The influence of stimulus and background colour on signal visibility in the lizard Anolis cristatellus

2001 ◽  
Vol 204 (9) ◽  
pp. 1559-1575 ◽  
Author(s):  
L.J. Fleishman ◽  
M. Persons
Keyword(s):  
Visual System ◽  
Brightness Contrast ◽  
System Response ◽  
Signal Design ◽  
Light Conditions ◽  
Chromatic Contrast ◽  
Long Wavelength ◽  
Peak Sensitivity ◽  
Multi Linear Regression ◽  
To Receive

Anoline lizards communicate with visual displays in which they open and close a colourful throat fan called the dewlap. We used a visual fixation reflex as an assay to test the effects of stimulus versus background chromatic and brightness contrast on the probability of detecting a moving coloured (i.e. dewlap-like) stimulus in Anolis cristatellus. The probability of stimulus detection depended on two additive visual-system channels, one responding to brightness contrast and one responding to chromatic contrast, independent of brightness. The brightness channel was influenced only by wavelengths longer than 450nm and probably received input only from middle- and/or long-wavelength photoreceptors. The chromatic contrast channel appeared to receive input from three, or possibly four, different classes of cone in the anoline retina, including one with peak sensitivity in the ultraviolet. We developed a multi-linear regression equation that described most of the results of this study to a reasonable degree of accuracy. In the future, this equation could be used to predict the relative visibility of different-coloured stimuli in different habitat light conditions, which should be very useful for testing hypotheses that attempt to relate habitat light conditions and visual-system response to the evolution of signal design.

Illusory Reversal of Brightness Contrast

1968 ◽  
Vol 27 (3_suppl) ◽  
pp. 1169-1170 ◽  
Author(s):  
Whitman Richards
Keyword(s):  
Visual System ◽  
Visual Angle ◽  
Low Frequency ◽  
Brightness Contrast ◽  
Linear Behavior ◽  
Non Linear

An illusion analogous to Cornsweet's is used to demonstrate how the non-linear behavior of the visual system can be used to obscure low-frequency gradients. The result is a reversal of brightness—from light to dark—as the visual angle of the display is changed.

Thurstonian Scaling and the Perception of Painterly Translucency

2020 ◽  
Vol 8 (3-4) ◽  
pp. 363-386
Author(s):  
M. W. A. Wijntjes ◽  
C. Spoiala ◽  
H. de Ridder
Keyword(s):  
Visual System ◽  
Natural Environment ◽  
Human Visual System ◽  
Light Conditions ◽  
Sea Waves ◽  
Online Experiment ◽  
Lab Experiment ◽  
Visual Material ◽  
Material Perception ◽  
Visual Variety

Abstract Visual material perception is often studied with physically well-defined stimuli that lack ecological variety. Yet, even the visual variety found in our natural environment is limited when compared to artistic depiction. A similar object can be depicted in numerous different ways that all make visual sense. We studied the perception of translucency using 38 paintings of sea waves as experimental stimuli. It has previously been shown that translucency depends on the shape of the translucent object and on the light conditions. Both shape and light appear in many variations in depictions of seas. In the first experiment we explored the use of Thurstonian scaling and introduce the concept of Number of Distinguishable Levels (NDL). We found that the NDL ranged between 1.5 in a set with small waves to 4 in a set with large waves. While Experiment 1 took place in the lab, Experiment 2 was performed online and replicated the data from Experiment 1 qualitatively, although the NDL was lower in the online experiment. Furthermore, in this experiment we conducted Thurstonian scaling on a number of other attributes that possibly contribute to translucency perception, such as wavetip shading, surface reflections and realism. We found that many of these correlated significantly with translucency. In sum, this study advocates and demonstrates the use of uncontrolled stimuli, in our case paintings, to explore the wide variety of input the human visual system can process.

Xerography as a Model of the Visual System

1969 ◽  
Vol 29 (2) ◽  
pp. 543-545
Author(s):  
Willard L. Brigner
Keyword(s):  
Visual System ◽  
Brightness Contrast ◽  
Simultaneous Brightness Contrast

Xerography has been suggested as a model of the perceptual processes of the visual system. The adequacy of the model was tested in two areas, simultaneous brightness contrast and geometric illusions. Results fail to support the model.

scholarly journals An investigation of visual cryptography and its applications in secure communications

2017 ◽  
Author(s):  
Elham Shahab ◽  
Hadi Abdolrahimpour
Keyword(s):  
Visual System ◽  
Secret Sharing ◽  
Human Visual System ◽  
Visual Cryptography ◽  
Input Image ◽  
Secure Communications ◽  
Security Issues ◽  
Main Input ◽  
To Receive ◽  
Distinguishing Features

Secret sharing approach and in particular Visual Cryptography (VC) try to address the security issues in dealing with images. In fact, VC is a powerful technique that combines the notions of perfect ciphers and secret sharing in cryptography. VC takes an image (secret) as an input and encrypts (divide) into two or more pieces (shares) that each of them can not reveal any information about the main input. The decryption way in this scenario is done through superimposing shares on top of each other to receive the input image. No computer participation is required, thus showing one of the distinguishing features of VC. It is claimed that VC is a unique technique in the sense that the encrypted message can be decrypted directly by the human visual system.

scholarly journals Opsin genes of select treeshrews resolve ancestral character states within Scandentia

2019 ◽  
Vol 6 (4) ◽  
pp. 182037
Author(s):  
Gwen Duytschaever ◽  
Mareike C. Janiak ◽  
Perry S. Ong ◽  
Konstans Wells ◽  
Nathaniel J. Dominy ◽  
...  
Keyword(s):  
Purifying Selection ◽  
Opsin Gene ◽  
Functional Variation ◽  
Long Wavelength ◽  
Living Fossils ◽  
Opsin Genes ◽  
Senior Synonym ◽  
Peak Sensitivity ◽  
Encoding Genes ◽  
Ancestral Character States

Treeshrews are small, squirrel-like mammals in the order Scandentia, which is nested together with Primates and Dermoptera in the superordinal group Euarchonta. They are often described as living fossils, and researchers have long turned to treeshrews as a model or ecological analogue for ancestral primates. A comparative study of colour vision-encoding genes within Scandentia found a derived amino acid substitution in the long-wavelength sensitive opsin gene ( OPN1LW ) of the Bornean smooth-tailed treeshrew ( Dendrogale melanura ). The opsin, by inference, is red-shifted by ca 6 nm with an inferred peak sensitivity of 561 nm. It is tempting to view this trait as a novel visual adaptation; however, the genetic and functional diversity of visual pigments in treeshrews is unresolved outside of Borneo. Here, we report gene sequences from the northern smooth-tailed treeshrew ( Dendrogale murina ) and the Mindanao treeshrew ( Tupaia everetti , the senior synonym of Urogale everetti ). We found that the opsin genes are under purifying selection and that D. murina shares the same substitution as its congener, a result that distinguishes Dendrogale from other treeshrews, including T. everetti. We discuss the implications of opsin functional variation in light of limited knowledge about the visual ecology of smooth-tailed treeshrews.

On the Attempt to Implement Social Addressability within a Robotic System

i-com ◽  
2017 ◽  
Vol 16 (2) ◽  
pp. 71-85
Author(s):  
Philipp Graf ◽  
Manuela Marquardt ◽  
Diego Compagna
Keyword(s):  
Experimental Approach ◽  
Human Robot Interaction ◽  
Light Conditions ◽  
Robot System ◽  
Robot Interaction ◽  
Additional Information ◽  
The Status ◽  
User Friendly ◽  
To Receive ◽  
Insight Into

AbstractWe conducted a Human-Robot Interaction (HRI) study during a science event, using a mixed method experimental approach with quantitative and qualitative data (adapted version of Godspeed Questionnaire and audio-visual material analysed videographically). The main purpose of the research was to gather insight into the relevance of the so-called “point of interaction” for a successful and user-friendly interaction with a non-anthropomorphic robot. We elaborate on this concept with reference to sociological theories under the heading of “addressability” and “social address” and generate hypotheses informed by former research and theoretical reflections. We implement an interface on our robot system, comprising two LEDs, which indicate the status of the robot/interaction, and which might possibly serve as basal form of embodied social address. In one experimental condition, the movements were accompanied by a light choreography, the other one was conducted without the LEDs. Our findings suggest a potential relevance of social address for the interaction partner to receive additional information, especially if the situation is a contingent one. Nevertheless, the overall rating on the Godspeed scales showed no significant differences between the light conditions. Several possible reasons for this are discussed. Limitations and advantages are pointed out in the conclusion.

scholarly journals Convergent spectral shifts to blue-green vision in mammals extends the known sensitivity of vertebrate M/LWS pigments

2020 ◽  
Vol 117 (15) ◽  
pp. 8303-8305 ◽  
Author(s):  
Hai Chi ◽  
Yimeng Cui ◽  
Stephen J. Rossiter ◽  
Yang Liu
Keyword(s):  
Phenotypic Variation ◽  
Ecological Significance ◽  
Light Conditions ◽  
Spectral Tuning ◽  
Mutant Proteins ◽  
Long Wavelength ◽  
Functional Convergence ◽  
Spectral Shifts ◽  
Elephant Shrew ◽  
Adaptive Shifts

Daylight vision in most mammals is mediated predominantly by a middle/long wavelength-sensitive (M/LWS) pigment. Although spectral sensitivity and associated shifts in M/LWS are mainly determined by five critical sites, predicted phenotypic variation is rarely validated, and its ecological significance is unclear. We experimentally determine spectral tuning of M/LWS pigments and show that two highly divergent taxa, the gerbil and the elephant-shrew, have undergone independent dramatic blue-green shifts to 490 nm. By generating mutant proteins, we identify additional critical sites contributing to these shifts. Our results, which extend the known range of spectral tuning of vertebrate M/LWS, provide a compelling case of functional convergence, likely related to parallel adaptive shifts from nocturnal to brighter light conditions in similar habitats.

scholarly journals Evolution and spectral tuning of visual pigments in birds and mammals

2009 ◽  
Vol 364 (1531) ◽  
pp. 2941-2955 ◽  
Author(s):  
David M. Hunt ◽  
Livia S. Carvalho ◽  
Jill A. Cowing ◽  
Wayne L. Davies
Keyword(s):  
Visual System ◽  
Visual Pigment ◽  
Spectral Characteristics ◽  
Marine Species ◽  
Visual Pigments ◽  
Common Mechanism ◽  
Light Conditions ◽  
Uv Sensitivity ◽  
Pigment Genes ◽  
Number Of Classes

Variation in the types and spectral characteristics of visual pigments is a common mechanism for the adaptation of the vertebrate visual system to prevailing light conditions. The extent of this diversity in mammals and birds is discussed in detail in this review, alongside an in-depth consideration of the molecular changes involved. In mammals, a nocturnal stage in early evolution is thought to underlie the reduction in the number of classes of cone visual pigment genes from four to only two, with the secondary loss of one of these genes in many monochromatic nocturnal and marine species. The trichromacy seen in many primates arises from either a polymorphism or duplication of one of these genes. In contrast, birds have retained the four ancestral cone visual pigment genes, with a generally conserved expression in either single or double cone classes. The loss of sensitivity to ultraviolet (UV) irradiation is a feature of both mammalian and avian visual evolution, with UV sensitivity retained among mammals by only a subset of rodents and marsupials. Where it is found in birds, it is not ancestral but newly acquired.

scholarly journals Alerting and Circadian Effects of Short-Wavelength vs. Long-Wavelength Narrow-Bandwidth Light during a Simulated Night Shift

2020 ◽  
Vol 2 (4) ◽  
pp. 502-522
Author(s):  
Erlend Sunde ◽  
Torhild Pedersen ◽  
Jelena Mrdalj ◽  
Eirunn Thun ◽  
Janne Grønli ◽  
...  
Keyword(s):  
Task Performance ◽  
Short Wavelength ◽  
Night Shift ◽  
Spectral Composition ◽  
Photon Density ◽  
Light Conditions ◽  
Long Wavelength ◽  
Narrow Bandwidth ◽  
Short Wavelength Light ◽  
Wavelength Light

Light can be used to facilitate alertness, task performance and circadian adaptation during night work. Novel strategies for illumination of workplaces, using ceiling mounted LED-luminaires, allow the use of a range of different light conditions, altering intensity and spectral composition. This study (ClinicalTrials.gov Identifier NCT03203538) investigated the effects of short-wavelength narrow-bandwidth light (λmax = 455 nm) compared to long-wavelength narrow-bandwidth light (λmax = 625 nm), with similar photon density (~2.8 × 1014 photons/cm2/s) across light conditions, during a simulated night shift (23:00–06:45 h) when conducting cognitive performance tasks. Light conditions were administered by ceiling mounted LED-luminaires. Using a within-subjects repeated measurements study design, a total of 34 healthy young adults (27 females and 7 males; mean age = 21.6 years, SD = 2.0 years) participated. The results revealed significantly reduced sleepiness and improved task performance during the night shift with short-wavelength light compared to long-wavelength light. There was also a larger shift of the melatonin rhythm (phase delay) after working a night shift in short-wavelength light compared to long-wavelength light. Participants’ visual comfort was rated as better in the short-wavelength light than the long-wavelength light. Ceiling mounted LED-luminaires may be feasible to use in real workplaces, as these have the potential to provide light conditions that are favorable for alertness and performance among night workers.

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