Sexual dimorphism of facial width-to-height ratio in human skulls and faces: A meta-analytical approach

Facial width-to-height ratio (FWHR), defined as the width of the face divided by the upper facial height, is a cue to behaviour. Explanations for this link often involve the idea that FWHR is sexually dimorphic, resulting from intersexual selection pressures. However, few studies have considered sexual dimorphism in skulls since the original paper on this topic, and it is possible that different explanations may be required if faces show sex differences but skulls do not. Here, meta-analyses of skulls found that men did have larger FWHR than women, although this effect was small. However, after categorising samples by ethnicity and geographical origin, meta-analyses only found evidence of sex differences in East Asians, and again, this effect was small. A re-analysis of previous studies after excluding skull samples found little evidence of sexual dimorphism in faces. Again, considering ethnicities separately, I found no differences for White samples but a medium-sized effect with East Asians, although this was not statistically significant with only three samples. Taken together, I found no reason to consider FWHR as a sexually dimorphic measure in skulls or faces, at least not universally, and so accounts based upon this assumption need rethinking if researchers are to explain the relationship between FWHR and behaviour.</p

Identifying Basic Emotions and Action Units from Facial Photographs with ChatGPT

Recognising facial expressions of emotion is crucial for social interactions. In addition, identifying these expressions underlies the study of social cognition, consumer behaviour, and many other fields. Using automated facial coding (AFC), this task can be completed more efficiently while potentially benefitting human-computer interactions. Here, I explored ChatGPT’s ability to recognise expressions of basic emotions using high quality images for which human performance, as well as that of FaceReader (a commercially available software), had previously been collected. In Experiment 1, a forced-choice labelling task found that ChatGPT outperformed both humans and FaceReader in identifying the intended emotions from their expressions. Experiment 2 focussed on the facial action coding system (FACS), requiring ChatGPT to identify activated action units (AUs) and their intensities from these same images. The chatbot’s overall agreement with a FACS-certified specialist was at least as high as FaceReader, and was around the criterion required for human certification. Further, ChatGPT’s detection of a large subset of AUs showed good or very good agreement with the specialist’s coding, comparable with FaceReader’s performance. Finally, although overall intensity ratings showed relatively poor agreement with the human specialist, ratings for several of the AUs agreed well with human coding, especially if a small level of tolerance were acceptable. Taken together, ChatGPT’s ability to perceive human facial expressions and their AUs from high quality images provides a possible alternative to current AFC tools, as well as an interesting avenue for investigation regarding advances in human-computer interactions.</p

Forgetting faces over a week: investigating self-reported face recognition ability and personality

BackgroundAlthough face recognition is now well studied, few researchers have considered the nature of forgetting over longer time periods. Here, I investigated how newly learned faces were recognised over the course of one week. In addition, I considered whether self-reported face recognition ability, as well as Big Five personality dimensions, were able to predict actual performance in a recognition task.MethodsIn this experiment (N = 570), faces were learned through short video interviews, and these identities were later presented in a recognition test (using previously unseen images) after no delay, six hours, twelve hours, one day, or seven days.ResultsThe majority of forgetting took place within the first 24 hours, with no significant decrease after that timepoint. Further, self-reported face recognition abilities were moderately predictive of performance, while extraversion showed a small, negative association with performance. In both cases, these associations remained consistent across delay conditions.DiscussionThe current work begins to address important questions regarding face recognition using longitudinal, real-world time intervals, focussing on participant insight into their own abilities, and the process of forgetting more generally.</p

The red power(less) tie: perceptions of political leaders wearing red

Research has demonstrated that wearing red can have significant effects on perceptions of the wearer. However, these findings are based on impressions formed while viewing static images. Here, I focus on perceptions of political leaders and show participants short videos in order to investigate color effects in stimuli with increased ecological validity. Viewers watched videos of politicians and made judgments regarding how dominant, how good a leader, and how believable the politicians appeared to be. The colors of the politicians' ties were digitally manipulated to be red or blue. Whether the politician was familiar (Study 1) or unfamiliar to viewers (Study 2), tie color had no effect on perceptions. Even when the sound was muted in order to increase the influence of visual cues (Study 3), I found no clothing color effect. Finally, when only presented with a static image (Study 4), wearing red still had no effect on judgments. These results suggest that, at least in a political setting, wearing red has no effect on perceptions. Therefore, real-world applications associated with red clothing may be limited.</p

Within-person variability in men's facial width-to-height ratio

Background. In recent years, researchers have investigated the relationship between facial width-to-height ratio (FWHR) and a variety of threat and dominance behaviours. The majority of methods involved measuring FWHR from 2D photographs of faces. However, individuals can vary dramatically in their appearance across images, which poses an obvious problem for reliable FWHR measurement. Methods. I compared the effect sizes due to the differences between images taken with unconstrained camera parameters (Studies 1 and 2) or varied facial expressions (Study 3) to the effect size due to identity, i.e., the differences between people. In Study 1, images of Hollywood actors were collected from film screenshots, providing the least amount of experimental control. In Study 2, controlled photographs, which only varied in focal length and distance to camera, were analysed. In Study 3, images of different facial expressions, taken in controlled conditions, were measured. Results. Analyses revealed that simply varying the focal length and distance between the camera and face had a relatively small effect on FWHR, and therefore may prove less of a problem if uncontrolled in study designs. In contrast, when all camera parameters (including the camera itself) are allowed to vary, the effect size due to identity was greater than the effect of image selection, but the ranking of the identities was significantly altered by the particular image used. Finally, I found significant changes to FWHR when people posed with four of seven emotional expressions in comparison with neutral, and the effect size due to expression was larger than differences due to identity. Discussion. The results of these three studies demonstrate that even when head pose is limited to forward facing, changes to the camera parameters and a person's facial expression have sizable effects on FWHR measurement. Therefore, analysing images that fail to constrain some of these variables can lead to noisy and unreliable results, but also relationships caused by previously unconsidered confounds.</p

The red power(less) tie: perceptions of political leaders wearing red

Research has demonstrated that wearing red can have significant effects on perceptions of the wearer. However, these findings are based on impressions formed while viewing static images. Here, I focus on perceptions of political leaders and show participants short videos in order to investigate color effects in stimuli with increased ecological validity. Viewers watched videos of politicians and made judgments regarding how dominant, how good a leader, and how believable the politicians appeared to be. The colors of the politicians' ties were digitally manipulated to be red or blue. Whether the politician was familiar (Study 1) or unfamiliar to viewers (Study 2), tie color had no effect on perceptions. Even when the sound was muted in order to increase the influence of visual cues (Study 3), I found no clothing color effect. Finally, when only presented with a static image (Study 4), wearing red still had no effect on judgments. These results suggest that, at least in a political setting, wearing red has no effect on perceptions. Therefore, real-world applications associated with red clothing may be limited.</p

No effect of birth month or season on height in a large international sample of adults

Although several studies in recent years have provided evidence of a relationship between month of birth and height during childhood, the association remains less clear for adult (final) height. Here, I investigated this relationship using a large international sample of adult actors. Analyses considered both the sample as a whole, as well as subsamples based on nationality, and treated men and women separately. In all instances, I found no relationship between birth month or season and height, even after controlling for year of birth. This may be due to the particular nature of samples of actors, who are taller than the general population, or could suggest more broadly that birth month effects are minimal or absent in adults.</p

Face to face: Comparing ChatGPT with human performance on face matching

ChatGPT’s large language model, GPT-4V, has been trained on vast numbers of image-text pairs and is therefore capable of processing visual input. This model operates very differently from cur- rent state-of-the-art neural networks designed specifically for face perception and so I chose to investigate whether ChatGPT could also be applied to this domain. With this aim, I focussed on the task of face matching, that is, deciding whether two photographs showed the same person or not. Across six different tests, ChatGPT demonstrated performance that was comparable with human accuracies despite being a domain-general ‘virtual assistant’ rather than a specialised tool for face processing. This perhaps surprising result identifies a new avenue for exploration in this field, while further research should explore the boundaries of ChatGPT’s ability, along with how its errors may relate to those made by humans.</p

Facial width-to-height ratio in a large sample of Commonwealth Games athletes

Evidence that facial width-to-height ratio (FWHR) is a sexually dimorphic morphological measure is mixed. Research has also linked FWHR with aggression and other behavioral tendencies, at least in men. Again, other research has found no such relationship. Here, I tested for both possible relationships using a sample of 2,075 male and 1,406 female athletes from the Glasgow 2014 Commonwealth Games. Men showed significantly greater FWHRs than women, but this difference could be attributed to differences in body size. In addition, I found greater FWHRs in men who competed in sports involving physical contact and those stereotyped as more masculine. Again, these results could be attributed to differences in body size between categories. For women, no differences in FWHR were found regarding the amount of contact involved in a sport and how that sport was stereotyped. Finally, the FWHRs of athletes showed no relationship with the amount of aggression and related traits that were judged as required for success in those sports, although FWHRs did correlate with perceived endurance demands in women. Therefore, in a large sample of athletes, the sex difference in FWHR could be attributed to body size, and little support was found for the predicted links between this facial measure and behavior.</p

Fusing ChatGPT and human decisions in unfamiliar face matching

Unfamiliar face matching involves deciding whether two face images depict the same person or two different people. Individual performance can be error-prone but is improved by aggregating (fusing) the responses of participant pairs. With advances in automated facial recognition systems (AFR), fusing human and algorithm responses also leads to performance improvements over individuals working alone. In the current work, I investigated whether ChatGPT could serve as the algorithm in this fusion. Using a common face matching test, I found that the fusion of individual responses with those provided by ChatGPT increased performance in comparison with both individuals working alone and simulated participant pairs. This pattern of results was evident when participants responded either using a rating scale (Experiment 1) or with a binary decision and associated confidence (Experiment 2). Taken together, these findings demonstrate the potential utility of ChatGPT in daily identification contexts where state-of-the-art AFR may not be available.</p