Facial expressions affect the memory of facial colors.

Facial color influences the perception of facial expressions, and emotional expressions bias how facial color is remembered. However, it remains unclear whether facial expressions affect daily facial color memory. The memory color effect demonstrates that knowledge about typical colors affects the perception of the actual color of given objects. To investigate the effect of facial color memory, we examined whether the memory color effect for faces varies depending on facial expression. We calculated the subjective achromatic point of the facial expression image stimulus and compared the degree to which it was shifted from the actual achromatic point between facial expression conditions. We hypothesized that if the memory of facial color is influenced by the facial expression color (e.g., anger is a warm color, fear is a cold color), then the subjective achromatic point would vary with facial expression. In Experiment 1, we recruited 13 participants who adjusted the color of facial expression stimuli (anger, neutral, and fear) and a banana stimulus to be achromatic. No significant differences in the subjective achromatic point between facial expressions were observed. Subsequently, we conducted Experiment 2 with 23 participants because Experiment 1 did not account for the sensitivity to color changes on the face; humans perceive greater color differences in faces than in non-faces. Participants selected which facial color they believed the expression stimulus appeared to be, choosing one of two options provided to them. The results indicated that the subjective achromatic points of anger and fear faces significantly shifted toward the opposite color direction compared with neutral faces in the brief presentation condition. This research suggests that the memory color of faces differs depending on facial expressions and supports the idea that the perception of emotional expressions can bias facial color memory.

The effect of facial colour on implicit facial expressions.

Humans recognise reddish-coloured faces as angry. However, does facial colour also affect "implicit" facial expression perception of which humans are not explicitly aware? In this study, we investigated the effects of facial colour on implicit facial expression perception. The experimental stimuli were "hybrid faces", in which the low-frequency component of the neutral facial expression image was replaced with the low-frequency component of the facial expression image of happiness or anger. In Experiment 1, we confirmed that the hybrid face stimuli were perceived as neutral and, therefore, supported implicit facial expression perception. In Experiment 2, the hybrid face stimuli were adjusted to natural and reddish facial colours, and their friendliness ratings were compared. The results showed that the expression of happiness was rated as more friendly than the expression of anger. In addition, the expression of happiness was rated as friendlier when the low-frequency happy component was red, but the friendliness rating of the expression of anger did not change when it was presented in red. In Experiment 3, we affirmed the implicit facial expression perception even in reddish colours. These results suggest that facial colour modulates the perception of implicit facial expressions in hybrid facial stimuli.

Cueing the Necker cube: Pupil dilation reflects the viewing-from-above constraint in bistable perception.

We hypothesized that a perceptually ambiguous or bistable object (Necker cube) can be more effectively biased to assume a point of view-from-above (VFA) than from below the object by cueing attention. Participants viewed a Necker cube in which one surface was temporarily shaded so as to prime a specific perspective on the cube. Subsequently, the standard (wireframe) Necker cube was viewed for 3 seconds, and participants reported what perspective they had seen initially and whether their perception shifted to the alternative perspective during the brief viewing. Concomitantly, pupil size was monitored with an eye-tracker to obtain an index of cognitive effort. There were two conditions: passive viewing and forced attention to sustain the initially primed perspective. We confirmed the presence of a VFA bias with forced attention, which was accompanied by reduced attentional effort, as indexed by a reduced pupil diameter, compared with the view-from-below. Participants showed no bias during passive viewing. We suggest that the level of intensive attention, when retrieving and maintaining a specific view from memory, is mirrored in the size of the eye pupils and may reflect ecological constraints on visual perception.

How Good Are RGB Cameras Retrieving Colors of Natural Scenes and Paintings?-A Study Based on Hyperspectral Imaging.

RGB digital cameras (RGB) compress the spectral information into a trichromatic system capable of approximately representing the actual colors of objects. Although RGB digital cameras follow the same compression philosophy as the human eye (OBS), the spectral sensitivity is different. To what extent they provide the same chromatic experiences is still an open question, especially with complex images. We addressed this question by comparing the actual colors derived from spectral imaging with those obtained with RGB cameras. The data from hyperspectral imaging of 50 natural scenes and 89 paintings was used to estimate the chromatic differences between OBS and RGB. The corresponding color errors were estimated and analyzed in the color spaces CIELAB (using the color difference formulas ΔE*ab and CIEDE2000), Jzazbz, and iCAM06. In CIELAB the most frequent error (using ΔE*ab) found was 5 for both paintings and natural scenes, a similarity that held for the other spaces tested. In addition, the distribution of errors across the color space shows that the errors are small in the achromatic region and increase with saturation. Overall, the results indicate that the chromatic errors estimated are close to the acceptance error and therefore RGB digital cameras are able to produce quite realistic colors of complex scenarios.

Expeditious prediction of post-mortem changes in frozen fish meat using three-dimensional fluorescence fingerprints.

The present study was conducted to characterize fluorophores in the fish body using three-dimensional fluorescence fingerprints (3D-FFs) and to utilize these 3D-FFs obtained from frozen horse mackerel (Trachurus japonicus) fillets to predict early post-mortem changes. Alive fish were sacrificed instantly, preserved in ice until 2 days, and then filleted, vacuum packed, and frozen. Subsequently, 3D-FFs of the frozen fillets were acquired using F-7000 aided with a fiber probe. Post-mortem freshness changes were tracked by measuring adenylate energy charge (AEC) values and nicotinamide adenine dinucleotide (NAD and NADH) content. Partial least squares regression models for predicting AEC values and NADH content in frozen fish meat showed good fittings, with R2 of 0.90 and 0.85, by utilizing eight and five excitation wavelengths, respectively, based on their fluorescence features acquired from standard fluorophores. This novel approach of 3D-FFs could be utilized as an efficient technique for at-line monitoring of frozen fish quality.

Development of the multispectral UV polarization reflectance imaging system (MUPRIS) for in situ monitoring of the UV protection efficacy of sunscreen on human skin.

BACKGROUND: Protection of the human skin from ultraviolet (UV) damage is one of the main issues in dermatology and cosmetology. The UV protection efficacy (UVPE) of the sunscreen film is decreased by sweat, sebum, and friction during the day. However, the technical relationship between the UVPE evaluated in a laboratory and the actual protection in daily use has not been clarified, because the UVPE measurement method in real-life setting has not been established. This study aimed to develop a novel UVPE evaluation system that allows in situ monitoring of the UVPE in real-life activities. METHODS: The multispectral UV polarization reflectance imaging system (MUPRIS) and a UVPE estimation algorithm were developed. The diffuse reflectance spectra were measured for a total of 48 sunscreen materials that were applied on 59 subjects. The UVPEs estimated from the diffuse reflectance spectra were compared with the in vivo SPFs. Finally, the UVPE before and after a marine leisure activity was evaluated using the MUPRIS as the practical use test. RESULTS: Compared with the conventional UV camera, the MUPRIS could visualize the applied sunscreen more clearly and showed good UVPE estimation accuracy (correlation coefficient for in vivo SPF, 0.82). In the practical use test, the degradation of the UVPE during a marine leisure activity was quantitatively monitored and was validated by the actual occurrence of sunburn. CONCLUSIONS: A novel in situ UVPE monitoring tool had been successfully developed. It can strongly support the development of innovative sunscreen products that can perfectly protect customers against UV irradiation in real-life situation.

Illuminations that improve color discrimination ability of people with red-green color vision deficiency.

In this research, three illuminants that improve color discrimination ability of people with red-green color vision deficiency were developed. The illuminants are close to daylight-colored and were produced by using spectral optimization. Deutans were the focus of this research, but a few protans were also tested for reference. The illuminants were produced by combining different types of LEDs, and their effects were tested with several test subjects with and without color vision deficiency using the Ishihara color vision test and the Farnsworth Panel D-15 test. The illuminant with the most powerful effect provided near perfect results with the Ishihara test for deutans, while the other two illuminants produced smaller improvements. The Farnsworth Panel D-15 test produced results that were similar to the Ishihara test though generally the color discrimination of blue hues was weaker under the most powerful illuminant.

Dissociation of equilibrium points for color-discrimination and color-appearance mechanisms in incomplete chromatic adaptation.

We compared the color-discrimination thresholds and supra-threshold color differences (STCDs) obtained in complete chromatic adaptation (gray) and incomplete chromatic adaptation (red). The color-difference profiles were examined by evaluating the perceptual distances between various color pairs using maximum likelihood difference scaling. In the gray condition, the chromaticities corresponding with the smallest threshold and the largest color difference were almost identical. In contrast, in the red condition, they were dissociated. The peaks of the sensitivity functions derived from the color-discrimination thresholds and STCDs along the L-M axis were systematically different between the adaptation conditions. These results suggest that the color signals involved in color discrimination and STCD tasks are controlled by separate mechanisms with different characteristic properties.

Robust brightness enhancement across a luminance range of the glare illusion.

The glare illusion refers to brightness enhancement and the perception of a self-luminous appearance that occurs when a central region is surrounded by a luminance gradient. The center region appears to be a light source, with its light dispersing into the surrounding region. If the luminous edge is critical for generating the illusion, modulating the perceived luminance of the image, and switching its appearance from luminous to nonluminous, would have a strong impact on lightness and brightness estimation. Here, we quantified the illusion in two ways, by assessing brightness enhancement and examining whether the center region appeared luminous. Thus, we could determine whether the two effects occurred jointly or independently. We examined a wide luminance range of center regions, from 0 to 200% relative to background. Brightness enhancement in the illusion was observed for a wide range of luminances (20% to 200% relative to background), while a luminous-white appearance was observed when the center region luminance was 145% of the background. These results exclude the possibility that brightness enhancement occurs because the stimuli appear self-luminous. We suggest that restoring the original image intensity precedes the perceptual process of lightness estimation.

Facial color processing in the face-selective regions: an fMRI study.

Facial color is important information for social communication as it provides important clues to recognize a person's emotion and health condition. Our previous EEG study suggested that N170 at the left occipito-temporal site is related to facial color processing (Nakajima et al., [2012]: Neuropsychologia 50:2499-2505). However, because of the low spatial resolution of EEG experiment, the brain region is involved in facial color processing remains controversial. In the present study, we examined the neural substrates of facial color processing using functional magnetic resonance imaging (fMRI). We measured brain activity from 25 subjects during the presentation of natural- and bluish-colored face and their scrambled images. The bilateral fusiform face (FFA) area and occipital face area (OFA) were localized by the contrast of natural-colored faces versus natural-colored scrambled images. Moreover, region of interest (ROI) analysis showed that the left FFA was sensitive to facial color, whereas the right FFA and the right and left OFA were insensitive to facial color. In combination with our previous EEG results, these data suggest that the left FFA may play an important role in facial color processing.

Glossiness perception and its pupillary response.

Recent studies have revealed that pupillary response changes depend on perceptual factors such as subjective brightness caused by optical illusions and luminance. However, the manner in which the perceptual factor that is derived from the glossiness perception of object surfaces affects the pupillary response remains unclear. We investigated the relationship between the glossiness perception and pupillary response through a glossiness rating experiment that included recording the pupil diameter. We prepared general object images (original) and randomized images (shuffled) that comprised the same images with randomized small square regions as stimuli. The image features were controlled by matching the luminance histogram. The observers were asked to rate the perceived glossiness of the stimuli presented for 3,000 ms and the changes in their pupil diameters were recorded. Images with higher glossiness ratings constricted the pupil size more than those with lower glossiness ratings at the peak constriction of the pupillary responses during the stimulus duration. The linear mixed-effects model demonstrated that the glossiness rating, image category (original/shuffled), variance of the luminance histogram, and stimulus area were most effective in predicting the pupillary responses. These results suggest that the illusory brightness obtained by the image regions of high-glossiness objects, such as specular highlights, induce pupil constriction.

Influence of global/local processing on perceived colour transparency.

Our cognitive processing is flexible and affected by global/local dominance in prior cognitive tasks. Similar to cognitive processing, perceptual processing, especially colour perception related to global/local processing, may be affected by prior global/local dominance; however, this possibility has not yet been assessed. Here, we examined whether prior tasks involving global/local processing influenced colour perception related to global/local processing. As colour perception is related to global/local processing, we focused on perceived colour transparency, in which a transparent layer is perceived in front of a background layer, even though these stimuli are physically in the same layer. When viewing the colour transparency stimulus, we expected that the perceived colour of a specific region, when focusing on only the local region, would differ from that when focusing on the whole image. In our study, the participants completed a global or local Navon task, followed by a colour-matching task that assessed how they saw colours using colour transparency stimuli. The degree of optical illusion (i.e., perceived colour transparency) after the global Navon task was greater than that after the local Navon task. Thus, prior global/local processing, a flexible mode of cognitive processing, influenced colour perception. This study provides new insight into perceptual flexibility, especially in colour perception.

Optimization of excitation-emission band-pass filter for visualization of viable bacteria distribution on the surface of pork meat.

A novel method of optically reducing the dimensionality of an excitation-emission matrix (EEM) by optimizing the excitation and emission band-pass filters was proposed and applied to the visualization of viable bacteria on pork. Filters were designed theoretically using an EEM data set for evaluating colony-forming units on pork samples assuming signal-to-noise ratios of 100, 316, or 1000. These filters were evaluated using newly measured EEM images. The filters designed for S/N = 100 performed the best and allowed the visualization of viable bacteria distributions. The proposed method is expected to be a breakthrough in the application of EEM imaging.

Detection and visualization of intracutaneous allergic type-specific elements using long-wavelength near-infrared hyperspectral imaging.

BACKGROUND/PURPOSE: This study aimed to develop a method for the assessment of allergic dermatitis by using the long-wavelength near-infrared spectrum (more than 1000 nm) to detect intracutaneous allergic type-specific elements. Such a method was realized by establishing a spectral classifier for the spectra of type I and type IV allergic dermatitis reactions. METHODS: Near-infrared spectral images of histamine-induced cutaneous reaction (type I) and contact hypersensitivity erythema elicited by squaric acid dibutylester (SADBE; type IV) were obtained, and the absorption spectra of normal and inflamed skin were extracted from these spectral images. A spectral classifier was established from these training datasets, and it was then applied to two test cases, red flare by methyl nicotinate (normal) and metal allergy (type IV). RESULTS: The spectral classifier established by canonical discriminant analysis (CDA) achieved very accurate detection (normal: 87.67%, type I: 87.00%, type IV: 98.5%). Furthermore, the test cases were also correctly classified: the red flare induced by methyl nicotinate was categorized as normal skin and the metal allergy was categorized as a type IV allergic reaction. CONCLUSIONS: These results suggest a possible application of near-infrared spectral imaging to the assessment of allergic dermatitis.

Congruency of color-sound crossmodal correspondence interacts with color and sound discrimination depending on color category.

People occasionally associate color (e.g., hue) with sound (e.g., pitch). Previous studies have reported color-sound associations, which are examples of crossmodal correspondences. However, the association between both semantic and perceptual factors with color/sound discrimination in crossmodal correspondence remains unclear. To clarify this, three psychological experiments were conducted, where Stroop tasks were used to assess automatic process on the association. We focused on the crossmodal correspondence between color (Experiment 1)/color word (Experiment 2) and sound. Participants discriminated the color/word or the sound presented simultaneously. The results showed the color-sound bidirectional enhancement/interference of the response by certain associations of the crossmodal correspondence (blue-drop and yellow-shiny) in both experiments. These results suggest that these Stroop effects were caused by the semantic factor (color category) and the perceptual factor (color appearance) was not necessary for the current results. In Experiment 3, response modulation by color labeling was investigated to clarify the influence of subjective labeling. Participants labeled a presented ambiguous color, which was a hue specification between two specific colors, by listening to the sound. The results revealed that the Stroop effect was caused only when the presented color was classified as the color related to the presented sound. This showed that subjective labeling played a role in the regulation of the effect of crossmodal correspondences. These findings should contribute to the explanation of crossmodal correspondences through semantic mediation.

Brightness Perception in World-Centered Coordinates Assessed by Pupillometry.

Subjective brightness perception reportedly differs among the peripheral visual fields owing to lower- and higher-order cognition. However, there is still a lack of information associated with subjective brightness perception in the world-centered coordinates, not in the visual fields. In this study, we aimed to investigate the anisotropy of subjective brightness perception in the world-centered coordinates based on pupillary responses to the stimuli in five locations by manipulating the world-centered coordinates through active (requiring head movement) and passive scenes (without head movement) in a virtual reality environment. Specifically, this study aimed to elucidate if there is an ecological advantage in the five different locations in the world-centered coordinates. The pupillary responses to glare and halo stimuli indicated that the brightness perception differed among the five locations in the world-centered coordinates. Furthermore, we found that the pupillary response to stimuli at the top location might be influenced by ecological factors (such as from the bright sky and the sun's existence). Thus, we have contributed to the understanding of the extraretinal information influence on subjective brightness perception in the world-centered coordinates, demonstrating that the pupillary response is independent of head movement.

Potential of fluorescence fingerprints for fish meat authentication: Differences in freshness evaluation in white and dark meat at frozen state.

As dark meat has a faster deterioration rate and its unintentional mixing occurs during processing, it is crucial to know the status and freshness indicators of dark meat to ensure fishery product quality. In this method, fluorescence fingerprints (FFs) was applied as a rapid and noninvasive quality authentication method to determine differences between white and dark meat in the evaluation of freshness indicators at frozen state. Spotted mackerel (Scomber australasicus) fish chunks with different postmortem conditions (0-40 h ice stored) were obtained and frozen. A new generation of fluorescence spectrophotometer (F-7100) was used to acquire FFs of the frozen fish chunks (containing white and dark meat). Adenosine triphosphate metabolites and pH were determined in both white and dark meat using their relevant biochemical methods. Higher K-values in dark meat might be attributed to a higher accumulation rate of inosine (HxR) in dark meat than in white meat. The pH decrease rate in white meat was higher than that in dark meat during postmortem ice storage periods of fish. Principal component analysis of FFs spectra demonstrated clear discrimination (PC1 + PC2 = 91.7%) between white and dark meat of frozen fish due to the influence of freshness parameters based on the fluorescence features of fish meat. Furthermore, partial least squares regression validation models revealed that freshness indicators of white meat could be predicted more accurately at the frozen state than those of dark meat. This method could be applied during the processing of fishery products, thereby facilitating quality control activities and making it a promising authentication tool for the fisheries industries.

Selection of optimal combinations of band-pass filters for ice detection by hyperspectral imaging.

Hyperspectral imaging captures rich information in spatial and spectral domains but involves high costs and complex data processing. The use of a set of optical band-pass filters (BPFs) in the acquisition of spectral images is proposed for reducing dimensionality of spectral data while maintaining target detection and/or categorization performance. A set of BPFs that could distinguish ice from surrounding water on various materials (e.g., asphalt), was designed as an example. Relatively high accuracy (90.28%) was achieved with only two BPFs, showing the potential of this approach for accurate target detection with lesser complexity than conventional methods.

Regularity of colour statistics in explaining colour composition preferences in art paintings.

This study explores the role of colour statistics in painting preferences and tests the 'matching-to-nature' hypothesis which posits that the preference for the colour composition of paintings depends on the extent to which the paintings resemble the colour statistics of natural scenes. A preference judgement experiment was conducted with 31,353 participants using original and hue-rotated versions of 1,200 paintings. Multiple regression analyses were performed between the measured preferences and paintings' colour statistics to reveal which colour statistics explained the preference data and to what extent. The colour statistics of art paintings that explained the preference data were compared to the colour statistics of natural scenes. The results identified the colour statistics that significantly contributed to explaining painting preferences, and the distributions of the paintings' colour statistics systematically differed from those of natural scenes. These findings suggest that the human visual system encodes colour statistics to make aesthetic judgements based on the artistic merit of colour compositions, and not on their similarity to natural scenes.

Backward and forward neck tilt affects perceptual bias when interpreting ambiguous figures.

The relationships between posture and perception have already been investigated in several studies. However, it is still unclear how perceptual bias and experiential contexts of human perception affect observers' perception when posture is changed. In this study, we hypothesized that a change in the perceptual probability caused by perceptual bias also depends on posture. In order to verify this hypothesis, we used the Necker cube with two types of appearance, from above and below, although the input is constant, and investigated the change of the probability of perceptual content. Specifically, we asked observers their perception of the appearance of the Necker cube placed at any of the five angles in the space of virtual reality. There were two patterns of neck movement, vertical and horizontal. During the experiment, pupil diameter, one of the cognitive indices, was also measured. Results showed that during the condition of looking down vertically, the probability of the viewing-from-above perception of the Necker cube was significantly greater than during the condition of looking up. Interestingly, the pupillary results were also consistent with the probability of the perception. These results indicate that perception was modulated by the posture of the neck and suggest that neck posture is incorporated into ecological constraints.