Color Stimuli Research Articles

Specification of just‐noticeable color difference for 2° and 10° stimuli using different color matching functions

AbstractJust‐noticeable color difference (JNCD) is important in color specification and characterization. The commonly referenced specification of JNCD (i.e., 0.004 or 0.0033 u′v′ unit) is thought to originate from the MacAdam ellipses, which were derived using 2° color stimuli and characterized using the CIE 1931 2° color matching functions (CMFs). However, there is no universally agreed or clear definition of JNCD. Also, such a specification is widely used in various ways based on an assumption that it is applicable regardless of the actual size of the stimuli and CMFs. In this study, an experiment using a constant stimuli method was carried out. The human observers evaluated a series pairs of test and reference stimuli, with a field of view (FOV) of 2° or 10°. The chromaticities of the test stimuli were carefully calibrated using four standard CIE CMFs (i.e., CIE 1931 2°, 1964 10°, 2006 2°, and 10° CMFs). The results suggested that the widely used specification of JNCD seems to be derived based on the one standard deviation ellipses, the use of these four CMFs has little effect on the specification, and the JNCD value for stimuli with an FOV of 10° is 0.0025–0.0027 u′v′ unit depending on the CMFs.

HaptoFloater: Visuo-Haptic Augmented Reality by Embedding Imperceptible Color Vibration Signals for Tactile Display Control in a Mid-Air Image.

We propose HaptoFloater, a low-latency mid-air visuo-haptic augmented reality (VHAR) system that utilizes imperceptible color vibrations. When adding tactile stimuli to the visual information of a mid-air image, the user should not perceive the latency between the tactile and visual information. However, conventional tactile presentation methods for mid-air images, based on camera-detected fingertip positioning, introduce latency due to image processing and communication. To mitigate this latency, we use a color vibration technique; humans cannot perceive the vibration when the display alternates between two different color stimuli at a frequency of 25 Hz or higher. In our system, we embed this imperceptible color vibration into the mid-air image formed by a micromirror array plate, and a photodiode on the fingertip device directly detects this color vibration to provide tactile stimulation. Thus, our system allows for the tactile perception of multiple patterns on a mid-air image in 59.5 ms. In addition, we evaluate the visual-haptic delay tolerance on a mid-air display using our VHAR system and a tactile actuator with a single pattern and faster response time. The results of our user study indicate a visual-haptic delay tolerance of 110.6 ms, which is considerably larger than the latency associated with systems using multiple tactile patterns.

Assessing the influence of visual stimulus properties on steady-state visually evoked potentials and pupil diameter

Steady-State Visual Evoked Potentials (SSVEPs) are brain responses measurable via electroencephalography (EEG) in response to continuous visual stimulation at a constant frequency. SSVEPs have been instrumental in advancing our understanding of human vision and attention, as well as in the development of brain-computer interfaces (BCIs). Ongoing questions remain about which type of visual stimulus causes the most potent SSVEP response. The current study investigated the effects of color, size, and flicker frequency on the signal-to-noise ratio of SSVEPs, complemented by pupillary light reflex measurements obtained through an eye-tracker. Six participants were presented with visual stimuli that differed in terms of color (white, red, green), shape (circles, squares, triangles), size (10,000 to 30,000 pixels), flicker frequency (8 to 25 Hz), and grouping (one stimulus at a time versus four stimuli presented in a 2×2 matrix to simulate a BCI). The results indicated that larger stimuli elicited stronger SSVEP responses and more pronounced pupil constriction. Additionally, the results revealed an interaction between stimulus color and flicker frequency, with red being more effective at lower frequencies and white at higher frequencies. Future SSVEP research could focus on the recommended waveform, interactions between SSVEP and power grid frequency, a wider range of flicker frequencies, a larger sample of participants, and a systematic comparison of the information transfer obtained through SSVEPs, pupil diameter, and eye movements.

EXPRESS: The effect of chronic academic stress on attentional bias towards value-associated stimuli.

Individuals typically exhibit attentional bias towards stimuli that are considered valuable. This study aimed to investigate the effect of chronic academic stress on attentional bias towards value-associated stimuli. Both the stress group (preparation for a critical academic examination) and the control group performed a modified dot-probe task. Two color stimuli were presented simultaneously, one of which was associated with high or low monetary rewards through the value-associated training. The participants were then instructed to respond to the location of a probe dot which was presented either congruent or incongruent towards the value-associated stimuli. In the neutral condition, both stimuli were not value-associated ones. The results showed that, 1) In the value-associated training task, shorter reaction times (RTs) and higher accuracies were observed for the high-value trials compared to the low-value trials in both groups, suggesting a successful association between neutral stimuli and value. 2) In the dot-probe task, the RTs were shorter for the high/low-value congruent conditions compared to the high/low-value incongruent conditions in both groups, suggesting an attentional bias towards value-associated stimuli. 3) Compared to the control group, the stress group showed an increased disengagement (RTincongruent - RTneutral) effect but a similar orienting (RTneutral - RTcongruent) effect. These results suggested that chronic academic stress may promote attentional bias towards value-associated stimuli by impairing attentional disengagement.

Aversive conditioning, anxiety, and the strategic control of attention

ABSTRACT What we pay attention to is influenced by both reward learning and aversive conditioning. Although early attention tends to be biased toward aversively conditioned stimuli, sustained ignoring of such stimuli is also possible. How aversive conditioning influences how a person chooses to search, or the strategic control of attention, has not been explored. In the present study, participants learned an association between a colour and an aversive outcome during a training phase, and in a subsequent test phase searched for one of two targets presented on each trial; one target was rendered in the aversively conditioned colour (CS+) and the other in a neutral colour (CS-). Given the distribution of colour stimuli in the search array, it was more optimal to search for and report a target in one of the two colours on some trials. Our results demonstrate that participants were biased away from the CS+ target, which resulted in non-optimal search on some trials. Surprisingly, rather than accentuate this bias, greater state anxiety was associated with a stronger tendency to find and report the CS+ target. Our findings have implications for our understanding of the learning-dependent control of attention and abnormal attentional biases observed in high-anxious individuals.

Color-induced cognitive conflicts affect muscle activity prior to gait initiation in the Go/No-go task.

In traffic rule, green/blue means go, and red means stop. It has been shown that this prior knowledge about traffic signal colors can affect reaction times (RTs). For example, RTs are longer when responding to a red "Go" signal and withholding the response to a blue "No-go" signal (Red Go/Blue No-go task) than when responding to a blue "Go" signal and withholding the response to a red "No-go" signal (Blue Go/Red No-go task), when responses are provided by button press. However, it remains unknown whether this holds in different actions. The aim of this study was to investigate the effect of prior knowledge of color on gait initiation in a Go/No-go task. Seventeen participants performed Green Go/Red No-go and Red Go/Green No-go tasks, in which they stepped forward from a force plate in response to a green or red signal and withhold the response to red or green signal, respectively. We recorded the center of pressure (COP) and electromyogram (EMG) from the bilateral tibialis anterior muscles during gait initiation. The onset of COP movement and toe-off time as well as COP displacements did not differ between the Go/No-go tasks. The EMG onset for the stance leg was delayed in the Red Go/Green No-go than Green Go/Red No-go task. These findings suggest that the conflict between prior knowledge of color related to traffic rule and the meaning of the stimulus color affects muscle activity but not COP characteristics during gait initiation, highlighting two distinct motor control mechanisms, where the initial phase is influenced by cognitive load while the subsequent phase remains unaffected. This dissociation suggests that the later phase of gait initiation relies on robust spinal loops and central pattern generators, which are less influenced by cognitive factors such as prior knowledge.

Influence of presentation duration on filtering of irrelevant stimuli in visual working memory

In environments teeming with distractions, the ability to selectively focus on relevant information is crucial for advanced cognitive processing. Existing research using event-related potential (ERP) technology has shown active suppression of irrelevant stimuli during the consolidation phase of visual working memory (VWM). In previous studies, participants have always been given sufficient time to consolidate VWM, while suppressing distracting information. However, it remains unclear whether the suppression of irrelevant distractors requires continuous effort throughout their presence or whether this suppression is only necessary after the consolidation of task-relevant information. To address this question, our study examines whether distractor suppression is necessary in scenarios where consolidation time is limited. This research investigates the effect of varying presentation durations on the filtering of distractors in VWM. We tasked participants with memorizing two color stimuli and ignoring four distractors, presented for either 50 ms or 200 ms. Using ERP technology, we discovered that the distractor-induced distractor positivity (PD) amplitude is larger during longer presentation durations compared to shorter ones. These findings underscore the significant impact of presentation duration on the efficacy of distractor suppression in VWM, as prolonged exposure results in a stronger suppression effect on distractors. This study sheds light on the temporal dynamics of attention and memory, emphasizing the critical role of stimulus timing in cognitive tasks. These findings provide valuable insights into the mechanisms underlying VWM and have significant implications for models of attention and memory.

Attentional boost effect: research based on source memory and emotional materials.

The attentional boost effect (ABE) refers to the phenomenon that stimuli which appear with targets in a detection task are better remembered than those that appear with distractors. Previous studies have consistently reported a robust ABE in item memory, but inconsistent conclusions have been drawn for source memory. Additionally, regarding the impact of emotional stimuli on the ABE, conclusions have also been inconsistent. The aim of this research was to clarify these inconsistencies. In Experiment 1, participants were asked to memorize different emotional background words (primary task), monitor the symbols above the words, press the spacebar when encountering the "+" (secondary task), and remember the size of the emotional background stimuli (as a source feature). Results revealed that the ABE of negative stimuli was stronger in item memory. For source memory, an ABE was observed only for large fonts. In Experiment 2, participants performed the same task as in Experiment 1, except for recalling the color of emotional stimuli instead of their size. Results indicated a stronger ABE for emotional stimuli in item memory, with no ABE observed in source memory. These findings suggest: (1) Item and source memory are regulated by distinct cognitive processes, leading to differential effects of emotionality on ABE in both types of memory. (2) Contrary to previous literature, emotional stimuli, such as negative words, do not consistently diminish the ABE.

Stimulus Color Wavelength Influences Performance in a Virtual Reality Go/No-Go Task.

This study investigated the influence of stimulus color wavelength on cognitive performance in a virtual reality (VR) Go/No-Go task by assessing participant's reaction time and accuracy. Previous research has indicated that color has a variety of cognitive, physiological, and behavioral effects on individuals, differentiating their performance. However, there is a gap in understanding the influence of color on performance on VR cognitive tasks. An understanding of how stimulus color wavelength influences human performance could enhance the control over the design and interpretation of assessment and training outcomes in VR. Participants (n = 99, 57 males, aged 18 to 33 years) were recruited from the University of Houston and surrounding areas. Participants completed a VR-based Go/No-Go task. In this task, participants were instructed to strike 3D shape stimuli only if they matched the color of one of 2 virtual sabers that participants hand in their hands in VR ("Go" trials). If neither virtual saber matched the presented shape color ("No-Go" trials), participants were instructed not to respond. Stimulus colors could be violet (407 nm), blue (478 nm), green (507 nm), yellow (612 nm), and red (679 nm). Participants' reaction times and accuracy were recorded. The study design and procedures were approved by the University of Houston's Institutional Review Board. Stimulus color wavelength had a significant influence on accuracy during the Go/No-Go saber color match condition task. In both Go and No-Go trials, longer wavelengths were associated with reduced accuracy. However, no significant findings on wavelength and reaction time were present. These findings emphasize the impact of stimulus color on task performance. Shorter color wavelengths were associated with higher accuracy in a VR Go/No-Go task. These findings support the importance of color selection in VR tasks and trainings, especially in scenarios that include decision-making and require accuracy. Realistic colors encountered in real-life military operations into VR training environments may better prepare individuals for real-world challenges. Future research in this area could explore color effects in additional tasks and incorporate realistic color-based cues in VR training scenarios.

Brainwave and Emotional Responses of Male and Females to Munsell’s Five Primary Colors

Purpose: The goal is to use quantified EEG and emotional responses to objectively assess the effects of color using gender-specific EEG data, as well as to analyze emotional responses concerning the psychological effects of color modulation. This study intends to apply these findings in various fields. Through this, we hope to better understand how color stimuli affect cognitive responses, brain activity, and emotional regulation.Methods: In this study, we evaluated the EEG and emotional responses to five basic color stimuli in male and females in their 20s. EEG analysis was performed using the Coefficient of Variation for the Brainwaves (CVBs), which is the ratio of the relative brainwave power difference to the baseline brainwave. The five colors were specified using the Munsell notation and RGB values. Emotional responses were evaluated using 10 pairs of adjectives to calculate the preference index(PI), average preference index(API), and favorability. The EEG and emotional evaluations were statistically analyzed using repeated-measures ANOVA in SPSS 22.Results: The EEG responses to the five-color stimuli revealed that both male and female experienced increased concentration and arousal with the red (R) and purple (P) stimuli. Colors yellow (Y) and green (G) caused relaxation and comfort in both genders. While male and females had different emotional responses to each color, the reactions were generally similar. Both male and females preferred the color R, while Y and P were equally popular. Color R significantly activated β and γ waves associated with concentration and arousal in both genders. Warm colors were found to elicit arousal, while cool colors induced feelings of comfort, as evidenced by EEG and emotional responses. The findings showed that EEG and emotional responses to color stimuli were similar across genders and that color had a significant and meaningful impact on brainwaves and emotions.Conclusion: The quantified findings of color-based brainwaves and emotional responses can be applied to various fields that use colors. By leveraging these findings, color perception is expected to have a strong influence on human brain activity and emotional regulation.

Hue and orientation pinwheels in macaque area V4.

Area V4 is an intermediate-level area of the macaque visual cortical hierarchy that serves key functions in visual processing by integrating inputs from lower areas such as V1 and V2 and providing feedforward inputs to many higher cortical areas. Previous V4 imaging studies have focused on differential responses to color, orientation, disparity, and motion stimuli, but many details of the spatial organization of significant hue and orientation tuning have not been fully described. We used support vector machine (SVM) decoding of intrinsic cortical single-condition responses to generate high-resolution maps of hue and orientation tuning and to describe the organization of hue and orientation pinwheels in V4. Like V1 and V2, V4 contains maps of orientation that are organized as pinwheels. V4 also contains maps of hue that are organized as pinwheels, whose circular organization more closely represents the perception of hue than is observed in antecedent cortical areas. Unlike V1, where orientation is continuously mapped across the surface, V4 hue and orientation pinwheels are organized in limited numbers of pinwheel sequences. The organization of these sequences and the distance between pinwheels may provide insight into the functional organization of V4. Regions significantly tuned for hue occupy roughly four times that of the orientation, are largely separated from each other, and overlap by roughly 5%. This spatial organization is largely consistent with segregated inputs arising from V2 thin and interstripes. This modular organization of V4 suggests that further integration of color and shape might occur in higher areas in inferotemporal cortical.NEW & NOTEWORTHY The representation of hue and orientation in macaque monkey area V4 was determined by intrinsic cortical imaging of responses to isoluminant hues and achromatic grating stimuli. Vector summation of support vector machine (SVM) decoded single-condition responses was used to generate hue and orientation maps that, like V1 orientation maps, were both characterized by distinct pinwheel patterns. These data suggest that pinwheels are an important structure to represent different stimulus features across multiple visual cortical areas.

Luminance and chromaticity discrimination sensitivities right after an abrupt decrease in background luminance

AbstractWhen we enter a dark place, such as a tunnel, from a bright exterior, our visual sensitivities take some time to adapt to lower light levels. However, there have been few reports on how quickly luminance and chromaticity discrimination sensitivities recover in this situation. This study aims to quantify the time course of discrimination sensitivity for luminance and chromaticity directions after an abrupt decrease in background luminance. In each trial, the background luminance was decreased from 100 to 1 cd/m2. Subsequently, one target and three reference stimuli of different colors were presented under four stimulus‐onset asynchrony (SOA) conditions. The participants discriminated the target stimulus from reference stimuli. The results showed that discrimination sensitivity was the lowest right after the background luminance changed and gradually improved with SOAs. The sensitivity decreases differed across color directions, with the greatest decrease in luminance, a moderate decrease in S−(L + M), and a negligible change in L−M. However, statistically significant differences were observed only between luminance and L−M, suggesting that the sensitivity decrease after the abrupt decrease in background luminance did not significantly differ between the chromaticity directions. We speculate that these results stem from the interaction between chromatic perception and luminance adaptation, and possibly from rod intrusions.

EFFECTS OF WARM, COOL, AND NEUTRAL COLORS ON SHORT TERM MEMORY IN YOUNG CHILDREN

This study investigates the impact of different color stimuli (neutral, warm, and cool) on short-term memory retention in children aged 9-10. A sample of 50 children was tested under varying color conditions, where participants viewed slides with different colored backgrounds (black for neutral, red for warm, and purple for cool) and recalled the words presented. The purpose of the research was to determine how these color conditions affect memory retention. Findings revealed that cool colors, particularly purple, significantly enhance memory retention more effectively than warm (red) and neutral (black) colors. These results suggest that incorporating cool colors into educational materials and environments can optimize learning by improving short-term memory retention. This study highlights the importance of considering environmental factors, such as color, in designing educational strategies and classroom settings to support cognitive development. The principal results indicate that specific color stimuli can positively influence cognitive functions in children, providing empirical insights for educators and curriculum developers. Major conclusions from this research include the potential benefits of using cool colors like purple in educational contexts to enhance memory performance and learning outcomes. Future research should explore the impact of various sensory stimuli on cognitive processes across different developmental stages to further refine educational practices. By understanding the relationship between color and memory, this study contributes to the development of targeted interventions aimed at improving cognitive performance and educational experiences for children.

Efficient photo-induced RTP materials based on phenothiazine and polycyclic aromatic hydrocarbons: Tunable emission color and thermal stimulus response

Efficient photo-induced RTP materials based on phenothiazine and polycyclic aromatic hydrocarbons: Tunable emission color and thermal stimulus response

Colour difference detection algorithm for warp‐knitted fabric based on image colour appearance model

AbstractDetecting colour differences in warp‐knitting fabric is essential to ensure its quality. Machine vision algorithms are commonly used for automatic colour difference detection. However, the current algorithm directly extracts RGB (red, green, blue) colour stimulus values from the image without considering the image's colour attributes, leading to a significant error in colour difference detection. To solve this issue, a colour appearance model is introduced into the field of colour difference detection for warp‐knitted fabric. Initially, a colour appearance model based on CAM16 is established, and the critical parameters are calculated to obtain the colour appearance attribute of the fabric. The colour difference calculation formula is then constructed in the uniform colour space of CAM16‐UCS. A template selection algorithm based on principal component analysis was designed to select warp‐knitted cloth images with standard colours. Subsequently, a cloth colour difference detection algorithm was developed using the cloth colour profile model. The performance of the colour difference formula based on the colour profile model was evaluated using the PF/3 method. To compare the CIELab, CMC(2:1), and CIEDE2000 colour difference formulas, standardised residual sum of squares was used. The results indicated that the colour difference formula based on the colour‐appearance model is about 5.32% different from the visual colour difference perceived by the human eye. However, it can perform as well as the CMC(2:1) colour difference formula, which is widely used in the textile industry.

Investigation through Animal-Computer Interaction: A Proof-of-Concept Study for the Behavioural Experimentation of Colour Vision in Zoo-Housed Primates.

Zoos are an important repository of animals, which have a wide range of visual systems, providing excellent opportunities to investigate many comparative questions in sensory ecology. However, behavioural testing must be carried out in an animal welfare-friendly manner, which is practical for zoo staff. Here, we present a proof-of-concept study to facilitate behavioural research on the sensory ecology of captive primates. A system consisting of a tablet computer and an automated feeder connected wirelessly was developed and presented to captive primate species to evaluate interactions with and without previous training. A colour stimulus, analogous to the Ishihara test, was used to check the level of interaction with the device, supporting future studies on sensory ecology with zoo animals. Animals were able to use the system successfully and displayed signs of learning to discriminate between the visual stimuli presented. We identified no risk for small primates in their interactions with the experimental setup without the presence of keepers. The use of electronic devices should be approached with caution to prevent accidents, as a standard practice for environmental enrichment for larger animals (e.g., spider monkeys). In the long term, the system developed here will allow us to address complex comparative questions about the functions of different visual systems in captive animals (i.e., dichromatic, trichromatic, etc.).

The role of extrinsic and intrinsic factors in perceptual filling-in of the blind-spot with variegated color and texture stimuli

Vision scientists dedicated their efforts to unraveling the mechanism of filling-in at the blind-spot (BS) through numerous psychophysical experiments. The prevalent interpretation, emphasizing active filling-in, has spurred extensive research endeavors. In a parallel vein, a pertinent study highlighted the predominance of the nasal Visual Field (VF) over the temporal one and postulated the role of the Cortical Magnification Factor (CMF) in explaining the asymmetry of filling-in. In this study, we first replicated this experiment and then conducted BS-specific psychophysical experiments employing various bi-colored and bi-textured (patterned) stimuli. We observed that nasal dominance is not persistent in the context of the spread of perception for BS filling-in. We posit that the visual information processing priority index (VIPPI), comprising the CMF (an intrinsic factor unaffected by stimulus characteristics) and relative luminance (an extrinsic factor dependent on stimulus characteristics), governs the spread of perception for filling-in in case of diverse neighborhoods of the BS.

Visual working memory models of delayed estimation do not generalize to whole-report tasks.

Whole-report working memory tasks provide a measure of recall for all stimuli in a trial and afford single-trial analyses that are not possible with single-report delayed estimation tasks. However, most whole-report studies assume that trial stimuli are encoded and reported independently, and they do not consider the relationships between stimuli presented and reported within the same trial. Here, we present the results of two independently conducted whole-report experiments. The first dataset was recorded by Adam, Vogel, and Awh (2017) and required participants to report color and orientation stimuli using a continuous response wheel. We recorded the second dataset, which required participants to report color stimuli using a set of discrete buttons. We found that participants often group their reports by color similarity, contradicting the assumption of independence implicit in most encoding models of working memory. Next, we showed that this behavior was consistent across participants and experiments when reporting color but not orientation, two circular variables often assumed to be equivalent.Finally, we implemented an alternative to independent encoding where stimuli are encoded as a hierarchical Bayesian ensemble and found that this model predicts biases that are not present in either dataset. Our results suggest that assumptions made by both independent and hierarchical ensemble encoding models-which were developed in the context of single-report delayed estimation tasks-do not hold for the whole-report task. This failure to generalize highlights the need to consider variations in task structure when inferring fundamental principles of visual working memory.

Gamma Responses to Colored Natural Stimuli Can Be Predicted from Local Low-Level Stimulus Features.

The role of gamma rhythm (30-80 Hz) in visual processing is debated; stimuli like gratings and hue patches generate strong gamma, but many natural images do not. Could image gamma responses be predicted by approximating images as gratings or hue patches? Surprisingly, this question remains unanswered, since the joint dependence of gamma on multiple features is poorly understood. We recorded local field potentials and electrocorticogram from two female monkeys while presenting natural images and parametric stimuli varying along several feature dimensions. Gamma responses to different grating/hue features were separable, allowing for a multiplicative model based on individual features. By fitting a hue patch to the image around the receptive field, this simple model could predict gamma responses to chromatic images across scales with reasonably high accuracy. Our results provide a simple "baseline" model to predict gamma from local image properties, against which more complex models of natural vision can be tested.

Association between DRD4 gene and perception of architectural spaces by using EEG

The psychological effects of the environment on humans have been well established. However, the genetic mechanisms of individuals in environmental perception and preferences have not been studied yet. In this research the correlation between the expression of the DRD4 gene and the preference for architectural spaces was investigated. Firstly, architectural spaces simulated in VR animation. The brain responses of the participants (N = 42) to architectural stimuli were recorded. Secondly, using the qPCR method, the DRD4 gene expression of individuals was compared based on the frequency of their brain waves. A significant difference was observed in the DRD4 gene expression of the participant groups. Based on the results, the increase in the expression of the DRD4 gene was associated with a decrease in the intensity of the brain's response to stimuli. Also, the highest correlation was seen between DRD4 gene expression and the stimuli of Low-privacy (91%), complexity (87.8%), and color (84.6%).