Search results for "Color Perception"
showing 10 items of 71 documents
Variable crab camouflage patterns defeat search image formation.
2021
Understanding what maintains the broad spectrum of variation in animal phenotypes and how this influences survival is a key question in biology. Frequency dependent selection – where predators temporarily focus on one morph at the expense of others by forming a “search image” – can help explain this phenomenon. However, past work has never tested real prey colour patterns, and rarely considered the role of different types of camouflage. Using a novel citizen science computer experiment that presented crab “prey” to humans against natural backgrounds in specific sequences, we were able to test a range of key hypotheses concerning the interactions between predator learning, camouflage and mor…
The biology of color
2017
In living color Animals live in a colorful world, but we rarely stop to think about how this color is produced and perceived, or how it evolved. Cuthill et al. review how color is used for social signals between individual animals and how it affects interactions with parasites, predators, and the physical environment. New approaches are elucidating aspects of animal coloration, from the requirements for complex cognition and perception mechanisms to the evolutionary dynamics surrounding its development and diversification. Science , this issue p. eaan0221
Which Attribute of Ceiling Color Influences Perceived Room Height?
2018
Objective:We investigate effects of the hue, saturation, and luminance of ceiling color on the perceived height of interior spaces.Background:Previous studies have reported that the perceived height of an interior space is influenced by the luminance of the ceiling, but not by the luminance contrast between ceiling and walls: brighter ceilings appeared higher than darker ceilings, irrespective of wall and floor luminance. However, these studies used solely achromatic colors. We report an experiment in which we extend these findings to effects of chromatic ceiling colors.Methods:We presented stereoscopic room simulations on a head-mounted display (Oculus Rift DK2) and varied hue (red, green,…
Can colours be used to segment words when reading?
2015
Rayner, Fischer, and Pollatsek (1998, Vision Research) demonstrated that reading unspaced text in Indo-European languages produces a substantial reading cost in word identification (as deduced from an increased word-frequency effect on target words embedded in the unspaced vs. spaced sentences) and in eye movement guidance (as deduced from landing sites closer to the beginning of the words in unspaced sentences). However, the addition of spaces between words comes with a cost: nearby words may fall outside high-acuity central vision, thus reducing the potential benefits of parafoveal processing. In the present experiment, we introduced a salient visual cue intended to facilitate the process…
Influence of the luminance level on visual performance with a disposable soft cosmetic tinted contact lens.
2001
The purpose of the present work was to study the effect on visual performance of wearing disposable soft tinted contact lenses for cosmetic purposes. Parameters such as contrast sensitivity (Vistech 6000), colour vision (Farnsworth-Munsell 100-Hue colour test), visual fields (static Goldmann perimetry) and subjective vision (what the wearer feels while wearing the lenses) were studied under different illumination levels in order to check for possible vision losses while wearing these contact lenses at low illumination levels. Sixteen emmetropic subjects were fitted consecutively with seven pairs of different colour lenses (Optima Colors lenses by BauschLomb), and the experimental parameters…
The effect of longitudinal chromatic aberration on the lag of accommodation and depth of field.
2016
Purpose Longitudinal chromatic aberration is present in all states of accommodation and may play a role in the accommodation response and the emmetropisation process. We study the change of the depth of field (DOFi) with the state of accommodation, taking into account the longitudinal chromatic aberration. Methods Subjective DOFi was defined as the range of defocus beyond which the blur of the target (one line of optotypes of 0.1 logMAR shown on a black-and-white microdisplay, seen through different colour filters) was perceived as objectionable. The subject's eye was paralysed and different, previously-measured accommodative states (corresponding to the accommodative demands of 0D, 2D and …
Prismatic lenses shift time perception
2009
Previous studies have demonstrated the involvement of spatial codes in the representation of time and numbers. We took advantage of a well-known spatial modulation (prismatic adaptation) to test the hypothesis that the representation of time is spatially oriented from left to right, with smaller time intervals being represented to the left of larger time intervals. Healthy subjects performed a time-reproduction task and a time-bisection task, before and after leftward and rightward prismatic adaptation. Results showed that prismatic adaptation inducing a rightward orientation of spatial attention produced an overestimation of time intervals, whereas prismatic adaptation inducing a leftward…
Colour Constancy in Goldfish and Man: Influence of Surround Size and Lightness
2002
Colour constancy was investigated by using a series of 10 simultaneously presented surface colours ranging in small steps from green through gray to red – purple. Goldfish were trained to select one medium test field when the entire setup was illuminated with white light. In the tests, either red or green illumination was used. Colour constancy, as inferred from the choice behaviour, was perfect under green illumination when the test fields were presented on a gray or a white background, but imperfect on a black background. Under red illumination and a white background, however, colour constancy was overcompensated. Here, a colour contrast effect was observed. The influence of background l…
Influence of stimulus color on the control of reaching-grasping movements.
2001
This kinematic study aimed to determine whether color is a stimulus property involved in the control of reaching-grasping movements. Subjects reached and grasped a target-object, located either on the right or on the left of the subject's midline. A distractor, placed along the subject's midline, could be randomly presented. The colors, i.e., both chromaticity (red and green stimuli were presented) and lightness, of the target and distractor were varied in experiment 1. Only stimulus lightness and only stimulus chromaticity were varied in experiments 2 and 3, respectively. In experiment 4 subjects matched with their thumb and index finger the size of the target-stimuli presented in experime…
Changes in pattern induced flicker colors are mediated by the blue-yellow opponent process.
1992
The colors of Benham's Top [pattern induced flicker colors (PIFCs)] were matched with color stimuli provided by a computer aided color mixer. Subjects viewed a series of specifically modified black and white disks and matched the resulting subjective color with a comparison field containing the color generated by additive mixing. Different phase relations between the apparently colored ring and the surround were tested. The color loci of all PIFCs were found to lie on a plane in receptor three-space which is given by the axis of the shortwave receptor excitation and a vector given by combining the middle and long wave receptor excitation directions in a fixed ratio of nearly 1:1. From the o…