Constancy Mechanisms Research Articles

Measurements of chromatic adaptation and luminous efficiency while wearing colored filters.

The visual system adapts dynamically to stabilize perception over widely varying illuminations. Such adaptation allows the colors of objects to appear constant despite changes in spectral illumination. Similarly, the wearing of colored filters also alters spectral content, but this alteration can be more extreme than typically encountered in nature, presenting a unique challenge to color constancy mechanisms. While it is known that chromatic adaptation is affected by surrounding spatial context, a recent study reported a gradual temporal adaptation effect to colored filters such that colors initially appear strongly shifted but over hours of wear are perceived as closer to an unfiltered appearance. Presently, it is not clear whether the luminance system adapts spatially and temporally like the chromatic system. To address this, spatial and temporal adaptation effects to a colored filter were measured using tasks that assess chromatic and luminance adaptation separately. Prior to and for 1 hour after putting on a pair of colored filters, participants made achromatic and heterochromatic flicker photometry (HFP) settings to measure chromatic and luminance adaptation, respectively. Results showed significant chromatic adaptation with achromatic settings moving closer to baseline settings over 1 hour of wearing the filters and greater adaptation with spatial context. Conversely, there was no significant luminance adaptation and HFP matches fell close to what was predicted photometrically. The results are discussed in the context of prior studies of chromatic and luminance adaptation.

Color constancy mechanisms in virtual reality environments.

Prior research has demonstrated high levels of color constancy in real-world scenarios featuring single light sources, extensive fields of view, and prolonged adaptation periods. However, exploring the specific cues humans rely on becomes challenging, if not unfeasible, with actual objects and lighting conditions. To circumvent these obstacles, we employed virtual reality technology to craft immersive, realistic settings that can be manipulated in real time. We designed forest and office scenes illuminated by five colors. Participants selected a test object most resembling a previously shown achromatic reference. To study color constancy mechanisms, we modified scenes to neutralize three contributors: local surround (placing a uniform-colored leaf under test objects), maximum flux (keeping the brightest object constant), and spatial mean (maintaining a neutral average light reflectance), employing two methods for the latter: changing object reflectances or introducing new elements. We found that color constancy was high in conditions with all cues present, aligning with past research. However, removing individual cues led to varied impacts on constancy. Local surrounds significantly reduced performance, especially under green illumination, showing strong interaction between greenish light and rose-colored contexts. In contrast, the maximum flux mechanism barely affected performance, challenging assumptions used in white balancing algorithms. The spatial mean experiment showed disparate effects: Adding objects slightly impacted performance, while changing reflectances nearly eliminated constancy, suggesting human color constancy relies more on scene interpretation than pixel-based calculations.

Underwater image clarifying based on human visual colour constancy using double‐opponency

AbstractUnderwater images are often with biased colours and reduced contrast because of the absorption and scattering effects when light propagates in water. Such images with degradation cannot meet the needs of underwater operations. The main problem in classic underwater image restoration or enhancement methods is that they consume long calculation time, and often, the colour or contrast of the result images is still unsatisfied. Instead of using the complicated physical model of underwater imaging degradation, we propose a new method to deal with underwater images by imitating the colour constancy mechanism of human vision using double‐opponency. Firstly, the original image is converted to the LMS space. Then the signals are linearly combined, and Gaussian convolutions are performed to imitate the function of receptive fields (RFs). Next, two RFs with different sizes work together to constitute the double‐opponency response. Finally, the underwater light is estimated to correct the colours in the image. Further contrast stretching on the luminance is optional. Experiments show that the proposed method can obtain clarified underwater images with higher quality than before, and it spends significantly less time cost compared to other previously published typical methods.

Perceptual constancy and perceptual representation

AbstractPerceptual constancy has played a significant role in philosophy of perception. It figures in debates about direct realism, color ontology, and the minimal conditions for perceptual representation. Despite this, there is no general consensus about what constancy is. I argue that an adequate account of constancy must distinguish it from three distinct phenomena: mere sensory stability through proximal change, perceptual categorization of a distal dimension, and stability through irrelevant proximal change. Standard characterizations of constancy fall short in one or more of these respects. I develop an account of constancy that overcomes these problems. The account has two parts: an analysis of constancy mechanisms, and an analysis of the conditions under which a constancy capacity is exercised. I then employ this account to evaluate whether constancy is a necessary condition for perceptual representation, as some have conjectured. I argue that explanatory practice in perceptual psychology fails to support this view. Rather, it fits better with the weaker principle that representation requires specific tracking of a distal dimension.

Fuel Cell Evolution

This paper focuses on the progress that has been made in fuel cells through four theories, namely thermodynamics, electrochemistry, electrolyte theories, direct generation physics and finally the application of Ohm's law physics to the fuel cell system. In order to identify the compatibility of the basic theories with these systems. Through this research, we have indicated the need for a unified theory to explain the mechanism of stability and constancy, which leads us to say that they are relatively perfect systems.

Time course of encoding and maintenance of stereoscopically induced size–distance scaling

ABSTRACT The mechanism of size constancy assures that an object is perceived to be constant in size despite that its retinal size varies with viewing distance. Conversely, an object can be perceived as illusorily larger if the perceived distance becomes greater, due to the size–distance scaling mechanism. The present study aimed at exploring how size–distance scaling is modulated by the encoding duration and how its memory is affected by the retention duration. In Experiment 1, we presented two stimuli simultaneously at two stereoscopic depth planes and manipulated the presentation duration, and found that the magnitude of the size scaling increased with presentation duration. In Experiment 2, we examined the maintenance of size–distance scaling when component stimulus was kept in working memory with variable delays. The results showed that the size scaling was reliably retrieved from working memory if there was no disparity manipulation on the to-be-memorized item, but it decreased with retention if a disparity was applied to the to-be-memorized item. The findings suggest that although the post-scaling size can be stored in working memory, the scaling mechanism may still be in effect when there were conflicts in the oculomotor cues and disparity cues that produces depth perception.

Can Constancy Mechanisms Draw the Limits of Intentionality?

Abstract What are the minimal conditions for intentionality that a sensory state should satisfy for it to constitute a representational state? That is, what are the limits of intentionality? This is the problem of demarcation. The goal of this paper is to assess a specific demarcation proposal for the minimal conditions of intentionality—the constancy mechanism proposal. Accordingly, it is a minimal condition for the intentionality of a given state that the sensory system should employ a constancy mechanism in the production of this state. First of all, I introduce the problem of demarcation and show its relevance for the debate on the viability of naturalist theories of mental representation. After that, I present the explanatory role requirement for the positing of representational states by intentional explanations of behaviour and show how it constitutes a criterion for the assessment of demarcation proposals for the limits of intentionality. Finally, I assess the constancy mechanism proposal and show that its viability is seriously jeopardised by the minimal distance problem.

Developmental changes in colour constancy in a naturalistic object selection task.

When the illumination falling on a surface change, so does the reflected light. Despite this, adult observers are good at perceiving surfaces as relatively unchanging-an ability termed colour constancy. Very few studies have investigated colour constancy in infants, and even fewer in children. Here we asked whether there is a difference in colour constancy between children and adults; what the developmental trajectory is between six and 11 years; and whether the pattern of constancy across illuminations and reflectances differs between adults and children. To this end, we developed a novel, child-friendly computer-based object selection task. In this, observers saw a dragon's favourite sweet under a neutral illumination and picked the matching sweet from an array of eight seen under a different illumination (blue, yellow, red, or green). This set contained a reflectance match (colour constant; perfect performance) and a tristimulus match (colour inconstant). We ran two experiments, with two-dimensional scenes in one and three-dimensional renderings in the other. Twenty-six adults and 33 children took part in the first experiment; 26 adults and 40 children took part in the second. Children performed better than adults on this task, and their performance decreased with age in both experiments. We found differences across illuminations and sweets, but a similar pattern across both age groups. This unexpected finding might reflect a real decrease in colour constancy from childhood to adulthood, explained by developmental changes in the perceptual and cognitive mechanisms underpinning colour constancy, or differences in task strategies between children and adults. HIGHLIGHTS: Six- to 11-year-old children demonstrated better performance than adults on a colour constancy object selection task. Performance decreased with age over childhood. These findings may indicate development of cognitive strategies used to overcome automatic colour constancy mechanisms.

The Effects of Adding Pictorial Depth Cues to the Poggendorff Illusion.

We tested if the misapplication of perceptual constancy mechanisms might explain the perceived misalignment of the oblique lines in the Poggendorff illusion. Specifically, whether these mechanisms might treat the rectangle in the middle portion of the Poggendorff stimulus as an occluder in front of one long line appearing on either side, causing an apparent decrease in the rectangle’s width and an apparent increase in the misalignment of the oblique lines. The study aimed to examine these possibilities by examining the effects of adding pictorial depth cues. In experiments 1 and 2, we presented a central rectangle composed of either large or small bricks to determine if this manipulation would change the perceived alignment of the oblique lines and the perceived width of the central rectangle, respectively. The experiments demonstrated no changes that would support a misapplication of perceptual constancy in driving the illusion, despite some evidence of perceptual size rescaling of the central rectangle. In experiment 3, we presented Poggendorff stimuli in front and at the back of a corridor background rich in texture and linear perspective depth cues to determine if adding these cues would affect the Poggendorff illusion. The central rectangle was physically large and small when presented in front and at the back of the corridor, respectively. The strength of the Poggendorff illusion varied as a function of the physical size of the central rectangle, and, contrary to our predictions, the addition of pictorial depth cues in both the central rectangle and the background decreased rather than increased the strength of the illusion. The implications of these results with regards to different theories are discussed. It could be the case that the illusion depends on both low-level and cognitive mechanisms and that deleterious effects occur on the former when the latter ascribes more certainty to the oblique lines being the same line receding into the distance.

Size Constancy Mechanisms: Empirical Evidence from Touch.

Several studies have shown the presence of large anisotropies for tactile distance perception across several parts of the body. The tactile distance between two touches on the dorsum of the hand is perceived as larger when they are oriented mediolaterally (across the hand) than proximodistally (along the hand). This effect can be partially explained by the characteristics of primary somatosensory cortex representations. However, this phenomenon is significantly attenuated relative to differences in acuity and cortical magnification, suggesting a process of tactile size constancy. It is unknown whether the same kind of compensation also takes place when estimating the size of a continuous object. Here, we investigate whether the tactile anisotropy that typically emerges when participants have to estimate the distance between two touches is also present when a continuous object touches the skin and participants have to estimate its size. In separate blocks, participants judged which of two tactile distances or objects on the dorsum of their hand felt larger. One stimulation (first or second) was aligned with the proximodistal axis (along the hand) and the other with the mediolateral axis (across the hand). Results showed a clear anisotropy for distances between two distinct points, with across distances consistently perceived as larger than along distances, as in previous studies. Critically, however, this bias was significantly reduced or absent for judgments of the length of continuous objects. These results suggest that a tactile size constancy process is more effective when the tactile size of an object has to be approximated compared to when the distance between two touches has to be determined. The possible mechanism subserving these results is described and discussed. We suggest that a lateral inhibition mechanism, when an object touches the skin, provides information through the distribution of the inhibitory subfields of the RF about the shape of the tactile RF itself. Such a process allows an effective tactile size compensatory mechanism where a good match between the physical and perceptual dimensions of the object is achieved.

A dual proposal of minimal conditions for intentionality

Naturalist theories of representation have been attacked on the grounds of being too liberal on the minimal conditions for intentionality: they treat several states that are not representational as genuine representations. Behind this attack lies the problem of demarcation: what are the minimal conditions for intentionality that a state should satisfy to be genuinely representational? What are the limits of intentionality? This paper develops a dual proposal to solve this problem. First, I defend the explanatory role criterion in order to assess proposals of minimal conditions for intentionality. I start by proposing the success pattern condition: a state represents a given external feature provided that there is a success pattern present in the behavioural output, and the system uses this state as a proxy for the presence of this external feature. However, this condition is not sufficient for minimal intentionality—there are both intentional and non-intentional success patterns. Another minimal condition is, hence, required to draw this distinction. I propose the constancy mechanism condition: a state is representational provided that the system employs a constancy mechanism in its production. The success pattern and constancy mechanism conditions jointly constitute the dual proposal for minimal intentionality. I argue that this proposal is explanatorily justified and, so, properly demarcates the limits of intentionality.

A novel biologically-inspired method for underwater image enhancement

Underwater images are usually characterized by color distortion, blurry, and severe noise, because light is severely scattered and absorbed when traveling in the water. In this paper, we propose a novel method motivated by the astonishing capability of the biological vision to address the low visibility of the real-world underwater images. Firstly, we simply imitate the color constancy mechanism in photoreceptors and horizontal cells (HCs) to correct the color distortion. In particular, HCs modulation provides a global color correction with gain control, in which light wavelength-dependent absorption is taken into account. Then, to solve the problems of blurry and noise, we introduce a straightforward and effective two-pathway dehazing method. The core idea is to decompose the color corrected image into structure-pathway and texture-pathway, corresponding to the Magnocellular (M-) and Parvocellular (P-) pathway in the early visual system. In the structure-pathway, we design an innovative biological normalization model to adjust the dynamic range of luminance by integrating the bright and dark regions. By using this approach, the proposed method leads to significant improvement in the contrast degradation of underwater images. Additionally, the detail preservation and noise suppression are implemented on the textural information. Finally, we merge the outputs of structure and texture pathways to reconstruct the enhanced underwater image. Both qualitative and quantitative evaluations show that the proposed biologically-inspired method achieves better visual quality, when compared with several related methods.

Mechanisms of perception constancy and recalibration of sensory systems

Possible mechanisms of contingent color aftereffects, in particular, the McCollough effect, are discussed. A hypothesis is proposed, which assumes that the McCollough effect occurs when color constancy mechanisms are activated. Experimental evidence of similarities between the mechanisms of perception constancy and mechanisms of formation of a psychological attitude in terms of the Uznadze theory is demonstrated. Actual activity indicators of recalibration mechanisms of sensory systems are presented using experimentally induced changes in color sensitivity as an example.

Impact of proprioception on the perceived size and distance of external objects in a virtual action task

Previous research has revealed changes in the perception of objects due to changes of object-oriented actions. In present study, we varied the arm and finger postures in the context of a virtual reaching and grasping task and tested whether this manipulation can simultaneously affect the perceived size and distance of external objects. Participants manually controlled visual cursors, aiming at reaching and enclosing a distant target object, and judged the size and distance of this object. We observed that a visual–proprioceptive discrepancy introduced during the reaching part of the action simultaneously affected the judgments of target distance and of target size (Experiment 1). A related variation applied to the grasping part of the action affected the judgments of size, but not of distance of the target (Experiment 2). These results indicate that perceptual effects observed in the context of actions can directly arise through sensory integration of multimodal redundant signals and indirectly through perceptual constancy mechanisms.

Constancy Mechanisms and Distal Content: a Reply to Garson

AbstractSensory perceptions represent things in the outside world. This mundane fact raises a major problem for naturalistic theories of content: the ‘distality problem’. In a previous paper for this journal, I presented a solution to this problem which makes central appeal to constancy mechanisms. Justin Garson, also in this journal, recently criticized my solution and suggested a Dretskean alternative to it. Here, I defend my proposal by arguing, first, that Garson's criticisms ultimately miss the mark, and secondly, that his Dretskean alternative is not viable, because it faces two fundamental problems: the empirical problem and the problem of changing response functions.

The nature of perceptual constancies

AbstractPerceptual constancies have been studied by psychologists for decades, but in recent years, they have also become a major topic in the philosophy of mind. One reason for this surge of interest is Tyler Burge’s (2010) influential claim that constancy mechanisms mark the difference between perception and mere sensitivity, and thereby also the difference between organisms with genuine representational capacities and ‘mindless’ beings. Burge’s claim has been the subject of intense debate. It is becoming increasingly clear, however, that we cannot hope to settle this debate (as well as related debates in the philosophy of mind) without a clear and substantive theoretical account of what perceptual constancies are. In the first part of this paper, I argue that the standard definitions in the literature fall short of providing such an account. Still, as I aim to show in the second part of the paper, by taking a closer look at some of the paradigm examples, it is possible to construct a plausible general account of perceptual constancies that is both clear and substantive, and that can serve as a firm foundation for settling debates like the dispute about Burge’s ‘constancy mechanism criterion’ for perception.

Robert Kentridge

Robert Kentridge

Explanation of the Colour Change in Alexandrites

Alexandrites are remarkable and rare gemstones. They display an extraordinary colour change according to the ambient lighting, from emerald green in daylight to ruby red in incandescent light from tungsten lamps or candles. While this colour change has been correctly attributed to chromium impurities and their absorption band in the yellow region of the visible light spectrum, no adequate explanation of the mechanism has been given. Here, the alexandrite effect is fully explained by considering the von Kries model of the human colour constancy mechanism. This implies that our colour constancy mechanism is real (objective) and primarily attuned to correct for the colour temperature of black-body illuminants.

Representation and the active consumer

One of the central tasks for naturalistic theories of representation is to say what it takes for something to be a representation, and some leading theories have been criticised for being too liberal. Prominent discussions of this problem have proposed a producer-oriented solution; it is argued that representations must be produced by systems employing perceptual constancy mechanisms. However, representations may be produced by simple transducers if they are consumed in the right way. It is characteristic of representations to be consumed by systems which are capable of independent action. This paper defends this claim; discusses more precise, naturalistic formulations; and shows how it can illuminate the explanatory payoffs which science achieves by appealing to representation.

Improved visual/infrared colour fusion method with double‐opponency colour constancy mechanism

To solve problems that colour distortion and low resolution of infrared and visible colour fusion images, the authors propose a fusion method based on the double-opponency colour constancy mechanism of human vision. First, Waxman's fusion method which imitated the neuro-dynamics mechanism of the rattlesnake bimodal cell is used to fuse the visible light with the source multi-band images to generate pseudo-colour images. Second, a double-opponent colour constancy computation model based on Rodieck's double difference-of-Gaussian is proposed to obtain the estimate of an illuminant of colour fusion images. Finally, the colour fusion images are corrected by the diagonal transformation model based on the cone adaptive mechanism. They also propose to use the three-dimensional RGB histogram to analyse the colour distribution of colour fusion images. In the comparison experiments with other approaches using the three-dimensional RGB histogram, one can see that the proposed fusion method gives colour image coinciding well with natural colour distribution and satisfies human perception needs.