1978 ◽  
Vol 43 (3) ◽  
pp. 631-633 ◽  
Author(s):  
Robert D. Regan ◽  
William J. Hinze
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Three Dimensional ◽  
Gravity Anomalies ◽  
Vertical Line ◽  
The Fourier Transform ◽  
Line Elements ◽  
Distribution Of Magnetization

Odegard and Berg (1965) have shown that the interpretational process can be simplified for several idealized bodies by utilizing the Fourier transform of the resultant theoretical gravity anomalies. Additional studies relating similar conclusions for other idealized bodies have been reported by Gladkii (1963), Roy (1967), Sharma et al (1970), Davis (1971), Eby (1972), and Saha (1975), and a summary of the spatial and frequency domain equations is given in Regan and Hinze (1976, Table 1); however, the transforms of the three‐dimensional prism and vertical line elements, often utilized in interpretation, have not been previously examined in this manner. Although Bhattacharyya and Chen (1977) have developed and utilized the transform of the 3-D prism in their method for determining the distribution of magnetization in a localized region, it is still of value to present the interpretive advantages of the transform equation itself.

Illusory Figures from Stereoscopically Three-Dimensional Inducers Depicting No Occlusion Event

Perception ◽  
1995 ◽  
Vol 24 (8) ◽  
pp. 905-918 ◽  
Author(s):  
Franco Purghé
Keyword(s):  
Three Dimensional ◽  
Illusory Figure ◽  
Pictorial Representations ◽  
Contrary Evidence

It has been claimed that an illusory figure is prevented from occurring when there is contrary evidence to occlusion, eg when the inducers are pictorial representations of ‘complete’ three-dimensional (3-D) objects. However, it was recently shown that illusory figures may also be induced by such pictorially 3-D inducers. Here, further evidence on this point is presented. Two experiments were carried out. The first was aimed at showing that an illusory figure can be induced even by stereoscopically 3-D ‘complete’ inducers; the second was aimed at checking whether inducers that are stereoscopically seen as closer than the induced figure can contribute to strengthen the illusion. The results show that stereoscopically 3-D inducing patterns can affect the illusion both in the absence of any occlusion cue and when there is contrary evidence to occlusion. These conclusions seriously challenge all the interpretations that regard occlusion, or interposition, cues as necessary for the formation of illusory figures.

Illusory Contours Do Not Capture Stereopsis—They Just Constrain the Depth Spreading

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 182-182
Author(s):  
J Häkkinen ◽  
I Kojo ◽  
M Liinasuo ◽  
G Nyman
Keyword(s):  
Central Area ◽  
Stereoscopic Depth ◽  
Illusory Figure ◽  
Illusory Contours ◽  
Background Texture ◽  
Background Pattern

If vertical cut-out sectors defining a Kanizsa square are given crossed disparity, the illusory figure appears in depth. Such an illusory figure can pull the background pattern inside the illusory figure to the same depth. It has been assumed that illusory contours are necessary for this phenomenon, which is called stereo capture (Ramachandran, 1986 Perception & Psychophysics39 361 – 373). However, we noticed that the vertical cut-out sectors of the inducing figures (‘pacmen’) are not the only structures that can capture the background texture. The rows of background dots that are enclosed between the disparate vertical cut-out sectors also have unambiguous stereoscopic depth. Thus it might be possible that the disparate rows alone capture the background texture. To investigate our hypothesis we created a stereogram in which the inducing figures were removed. It consisted of a dotted background texture and four areas devoid of dots. The dotless areas corresponded to the areas which were occluded by the original inducing figures. Because of this, the top and bottom rows inside the central area were in crossed disparity. According to our results (a) depth capture also occurred without illusory contours; (b) when illusory contours were not present, the depth of the disparate rows spread more often to other areas. Usually the depth spread first to the central area of the figure and after that horizontally to other areas of the figure. Therefore, we conclude that illusory contours do not capture stereopsis—they just constrain the depth spreading.

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