On the genesis and processing of facial representations and prototypes

Face researchers address a huge variety of perceptual and processing issues of faces while hardly addressing how exactly facial representations and prototypes are generated and on which experiences they are established. Scientific recognized theories like the “recognition by prototypes” theory (Basri, 1996) define (facial) prototypes as results of principal components or averages of given exemplars (Burton, Jenkins, Hancock,& Withe, 2005).

Furthermore, several theories (e.g. Valentin, 1991; Busey, 1998) postulate a so called “face-­‐space” as the respective prototype (most typical face) provides the centroid and the unique exemplars of a face are encoded as a point in this n-­‐dimensional space along dimensions which discriminate faces, such as age, ethnicity, etc. Distances between two points are analogous to the similarity between the respective faces. It is assumed that this face-­‐space corresponds to one’s facial representation of a certain person. However, there is no knowledge about the genesis of
such a face-­‐space and the dynamics of changes over time. Moreover, it is not clear, if these representations actually can be seen as averages of agiven face, or as a combination of multiple prototypes. Consequently, this study attempts to investigate the characteristics of facial representation and the possibility of multiple prototypes.

 The genesis and processing of facial representations and prototypes

Burton et al. (2005) proposed a convincing and sparse theoretical framework for the representation of faces which was further empirically proved by showing that averaged faces provide the best representation of a person's facial outward appearance (e.g. Webster & MacLeod, 2011). However, the theory seems to be limited to a certain period of time in a human’s life and neglects temporal dynamics due to dramatic changes in the first years of a life and a less pronounced but still available development of facial characteristics over time (see also Wirth & Carbon, 2010; Carbon, 2009). Here we showed that it is even more economical and more precise to propose "episodic prototypes" which represent a characteristic time span of a human life, e.g. the "baby episode", the "youngster episode", "the aged episode" etc.

Further research will be directed towards optimizing these episodic prototypes by utilizing, e.g. weighting procedures for generating such prototypes.

Schneider, T. M., & Carbon, C. C. (2021). The Episodic Prototypes Model (EPM): On the nature and genesis of facial representations. I-Perception, 12(5), 1-46. {IF=1.535}

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Taking the perfect selfie: Investigating the impact of perspective on the perception of higher cognitive variables

Taking selfies is now becoming a standard human habit. However, as a social phenomenon, research is still in the fledgling stage and the scientific framework is sparse. Selfies allow us to share social information with others in a compact format. Furthermore, we are able to control important photographic and compositional aspects, such as perspective, which have a strong impact on the assessment of a face (e.g., demonstrated by the height-weight illusion, effects of gaze direction, faceism-index). In Study 1, we focused on the impact of perspective (left/right hemiface, above/below vs. frontal presentation) on higher cognitive variables and let 172 participants rate the perceived attractiveness, helpfulness, sympathy, dominance, distinctiveness and intelligence, plus important information on health issues (e.g. body weight), on the basis of fourteen 3D faces. We could show that lateral snapshots yielded higher ratings for attractiveness compared to the classical frontal view. However, this effect was more pronounced for left hemifaces and especially female faces. Compared to the frontal condition, 30° right hemifaces were rated as more helpful, but only for female faces while faces viewed from above were perceived as significant less helpful. Direct comparison between left vs. right hemifaces revealed no effect.Relating to sympathy, we only found a significant effect for 30° right male hemifaces, but only in comparison to the frontal condition. Furthermore, female 30° right hemifaces were perceived as more intelligent. Relating to body weight, we replicated the so-called ‘height-weight illusion’. Other variables remained unaffected.  

In Study 2, we investigated the impact of a typical selfie-style condition by presenting the respective faces from a lateral (left/right) and tilted (lower/higher) vantage point. Most importantly, depending on what persons wish to express with a selfie, a systematic change of perspective can strongly optimize their message; e.g., increasing their attractiveness by shooting from above left, and in contrast, decreasing their expressed helpfulness by shooting from below. We could further extent past findings relating to the height-weight illusion and showed that an additional rotation of the camera positively affected the perception of body weight (lower body weight). We discuss potential explanations for perspective-related effects, especially gender-related ones.


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The height-Weight illusion: Why do we often look fat on unprofessional / unstandardized photos?

Losing weight without dieting: viewpoint-dependent weight assessment on basis of faces (Schneider, Hecht, & Carbon, 2011)

Judging body weight from faces: The height - weight illusion (Schneider, Hecht, & Carbon, 2012)

Being able to exploit features of the human face to predict health and fitness can serve as an evolutionary advantage. Surface features such as facial symmetry, averageness, and skin colour are known to influence attractiveness. We sought to determine whether observers are able to extract more complex features, namely body weight. If possible, it could be used as a predictor for health and fitness. For instance, facial adiposity could be taken to indicate a cardiovascular challenge or proneness to infections. Observers seem to be able to glean body weight information from frontal views of a face. Is weight estimation robust across different viewing angles? We showed that participants strongly overestimated body weight for faces photographed from a lower vantage point while underestimating it for faces photographed from a higher vantage point. The perspective distortions of simple facial measures (eg width-to-height ratio) that accompany changes in vantage point do not suffice to predict body weight. Instead, more complex patterns must be involved in the height - weight illusion.

Illustration of used viewing angles

Fig. 1: Illustration of used viewing angles (eg the last picture; +30°: observer's vantage point is below the observed face). (Faces were taken from the di3d-face database by Claus-Christian Carbon)

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Copyright © 2019 - Tobias Schneider