The Development of Color Perception and Cognition

Non-visual colour: A qualitative study of how the totally blind and an achromatope navigate colour in the sighted world

Colour plays an important role in the sighted world, not only by guiding and warning, but also by helping to make decisions, form opinions, and influence emotional landscape. While not everyone has direct access to this information, even people without colour vision (i.e., blind, achromatope) understand the meanings of colour terms and can assign sensory and affective properties to colours. To learn which aspects of colour are transmitted non-visually, and thus, are pertinent to those without colour vision, we conducted qualitative interviews with 11 participants (2 congenitally blind, 2 early blind, 4 late blind, 2 late blind with synaesthesia, and 1 achromatope). Our thematic analysis revealed that all participants had detailed knowledge of colours and displayed opinions and attitudes. Colour was important to them as it allowed to take part in the sighted world, navigate the surroundings, and communicate with the sighted peers. While participants with non-congenital colour vision absence could remember and even visualise colours, colour was more abstract to participants with congenital colour vision absence. This was possibly a reason why colour was not very important to their personal lives. Nonetheless, all our participants associated colours with diverse objects, concepts, and emotions, and also had colour preferences, indicating that semantic (conceptual, symbolic, affective) meanings of colour can be transmitted without direct visual experience. Future quantitative and qualitative studies are needed for a systematic understanding of such connotations in the visually impaired population, and their implications to those who can and cannot see colour.

Do we feel colours? A systematic review of 128 years of psychological research linking colours and emotions

Colour is an integral part of natural and constructed environments. For many, it also has an aesthetic appeal, with some colours being more pleasant than others. Moreover, humans seem to systematically and reliably associate colours with emotions, such as yellow with joy, black with sadness, light colours with positive and dark colours with negative emotions. To systematise such colour-emotion correspondences, we identified 132 relevant peer-reviewed articles published in English between 1895 and 2022. These articles covered a total of 42,266 participants from 64 different countries. We found that all basic colour categories had systematic correspondences with affective dimensions (valence, arousal, power) as well as with discrete affective terms (e.g., love, happy, sad, bored). Most correspondences were many-to-many, with systematic effects driven by lightness, saturation, and hue ('colour temperature'). More specifically, (i) LIGHT and DARK colours were associated with positive and negative emotions, respectively; (ii) RED with empowering, high arousal positive and negative emotions; (iii) YELLOW and ORANGE with positive, high arousal emotions; (iv) BLUE, GREEN, GREEN-BLUE, and WHITE with positive, low arousal emotions; (v) PINK with positive emotions; (vi) PURPLE with empowering emotions; (vii) GREY with negative, low arousal emotions; and (viii) BLACK with negative, high arousal emotions. Shared communication needs might explain these consistencies across studies, making colour an excellent medium for communication of emotion. As most colour-emotion correspondences were tested on an abstract level (i.e., associations), it remains to be seen whether such correspondences translate to the impact of colour on experienced emotions and specific contexts.

The origin of color categories

To what extent does concept formation require language? Here, we exploit color to address this question and ask whether macaque monkeys have color concepts evident as categories. Macaques have similar cone photoreceptors and central visual circuits to humans, yet they lack language. Whether Old World monkeys such as macaques have consensus color categories is unresolved, but if they do, then language cannot be required. If macaques do not have color categories, then color categories in humans are unlikely to derive from innate properties of visual encoding and likely to depend on cognitive abilities such as language that differ between monkeys and humans. We tested macaques by adapting a match-to-sample paradigm used in humans to uncover color categories from errors in matches, and we analyzed the data using computational simulations that assess the possibility of unrecognized distortions in the perceptual uniformity of color space. The results provide evidence that humans have consensus cognitive color categories and macaques do not. One animal showed evidence for a private color category, demonstrating that monkeys have the capacity to form color categories even if they do not form consensus color categories. Taken together, the results imply that consensus color categories in humans, for which there is ample evidence, must depend upon language or other cognitive abilities.

Exploring the categorical nature of colour perception: Insights from artificial networks

The electromagnetic spectrum of light from a rainbow is a continuous signal, yet we perceive it vividly in several distinct colour categories. The origins and underlying mechanisms of this phenomenon remain partly unexplained. We investigate categorical colour perception in artificial neural networks (ANNs) using the odd-one-out paradigm. In the first experiment, we compared unimodal vision networks (e.g., ImageNet object recognition) to multimodal vision-language models (e.g., CLIP text-image matching). Our results show that vision networks predict a significant portion of human data (approximately 80%), while vision-language models account for the remaining unexplained data, even in non-linguistic experiments. These findings suggest that categorical colour perception is a language-independent representation, though it is partly shaped by linguistic colour terms during its development. In the second experiment, we explored how the visual task influences the colour categories of an ANN by examining twenty-four Taskonomy networks. Our results indicate that human-like colour categories are task-dependent, predominantly emerging in semantic and 3D tasks, with a notable absence in low-level tasks. To explain this difference, we analysed kernel responses before the winner-takes-all stage, observing that networks with mismatching colour categories may still align in underlying continuous representations. Our findings quantify the dual influence of visual signals and linguistic factors in categorical colour perception and demonstrate the task-dependent nature of this phenomenon, suggesting that categorical colour perception emerges to facilitate certain visual tasks.

Thermo-sensitive Poloxamer based antibacterial anti-inflammatory and photothermal conductive multifunctional hydrogel as injectable, in situ curable and adjustable intraocular lens

Cataract patients look forwards to fewer postoperative complications and higher vision quality after surgery. However, the current intraocular lens (IOL) implanted after cataract surgery neither can adjust focal length in response to ciliary muscle contraction as natural lens nor have the ability to prevent postoperative complications. Herein, a thermosensitve Poloxamer based hybrid hydrogel with antibacterial anti-inflammatory and photothermal functional elements doping was designed and used as injectable, in situ curable, and adjustable IOL (FHTAB IOL). The FHTAB IOL was composed of thermosensitve triblock-polymer F127DA and a small amount of HAMA, combined with BP NS, TA, and Ag NPs. FHTAB IOL can be injected into the empty lens capsule after cataract surgery via an injectable thermos-gel under NIR illumination and then be rapidly cured to form a full-size IOL under short-time blue light irradiation. The designed injectable FHTAB IOL possesses high transparency and transmittance, with a refractive index similar to the natural lens and adjustable properties. It was stabilized as a refractive medium without any leakage in the eye. In addition, the TA and Ag NPs loaded in the FHTAB IOL displayed significant antibacterial and anti-inflammatory effects in vitro and vivo. This study presents a potentially effective new strategy for the development of multifunctional adjustable IOLs.

Visual stimulus structure, visual system neural activity, and visual behavior in young human infants

In visual perception and information processing, a cascade of associations is hypothesized to flow from the structure of the visual stimulus to neural activity along the retinogeniculostriate visual system to behavior and action. Do visual perception and information processing adhere to this cascade near the beginning of life? To date, this three-stage hypothetical cascade has not been comprehensively tested in infants. In two related experiments, we attempted to expose this cascade in 6-month-old infants. Specifically, we presented infants with two levels of visual stimulus intensity, we measured electrical activity at the infant cortex, and we assessed infants' preferential looking behavior. Chromatic saturation provided a convenient stimulus dimension to test the cascade because greater saturation is known to excite increased activity in the primate visual system and is generally hypothesized to stimulate visual preference. Experiment 1 revealed that infants prefer (look longer) at the more saturated of two colors otherwise matched in hue and brightness. Experiment 2 showed increased aggregate neural cortical excitation in infants (and adults) to the more saturated of the same pair of colors. Thus, experiments 1 and 2 taken together confirm a cascade: Visual stimulation of relatively greater intensity evokes relatively greater levels of bioelectrical cortical activity which in turn is associated with relatively greater visual attention. As this cascade obtains near the beginning of life, it helps to account for early visual preferences and visual information processing.

The vertebrate retina: a window into the evolution of computation in the brain

Animal brains are probably the most complex computational machines on our planet, and like everything in biology, they are the product of evolution. Advances in developmental and palaeobiology have been expanding our general understanding of how nervous systems can change at a molecular and structural level. However, how these changes translate into altered function - that is, into 'computation' - remains comparatively sparsely explored. What, concretely, does it mean for neuronal computation when neurons change their morphology and connectivity, when new neurons appear or old ones disappear, or when transmitter systems are slowly modified over many generations? And how does evolution use these many possible knobs and dials to constantly tune computation to give rise to the amazing diversity in animal behaviours we see today? Addressing these major gaps of understanding benefits from choosing a suitable model system. Here, I present the vertebrate retina as one perhaps unusually promising candidate. The retina is ancient and displays highly conserved core organisational principles across the entire vertebrate lineage, alongside a myriad of adjustments across extant species that were shaped by the history of their visual ecology. Moreover, the computational logic of the retina is readily interrogated experimentally, and our existing understanding of retinal circuits in a handful of species can serve as an anchor when exploring the visual circuit adaptations across the entire vertebrate tree of life, from fish deep in the aphotic zone of the oceans to eagles soaring high up in the sky.

Estimation of daylight spectral power distribution from uncalibrated hyperspectral radiance images

This paper introduces a novel framework for estimating the spectral power distribution of daylight illuminants in uncalibrated hyperspectral images, particularly beneficial for drone-based applications in agriculture and forestry. The proposed method uniquely combines image-dependent plausible spectra with a database of physically possible spectra, utilizing an image-independent principal component space (PCS) for estimations. This approach effectively narrows the search space in the spectral domain and employs a random walk methodology to generate spectral candidates, which are then intersected with a pre-trained PCS to predict the illuminant. We demonstrate superior performance compared to existing statistics-based methods across various metrics, validating the framework's efficacy in accurately estimating illuminants and recovering reflectance values from radiance data. The method is validated within the spectral range of 382-1002 nm and shows potential for extension to broader spectral ranges.

Colour perception develops throughout childhood with increased risk of deficiencies in children born prematurely

AIM

To quantify the impact of prematurity on chromatic discrimination throughout childhood, from 2 to 15 years of age.

METHODS

We recruited two cohorts of children, as part of the TrackAI Project, an international project with seven different study sites: a control group of full-term children with normal visual development and a group of children born prematurely. All children underwent a complete ophthalmological exam and an assessment of colour discrimination along the three colour axes: deutan, protan and trytan using a DIVE device with eye tracking technology.

RESULTS

We enrolled a total of 1872 children (928 females and 944 males) with a mean age of 6.64 years. Out of them, 374 were children born prematurely and 1498 were full-term controls. Using data from all the children born at term, reference normative curves were plotted for colour discrimination in every colour axis. Pre-term children presented worse colour discrimination than full-term in the three colour axes (p < 0.001). Even after removing from the comparison, all pre-term children with any visual disorder colour discrimination outcomes remained significantly worse than those from full-term children.

CONCLUSION

While colour perception develops throughout the first years of life, children born pre-term face an increased risk for colour vision deficiencies.

Using head-mounted eye trackers to explore children's color preferences and perceptions of toys with different color gradients

This study investigated how color gradients affect the attraction and visual comfort of children aged 4 to 7 years. We analyzed 108 eye-tracking datasets, including the color attraction index (COI), visual comfort index (PUI), and saccade rate (SR). The findings revealed that children are more attracted to colors as saturation decreases and brightness increases within a specific range. Beyond this range, reduced saturation diminishes color appeal. Moderate brightness and contrast enhance visual comfort during play, while extremely low contrast hinders concentration. Warm colors (red, orange, and yellow) slightly dominate preferences; however, the roles of hue, saturation, and brightness in children's color preferences remain inconclusive. These insights have practical implications for age-appropriate toy design and marketing. Future research should explore age-specific color preferences for more targeted design strategies.

Color and newborn intensive care unit design: executive summary

Research on color in the design of healthcare settings is minimal. This paper provides an executive summary of a recent review on this topic, focusing on application to newborn intensive care units. The review focuses on the following question: Does the use of color in the design of the newborn intensive care units impact health outcomes in infants, families, and/or staff? We employed a structured review process, resulting in four studies involving the use of color in NICUs. The search was expanded to include general research on responses to color and studies in other healthcare settings. The literature clustered around preferences and psychobiological impact of color on infants and adults in NICUs, the interaction of color and light, and the impact of color on adults in general medical settings. Recommendations are made regarding the importance of modifiability and flexibility in the use of color in NICUs and colors that are associated with stress reduction and stimulation.

Assessment of color preference, purchase intention and sexual attractiveness of lipstick colors under multiple lighting conditions

Lipstick is one of the most commonly used cosmetics, which is closely associated with female attractiveness and influences people's perception and behavior. This study aimed to investigate the impact of light sources, lipstick colors, as well as gender on the subjective assessment of lipstick color products from the prospective of color preference, purchase intention and sexual attractiveness. The correlation between color preference evaluations when applying lipstick on lips and on forearms was also explored. Sixty participants completed their visual assessment of 15 lipsticks worn by 3 models under 5 light sources, with uniformly sampled correlated color temperature (CCT) values ranging from 2,500 K to 6,500 K. The results indicated that the light source significantly influenced color preference and purchase intention, while lipstick color significantly impacted on sexual attractiveness. The interactions between gender and other factors were also observed and are discussed. Compared to men, women were found to be more sensitive to different light sources and hold different attitudes toward different lipstick colors under different CCTs. Interestingly, no significant correlation was found between lipstick color preference ratings on the lips and forearm, which conflicted with the commonly recognized way of lipstick color selection. These findings should contribute to a deeper understanding of the consumer attitude toward lipstick colors and provide a useful reference for lighting design in situations where cosmetics are specified, manufactured, retailed and generally used, both professionally and in the home.

Brain activity characteristics of RGB stimulus: an EEG study

The perception of color is a fundamental cognitive feature of our psychological experience, with an essential role in many aspects of human behavior. Several studies used magnetoencephalography, functional magnetic resonance imaging, and electroencephalography (EEG) approaches to investigate color perception. Their methods includes the event-related potential and spectral power activity of different color spaces, such as Derrington-Krauskopf-Lennie and red-green-blue (RGB), in addition to exploring the psychological and emotional effects of colors. However, we found insufficient studies in RGB space that considered combining all aspects of EEG signals. Thus, in the present study, focusing on RGB stimuli and using a data-driven approach, we investigated significant differences in the perception of colors. Our findings show that beta oscillation of green compared to red and blue colors occurs in early sensory periods with a latency shifting in the occipital region. Furthermore, in the occipital region, the theta power of the blue color decreases noticeably compared to the other colors. Concurrently, in the prefrontal area, we observed an increase in phase consistency in response to the green color, while the blue color showed a decrease. Therefore, our results can be used to interpret the brain activity mechanism of color perception in RGB color space and to choose suitable colors for more efficient performance in cognitive activities.

Color and NICU Design

PURPOSE

The appropriate use of color in healthcare settings has been a topic of interest for designers and researchers, and the need for evidence-based standards evident. The purpose of this article is to summarize recent research on color as applicable to neonatal intensive care units and to propose standards for color in these settings.

BACKGROUND

Research on this topic is limited due to difficulties associated with constructing research protocols, challenges in setting parameters for the independent variable (color), and the need to simultaneously address infants, families, and caregivers.

METHODS

For our literature review, the following research question was developed: Does the use of color in the design of the neonatal intensive care units (NICUs) impact health outcomes in newborn infants, families, and/or staff? Using Arksey and O'Malley's framework for conducting a structured literature review, we (1) identified the research question, (2) identified relevant studies, (3) selected studies, and (4) collated and summarized the results. Only four papers were found regarding NICUs, so the search was expanded to include related healthcare and authors reporting on best practice.

RESULTS

Overall, the primary research focused on behavioral or physiological outcomes including the role of wayfinding and art, the impact of lighting on color, and tools for evaluating the impact of color. Best practice recommendations sometimes reflected the primary research but occasionally provided contradictory advice.

CONCLUSIONS

Based on the reviewed literature, five topics are addressed: palette malleability; the use of the primary colors, blue, red, and yellow; and the relationship between light and color.