THE DETECTION AND RECOGNITION OF COLOR STIMULI BY HONEYBEES: PERFORMANCE AND MECHANISMS

1997 ◽  
Vol 45 (2-3) ◽  
pp. 129-140 ◽  
Author(s):  
Martin Giurfa ◽  
Misha Vorobyev
Keyword(s):  
Visual Angle ◽  
Angular Size ◽  
Detection Task ◽  
Experimental Paradigm ◽  
Chromatic Contrast ◽  
Y Maze ◽  
Colored Spot ◽  
Colored Disk ◽  
Colored Target ◽  
Detection And Recognition

In a detection paradigm, honeybees Apis mellifera were trained to distinguish between the presence and the absence of a rewarded colored spot, presented on a vertical, achromatic plane in a Y-maze. In a recognition paradigm, bees were trained to distinguish between a trained colored disk and alternative stimuli differing in their green contrast and/or chromatic contrast. Results from the first experimental paradigm allowed the establishment of αmin, the visual angle subtended by a colored target at the bee eye at which the bees detect a given stimulus with a probability Po = 0.6. This angle was 5° for stimuli presenting both chromatic contrast and green contrast, and 15° for stimuli presenting chromatic but no green contrast. Therefore, green contrast contributes decisively to the detection task. Results from the second experimental paradigm showed that chromatic and green contrasts are alternatively used depending on the visual angle subtended by a trained chromatic target and that bees also learn the green-contrast difference between a trained and a nonrewarded alternative. Finally, when trained at different visual angles with an achromatic stimulus providing green contrast, bees were capable of learning and detecting the achromatic target only for visual angles from 10° to 5°. Thus, green-contrast and chromatic-contrast channels are tuned to signals of different angular sizes: the chromatic channel conveys the signals of objects of large angular size, while the green contrast channel conveys those of objects of reduced angular size.

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.

Modeling chromatic contrast sensitivity across different background colors and luminance

2021 ◽  
Vol 2021 (29) ◽  
pp. 99-104
Author(s):  
Marcel Lucassen ◽  
Dragan Sekulovski ◽  
Marc Lambooij ◽  
Qiang Xu ◽  
Ronnier Luo
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Constant Stimulus ◽  
Stimulus Size ◽  
Experimental Paradigm ◽  
Chromatic Contrast ◽  
Data Set ◽  
Contrast Model ◽  
Model Based ◽  
Chromatic Contrast Sensitivity

In this research we compare chromatic contrast sensitivity models for two separate datasets and for the pooled dataset. They were obtained from two studies employing a very similar experimental paradigm. The data represent threshold visibilities of chromatic Gabor patterns varying in spatial frequency, background chromaticity, direction of color modulation and luminance, at constant stimulus size. Using the extended data set, we reconfirm our previously reported finding that a model based on coloropponent contrast signals is an improvement over a cone contrast model. However, when linear background scaling in classic cone contrast is replaced by nonlinear background scaling, an improvement of almost similar size is obtained. The results of this study can be of interest for the development of vision models employing the processing of spatio-chromatic information.

Apparent Afterimage Size, Emmert's Law, and Oculomotor Adjustment

Perception ◽  
10.1068/p5513 ◽  
2007 ◽  
Vol 36 (8) ◽  
pp. 1214-1228 ◽  
Author(s):  
Liang Lou
Keyword(s):  
Visual Angle ◽  
Angular Size ◽  
Apparent Size ◽  
Object Size ◽  
Focal Distance ◽  
Fixed Distance ◽  
Matching Procedure ◽  
Emmert’S Law

The apparent size of an afterimage viewed from distances between 5 cm and 580 cm was matched to that of a size-adjustable stimulus at a fixed distance (20, 30, 90, and 200 cm). The experiment was conducted under normal indoor illumination with a procedure that facilitated matching for angular size. The matched size was found to increase with focal distance within 1 m and very little beyond 1 m. Similar results were obtained with an equivalent series of real stimuli subtending a constant visual angle. These findings suggest a scaling in perceived angular size in proportion to the oculomotor adjustments for accommodation and convergence. The observations of perceived angular size of the afterimage complement what Emmert's law is meant to describe (perceived object size of the afterimage), even though as the focal distance decreases it may be increasingly difficult to tease out perceived object size and perceived angular size with the matching procedure.

scholarly journals V1 mechanisms underlying chromatic contrast detection

2013 ◽  
Vol 109 (10) ◽  
pp. 2483-2494 ◽  
Author(s):  
Charles A. Hass ◽  
Gregory D. Horwitz
Keyword(s):  
Detection Threshold ◽  
Detection Task ◽  
Response Functions ◽  
High Contrast ◽  
Signal To Noise ◽  
Chromatic Contrast ◽  
V1 Neurons ◽  
Detection Analysis ◽  
Contrast Response ◽  
The Relationship

To elucidate the cortical mechanisms of color vision, we recorded from individual primary visual cortex (V1) neurons in macaque monkeys performing a chromatic detection task. Roughly 30% of the neurons that we encountered were unresponsive at the monkeys' psychophysical detection threshold (PT). The other 70% were responsive at threshold but on average, were slightly less sensitive than the monkey. For these neurons, the relationship between neurometric threshold (NT) and PT was consistent across the four isoluminant color directions tested. A corollary of this result is that NTs were roughly four times lower for stimuli that modulated the long- and middle-wavelength sensitive cones out of phase. Nearly one-half of the neurons that responded to chromatic stimuli at the monkeys' detection threshold also responded to high-contrast luminance modulations, suggesting a role for neurons that are jointly tuned to color and luminance in chromatic detection. Analysis of neuronal contrast-response functions and signal-to-noise ratios yielded no evidence for a special set of “cardinal color directions,” for which V1 neurons are particularly sensitive. We conclude that at detection threshold—as shown previously with high-contrast stimuli—V1 neurons are tuned for a diverse set of color directions and do not segregate naturally into red–green and blue–yellow categories.

Target Detection and Texture Segmentation in Briefly Presented Displays of Curved-line Elements

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 135-135
Author(s):  
C J Savage ◽  
D H Foster
Keyword(s):  
Target Detection ◽  
Visual Angle ◽  
Texture Segmentation ◽  
Detection Task ◽  
Percent Correct ◽  
Foreground Region ◽  
Segmentation Task ◽  
Line Elements ◽  
Large Background ◽  
Target Detection Task

Similar pre-attentive processes are often thought to underlie rapid texture segmentation and target ‘pop-out’ in multi-element displays (but see Wolfe, 1992 Vision Research32 757 – 763). Performance in target-detection and texture-segmentation tasks was measured here for briefly presented displays of curved-line elements. In both tasks 49 curved-line elements, each subtending 1 deg of visual angle, were presented in a circular display for 100 ms and followed by a mask. The position of each element in the array was jittered to reduce any possible collinearity or luminance cues. In the target-detection task, observers determined whether the display contained a target which differed in curvature from the other, background elements. In the texture-segmentation task, observers determined the orientation, horizontal or vertical, of a foreground region of 4 × 2 elements which differed in curvature from the background elements. Performance, quantified as percent correct, was measured as a function of target (or foreground) and background curvatures. At small background curvatures, performance in the two tasks was very similar: performance was best when target or foreground curvature was large. Performance differed, however, at large background curvatures: for texture segmentation there was a marked peak in performance when foreground curvature was close to zero, but there was no corresponding peak for target detection. It seems that some additional, global cue can be extracted from a group of straight or slightly curved lines that is not available from a single line, thereby facilitating texture segmentation but not target detection.

The Effects of Age and Visual Capability on Performance with Plane and Convex Mirrors

1974 ◽  
Vol 18 (2) ◽  
pp. 123-128
Author(s):  
Ronald R. Mourant ◽  
Ruth E. DeWalo
Keyword(s):  
Visual Acuity ◽  
Reaction Times ◽  
Recognition Task ◽  
Detection Task ◽  
Target Orientation ◽  
Convex Mirror ◽  
Landolt Ring ◽  
Young Subjects ◽  
Detection And Recognition

Reaction times were measured for a detection task and a recognition task when using plane mirrors and when using convex mirrors. Three groups of nine drivers each (Young, Mature-with Bifocals, and Mature-No Glasses) were studied. The detection task consisted of reporting the number of Landolt Rings (0,1,2,3, or 4) that were made to appear in a mirror. The recognition task consisted of reporting the orientation (left, right, up, or down) of the Landolt Ring gaps. On both the detection and recognition tasks differences between types of subjects increased as the convexity of the mirror increased. The largest differences occured when the images were displayed in a 40 inch convex mirror. Here, Mature-No Glasses subjects took .77 seconds longer to report target orientation than Young subjects. On the same task Mature-Bifocaled subjects took only .18 seconds longer than the Young subjects. Since the longer reaction times of Mature-No Glasses subjects appears to be due to their poorer visual acuity it is recommended that states require higher visual standards with respect to far visual acuity.

Terrestrial-Passage Theory: Failing a Test

Perception ◽  
10.1068/p6162 ◽  
2009 ◽  
Vol 38 (5) ◽  
pp. 740-747
Author(s):  
Charles F Reed ◽  
Elizabeth A Krupinski
Keyword(s):  
Visual Angle ◽  
Angular Size ◽  
The Moon ◽  
Daily Movement ◽  
Significant Difference ◽  
Angular Expansion

Terrestrial-passage theory proposes that the ‘moon’ and ‘sky’ illusions occur because observers learn to expect an elevation-dependent transformation of visual angle. The transformation accompanies daily movement through ordinary environments of fixed-altitude objects. Celestial objects display the same visual angle at all elevations, and hence are necessarily non-conforming with the ordinary transformation. On hypothesis, observers should target angular sizes to appear greater at elevation than at horizon. However, in a sample of forty-eight observers there was no significant difference between the perceived angular size of a constellation of stars at horizon and that predicted for a specific elevation. Occurrence of the illusion was not restricted to those observers who expected angular expansion. These findings fail to support the terrestrial-passage theory of the illusion.

Bees can combine range and visual angle to estimate absolute size

1992 ◽  
Vol 337 (1279) ◽  
pp. 49-57 ◽  
Keyword(s):  
Visual Angle ◽  
Horizontal Plane ◽  
Angular Size ◽  
Vertical Plane ◽  
Vertical Surface ◽  
Sugar Solution ◽  
Absolute Size ◽  
The Absolute ◽  
Circular Target ◽  
Angular Subtense

Previous work has shown that bees can discriminate objects viewed on a vertical plane on the basis of angular size, as well as objects on a horizontal plane on the basis of range. In the present study, we first demonstrate the bees’ ability to measure range to a vertical surface, and discriminate angular subtense to objects on a horizontal plane. The question whether they can combine the independent measurements of angular size and range to infer the absolute size of an object is then examined for the horizontal and vertical planes. Bees were trained to expect a reward of sugar solution when they correctly discriminate a black circular target of fixed absolute size from a similar target which is of different absolute size. Apart from absolute size, the two targets may differ from each other in either angular size, or range, or both, depending on the experiment. In the experiments conducted on a vertical plane, the two targets were each placed in one arm of an Y-shaped choice box. In the experiments on the horizontal plane the bees could freely fly above the targets. In both types of experiments, using a variety of test situations, the bees discriminate the target of a given absolute size irrespective of angular size or range.

Angular size of OH emission regions

1967 ◽  
Vol 31 ◽  
pp. 71-72
Author(s):  
B. F. Burke ◽  
P. P. Crowther ◽  
J. M. Moran ◽  
A. E. E. Rogers ◽  
J. A. Ball ◽  
...  
Keyword(s):  
Angular Size ◽  
Emission Sources ◽  
Ngc 6334

Interferometry gives effective diameters less than 20″ for the OH emission sources in W3and Sgr B2. The sources in W49and NGC 6334 contain two or more components, some of which are smaller than 25″.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

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