Contrast Perception Research Articles

Willingness of healthcare workers to treat COVID-19 patients during the pandemic: Extended theory of planned behavior

During the COVID-19 pandemic, healthcare workers played a significant role in minimizing the maximum spread of the virus. This study aims to investigate the relationship between healthcare workers’ attitudes, subjective norms, perceived behavioral control, perceived effectiveness of the pandemic, risk perception of the COVID-19 pandemic, and willingness to treat COVID-19 patients in Lahore, Pakistan. However, the extended theory of planned behavior was applied and included two key constructs (perceived effectiveness and risk perception of the COVID-19 pandemic). Data were collected from 253 male and female respondents working in public, private, and semi-government hospitals. Structural equation modeling (SEM) was applied to test the proposed hypotheses. Overall, the findings show that healthcare workers’ attitudes, social norms, and perceived behavioral control significantly impact healthcare workers’ willingness to treat COVID-19 patients. In contrast, perceived effectiveness and risk perception of the pandemic showed a negative effect. The results suggested that healthcare workers showed positive attitudes, subjective norms, and perceived behavioral control to COVID-19 patients. On the other hand, due to the virus novelty, effectiveness and risk perception of the pandemic was very high, which shows that healthcare workers feel stressed and scared to treat COVID-19 patients.

The Müller-Lyer illusion through mental imagery

Previous studies have pointed to a link between visual perception and mental imagery. The present experiment focuses on one of the best-known illusions, the Müller-Lyer illusion, now reproduced under conditions of real perception and by means of imagery. To that purpose, a tailored ad-hoc set of combined figures was presented to a total of 161 fine art students (M age = 20,34, SD = 1,75) who individually worked with two different variations of the Müller-Lyer figures which consisted of a 10 mm long shaft and two fins set at an angle of 30º, being 15 mm long in one instance and 45 mm long in the other. In small groups, participants also completed an image control questionnaire. Results yielded that the longer the oblique lines, the larger the magnitude of the illusion both in the situation of real perception and in the imaginary situation. Also, the magnitude of the illusion augmented in the situation of perception in contrast to the imaginary situation, both with 15 mm long fins and with those of 45 mm. However, no significant differences were found in the magnitude of the illusion between high and low individuals in image control, although interactions between image control and other variables were indeed significant. The consistency of the outcome is a step forward in the study of illusions through mental images and opens the door to new lines of research that could involve innovative methods of analysis, different versions of the illusion and wider groups of participants.

Improvements in image quality after optimization in digital intraoral radiographs

BackgroundDigital intraoral radiographic exposures are optimized largely on the basis of subjective assessment of diagnostic image quality. This study presents an objective approach to optimize radiographic exposure settings for digital intraoral radiographic systems. MethodsSeven size 2 digital intraoral systems were assessed for image quality and determination of optimal exposure following the protocol specified in American National Standard Institute/American Dental Association Standard No. 1094: Quality Assurance for Digital Intra-Oral Radiographic Systems. A ProX radiograph unit (Planmeca) at 63 kVp and 6 mA was used to obtain radiographs of the Dental Digital Quality Assurance phantom. ImageJ software (National Institutes of Health) was used to quantify dynamic range and spatial resolution, and contrast perceptibility was evaluated visually. Optimal exposure is the setting with the maximal contrast perceptibility and spatial resolution while displaying the full dynamic range. After image optimization, a custom phantom consisting of an endodontically prepared tooth was imaged to evaluate the file position relative to the apex for each system. Differences in distances between file position relative to the root apex at the optimal exposure as well as 1 increment above and below were measured. ResultsRadiographic images obtained at the optimal exposure yielded better visualization and more accurate measurements of the file tip relative to the apex. ConclusionsOptimizing radiographic exposures improves image quality and accuracy in clinical decisions. Practical ImplicationsImprovement in image quality and better accuracy in actual distance of the endodontic file to the radiographic apex coupled with complete cleaning, shaping, and obturation of the canal should lead to better endodontic treatment outcomes.

The effect of spatial structure on binocular contrast perception.

To obtain a single percept of the world, the visual system must combine inputs from the two eyes. Understanding the principles that govern this binocular combination process has important real-world clinical and technological applications. However, most research examining binocular combination has relied on relatively simple visual stimuli and it is unclear how well the findings apply to real-world scenarios. For example, it is well-known that, when the two eyes view sine wave gratings with differing contrast (dichoptic stimuli), the binocular percept often matches the higher contrast grating. Does this winner-take-all property of binocular contrast combination apply to more naturalistic imagery, which include broadband structure and spatially varying contrast? To better understand binocular combination during naturalistic viewing, we conducted psychophysical experiments characterizing binocular contrast perception for a range of visual stimuli. In two experiments, we measured the binocular contrast perception of dichoptic sine wave gratings and naturalistic stimuli, and asked how the contrast of the surrounding context affected percepts. Binocular contrast percepts were close to winner-take-all across many of the stimuli when the surrounding context was the average contrast of the two eyes. However, we found that changing the surrounding context modulated the binocular percept of some patterns and not others. We show evidence that this contextual effect may be due to the spatial orientation structure of the stimuli. These findings provide a step toward understanding binocular combination in the natural world and highlight the importance of considering the effect of the spatial interactions in complex stimuli.

Always look on the bright side of logic? Testing explanations of intuitive sensitivity to logic in perceptual tasks.

Much recent research and theorizing in the field of reasoning has been concerned with intuitive sensitivity to logical validity, such as the logic-brightness effect, in which logically valid arguments are judged to have a "brighter" typeface than invalid arguments. We propose and test a novel signal competition account of this phenomenon. Our account makes two assumptions: (a) as per the demands of the logic-brightness task, people attempt to find a perceptual signal to guide brightness judgments, but (b) when the perceptual signal is hard to discern, they instead attend to cues such as argument validity. Experiment 1 tested this account by manipulating the difficulty of the perceptual contrast. When contrast discrimination was relatively difficult, we replicated the logic-brightness effect. When the discrimination was easy, the effect was eliminated. Experiment 2 manipulated the ambiguity of the perceptual task, comparing discrimination performance when the perceptual contrast was labeled in terms of rating "brightness" or "darkness". When the less ambiguous darkness labeling was used, there was no evidence of a logic-brightness effect. In both experiments, individual sensitivity to the perceptual discrimination was negatively correlated with sensitivity to argument validity. Hierarchical latent mixture modeling revealed distinct individual strategies: responses based on perceptual cues, responses based on validity or guessing. Consistent with the signal competition account, the proportion of those responding to validity increased with perceptual discrimination difficulty or task ambiguity. The results challenge explanations of the logic-brightness effect based on parallel dual-process models of reasoning. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Crowding and Perceived Travel Time in Public Transit: Virtual Reality Compared With Stated Choice Surveys

In-vehicle crowding and travel time are two important factors that determine passenger transportation preferences in public transit. A widely used approach to obtain the relative magnitude of these preferences is the stated choice (SC) survey. However, such imaginary choice situations do not capture automatic cognitive biases during the immersive experience of trips. In a previous study, we used virtual reality (VR) technology to simulate short immersive virtual subway trips with different levels of crowding. We asked participants to indicate the level of pleasantness and estimate the duration of each trip. In this paper, we compare and contrast perceptions of participants in the VR task with preferences in a SC survey taken from the same participants. The SC task consisted of two-alternative choice scenarios, asking for preference between more crowded shorter trips and less crowded longer trips. Discrete choice modeling was used to analyze the SC results. There are two main findings. First, individuals who perceived passenger density more negatively in the SC task also felt more negatively during higher density VR trips. This confirms that hypothetical SC surveys can reflect feelings induced by crowding during more realistic experiences. Secondly, a more crowded VR trip was perceived as longer compared with a less crowded trip, whereas this effect was not reflected in the SC task. It therefore suggests that SC surveys may not be capable of capturing systematic temporal biases induced by crowding. Results shed light on potential caveats of the SC surveys and introduce an avenue for the use of VR in passenger preference research.

Suprathreshold Contrast Perception Is Altered by Long-term Adaptation to Habitual Optical Blur.

PurposeTo investigate whether visual experience with habitual blur alters the neural processing of suprathreshold contrast in emmetropic and highly aberrated eyes.MethodsA large stroke adaptive optics system was used to correct ocular aberrations. Contrast constancy was assessed psychophysically in emmetropic and keratoconic eyes using a contrast matching paradigm. Participants adjusted the contrasts of gratings at various spatial frequencies to match the contrast perception of a reference grating at 4 c/deg. Matching was done both with fully corrected and uncorrected ocular aberrations. Optical correction allowed keratoconus patients to perceive high spatial frequencies that they have not experienced for some time.ResultsEmmetropic observers exhibited contrast constancy both with their native aberrations and when their aberrations were corrected. Keratoconus patients exhibited contrast constancy with their uncorrected, native optics but they did not exhibit constancy during adaptive optics correction. Instead. they exhibited striking underconstancy: they required more contrast at high spatial frequencies than the contrast of the 4-c/deg stimulus to make them seem to have the same contrast.ConclusionsThe presence of contrast constancy in emmetropes and keratoconus patients viewing with their native optics suggests that they have learned to amplify neural signals to offset the effects of habitual optical aberrations. The fact that underconstancy was observed in keratoconus patients when their optics were corrected suggests that they were unable to learn the appropriate neural amplification because they did not have experience with fine spatial detail. These results show that even adults can learn neural amplification to counteract the effects of their own optical aberrations.

Bringing nature into private urban housing: Environmental, social and food connections for urban resilience

Ongoing confinement for millions of urban citizens due to the Covid-19 pandemic has raised ecological consciousness, changed food habits and questioned the relationship urban dwellers have with nature. There is more interest in bringing plants into urban homes and in sustainable food sources, but no research have studied the relationships between food behaviours and plant-care activities. To address this gap and explore urban citizens' nature relatedness through the greening of private areas, we conducted a national survey of French, young urban citizens (n = 1000), who are more committed to ‘edible’ cities than older generations but have the lowest rate of plant purchasers. A quantitative approach reveals the prevalence of aesthetic/hedonistic expectations for plants in private housing but also demonstrates contrasting perceptions of tasks for plant maintaining and unequal valuation of social issues around plants. We discuss continuities between environmental awareness, commitment to sustainable food and natural/social uses of plants and argue that urban planning processes should address potential synergies for more integrative resilience. Community building around green areas, urban agriculture or collective gardens, in cities, can have ripple effects towards the greening of private housing. Lastly, the multi-disciplinary approach bridging psychosociology and urban studies can inspire multi-scalar urban planning.

A mathematical perspective of ultrasound image representations and image quality criteria

What is an ultrasound “image”? Where an engineer or physicist may see a quantitative map of physical properties, a physician may see qualitative anatomical features and pathologies. In the past, each image type was evaluated appropriately within its respective context: quantitative image quality was measured with criteria like the contrast-to-noise ratio (CNR), and qualitative images underwent dynamic range transformations to optimize human perception of contrast. Recent non-linear beamforming methods have blurred this line: the produced images are transformed like qualitative images but evaluated with quantitative criteria like CNR. Here, we identify the mathematical flaws in reasoning and suggest rigorous alternatives.An image assigns values to spatial coordinates. Let X denote the set of all possible image values. The mathematical structure endowed on X determines the set of equivalence-preserving transformations. For instance, qualitative images treat X as a general topological space, where images are equivalent under homeomorphisms of X (dynamic range transformations). Quantitative images treat X as a metric space and have fewer equivalence-preserving transformations. These structures determine when criteria like contrast, CNR, generalized CNR, and spatial resolution can be used. To extrapolate these criteria to other contexts, one must use relevant structure-preserving isomorphisms (e.g., histogram matching to preserve information content).

Effectiveness of image optimization in digital intraoral radiographic systems

<h3>Objective</h3> To evaluate the effectiveness of image optimization in digital intraoral radiographic systems. <h3>Study Design</h3> Radiographic images from seven size 2 intraoral sensors (Carestream 6200, Dexis Platinum, Gendex GXS700, LEDTuxedo, Planmeca ProSensor HD, Sirona Schick 33, and XDR Radiology) were optimized in accordance with ANSI/ADA Standard 1094 Quality Assurance for Digital Intra-Oral Radiographic Systems to investigate the benefits of image optimization. The Dental Digital Quality Assurance (DDQA) phantom provided reference objects for assessment of dynamic range, spatial resolution, and contrast perceptibility. Images were analyzed with NIH ImageJ to objectively assess dynamic range and spatial resolution. Contrast perceptibility was subjectively scored based on the visibility of individual wells in two rows of the DDQA phantom. All radiographic images were acquired with the same DC x-ray source (Planmeca ProX) using the sensor's native software on a Gigabyte Laptop Model P34 with a display calibrated using the SMPTE monitor test pattern. To simulate clinically relevant scenarios, a second phantom of an endodontically prepared molar tooth was fabricated, consisting of a #6 K endodontic file placed to the apex of the palatal root of a maxillary molar. File position was confirmed using a scanning electronic microscope and then fixed in place within the root canal. The instrumented tooth was stabilized in acrylic to simulate soft tissue and bone absorption. Three exposures of the endodontic phantom were made using each sensor: one at the optimal exposure time and two at exposure settings one increment above and below. ImageJ was used to measure the distance from the file tip to the radiographic apex. <h3>Results</h3> While optimal exposure parameters varied among sensors, in all cases, the measured distance from the endodontic file to the apex was superior on images acquired at optimum exposure rather than radiographic images acquired with exposures just one increment higher or lower than the optimal parameters. <h3>Conclusion</h3> Optimization of radiographic images using the approach specified in ANSI/ADA Standard1094 enhances clinical diagnostic accuracy. <b>Statement of Ethical Review</b> Ethical Review or exemption was not warranted for this study

Long cone versus short cone for digital intraoral radiographic imaging

<h3>Background</h3> Intraoral radiographs are acquired by one of two methods: the long cone paralleling technique that uses a 30 cm distance from the focal spot to the end of the beam indicating device (BID) versus the short cone technique of 20 cm. The long cone paralleling technique (LCPT) reduces x-ray beam divergence, scatter radiation, penumbra, and magnification as well as entrance skin exposure. LCPT has been recommended for use with digital intraoral radiographic imaging. However, most intraoral generators are supplied with only a short cone BID. <h3>Objective</h3> This research project evaluated image quality of digital radiographs acquired with both long cone and short cone techniques. <h3>Study Design</h3> A series of incrementally increasing exposures of a digital intraoral quality assurance phantom was acquired with both long and short cone methods over a range of exposures from 10 ms to 800 ms to encompass all exposures in the clinical range. Image quality was evaluated using a scientifically validated method that has been published in other research studies on digital intraoral image quality. The image quality parameters assessed were dynamic range, contrast perceptibility, and spatial resolution as specified in ANSI /ADA Standard No. 1094 Quality Assurance for Digital Intra-oral Radiographic Systems. Images were visually evaluated and then objectively evaluated using the NIH ImageJ software for validation. <h3>Results</h3> The results support the use of the LCPT for the acquisition of digital intraoral radiographic images. <h3>Conclusion</h3> The additional purchase of the BID extension is substantiated by the results. <b>Statement of Ethical Review</b> Ethical Review or exemption was not warranted for this study

Applying ADA/ANSI Standard 1094: Impact of image adjustments and display device on subjective assessments

<h3>Objective</h3> To examine operator and device factors that impact subjective assessment of digital radiographic image quality. <h3>Study design</h3> The DDQA phantom was used to generate images to assess spatial resolution, contrast perceptibility, and latitude. The phantom was imaged using an XDR size 2 sensor with a Gendex Expert DC intraoral x-ray source (65 kVp, 7.5mA) at 8 exposure times. Five observers analyzed the images in the native XDR software. Observers were allowed to adjust brightness and contrast to facilitate visualization. Images were analyzed in two environments: a diagnostic radiology reading room with lowered ambient lighting and a Dell Ultrasharp monitor, and an intraoral radiographic room with bright ambient light (450 lux) and an HP EliteOne Computer. The optimum exposure, defined as the lowest exposure that provided the highest feature visualization, was recorded. <h3>Results</h3> In the radiology reading environment, observers were able to discern the full latitude of grayscales at all exposure times. The mean optimal exposure was 0.25s for discerning contrast wells and 0.32s for discerning spatial resolution. Scoring the same images in the intraoral radiography room environment yielded identical results. All observers were able to discern the full image latitude, and the identified optimal exposures were unchanged (0.25s for contrast wells and 0.32s for spatial resolution). <h3>Conclusions</h3> We demonstrate that establishing optimal exposure using the DDQA phantom is reliable, with minimal individual variation. Image adjustments cannot compensate for decreased information. Interestingly, room lighting conditions and display device did not change observer assessments of image quality and optimal exposure times when the observers were allowed to manually adjust brightness and contrast of the presented image. This further validates image quality-guided approaches to establish optimal exposure times in dental clinic settings. In ongoing studies, we will study different display models and ambient lighting settings that are more typical of chair-side settings. <b>Statement of Ethical Review</b> Ethical Review or exemption was not warranted for this study

Capital Market Knowledge, Return, Risk Perception, Technological Advancement, and Investment Interest in Social Media

Purpose: This study aims to determine and investigate the effect of capital market knowledge, return, risk perception, and technological advancement on investment interest in social media. Methodology: The present study employs a descriptive research design that utilizes quantitative methods. The study's population consisted of followers of the @ngertisaham account on Instagram. A sample of 100 respondents was collected using the Slovin formula. The data collection methodology applies a questionnaire, and next, the acquired data is processed employing the IBM SPSS Statistics version 25 software application. The data analysis technique uses a validity test, reliability test, classical assumption test, and hypothesis testing (multiple linear regression analysis, coefficient of determination, f-test, and t-test). Findings: The findings of this study show that there is only a partial relationship between capital market knowledge, technological advancement, and investment interest among Instagram followers of the @ngertisaham account. However, this relationship is not significant. In contrast, the return and risk perception variables show positive and statistically significant effects on investment interest among Instagram followers of the @ngertisaham account. Novelty: The novelty aspect of this study is using respondents of Instagram followers of the @ngertisaham account.

The importance of the ANSI ADA Standard for digital intraoral radiographic systems—a pragmatic approach to quality assurance

The need for quality assurance (QA) for digital dental radiography has existed since the introduction of digital imaging; however, the methods and phantoms required to achieve it were not available. This resulted in a chaotic approach to address QA based largely upon subjective analysis of image quality. The American National Standards Institute (ANSI)/American Dental Association (ADA) Quality Assurance Standard 1094 for Digital Intraoral Radiographic Systems (DIRS) presents a paradigm shift to a scientific and objective method of QA rather than one based on subjective assessments. This standard takes into account the contributions of all components of the digital imaging chain that affect final image quality rather than assessing the various components in isolation. The optimal image is determined for each DIRS through objective analysis of the image quality properties of dynamic range, spatial resolution, and contrast perceptibility. Image optimization, a critical component of a quality assurance program, is the proper balance between diagnostic image quality and radiation dose to the patient. This publication counters disseminated myths and misconceptions with scientific evidence and will help dental practitioners appreciate and understand the benefits of the new ANSI/ADA Standard on QA for DIRS.

Contrasting Perceptions of Construction Managers and Project Managers Around Failure in Light of Morris and Geraldi’s Institutional Context

In their 2011 paper titled “Managing the Institutional Context for Projects” Morris and Geraldi raised the importance of the institutional context in the management of projects. Building on that, this study proposes the conceptualisation and understanding of project-related failure and success through an institutional perspective. This is based on an understanding that projects are distinctive, time-constrained, undertakings meant to generate benefits for all associated stakeholders whose perception of failure varies. Yet, little attention has been given to explaining how such perception is influenced by underlying institutional contexts. Therefore, the aim of the study was to examine the knowledge base for contrasting perspectives of project managers and construction managers around project-related failure in light of the institutional perspectives. To do this, a systematic literature review (SLR) approach was adopted. The first finding of note from this SLR is the dominance of interest in and from the UK Construction Industry (UKCI). This may be attributed to the culture and structure of the UKCI driven by the autonomy and authority of organisations such as the National Audit Office (NAO). The findings further reveal that in the general Project Management (PM) literature, considerations of failure are more introspective and discussed more in terms of project outputs with the causes associated with project management limitations. Considering the three levels discussed by Morris and Geraldi (2011) the PM perspective of failure and success can be associated with the technical level of analysis of project outputs. In contrast, the Construction Management (CM) literature focuses predominantly on specific failures, and on external failures. Causes are more attributed to profitability and the wider supply chain and this can be associated with Morris’s strategic level focus on effectiveness and value. The results from this study call for a systemic approach by heeding the call of Prof. Peter Morris to consider the institutional context level in the perception and analysis of failure instead of solely focusing on output or technical level parameters of time cost and quality.

Expectance of low contrast retro-cues does not modulate anticipatory alpha power

It has been proposed that alpha oscillations reflect the endogenous modulation of visual cortex excitability. In particular, alpha power increases during the maintenance period in Working Memory (WM) tasks have been interpreted as a mechanism to avoid potential interference of incoming stimuli. In this study we tested whether alpha power was modulated during the maintenance of WM to enhance the processing of relevant incoming perceptual stimuli. To this aim, we manipulated the contrast of a stimulus presented during the maintenance period of a WM task. The to-be-detected stimulus could indicate which of the encoded representations was going to be probed after the delay (spatial retro-cue) or could signal that all the representations had equal probability to be tested (neutral retro-cue). Time-frequency analysis revealed that alpha power preceding retro-cue presentation was not differently modulated by the two different contrast conditions. This is, participants did not endogenously modulate alpha oscillations upon low perceptual contrast stimuli incoming. These results suggest that alpha delay activity is not a goal directed mechanism to control the inflow of information during WM maintenance. Instead, current data suggest that alpha delayed activity might be an index of increased allocation of attentional resources to the processing of the WM representations.

The Long-Term Effect of Blue-Light Blocking Spectacle Lenses on Adults' Contrast Perception.

PurposeTo evaluate the long-term effect of two different degrees of blue-light blocking (BB) spectacle lenses on adults’ contrast perception under various lighting conditions.MethodsIn total, 144 healthy adults aged 24.70 (±4.32 years) were recruited to this randomized controlled trial. The participants were randomly divided into three groups and used three different spectacle lenses (15% BB: 15% blue-blocking spectacle lenses; 30% BB: 30% blue-blocking spectacle lenses; RC: regular clear lenses serving as control). Contrast sensitivity under four light conditions (scotopic and photopic, both with/without glare) was measured using standard clinical tests at baseline, 1 month, 3 months and 6 months of use. The area under the log contrast sensitivity function (AULCSF) was also computed as an index for their overall contrast sensitivity across spatial frequencies.ResultsThere was no significant difference in AULCSFs among the three types of spectacle lenses under any light condition (all P > 0.81). No statistical difference was found in the AULSCF among the four time points (all P > 0.39), with no interaction between the effects of group and time (all P > 0.42).ConclusionWearing blue-light blocking lens had no clinically significant effect on adults’ long-term contrast perception under scotopic or photopic conditions, or with glare.

POLITICAL FORMATION OF GENDER RELATIONS IN THE PERIOD OF INDEPENDENCE

This article analyzes the political formation of modern gender issues. The unique features of the female perception of the world contrast with the active male dominance. Women in Kyrgyz society, their place in society, problems, responsibilities, connections, and relationships with men were analyzed. The struggle for a gender policy for social equality was discussed. Political processes with the regularity of gender relations were discussed. One area that clearly indicates inequality between the sexes is the inequality that exists along with employment or a work environment in which both female and male status exists. It has been studied that women spend more time with their children than with their fathers, even when they reach adulthood. The author draws attention to the need for legal solutions to gender conflicts in order to avoid destructive processes in the socio-cultural space.

Luminance dependency of perceived color shift after color contrast adaptation caused by higher-order color channels.

Color adaptation is a phenomenon in which, after prolonged exposure to a specific color (i.e. adaptation color), the perceived color shifts to approximately the opposite color direction of the adaptation color. Color adaptation is strongly related to sensitivity changes in photoreceptors, such as von Kries adaptation and cone-opponent mechanisms. On the other hand, the perceptual contrast of colors (e.g. perceptual saturation of the red-green direction) decreases after adaptation to a stimulus with spatial and/or temporal color modulation along the color direction. This phenomenon is referred to as color contrast adaptation. Color contrast adaptation has been used to investigate the representation of colors in the visual system. In the present study, we measured color perception after color contrast adaptation to stimuli with temporal color modulations along complicated color loci in a luminance-chromaticity plane. We found that, after the observers adapted to color modulations with different chromaticities at higher, medium, and lower luminance (e.g. temporal alternations among red, green, and red, each at a different luminance level), the chromaticity corresponding to perceptual achromaticity (the achromatic point) shifted to the same color direction as the adaptation chromaticity in each test stimulus luminance. In contrast, this luminance dependence of the achromatic point shift was not observed after adaptation to color modulations with more complex luminance-chromaticity correspondences (e.g. alternating red, green, red, green, and red, at five luminance levels, respectively). In addition, the occurrence or nonoccurrence of the luminance-dependent achromatic point shift was qualitatively predicted using a noncardinal model composed of channels preferring intermediate color directions between the cardinal chromaticity and luminance axes. These results suggest that the noncardinal channels are involved in the luminance-dependent perceived color shift after adaptation.

Can Sensory Drive Explain the Evolution of Visual Signal Diversity in Terrestrial Species? A Test with Anolis Lizards.

AbstractAnimal signal colors evolve to efficiently stimulate conspecific visual systems. The sensory drive hypothesis proposes that species differences in habitat light conditions favor the evolution of color diversity. The strongest support comes from aquatic systems, while terrestrial systems offer fewer convincing examples. Anolis lizards occupy diverse habitats and signal with a colorful dewlap. Dewlap visibility depends on perceived chromatic contrast with the background. Visual system modeling has shown that red dewlaps are most visible in most habitat types. However, a majority of species possess white or yellow dewlaps. In a recent behavioral study, we showed that low light conditions can sometimes make yellow and white colors more visible by altering chromatic contrast perception with the background. Using 17 Caribbean Anolis species, we showed that cut-on wavelength, a measure of dewlap color in a white to red continuum, correlates with habitat light intensity. Pairwise comparisons revealed that red dewlaps are most visible in bright habitats, whereas yellow and white are more visible in darker habitats. We conclude that sensory drive has contributed to the evolution of dewlap color differences through the interactive effects of total habitat light intensity and chromatic contrast perception and may provide a mechanism for speciation among anoles.