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The evolution of floral traits in animal-pollinated plants involves the interaction between flowers as signal senders and pollinators as signal receivers. Flower colors are very diverse, effect pollinator attraction and flower foraging behavior, and are hypothesized to be shaped through pollinator-mediated selection. However, most of our current understanding of flower color evolution arises from variation between discrete color morphs and completed color shifts accompanying pollinator shifts, while evidence for pollinator-mediated selection on continuous variation in flower colors within populations is still scarce. In this review, we summarize experiments quantifying selection on continuous flower color variation in natural plant populations in the context of pollinator interactions. We found that evidence for significant pollinator-mediated selection is surprisingly limited among existing studies. We propose several possible explanations related to the complexity in the interaction between the colors of flowers and the sensory and cognitive abilities of pollinators as well as pollinator behavioral responses, on the one hand, and the distribution of variation in color phenotypes and fitness, on the other hand. We emphasize currently persisting weaknesses in experimental procedures, and provide some suggestions for how to improve methodology. In conclusion, we encourage future research to bring together plant and animal scientists to jointly forward our understanding of the mechanisms and circumstances of pollinator-mediated selection on flower color.

Previous studies of preference for and harmony of color combinations have produced confusing results. For example, some claim that harmony increases with hue similarity, whereas others claim that it decreases. We argue that such confusions are resolved by distinguishing among three types of judgments about color pairs: (1) preference for the pair as a whole, (2) harmony of the pair as a whole, and (3) preference for its figural color when viewed against its colored background. Empirical support for this distinction shows that pair preference and harmony both increase as hue similarity increases, but preference relies more strongly on component color preference and lightness contrast. Although pairs with highly contrastive hues are generally judged to be neither preferable nor harmonious, figural color preference ratings increase as hue contrast with the background increases. The present results thus refine and clarify some of the best-known and most contentious claims of color theorists.

Abstract Background Flower coloration is a key enabler for pollinator attraction. Floral visual signals comprise several components that are generated by specific anatomical structures and pigmentation, and often have different functions in pollinator attraction. Anatomical studies have advanced our understanding of the optical properties of flowers, and evidence from behavioural experiments has elucidated the biological relevance of different components of floral visual signals, but these two lines of research are often considered independently. Scope Here, we review current knowledge about different aspects of the floral visual signals, their anatomical and optical properties, and their functional significance in plant–pollinator visual signalling. We discuss common aspects, such as chromatic and achromatic contrast, hue, saturation and brightness, as well as less common types of visual signals, including gloss, fluorescence, polarization and iridescence in the context of salience of floral colour signals and their evolution, and highlight promising avenues for future research.

Most of the research on color vision related behaviors in dogs has involved training the dogs to perform visual discrimination tasks. We investigated the importance of color to untrained Indian free-ranging dogs (FRDs). Using one-time multi-option choice tests for color preference in 134 adult dogs, we found the dogs to prefer yellow objects over blue or gray ones while there was no preference between blue and gray. We next pitted a yellow object against a gray object that had food. Here, the dogs ignored the food (biscuit or chicken) to approach the yellow object first indicating the color preference to be quite strong. Color preference has previously been investigated in many other animals and has implications for behaviors like mate choice and foraging. Our study provides a new perspective into the ecology of Indian FRDs and might have implications for companion dogs as well, if they too show this preference. Highlights Indian free-ranging dogs (FRDs) show preference for the color yellow over blue and gray. Indian FRDs show no preference between blue and gray colors. Attraction towards a yellow object can be stronger than attraction towards food rewards for Indian FRDs.

Leptin, a hormone secreted by peripheral adipose tissues, regulates the appetite in animals. Recently, evidence has shown that leptin also plays roles in behavioral response in addition to controlling appetite. In this study, we examined the potential function of leptin on non-appetite behaviors in zebrafish model. By using genome editing tool of Transcription activator-like effector nuclease (TALEN), we successfully knocked out leptin a (lepa) gene by deleting 4 bp within coding region to create a premature-translation stop. Morphological and appetite analysis showed the lepa KO fish display a phenotype with obese, good appetite and elevation of Agouti-related peptide (AgRP) and Ghrelin hormones, consistent with the canonical function of leptin in controlling food intake. By multiple behavior endpoint analyses, including novel tank, mirror biting, predator avoidance, social interaction, shoaling, circadian rhythm, and color preference assay, we found the lepa KO fish display an anxiogenic phenotype showing hyperactivity with rapid swimming, less freezing time, less fear to predator, loose shoaling area forming, and circadian rhythm and color preference dysregulations. Using biochemical assays, melatonin, norepinephrine, acetylcholine and serotonin levels in the brain were found to be significantly reduced in lepa KO fish, while the levels of dopamine, glycine and cortisol in the brain were significantly elevated. In addition, the brain ROS level was elevated, and the anti-oxidative enzyme catalase level was reduced. Taken together, by performing loss-of-function multiple behavior endpoint testing and biochemical analysis, we provide strong evidence for a critical role of lepa gene in modulating anxiety, aggression, fear, and circadian rhythm behaviors in zebrafish for the first time.

The tendency toward the aesthetic preference affects an individual’s intention to purchase furniture. Color and form are two fundamental elements of furniture appearance. However, there is a significant lack of human–computer interaction research on the aesthetic evaluation of furniture with various colors and forms, necessitating a comprehensive study to provide theoretical and empirical support to furniture designers and businesses. Thus, this study introduces a multimodal method by integrating various modalities, which allowed us to investigate the factors that significantly affect subjective preference evaluation and physiological feedback. The results indicated significant correlations between behavioral data, first fixation duration, and average pupil diameter. Meanwhile, the correlation between multimodal measurement data and product aesthetic ratings was analyzed, and an evaluation model of the leisure chair aesthetic correlation mechanism was proposed.

Girls and boys differ in their preferences for toys such as dolls and trucks. These sex differences are present in infants, are seen in non-human primates, and relate, in part, to prenatal androgen exposure. This evidence of inborn influences on sex-typed toy preferences has led to suggestions that object features, such as the color or the shape of toys, may be of intrinsically different interest to males and females. We used a preferential looking task to examine preferences for different toys, colors, and shapes in 120 infants, ages 12, 18, or 24 months. Girls looked at dolls significantly more than boys did and boys looked at cars significantly more than girls did, irrespective of color, particularly when brightness was controlled. These outcomes did not vary with age. There were no significant sex differences in infants’ preferences for different colors or shapes. Instead, both girls and boys preferred reddish colors over blue and rounded over angular shapes. These findings augment prior evidence of sex-typed toy preferences in infants, but suggest that color and shape do not determine these sex differences. In fact, the direction of influence could be the opposite. Girls may learn to prefer pink, for instance, because the toys that they enjoy playing with are often colored pink. Regarding within sex differences, as opposed to differences between boys and girls, both boys and girls preferred dolls to cars at age 12-months. The preference of young boys for dolls over cars suggests that older boys’ avoidance of dolls may be acquired. Similarly, the sex similarities in infants’ preferences for colors and shapes suggest that any subsequent sex differences in these preferences may arise from socialization or cognitive gender development rather than inborn factors.

Building façade color plays a key role in shaping urban image, enhancing urban vitality, and optimizing citizens’ living experience. Moreover, colors can influence people’s perception of space, but the multiple interrelationships between color elements and users’ color evaluation and visual perception have not yet been thoroughly studied. In order to explore the relationships between color elements and visual perception and subjective comfort, this study discusses the matching relationship between color and the comfort of a residential building façade from three levels of color hue, lightness, and saturation by combining eye movement technology and a subjective evaluation. Taking Anshan San Village in Shanghai as the research object, the relationship model between color elements, visual perception, and subjective comfort is established through correlation analysis, linear regression, and multifactor regression analysis, and the correlation between single elements and multiple elements is explored from multi-dimensional perspectives. It aims to assess the operability of eye movement data as a measure of the visual comfort with the residential building façade color through multiple indicators and to explore and establish a new correlation assessment framework between the three attributes of façade color and users’ visual comfort. The results show that (1) highly saturated façade colors significantly increase cognitive load and decrease color evaluation. (2) Brightness has a non-linear relationship with visual perception and subjective evaluation, either too high or too low a brightness value will cause visual fatigue and thus reduce the color evaluation, and when the brightness is maintained at 40–80%, there will be a better color experience. (3) Warm tones such as red, orange, and yellow can strengthen the color perception to enhance the color evaluation of the façade; among cold tones, cyan and purple can also strengthen the visual perception of the color of the façade to enhance the color evaluation. After validation, the proposed new color comfort assessment method is feasible and comprehensive, and we hope it can provide a reference for the planning of old residential buildings and communities in the future.

In order to study the aesthetic preferences of individuals in terms of wood color, the authors explored the preference for red sandalwood and wenge wood of different hues and lightness values through a combination of an eye movement technique and subjective evaluation. The experimental results showed that: (1) sex factors had a significant effect on the eye movement indexes in a modern aesthetic preference experiment; (2) the preferences of the subjects varied slightly with different wood types but in a lower range; and (3) the effective eye movement indexes in this study were fixation duration, number of fixations, and number of last-sampling positions; in addition, there were differences in the effective eye movement indicators in different experiments. The subjects preferred a low lightness value or color of the chair.

Color plays an essential role in the design of user interfaces and significantly impacts the user experience. To create aesthetically pleasing and user-friendly interfaces, the colors of the user interface should be consistent with the images. The latter can be challenging to achieve, as images often have different colors and are often changed by editors or authors who do not have sufficient design knowledge. To solve this problem, we have developed a model that automatically determines the color theme of the user interface based on a given image. The model first extracts the most prominent colors from the image and then considers both aesthetic (color harmony and compatibility with the image) and usability aspects (color contrast, color diversity, and color strength). All color calculations are performed in the perceptually uniform color space CAM02-UCS. In addition, the model can be adapted to the user’s needs and requirements. To test the model, we implemented it in a web-based application in which the colors were automatically selected based on the featured image. The resulting color themes were then evaluated by the users, who were mainly professional designers. According to the results, the model generates color themes that are consistent with the image, aesthetic, and user-friendly. An important observation was also that color harmony can be achieved simply by using the most prominent colors of the image (regardless of their hue), suggesting that color harmony is strongly influenced by the context of use. The presented model holds significant practical importance as it can be utilized in various applications and tools. For instance, it can automatically choose a color theme for a user interface based on a particular image, such as a company logo or a product image. Moreover, it can dynamically adjust the colors of elements in real time based on the image that is visible simultaneously with the elements.