Apparent Relative Motion from a Checkerboard Surround

Perception ◽  
1997 ◽  
Vol 26 (7) ◽  
pp. 831-846 ◽  
Author(s):  
Byung-Geun Khang ◽  
Edward A Essock
Keyword(s):  
Phase Shift ◽  
Relative Motion ◽  
Gain Control ◽  
Chromatic Contrast ◽  
Common Fate ◽  
Spatial Properties ◽  
Test Grating ◽  
Achromatic Contrast ◽  
Constituent Elements ◽  
Possible Cause

To better understand the Ouchi illusion in which a stationary picture generates illusory relative motion, the spatial properties of the constituent elements of the rectangular checkerboard background were examined. Results of experiment 1 revealed that the largest illusion was obtained with elements of approximately 20–30 min in width and 4–6 min in height, an orientation of the constituents that was orthogonal to that of the test grating, and a phase shift of the alternate stripes that was close to 180°. In experiment 2 it was found that the illusion increased in magnitude with increasing achromatic contrast but was minimal with a pattern of high chromatic contrast near isoluminance. In experiment 3, two test patches were presented simultaneously in the checkerboard background and were varied independently in their orientation to explore whether or not their motions were perceived as coherent (common fate). Patches having identical orientations, and nearly orthogonal to the surround, were synchronized more strongly than those having reflected orientations. Hysteresis related to the gain control of spatially overlapping visual units differing in their polarity (ON/OFF) was discussed as a possible cause of this phenomenon.

scholarly journals Triggerfish uses chromaticity and lightness for object segregation

2017 ◽  
Vol 4 (12) ◽  
pp. 171440 ◽  
Author(s):  
Laurie Mitchell ◽  
Karen L. Cheney ◽  
Fabio Cortesi ◽  
N. Justin Marshall ◽  
Misha Vorobyev
Keyword(s):  
Visual Perception ◽  
Human Visual Perception ◽  
Chromatic Contrast ◽  
Visual Patterns ◽  
Ishihara Test ◽  
Achromatic Contrast ◽  
Chromatic Cues ◽  
Object Segregation

Humans group components of visual patterns according to their colour, and perceive colours separately from shape. This property of human visual perception is the basis behind the Ishihara test for colour deficiency, where an observer is asked to detect a pattern made up of dots of similar colour with variable lightness against a background of dots made from different colour(s) and lightness. To find out if fish use colour for object segregation in a similar manner to humans, we used stimuli inspired by the Ishihara test. Triggerfish ( Rhinecanthus aculeatus ) were trained to detect a cross constructed from similarly coloured dots against various backgrounds. Fish detected this cross even when it was camouflaged using either achromatic or chromatic noise, but fish relied more on chromatic cues for shape segregation. It remains unknown whether fish may switch to rely primarily on achromatic cues in scenarios where target objects have higher achromatic contrast and lower chromatic contrast. Fish were also able to generalize between stimuli of different colours, suggesting that colour and shape are processed by fish independently.

scholarly journals Spatio-chromatic contrast sensitivity across the lifespan: interactions between age and light level in high dynamic range

2020 ◽  
Vol 2020 (28) ◽  
pp. 65-69
Author(s):  
Maliha Ashraf ◽  
Sophie Wuerger ◽  
Minjung Kim ◽  
Jasna Martinovic ◽  
Rafał K. Mantiuk
Keyword(s):  
Contrast Sensitivity ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Light Level ◽  
Background Luminance ◽  
Age Group ◽  
Chromatic Contrast ◽  
Achromatic Contrast ◽  
High Dynamic ◽  
Chromatic Contrast Sensitivity

We investigated spatio-chromatic contrast sensitivity in both younger and older color-normal observers. We tested how the adapting light level affected the contrast sensitivity and whether there was a differential age-related change in sensitivity. Contrast sensitivity was measured along three directions in colour space (achromatic, red-green, yellowish-violet), at background luminance levels from 0.02 to 2000 cd/m2, and different stimuli sizes using 4AFC method on a high dynamic range display. 20 observers with a mean age of 33 y. o. a. and 20 older observers with mean age of 65 participated in the study. Within each session, observers were fully adapted to the fixed background luminance. Our main findings are: (1) Contrast sensitivity increases with background luminance up to around 200 cd/m2, then either declines in case of achromatic contrast sensitivity, or remains constant in case of chromatic contrast sensitivity; (2) The sensitivity of the younger age group is higher than that for the older age group by 0.3 log units on average. Only for the achromatic contrast sensitivity, the old age group shows a relatively larger decline in sensitivity for medium to high spatial frequencies at high photopic light levels; (3) Peak frequency, peak sensitivity and cut-off frequency of contrast sensitivity functions show decreasing trends with age and the rate of this decrease is dependent on mean luminance. The data is being modeled to predict contrast sensitivity as a function of age, luminance level, spatial frequency, and stimulus size.

scholarly journals A scalar geodesic deviation equation and a phase theorem

1983 ◽  
Vol 6 (4) ◽  
pp. 795-802 ◽  
Author(s):  
P. Choudhury ◽  
P. Dolan ◽  
N. S. Swaminarayan
Keyword(s):  
Gravitational Field ◽  
Phase Shift ◽  
Relative Motion ◽  
Plane Waves ◽  
Relative Energy ◽  
Positive Definite ◽  
Geodesic Deviation ◽  
Deviation Equation ◽  
Test Particles ◽  
Geodesic Deviation Equation

A scalar equation is derived forη, the distance between two structureless test particles falling freely in a gravitational field:η¨+(K−Ω2)η=0. An amplitude, frequency and a phase are defined for the relative motion. The phases are classed as elliptic, hyperbolic and parabolic according asK−Ω2>0,<0,=0.In elliptic phases we deduce a positive definite relative energyEand a phase-shift theorem. The relevance of the phase-shift theorem to gravitational plane waves is discussed.

scholarly journals Assessing bird avoidance of high-contrast lights using a choice test approach: implications for reducing human-induced avian mortality

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5404 ◽  
Author(s):  
Benjamin Goller ◽  
Bradley F. Blackwell ◽  
Travis L. DeVault ◽  
Patrice E. Baumhardt ◽  
Esteban Fernández-Juricic
Keyword(s):  
Light Emitting Diode ◽  
Visual Saliency ◽  
Choice Test ◽  
Visual Perspective ◽  
Chromatic Contrast ◽  
Light Emitting ◽  
Behavioral Assay ◽  
Achromatic Contrast ◽  
Species Specific ◽  
Led Lights

Background Avian collisions with man-made objects and vehicles (e.g., buildings, cars, airplanes, power lines) have increased recently. Lights have been proposed to alert birds and minimize the chances of collisions, but it is challenging to choose lights that are tuned to the avian eye and can also lead to avoidance given the differences between human and avian vision. We propose a choice test to address this problem by first identifying wavelengths of light that would over-stimulate the retina using species-specific perceptual models and by then assessing the avoidance/attraction responses of brown-headed cowbirds to these lights during daytime using a behavioral assay. Methods We used perceptual models to estimate wavelength-specific light emitting diode (LED) lights with high chromatic contrast. The behavioral assay consisted of an arena where the bird moved in a single direction and was forced to make a choice (right/left) using a single-choice design (one side with the light on, the other with the light off) under diurnal light conditions. Results First, we identified lights with high saliency from the cowbird visual perspective: LED lights with peaks at 380 nm (ultraviolet), 470 nm (blue), 525 nm (green), 630 nm (red), and broad-spectrum (white) LED lights. Second, we found that cowbirds significantly avoided LED lights with peaks at 470 and 630 nm, but did not avoid or prefer LED lights with peaks at 380 and 525 nm or white lights. Discussion The two lights avoided had the highest chromatic contrast but relatively lower levels of achromatic contrast. Our approach can optimize limited resources to narrow down wavelengths of light with high visual saliency for a target species leading to avoidance. These lights can be used as candidates for visual deterrents to reduce collisions with man-made objects and vehicles.

scholarly journals In a Neotropical Periurban Park, Fruit Consumption by Birds Seems to Be a Random Process

2021 ◽  
Vol 9 ◽  
Author(s):  
Issaac Azrrael Teodosio-Faustino ◽  
Edgar Chávez-González ◽  
Ernesto Ruelas Inzunza
Keyword(s):  
Random Process ◽  
Probabilistic Models ◽  
Null Model ◽  
Interaction Network ◽  
Chromatic Contrast ◽  
Fruit Consumption ◽  
Pairwise Interactions ◽  
Multiple Variable ◽  
Achromatic Contrast

Frugivory interactions between birds and fruit-bearing plants are shaped by the abundance of its interacting species, their temporal overlap, the matching of their morphologies, as well as fruit and seed characteristics. Our study evaluates the role of seven factors of fruits and plants in determining the frequency of whole-fruit consumption by birds. We studied the frugivory network of a Neotropical periurban park in Xalapa, Veracruz, Mexico, and quantified relative abundance and phenology of birds and fruit, as well as fruit morphology, chromatic and achromatic contrast, and nutritional content. Using a maximum likelihood approach, we compared the observed interaction network with 62 single- and multiple-variable probabilistic models. Our network is composed of 11 plants and 17 birds involved in 81 frugivory interactions. This network is nested, modular, and relatively specialized. However, the frequency of pairwise interactions is not explained by the variables examined in our probabilistic models and found the null model has the best performance. This indicates that no single predictor or combination of them is better at explaining the observed frequency of pairwise interactions than the null model. The subsequent four top-ranking models, with ΔAIC values &lt; 100, are single-variable ones: carbohydrate content, lipid content, chromatic contrast, and morphology. Two- and three-variable models show the poorest fit to observed data. The lack of a deterministic pattern does not support any of our predictions nor neutral- or niche-based processes shaping the observed pattern of fruit consumption in our interaction network. It may also mean that fruit consumption by birds in this periurban park is a random process. Although our study failed to find a pattern, our work exemplifies how investigations done in urban settings, poor in species and interactions, can help us understand the role of disturbance in the organization of frugivory networks and the processes governing their structure.

NONCONTACT MONITORING OF RESPIRATION BASED ON AN ULTRASONIC PHASE-SHIFT RECONSTRUCTION METHOD

2002 ◽  
Vol 14 (06) ◽  
pp. 262-268 ◽  
Author(s):  
K. N. HUANG ◽  
Y. C. LI ◽  
M. S. YOUNG
Keyword(s):  
Phase Shift ◽  
Phase Angle ◽  
Relative Motion ◽  
Low Cost ◽  
Sleep Apnea Syndrome ◽  
Ultrasonic Transducers ◽  
Vibration Measurement ◽  
Reconstruction Method ◽  
Respiration Monitoring ◽  
Ingenious Method

We have developed a novel noncontact respiration monitoring that utilized an ultrasonic phase-shift reconstruction method for measuring the normal vibration of chest-wall. In this paper, a simple but efficient method for vibration measurement is adopted for the sleep apnea syndrome. The instrument consists of a pair of 40 kHz ultrasonic transducers which are used in a transmit-receive mode to get the motion of a point on a vibration object. The relative motion of the object modulates the phase angle between transmitted and received ultrasound signals. We have also developed an ingenious method to reconstruct the relative motion of an object from the acquired data of the phase angle changes. The measurement accuracy of the system in the reported experiments is within +/− 0.07 mm. The main advantages of this vibration measurement system are high resolution, low cost, and noncontact measurement.

scholarly journals Chromatic and achromatic monocular deprivation produce separable changes of eye dominance in adults

2017 ◽  
Vol 284 (1867) ◽  
pp. 20171669 ◽  
Author(s):  
Jiawei Zhou ◽  
Alexandre Reynaud ◽  
Yeon Jin Kim ◽  
Kathy T. Mullen ◽  
Robert F. Hess
Keyword(s):  
Contrast Sensitivity ◽  
Monocular Deprivation ◽  
Chromatic Contrast ◽  
Eye Dominance ◽  
Colour Contrast ◽  
Human Adults ◽  
Achromatic Contrast ◽  
Perceptual Changes ◽  
Chromatic Contrast Sensitivity

Temporarily depriving one eye of its input, in whole or in part, results in a transient shift in eye dominance in human adults, with the patched eye becoming stronger and the unpatched eye weaker. However, little is known about the role of colour contrast in these behavioural changes. Here, we first show that the changes in eye dominance and contrast sensitivity induced by monocular eye patching affect colour and achromatic contrast sensitivity equally. We next use dichoptic movies, customized and filtered to stimulate the two eyes differentially. We show that a strong imbalance in achromatic contrast between the eyes, with no colour content, also produces similar, unselective shifts in eye dominance for both colour and achromatic contrast sensitivity. Interestingly, if this achromatic imbalance is paired with similar colour contrast in both eyes, the shift in eye dominance is selective, affecting achromatic but not chromatic contrast sensitivity and revealing a dissociation in eye dominance for colour and achromatic image content. On the other hand, a strong imbalance in chromatic contrast between the eyes, with no achromatic content, produces small, unselective changes in eye dominance, but if paired with similar achromatic contrast in both eyes, no changes occur. We conclude that perceptual changes in eye dominance are strongly driven by interocular imbalances in achromatic contrast, with colour contrast having a significant counter balancing effect. In the short term, eyes can have different dominances for achromatic and chromatic contrast, suggesting separate pathways at the site of these neuroplastic changes.

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