Daltonization or colour enhancement: potential uses and limitations [Invited].

The main perceptual-cognitive limitations of CDOs (Colour Deficient Observers) are analysed, along with the uses and limitations of tools that either transform images so that CNOs (Colour Normal Observers) see them as CDOs (simulation) or transform images so that CDOs can use them as CNOs (daltonization). The four main uses of colour (comparative, denotative, connotative, and aesthetic) are analysed, along with their relation to, alternatively, the ability to discriminate colour stimuli or to categorize colours. These uses of colour are applied to analyse the possible effects of daltonization tools.

"Red-Green" or "Brown-Green" Dichromats? The Accuracy of Dichromat Basic Color Terms Metacognition Supports Denomination Change.

Two experiments compared "Red-Green" (R-G) dichromats' empirical and metacognized capacities to discriminate basic color categories (BCCs) and to use the corresponding basic color terms (BCTs). A first experiment used a 102-related-colors set for a pointing task to identify all the stimuli that could be named with each BCT by each R-G dichromat type (8 protanopes and 9 deuteranopes). In a second experiment, a group of R-G dichromats (15 protanopes and 16 deuteranopes) estimated their difficulty discriminating BCCs-BCTs in a verbal task. The strong coincidences between the results derived from the pointing and the verbal tasks indicated that R-G dichromats have very accurate metacognition about their capacities (they only had considerable difficulty discriminating 13 out of the total of 55 possible BCT pairs) and limitations (Brown-Green and Blue-Purple pairs were rated especially difficult to differentiate) in the use of BCTs. Multidimensional scaling (MDS) solutions derived from both tasks were very similar: BCTs in R-G dichromats were properly represented in 2D MDS solutions that clearly show one chromatic dimension and one achromatic dimension. Important concordances were found between protanopes and deuteranopes. None of these dichromats showed substantial difficulty discriminating the Red-Green pair. So, to name them "R-G" dichromats is misleading considering their empirical capacities and their metacognition. Further reasons to propose the use of the alternative denomination "Brown-Green" dichromats are also discussed. We found some relevant differences between the "Brown-Green" dichromats' empirical and self-reported difficulties using BCTs. Their metacognition can be considered a "caricature" of their practical difficulties. This caricature omits some difficulties including their problems differentiating "white" and "black" from other BCTs, while they overestimate their limitations in differentiating the most difficult pairs (Brown-Green and Blue-Purple). Individual differences scaling (INDSCAL) analyses indicated that the metacognition regarding the use of BCTs in "Brown-Green" dichromats, especially deuteranopes, is driven slightly more by the chromatic dimension and driven slightly less by the achromatic dimension, than their practical use of BCTs. We discuss the relevance of our results in the framework of the debate between the linguistic relativity hypothesis (LRH) and the universal evolution (UE) theories.

Exposure to virtual reality as a tool to reduce peri-operative anxiety in patients undergoing colorectal cancer surgery: a single-center prospective randomized clinical trial.

BACKGROUND: More than 60% of patients who undergo surgery for colorectal cancer experience anxiety at some point during the perioperative period. In addition to the obvious impact on the experience of the therapeutic process, the presence of anxiety has also been associated with the appearance of complications. Virtual reality could reduce it by simulating the controlled exposure of the patient to the conscious part of the surgical process. METHODS: Single-center randomized clinical trial (NCT04058600) in which patients who were to undergo surgery for colorectal cancer and who had not previously undergone surgery as adults were exposed, prior to hospital admission, to virtual reality software in which all perioperative phases in which the patient is awake, from admission to discharge, were recreated. The main objective was to determine the presence of pre- and post-exposure anxiety using the validated State-Trait Anxiety Inventory Scale (STAI-S) and Hospital Anxiety and Depression Scale (HADS). RESULTS: A total of 126 patients were recruited (58 exposed, 68 unexposed). There were no differences between the groups in terms of age, gender, anesthetic risk, type of surgery. or levels of preoperative anxiety or depression. After exposure, all anxiety/depression rating scales decreased significantly. CONCLUSIONS: The use of simulation using virtual reality can reduce perioperative anxiety in patients undergoing surgery for colorectal cancer.

Performance of Indocyanine-Green Imaging for Sentinel Lymph Node Mapping and Lymph Node Metastasis in Esophageal Cancer: Systematic Review and Meta-Analysis.

BACKGROUND AND OBJECTIVES: Lymphatic mapping with indocyanine-green (ICG) and near-infrared light fluorescent imaging is widely used for sentinel lymph node staging in different types of cancer but is not fully accepted for all procedures because studies have reported heterogeneous results. This study aimed to assess the detection rate (DR) of ICG imaging for sentinel lymph node mapping (SLNM) and lymph node metastases (LNMs) in esophageal cancer. METHODS: A systematic search was performed to identify relevant studies examining the use of ICG imaging for SLNM in patients with esophageal cancer. Extracted results were pooled in a single-proportion meta-analysis, with a random-effects model, presented as forest plots. RESULTS: Six studies were included in the analysis. The ICG DR for SLNM was 89% [95% confidence interval (CI) 71%-96%]. The pooled sensitivity and specificity values for the detection of LNMs were 84% (95% CI 64%-94%) and 15% (95% CI 3%-45%), respectively. A trend towards a lower DR was found with increasing mean latency time between ICG injection and SLNM. CONCLUSIONS: ICG imaging is a technique that potentially could improve lymph node yield excision and, as a consequence, improve the detection of lymph node metastases.

Basic Color Terms (BCTs) and Categories (BCCs) in Three Dialects of the Spanish Language: Interaction Between Cultural and Universal Factors.

Two experiments were performed to identify and compare the Basic Color Terms (BCTs) and the Basic Color Categories (BCCs) included in three dialects (Castilian, Mexican, and Uruguayan) of the Spanish language. Monolexemic Elicited lists were used in the first experiment to identify the BCTs of each dialect. Eleven BCTs appeared for the Spanish and the Mexican, and twelve did so for the Uruguayan. The six primary BCTs (rojo "red," verde "green," amarillo "yellow," azul "blue," negro "black," and blanco "white") appeared in the three dialects. This occurred for only three derived BCTs (gris "gray," naranja "orange," and rosa "pink") but not for the other five derived BCTs (celeste "sky blue," marrón "brown," café "brown," morado "purple," and violeta "purple"). Color transitions were used in the second experiment for two different tasks. Extremes naming task was used to determine the relation between two different dialects' BCTs: equality, equivalence or difference. The results provided the first evidence for marrón "brown" and café "brown" being equivalent terms for the same BCC (brown in English) as is the case of morado "purple" and violeta "purple." Uruguayan celeste "sky blue" had no equivalent BCT in the other two dialects. Boundary delimitation task required the selection of the color in the boundary between two categories. The task was used to reasonably estimate the volume occupied by each BCC in the color space considering its chromatic area and lightness range. Excluding sky blue (celeste "sky blue") and blue (azul "blue"), the other BCCs color volumes were similar across the three dialects. Uruguayan sky blue and blue volumes conjointly occupied the portion of the color space corresponding to the Castilian and Mexican blue BCC. The fact that the BCT celeste "sky blue" only appeared in Uruguayan very probably derived from specific cultural factors (the use of the color in the flags and the arrival of an important number of Italian immigrants). Nevertheless, these cultural factors seem to nurture from a perceptive structuring of the color space, which nature is universal, as the boundaries of this category can be delimited from the responses of Spanish and Mexican participants.

Robust colour constancy in red-green dichromats.

Colour discrimination has been widely studied in red-green (R-G) dichromats but the extent to which their colour constancy is affected remains unclear. This work estimated the extent of colour constancy for four normal trichromatic observers and seven R-G dichromats when viewing natural scenes under simulated daylight illuminants. Hyperspectral imaging data from natural scenes were used to generate the stimuli on a calibrated CRT display. In experiment 1, observers viewed a reference scene illuminated by daylight with a correlated colour temperature (CCT) of 6700K; observers then viewed sequentially two versions of the same scene, one illuminated by either a higher or lower CCT (condition 1, pure CCT change with constant luminance) or a higher or lower average luminance (condition 2, pure luminance change with a constant CCT). The observers' task was to identify the version of the scene that looked different from the reference scene. Thresholds for detecting a pure CCT change or a pure luminance change were estimated, and it was found that those for R-G dichromats were marginally higher than for normal trichromats regarding CCT. In experiment 2, observers viewed sequentially a reference scene and a comparison scene with a CCT change or a luminance change above threshold for each observer. The observers' task was to identify whether or not the change was an intensity change. No significant differences were found between the responses of normal trichromats and dichromats. These data suggest robust colour constancy mechanisms along daylight locus in R-G dichromacy.

Color preference in red-green dichromats.

Around 2% of males have red-green dichromacy, which is a genetic disorder of color vision where one type of cone photoreceptor is missing. Here we investigate the color preferences of dichromats. We aim (i) to establish whether the systematic and reliable color preferences of normal trichromatic observers (e.g., preference maximum at blue, minimum at yellow-green) are affected by dichromacy and (ii) to test theories of color preference with a dichromatic sample. Dichromat and normal trichromat observers named and rated how much they liked saturated, light, dark, and focal colors twice. Trichromats had the expected pattern of preference. Dichromats had a reliable pattern of preference that was different to trichromats, with a preference maximum rather than minimum at yellow and a much weaker preference for blue than trichromats. Color preference was more affected in observers who lacked the cone type sensitive to long wavelengths (protanopes) than in those who lacked the cone type sensitive to medium wavelengths (deuteranopes). Trichromats' preferences were summarized effectively in terms of cone-contrast between color and background, and yellow-blue cone-contrast could account for dichromats' pattern of preference, with some evidence for residual red-green activity in deuteranopes' preference. Dichromats' color naming also could account for their color preferences, with colors named more accurately and quickly being more preferred. This relationship between color naming and preference also was present for trichromat males but not females. Overall, the findings provide novel evidence on how dichromats experience color, advance the understanding of why humans like some colors more than others, and have implications for general theories of aesthetics.

An experimental method for the assessment of color simulation tools.

The Simulcheck method for evaluating the accuracy of color simulation tools in relation to dichromats is described and used to test three color simulation tools: Variantor, Coblis, and Vischeck. A total of 10 dichromats (five protanopes, five deuteranopes) and 10 normal trichromats participated in the current study. Simulcheck includes two psychophysical tasks: the Pseudoachromatic Stimuli Identification task and the Minimum Achromatic Contrast task. The Pseudoachromatic Stimuli Identification task allows determination of the two chromatic angles (h(uv) values) that generate a minimum response in the yellow­blue opponent mechanism and, consequently, pseudoachromatic stimuli (greens or reds). The Minimum Achromatic Contrast task requires the selection of the gray background that produces minimum contrast (near zero change in the achromatic mechanism) for each pseudoachromatic stimulus selected in the previous task (L(R) values). Results showed important differences in the colorimetric transformations performed by the three evaluated simulation tools and their accuracy levels. Vischeck simulation accurately implemented the algorithm of Brettel, Viénot, and Mollon (1997). Only Vischeck appeared accurate (similarity in huv and L(R) values between real and simulated dichromats) and, consequently, could render reliable color selections. It is concluded that Simulcheck is a consistent method because it provided an equivalent pattern of results for huv and L(R) values irrespective of the stimulus set used to evaluate a simulation tool. Simulcheck was also considered valid because real dichromats provided expected huv and LR values when performing the two psychophysical tasks included in this method.

Basic color terms use by aged observers: lens aging and perceptual compensation.

Basic Color Terms (BCTs) use by aged people (normal and tritanomalous) was analysed on the basis of the results provided by two visual search tasks. One task (mapping) required participants to select every stimulus that could be included in a specific BCT. Another task (best representative) required participants to select the stimulus that most accurately identified a BCT. Both tasks' results were used for two different goals. First (descriptive level), to specify the main differences between aged and young people in their use of BCTs (dimensions provided by multidimensional scaling, confusions between specific pairs of BCTs). Second (explicative level), to compare the accuracy of three models for predicting aged people's performance. Model A (filtering without compensation) assumed that aged people must use BCTs as young people do when responding to stimuli similar to the ones produced by lens aging. On the contrary, model B (filtering with compensation) assumed that lens aging effects were partially compensated by a von Kries-type mechanism (white normalisation). Finally, model C (tritan lines) assumed that ocular aging only influences S cone responses (tritan responses). Results showed that model B was the most accurate with the percentage of explained variance over 90% for both aged groups.

Basic Color Terms Use by Aged observers: lens aging and perceptual compensation

Basic Color Terms (BCTs) use by aged people (normal and tritanomalous) was analysed on the basis of the results provided by two visual search tasks. One task (mapping) required participants to select every stimulus that could be included in a specific BCT. Another task (best representative) required participants to select the stimulus that most accurately identified a BCT. Both tasks’ results were used for two different goals. First (descriptive level), to specify the main differences between aged and young people in their use of BCTs (dimensions provided by multidimensional scaling, confusions between specific pairs of BCTs). Second (explicative level), to compare the accuracy of three models for predicting aged people’s performance. Model A (filtering without compensation) assumed that aged people must use BCTs as young people do when responding to stimuli similar to the ones produced by lens aging. On the contrary, model B (filtering with compensation) assumed that lens aging effects were partially compensated by a von Kries-type mechanism (white normalisation). Finally, model C (tritan lines) assumed that ocular aging only influences S cone responses (tritan responses). Results showed that model B was the most accurate with the percentage of explained variance over 90 % for both aged groups (AU)

Los resultados proporcionados por dos tareas de búsqueda visual sirvieron para analizar el uso de los términos básicos de color (TBCs) en personas mayores (normales y tritanómalas). Una tarea (delimitación) requirió que los participantes seleccionasen todos los estímulos que podían incluirse en cada TBC concreto. La otra tarea (mejor representante) requirió que seleccionasen el estímulo que mejor identificaba a un TBC. Los resultados de ambas tareas se utilizaron con dos finalidades diferentes. La primera (nivel descriptivo) fue la de especificar las diferencias principales entre las personas mayores y jóvenes en su forma de usar los TBCs (dimensiones proporcionadas por el escalamiento multidimensional, confusiones entre pares específicos de TBCs). La segunda (nivel explicativo) fue la de comparar la adecuación de tres modelos para predecir el desempeño de las personas mayores. El modelo A (filtrado sin compensación) asumió que las personas mayores debían usar los TBCs como lo hacen las personas jóvenes al responder a estímulos similares a los que produce el envejecimiento del cristalino. Por el contrario, el modelo B (filtrado con compensación) asumió que los efectos del envejecimiento del cristalino fueron parcialmente compensados por un mecanismo tipo von Kries (normalización al blanco). Finalmente el modelo C (líneas tritán) asumió que el envejecimiento del cristalino sólo influye en las respuestas de los conos S (respuestas tritán). Los resultados mostraron que el modelo B fue el más adecuado, ya que llegó a explicar más del 90% de la varianza en ambos grupos de personas mayores (AU)

Locating basic Spanish colour categories in CIE L*u*v* space: Identification, lightness segregation and correspondence with English equivalents

Se realizaron cinco experimentos para identificar las categorías cromáticas básicas (CCB) del español y ubicarlas en el espacio CIE L*u*v*. Empleando una tarea de listas elicitadas y otra de denominación monolexémica libre, se confirmó la existencia de 11 CCB. Mediante una tarea de estimación de sinonimia, se concluyó que, en español, se emplean 2 términos sinónimos (morado y violeta) para denominar una categoría equivalente a la inglesa purple. Tres experimentos proporcionaron información acerca de la localización colorimétrica de las 11 CCB del español. Dos emplearon tareas de denominación monolexémica (libre y restringida) y el tercero requirió la señalización de prototipos y de buenos ejemplares. Se observó que las CCB del español y del inglés son esencialmente equivalentes en número y delimitación colorimétrica, por lo puede considerarse que nuestro trabajo extiende y complementa la investigación previa (sobre CCB inglesas) en lo referente a la localización de las categorías acromáticas en el espacio de color, los vínculos entre categorías cromáticas y acromáticas (ni rojo ni naranja tienen vínculos directos con las categorías acromáticas), y la dependencia de la claridad que muestra el uso de las CCB. Por último, destaca la existencia de 2 categorías próximas a ser básicas: beige y granate(AU)

Five experiments were performed to identify the basic Spanish colour categories (BCCs) and to locate them in the CIE L*u*v* space. The existence of 11 BCCs was confirmed using an elicited list task and a free monolexemic naming task. From the results provided by a synonymicity estimation task, it was concluded that, in Spanish, 2 synonymous terms (morado and violeta) are used to name a category equivalent to the English category purple. Three experiments provided information about the colourimetric localization of the 11 Spanish BCCs. Two experiments used monolexemic naming tasks (free and restricted) and a third required the free signalling of prototypes and good exemplars. It was observed that Spanish and British BCCs are essentially equivalents in number and colourimetric delimitation and, therefore, our work can be considered to extend and complement previous research (on English BCCs) insofar as achromatic categories in colour space localization, the links between chromatic and achromatic categories (red and orange have no direct links with achromatic categories), and the dependence of the use of BCCs on lightness are concerned. Lastly, our results indicate the existence of 2 categories that are nearly basic: beige and garnet(AU)

Lightness compression and hue changes.

Two experiments were performed to relate the Bezold-Brücke (B-B) and lightness compression effects. The first used a calibrated screen to present an achromatic luminance staircase. In addition, it reproduced, the methodology and the essential aspects the lightness compression effect discovered by Cataliotti and Gilchrist (1995). That is, observers perceived a truncated grey scale (from white to medium grey) when the staircase was the only stimulation in the near background (Gelb condition), but not when presented on a Mondrian background, because of the high articulation level provided by this background. Experiment 1 design also included two other backgrounds that produced a partial compression effect. In Experiment 2, two chromatic staircases were used. Employing a naming task, changes in hue perception were only observed for the susceptible staircase. The observed changes were of two types. First, for the full staircase presentations, a Gelb background produced maximum lightness compression (more similarity in the lightness of the staircase stimuli) and, also, a minimum B-B effect (fewer differences in hue). Second, only for the Gelb condition, there were changes in the hue of the lowest luminance staircase stimuli depending on the staircase extension. Results are discussed in the framework of the anchoring theory of lightness perception.

Lightness compression and Hue changes

Two experiments were performed to relate the Bezold-Brücke (B-B) and lightness compression effects. The first used a calibrated screen to present an achromatic luminance staircase. In addition, it reproduced, the methodology and the essential aspects the lightness compression effect discovered by Cataliotti and Gilchrist (1995). That is, observers perceived a truncated grey scale (from white to medium grey) when the staircase was the only stimulation in the near background (Gelb condition), but not when presented on a Mondrian background, because of the high articulation level provided by this background.Experiment 1 design also included two other backgrounds that produced a partial compression effect. In Experiment 2, two chromatic staircases were used. Employing an aming task, changes in hue perception were only observed for the susceptible staircase. The observed changes were of two types. First, for the full staircase presentations, a Gelb background produced maximum lightness compression (more similarity in the lightness of the staircase stimuli) and, also, a minimum B-B effect (fewer differences in hue). Second, only for the Gelb condition, there were changes in the hue of the lowest luminance staircase stimuli depending on the staircase extension. Results are discussed in the framework of the anchoring theory of lightness perception (AU)

Se realizaron dos experimentos para relacionar el efecto Bezold-Brücke y el de compresión de la claridad. En el primero se utilizó un monitor calibrado para presentar una escalera acromática de luminancias. Aparte de ello, el experimento reprodujo la metodología y los aspectos esenciales del efecto de compresión de la claridad descubierto por Cataliotti y Gilchrist (1995). Esto es, los observadores percibieron una escala de grises truncada (del blanco al gris medio) cuando la escalera fue la única estimulación presentada en el entorno próximo (condición Gelb), pero no cuando se presentó sobre un Mondrian, debido al alto nivel de articulación proporcionado por este fondo. El diseño del primer experimento también incluyó otros dos fondos que produjeron un efecto de compresión parcial. En el segundo experimento se utilizaron dos escaleras cromáticas. Una tarea de denominación permitió apreciar cambios en la percepción del matiz sólo en la escalera susceptible.Los efectos observados fueron de dos tipos. Primero, cuando se presentó la escalera completa, se observó que el fondo Gelb produjo una máxima compresión de la claridad(máxima similitud entre los estímulos de la escalera) y, también, un grado mínimo de efectos B-B (menos diferencias en matiz). Segundo, sólo para la condición Gelb hubo cambios en el matiz del estímulo de menor luminancia de la escalera, dependiendo dela extensión de la escalera. Los resultados se comentan en el marco de referencia proporcionado por la teoría del anclaje de la percepción de la claridad (AU)

Claridad y percepción del matiz: el efecto Bezold-Brücke y las categorías cromáticas básicas / Lightness and hue perception: the Bezold-Brücke effect and colour basic categories

La investigación se efectuó en el ámbito de los colores de superficie y tuvo las dos siguientes finalidades: (1) Determinar los ángulos cromáticos asociados a la aparición de efectos categoriales tipo B-B (Bezold-Brücke) (2) Delimitar las características colorimétricas compatibles con el uso de cada categoría cromática básica del Español. Para alcanzar los objetivos indicados se empleó el conjunto de fichas contenidas en el atlas NCS, como fuente de estimulación en una tarea de denominación monolexémica. Los resultados mostraron que la utilización de las categorías cromáticas básicas no sólo dependen del valor del ángulo cromático (Hu'v') sino también del de la saturación (Su'v') y la claridad (L*). La importancia de este último parámetro fue especialmente relevante para, aproximadamente, la mitad del círculo cromático (de G50Y a R50B en la nomenclatura NCS). Ante esta mitad se dieron frecuentes efectos categoriales tipo B-B y, por tanto, estímulos semejantes en ángulo cromático, pero diferentes en claridad, recibieron denominaciones diferentes. (AU)

Reflectancia y Desequilibrio energético: Evaluación colorimétrica del atlas de color NCS / Reflectance and Energetic Imbalance: Colourimetric Evaluation of the NCS Colour Atlas

Se evaluó al atlas NCS de dos maneras. La primera se basó en una serie de mediciones colorimétricas exhaustivas (a las que se puede acceder mediante el apéndice electrónico que figura en http://www.uv.es/psicologica) y que fueron utilizadas para: (1) Relacionarlas con los parámetros descriptivos utilizados por el atlas, y (2) analizar las propiedades colorimétricas generales de los colores de superficie.El segundo tipo de evaluación examinó el resultado de usar el atlas NCS para especificar colorimetricamente muestras de color no pertenecientes a él. El análisis de las relaciones existentes entre el NCS con los parámetros colorimétricos mostró que cada matiz-NCS se asoció con un ángulo cromático específico y, consiguientemente, con una longitud de onda dominante. La relaciones existentes entre, por una parte, la blancura NCS y la claridad CIE y, por otra, entre los parámetros de croma CIE y NCS, fueron altas pero sin alcanzar niveles máximos. Cuando se consideró globalmente al atlas se observó que el nivel de claridad determinaba en gran medida la saturación y el ángulo cromático de los estímulos. Concretamente, para claridades bajas se observaron los niveles más altos de saturación CIE para los ángulos cromáticos asociados a cualquiera de los extremos del espectro o de la línea de los morados. Para claridades altas, por el contrario, se observaron los niveles más altos de saturación para los ángulos cromáticos relacionados con la porción media del espectro. El segundo tipo de evaluación del NCS consideró su posible utilidad para inferir los parámetros colorimétricos de muestras no incluidas en el atlas. Puesto que se detectó un nivel de error relativamente bajo ( E < 8), se concluyó que el atlas puede utilizarse para aquellas aplicaciones prácticas que implican cálculos colorimétricos con un nivel de precisión medio o bajo. (AU)