What’s in a face? The role of facial features in ratings of dominance, threat, and stereotypicality

Faces judged as stereotypically Black are perceived negatively relative to less stereotypical faces. In this experiment, artificial faces were constructed to examine the effects of nose width, lip fullness, and skin reflectance, as well as to study the relations among perceived dominance, threat, and Black stereotypicality. Using a multilevel structural equation model to isolate contributions of the facial features and the participant demographics, results showed that stereotypicality was related to wide nose, darker reflectance, and to a lesser extent full lips; threat was associated with wide nose, thin lips, and low reflectance; dominance was mainly related to nose width. Facial features explained variance among faces, suggesting that face-type bias in this sample was related to specific face features rather than particular characteristics of the participant. People’s perceptions of relations across these traits may underpin some of the sociocultural disparities in treatment of certain individuals by the legal system.

Automated video-based heart rate tracking for the anesthetized and behaving monkey

Heart rate (HR) is extremely valuable in the study of complex behaviours and their physiological correlates in non-human primates. However, collecting this information is often challenging, involving either invasive implants or tedious behavioural training. In the present study, we implement a Eulerian video magnification (EVM) heart tracking method in the macaque monkey combined with wavelet transform. This is based on a measure of image to image fluctuations in skin reflectance due to changes in blood influx. We show a strong temporal coherence and amplitude match between EVM-based heart tracking and ground truth ECG, from both color (RGB) and infrared (IR) videos, in anesthetized macaques, to a level comparable to what can be achieved in humans. We further show that this method allows to identify consistent HR changes following the presentation of conspecific emotional voices or faces. EVM is used to extract HR in humans but has never been applied to non-human primates. Video photoplethysmography allows to extract awake macaques HR from RGB videos. In contrast, our method allows to extract awake macaques HR from both RGB and IR videos and is particularly resilient to the head motion that can be observed in awake behaving monkeys. Overall, we believe that this method can be generalized as a tool to track HR of the awake behaving monkey, for ethological, behavioural, neuroscience or welfare purposes.

Automated video-based heart rate tracking for the anesthetized and behaving monkey

BackgroundHeart rate is extremely valuable in the study of complex behaviours and their physiological correlates in non-human primates. However, collecting this information is often challenging, involving either invasive implants or tedious behavioural training.New MethodIn the present study, we implement a Eulerian Video Magnification (EVM) heart tracking method in the macaque monkey combined with wavelet transform. This is based on a measure of image to image fluctuations in skin reflectance due to changes in blood influx.ResultsWe show a strong temporal coherence and amplitude match between EVM-based heart tracking and ground truth ECG, from both color (RGB) and infrared (IR) videos, in anesthetized macaques, to a level comparable to what can be achieved in humans. We further show that this method allows to identify consistent heart rate changes following the presentation of conspecific emotional voices or faces.Comparison with Existing Method(s)Eulerian Video Magnification (EVM) is used to extract heart rate in humans but has never been applied to non-human primates. Video photoplethysmography allows to extract awake macaques heart rate from RGB videos. In contrast, our method allows to extract awake macaques heart rate from both RGB and IR videos and is particularly resilient to the head motion that can be observed in awake behaving monkeys.ConclusionsOverall, we believe that this method can be generalized as a tool to track heart rate of the awake behaving monkey, for ethological, behavioural, neuroscience or welfare purposes.HighlightsHeart rate varies during complex non-human primate (NHP) behaviour and cognition.We apply Eulerian Video Magnification to track NHP heart rate (EVM-HR).EVM-HR can be used with RGB & IR videos, and anesthetized or awake NHPs.NHP EVM-HR vary with emotional content of presented stimuli.EVM-HR is of interest to ethology, behavioural, neuroscience & welfare purposes.

The Reflectance of Human Skin in the Millimeter-Wave Band

The millimeter-wave band is an ideal part of the electromagnetic radiation to diagnose human skin conditions because this radiation interacts only with tissue down to a depth of a millimetre or less over the band range from 30 GHz to 300 GHz. In this paper, radiometry is used as a non-contact sensor for measuring the human skin reflectance under normal and wet skin conditions. The mean reflectance of the skin of a sample of 50 healthy participants over the (80–100) GHz band was found to be ~0.615 with a standard deviation of ~0.088, and an experimental measurement uncertainty of ±0.005. The thinner skin regions of the back of the hand, the volar forearms and the inner wrist had reflectances 0.068, 0.068 and 0.062 higher than the thicker skin regions of the palm of the hand, the dorsal forearm and the outer wrist skin. Experimental measurements of human skin reflectance in a normal and a wet state on the back of the hand and the palm of the hand regions indicated that the mean differences in the reflectance before and after the application of water were ~0.078 and ~0.152, respectively. These differences were found to be statistically significant as assessed using t-tests (34 paired t-tests and six independent t-tests were performed to assess the significance level of the mean differences in the reflectance of the skin). Radiometric measurements in this paper show the quantitative variations in the skin reflectance between locations, sexes, and individuals. The study reveals that these variations are related to the skin thickness and water content, a capability that has the potential to allow radiometry to be used as a non-contact sensor to detect and monitor skin conditions such as eczema, psoriasis, malignancy, and burn wounds.