1,721,015 research outputs found
Variation of saturation across hue affects unique and typical hue choices
Full text link<p>This Excel-file contains the individual data for the article:</p>
<p>Witzel (2019) Variation of saturation across hue affects unique and typical hue choices, <em>iperception</em>.</p>
<p>1. Sheet "Participants": gender and age of participants</p>
<p>2. Sheet "Stimuli": Munsell specifications for the stimuli in each set; the set is identified in the first raw. The specifications correspond to table A1 in the Appendix of the article.</p>
<p>The other six sheets contain the actual data with each row corresponding to one participant as in sheet "Participants". For red, note that participants 1 to 10 were presented with the first version of the red stimulus sets, the others with the second version.</p>
<p>3. Prototype choices with set1</p>
<p>4. Prototype choices with set2</p>
<p>5. Unique hue choices with set1</p>
<p>6. Unique hue choices with set1</p>
<p>7. Binary hue choices with set1</p>
<p>8. Binary hue choices with set1</p>
The non-opponent nature of colour afterimages
No full textComplementary colour afterimages have driven our understanding of human colour perception since the foundations of modern colour science. Despite their fundamental importance, decades of research have failed to establish the precise nature of colour afterimages and the neural mechanisms of adaptation at their origin. To date, it is unclear whether afterimage formation is caused by adaptation in the cone photoreceptors, of colour-opponent neurons in the subcortical pathway, or requires the assumption of yet unknown cortical mechanisms. To establish the neural mechanisms underlying afterimage formation, this study exploited the fact that different candidate mechanisms make fundamentally different predictions about the hue and saturation of afterimages. Using tailormade experimental paradigms, the exact colours perceived in afterimages were measured for a large range of inducers to test those predictions. Three experiments tested predictions of afterimage hue and saturation with varying inducer hues, and changes of afterimage hues depending on inducer saturation (Exp. 1.a: 8 colours, tested across 31 participants; Exp. 1.b: 24 colours, tested across 52 participants; Exp.2.a: 72 colours, replicated with 10 participants; Exp. 2b: 72 colours, replicated with 2 participants; Exp. 3: 48-216 colours, replicated with 5 participants). Results across all three experiments very consistently demonstrated that afterimage colours are not colour-opponent, as widely assumed, but closely follow a quantitative model of adaptation in the cone photoreceptors. These findings unequivocally establish the origin of afterimages along the hierarchy of neural processing, hence resolving all prevailing misconceptions and contradictions. By linking the perceptual nature and the neural origin of afterimages, the present paradigm also provides a technique for probing those neural mechanisms behaviourally and in first-person experience
An easy way to show memory colour effects
No full textThis study proposes and evaluates a simple stimulus display that allows one to measure memory color effects (the effect of object knowledge and memory on color perception). The proposed approach is fast and easy and does not require running an extensive experiment. It shows that memory color effects are robust to minor variations due to a lack of color calibration
New insights into the evolution of color terms or an effect of saturation?
No full textThrough their thorough investigation of the Hadza, a nonindustrialized language community in Tanzania, Lindsey and colleagues (2015) developed a new approach to understand the evolution of color terms. In the present commentary, I discuss the possibility that some of their results might be explained by the lacking control of saturation of their color stimuli. The saturation of colors plays an important yet widely neglected role in color naming. The additional analyses presented here suggest that the results on Hadzane color naming could be due to variations in saturation in the stimulus set rather than being evidence for universal constraints on color term evolution
Misconceptions about colour categories
No full textThe origin of colour categories and their relationship to colour perception have been the prime example for testing the influence of language on perception and thought (Sapir-Whorf hypothesis) and more generally for investigating the biological, ecological and cultural determination of human cognition (nature-nurture debate). These themes are central to a broad range of disciplines, including vision research, neuroscience, cognitive psychology, developmental science, cultural anthropology, linguistics, computer science, and philosophy. Unfortunately, though, it has been tacitly taken for granted that the conceptual assumptions and methodological practices from the dawn of empirical research on colour categorisation are the gold standard for current colour category research. Here, we show that these assumptions and practices are obsolete and flawed and have led to four fundamental and widespread misconceptions about colour categorisation: 1.) that colour perception is inherently categorical; 2.) that English Basic Colour Terms correspond to universal categories that are the end point of a fixed evolutionary sequence; 3.) that the prototypes of English basic colour terms are perceptually salient and qualify as focal colours; and 4.) that colour category research essentially revolves around the universalism-realism debate. State-of-the-art research on colour categorisation provides new, more sophisticated approaches and allows for rectifying those four statements. At the same time, some of the questions underlying those statements are not convincingly answered yet and constitute major challenges to future research. The critical considerations on colour categorisation may be transferred to research on other kinds of perceptual categorisation to inspire new, more general research questions
Data for "Why Bananas Look Yellow: The Dominant Hue of Object Colours"
No full textThese extended supplementary materials go with the article: Witzel &amp; Dewis (2022) Why Bananas Look Yellow: The Dominant Hue of Object Colours. Vision Research.</span
Why bananas look yellow: the dominant hue of object colours
No full textIn this study, we propose a new approach to the perceptual representation of object colours. Three-dimensional objects have a polychromatic colour distribution. Yet, human observers abstract from the variation along the three perceptual colour dimensions when describing objects, such as when we say, “a banana is yellow”. We propose that the perceived object colour is determined by the dominant hue. The dominant hue corresponds to the first principal component of an object’s chromaticities. Across three experiments, we show for a sample of objects that the chromatic variation away from the dominant hue is almost completely neglected by human observers under non-laboratory viewing conditions. This is partly due to the low visibility of this variation, and partly to attentional change blindness. These findings reveal the potential role of dominant hue in the perception of object colours. Dominant hue may enable us to determine the most representative colours of objects because perceived object colours tend to be maximally bright and saturated. The present findings also imply that we can simplify the colour distributions of objects by projecting them onto their dominant hue. This may be useful for computational applications
Colour expectations across illumination changes
No full textThis study investigates human expectations towards naturalistic colour changes under varying illuminations. Understanding colour expectations is key to both scientific research on colour constancy and applications of colour and lighting in art and industry. We reanalysed data from asymmetric colour matches of a previous study and found that colour adjustments tended to align with illuminant-induced colour shifts predicted by naturalistic, rather than artificial, illuminants and reflectances. We conducted three experiments using hyperspectral images of naturalistic scenes to test if participants judged colour changes based on naturalistic illuminant and reflectance spectra as more plausible than artificial ones, which contradicted their expectations. When we consistently manipulated the illuminant (Experiment 1) and reflectance (Experiment 2) spectra across the whole scene, observers chose the naturalistic renderings significantly above the chance level (>25 %) but barely more often than any of the three artificial ones, collectively (>50 %). However, when we manipulated only one object/ area’s reflectance (Experiment 3), observers more reliably identified the version in which the object had a naturalistic reflectance like the rest of the scene. Results from Experiments 2–3 and additional analyses suggested that relational colour constancy strongly contributed to observer expectations, and stable cone-excitation ratios are not limited to naturalistic illuminants and reflectances but also occur for our artificial renderings. Our findings indicate that relational colour constancy and prior knowledge about surface colour shifts help to disambiguate surface colour identity under illumination changes, enabling human observers to recognise surface colours reliably in naturalistic conditions. Additionally, relational colour constancy may even be effective in many artificial conditions
The allocation of resources in visual working memory and multiple attentional templates
No full textIn a visual search task, sensory input is matched to a representation of the search target in visual working memory (VWM). This representation is referred to as attentional template. We investigated the conditions that allow for more than a single attentional template. The attentional template of color targets was measured by means of the contingent attentional capture paradigm. We found that attentional templates did not differ between search with 1 and 2 memorized target colors, suggesting that dual target search allowed for multiple attentional templates. In the same paradigm, we asked participants to memorize target and distractor color with equal precision. Both were presented before the search task. An attentional template was set up for the target, but not for the distractor color, suggesting that keeping a color in VWM does not automatically result in the creation of multiple attentional templates. Importantly, the precision of recall of the distractor color was worse than the precision of recall of the target color, regardless of instructions, suggesting that participants always allocated fewer VWM resources to the distractor color. Thus, 2 attentional templates may be set up, but only when the 2 colors receive an equal amount of resources in VWM (i.e., in dual target search). In contrast, when 1 item is deprioritized because of task demands, it receives fewer resources in VWM and multiple attentional templates cannot be established. Thus, unequal roles in the search task prevented the simultaneous operation of multiple attentional templates in VWM
How to make a #theDress
No full textIf we completely understand how a phenomenon works, we should be able to produce it ourselves. However, the individual differences in color appearance observed with #theDress seem to be a peculiarity of that photo, and it remains unclear how the proposed mechanisms underlying #theDress can be generalized to other images. Here, we developed a simple algorithm that transforms any image with bicolored objects into an image with the properties of #theDress. We measured the colors perceived in such images and compared them to those perceived in #theDress. Color adjustments confirmed that observers strongly differ in how they perceive the colors of the new images in a similar way as for #theDress. Most importantly, these differences were not unsystematic, but correlated with how observers perceive #theDress. These results imply that the color distribution is sufficient to produce the striking individual differences in color perception originally observed with #theDress—at least as long as the image appears realistic and hence compels the viewer to make assumptions about illuminations and surfaces. The algorithm can be used for stimulus production beyond this study
- …
