Time/Room: Friday, May 13, 2016, 2:30 – 4:30 pm, Pavilion
Organizer(s): Annette Werner; Institute for Ophthalmic Research, Tübingen University, Germany
Presenters: Annette Werner, Anya Hurlbert, Christoph Witzel, Keiji Uchikawa, Bevil Conway, Lara Schlaffke
Symposium Description
Few topics in colour research have generated so much interest in the science community and public alike, as the recent #TheDress. The phenomenon refers to the observation that observers cannot agree on colour names for a dress seen in a particular photograph, i.e. colour judgements fall into at least two categories, namely blue&black and white&gold. Although individual differences in colour perception are well known, this phenomenon is still unprecendented since it uncovers a surprising ambiguity in colour vision – surprising because our visual brain was thought to reconstruct surface colour so successfully that it is experienced by the naive observer as an inherent property of objects. Understanding the origin of the perceptual dichotomy of #TheDress is therefore important not only in the context of the phenomenon itself but also for our comprehension of the neural computations of colour in general. Since it’s discovery, a number of hypotheses have been put forward, in order to explain the phenomenon; these include individual differences in peripheral or sensory properties such as variations in the entopic filters of the eye, or in the spectral sensitivities of the chromatic pathways; „high end“ explanations concern differences at cognitive stages, e.g. regarding the interpretation of the lightfield in a scene, or the use of priors for estimating the illuminant or the surface colour. The ambiguity in case of #TheDress may arise because of the peculiar distribution of surface colours in the photo and the lack of further information in the background. The symposium shall gather the actual experimental evidence, and provide a profound basis for the discussion and evaluation of existing and novel hypotheses. The topic will be introduced by the organizer and concluded by a general discussion of the experimental findings of all presentations. Because of the wide spread interest for the topic of #TheDress and it’s general importance for colour vision, we expect a large VSS audience, including students, postdocs, and senior scientists from all fields in vision research.
Presentations
The #Dress phenomenon – an empirical investigation into the role of the background
Speaker: Annette Werner; Institute for Ophthalmic Research, Tübingen University, Germany
Authors: Alisa Schmidt, Institute for Ophthalmic Research, Tübingen University, Germany
The #TheDress phenomenon refers to a dichotomy in colour perception, which is specific to the foto of a blue&black dress, namely that most observers judge its colours as either blue/black or white/gold. Hypotheses explaining the phenomenon include individual variations of information pocessing at sensory as well as cognitive stages. In particular it has been proposed that the lack of/ambiguity in background information leads observers to different conclusions about the illuminant and the light field. We will present result of matching experiments involving the presentations of the real blue/black dress, mounted on differently colour backgrounds and under the illuminations of two slide projectors, thereby mimicking the ambiguity of the photo. The results identify the use of information from the background as a source for the observed individual differences. The results are discussed in the context of the aquisition, the content and the use of “scene knowledge“.
Is that really #thedress? Individual variations in colour constancy for real illuminations and objects
Speaker: Anya Hurlbert; Institute of Neuroscience, University of Newcastle upon Tyne, UK
Authors: Stacey Aston, Bradley Pearce: Institute of Neuroscience, University of Newcastle upon Tyne, UK
One popular explanation for the individual variation in reported colours of #thedress is an individual variation in the underlying colour constancy mechanisms, which cause differences in the illumination estimated and subsequently discounted. Those who see the dress as ‘white/gold’ are discounting a ‘blueish’ illumination, while those who see it as ‘blue/black’ are discounting a ‘yellowish’ illumination. These underlying differences are brought into relief by the ambiguity of the original photograph. If this explanation holds, then similarly striking individual differences in colour constancy might also be visible in colour matching and naming tasks using real objects under real illuminations, and the conditions under which they are elicited may help to explain the particular power of #thedress. I will discuss results of colour constancy measurements using the real dress, which is almost universally reported to be ‘blue/black’ when illuminated by neutral, broad-band light, yet elicits similar variability in colour naming to the original photograph, across observers within certain illumination conditions, most pronouncedly for ambiguous and/or atypical illuminations. Colour constancy by both naming and matching is in fact relatively poor for the real dress and other unfamiliar items of clothing, but better for “blueish” illuminations than other chromatic illuminations or ambiguous multiple-source illuminations. Overall, individual variations in colour constancy are significant, and depend on age and other individual factors.
Variation of subjective white-points along the daylight axis and the colour of the dress
Speaker: Christoph Witzel; Laboratoire Psychologie de la Perception, University Paris Descartes, France
Authors: Sophie Wuerger, University of Liverpool, UK, Anya Hurlbert, Institute of Neuroscience, University of Newcastle upon Tyne, UK
We review the evidence, from different data sets collected under different viewing conditions, illumination sources, and measurement protocols, for intra- and interobserver variability in “generic subjective white-point” settings along the daylight locus. By “generic subjective white-point” we mean the subjective white-point independent of the specific context. We specifically examine the evidence across all datasets for a “blue” bias in subjective white-points (i.e. increased variability or reduced sensitivity in the bluish direction). We compare the extent of daylight-locus variability generally and variability in the “bluish” direction specifically of subjective white points across these data sets (for different luminance levels and light source types). The variability in subjective white-point may correspond to subjective “priors” on illumination chromaticity. In turn, individual differences in assumptions about the specific illumination chromaticity on “the dress” (in the recent internet phenomenon) is widely thought to explain the individual differences in reported dress colours. We therefore compare the variability in generic white-point settings collated across these datasets with the variability in generic white-point settings made in the specific context of the dress (Witzel and O’Regan, ECVP 2015). Our analysis suggests that (1) there is an overall “blue” bias in generic subjective white-point settings and (2) the variability in generic subjective white-point settings is insufficient to explain the variability in reported dress colours. Instead, the perceived colors of the dress depend on assumptions about the illumination that are specific to that particular photo of the dress.
Prediction for individual differences in appearance of the “dress” by the optimal color hypothesis
Speaker: Keiji Uchikawa; Department of Information Processing, Tokyo Institute of Technology, Japan
Authors: Takuma Morimoto, Tomohisa Matsumoto; Department of Information Processing, Tokyo Institute of Technology, Japan
When luminances of pixels in the blue-black/white-gold “dress” image were plotted on the MacLeod-Boynton chromaticity diagram they appeared to have two clusters. They corresponded to the white/blue and the gold/black parts. The approach we took to solve the dress problem was to apply our optimal color hypothesis to estimate an illuminant in the dress image. In the optimal color hypothesis, the visual system picks the optimal color distribution, which best fits to the scene luminance distribution. The peak of the best-fit optimal color distribution corresponds to the illuminant chromaticity. We tried to find the best-fit optimal color distribution to the dress color distribution. When illuminant level was assumed to be low, the best-fit color temperature was high (20000K). Under this dark-blue illuminant the dress colors should look white-gold. When illuminant level was assumed to be high, the lower temperature optimal color distribution (5000K) fitted the best. Under this bright-white illuminant the dress colors should appear blue-black. Thus, for the dress image the best-fit optimal color distribution changed depending on illuminant intensity. This dual-stable illuminant estimations may cause the individual difference in appearance of the dress. If you choose a bright (or dark) illuminant the dress appears blue-black (or white-gold). When the chromaticity of the dress was rotated in 180 degree in the chromaticity diagram it appeared blue-gold without individual difference. In this case the optimal color hypothesis predicted an illuminant with almost no ambiguity. We tested individual differences using simple patterns in experiments. The results supported our prediction.
Mechanisms of color perception and cognition covered by #thedress
Speaker: Bevil Conway; Department of Brain and Cognitive Sciences, MIT, Cambridge MA, USA
Authors: Rosa Lafer-Sousa, Katherine Hermann
Color is notoriously ambiguous—many color illusions exist—but until now it has been thought that all people with normal color vision experience color illusions the same way. How does the visual system resolve color ambiguity? Here, we present work that addresses this question by quantifying people’s perception of a particularly ambiguous image, ‘the dress’ photograph. The colors of the individual pixels in the photograph when viewed in isolation are light-blue or brown, but popular accounts suggest the dress appears either white/gold or blue/black. We tested more than 1400 people, both on-line and under controlled laboratory conditions. Subjects first completed the sentence: “this is a ___and___dress”. Then they performed a color-matching experiment that did not depend on language. Surprisingly, the results uncovered three groups of subjects: white/gold observers, blue/black observers and blue/brown observers. Our findings show that the brain resolves ambiguity in ‘the dress’ into one of three stable states; a minority of people switched which colors they saw (~11%). It is clear that what we see depends on both retinal stimulation and internal knowledge about the world. Cases of multi-stability such as ‘the dress’ provide a rare opportunity to investigate this interplay. In particular, we go on to demonstrate that ‘the dress’ photograph can be used as a tool to discover that skin reflectance is a particularly important implicit cue used by the brain to estimate the color of the light source, to resolve color ambiguity, shedding light on the role of high-level cues in color perception.
The Brain’s Dress Code: How The Dress allows to decode the neuronal pathway of an optical illusion
Speaker: Lara Schlaffke; Department of Neurology, BG University Hospital Bergmannsheil, Bochum, Germany
Authors: Anne Golisch , Lauren M. Haag, Melanie Lenz, Stefanie Heba, Silke Lissek, Tobias Schmidt-Wilcke, Ulf T. Eysel , Martin Tegenthoff
Optical illusions have broadened our understanding of the brains role in visual perception 1–3. A modern day optical illusion emerged from a posted photo of a striped dress, which some perceived as white and gold and others as blue and black. Theories on the differences have been proposed and included e.g. colour constancy, contextual integration, and the principle of ambiguous forms4, however no consensus has yet been reached. The fact that one group sees a white/gold dress, instead of the actual blue/black dress, provides a control and therefore a unique opportunity in vision research, where two groups perceive the same object differently. Using functional magnetic resonance imaging (fMRI) we can identify human brain regions that are involved in this optical illusion concerning colour perception and investigate the neural correlates that underlie the observed differences. Furthermore open questions in visual neuroscience concerning the computation of complex visual scenes can be addressed. Here we show, using fMRI, that those who perceive The Dress as white/gold (n=14) have higher activation in response to The Dress in brain regions critically involved in visual processing and conflict management (V2, V4, as well as frontal and parietal brain areas), as compared to those who perceive The Dress as blue/black (n=14). These results are consistent with the theory of top-down modulation5 and extend the Retinex theory6 to include differing strategies the brain uses to form a coherent representation of the world around us. This provides a fundamental building block to study interindividual differences in visual processing.