The Threatening Mask
Oh!—fruit loved of boyhood!—the old days recalling,
When wood-grapes were purpling and brown nuts were falling!
When wild, ugly faces we carved in its skin,
Glaring out through the dark with a candle within!
—John Greenleaf Whittier, The Pumpkin (1850)
The stanza above captures both the joyful abundance of the fall and the terrible artistic skills of New England farm boys in the early 19th century. Joking aside, the two key words used to describe those beloved squash carvings are not by coincidence “wild” and “ugly”. Despite general uncertainty over the original purpose of carved pumpkins, there is some indication that Old World turnip-carvings—the likely predecessors of contemporary pumpkin art—were meant for warding off evil spirits , most likely through the capacity of the “wild” and “ugly” to induce fear in the beholder.
In other parts of the world, the use of threatening facial depictions—which traditional pumpkin carvings certainly are—to induce fear also has a long and remarkable record: from Hesiod’s description of Heracles’s painted shield (“In the centre was Phobos (god of fear) … fearful and daunting”)  to the Four Heavenly Kings statues in the Hindu/Buddhist traditions (“eliminate evil influences and suppress the enemies (Asura, or destructive spirits)”) , threatening aggressiveness has been unsurprisingly embodied and encapsulated in numerous creative forms over the history of mankind.
The most prominent examples of “distilled threatening expression”, I think, can be found in masks, be they theatric, ritualistic, or festive. Here is a collection of traditional Tibetan ritual and theatre masks, the former category of which supposedly represent guardian spirits. Here is a blog dedicated to modern U.S. Halloween masks, from the horribly tacky to the tackily horrible. All this is meant to demonstrate that the phenomenon of repugnant face-making is arguably universal and stems from some unique facet of humanity that may transcend times and cultures. One can, therefore, stipulate that there is some evolutionary meaning to this creative drive—some neuronal capacity common to us all that allows us to recognize the threats in artificial faces, respond with appropriate emotions, and expect others—who may or may not be human—to do so as well.
How do we do it, then? How is it that we can recognize aggressive emotions from static images of faces—be it shield-paintings, statues, or masks—and react accordingly? Granted, masks used for theatre, such as the Japanese Noh masks, can display emotions more effectively with motion, perhaps due to the face-in-motion being more readily recognized by us as showing “expressions” [6, summary]. There was even an attempt to use those masks as psychiatric tools for detecting dysfunctional recognition of facial expressions , and the effort to decipher how such an “emotional range” is created is apparently ongoing . It should be fair to presume, however, that the modern readers of intellectual blogs are not treated to moving masks in dramatic and ritualistic settings very often, and yet the emotional “messages” of those masks are well-preserved even when they are, as shown in the figure below , static.
Of course, neuroscience is not new to static angry-face like imagery; a decade ago, in a thousand-citation review , “anger” was categorized as one of the so-called “basic”, or easily recognizable, emotions . The review went on to postulate that both the amygdala and the prefrontal cortex are specifically important in recognizing anger, based on lesion study in amygdala-damaged patients  and fMRI evidence , respectively. That is to say, aside from activation of regions important to visual recognition of face-like objects, such as the famous fusiform face area, there seems to be the need for specific emotional tags that are cooperatively constructed by both the amygdala and the prefrontal cortex. In addition, damage to the insular cortex was also associated with impaired recognition of disgust . The story so far, therefore, seems to be that what we perceive as “emotion” is a static quality that we assign to an image of an emotional face from a pre-existing pool of tags, based on the (yet unexplored) features of said image. In the dynamic case of theatre masks (and, indeed, everyday life), then, we could simply be updating those tags regularly.More recently, in a publication by an NIH-Dartmouth-UCL joint group in Current Biology , the authors claimed to have shown evidence that “dynamic and static facial aspects are processed via dissociable cortical pathways that begin in early visual cortex”. In normal English it means that, according to the authors, we perceive emotions as movement features of the human face, despite our ability to recognize emotions in masks. The authors used transcranial magnetic stimulation to disrupt the occipital face area (OFA, functionally defined as around inferior occipital gyrus, near the striate cortex ) and posterior superior temporal sulcus (pSTS, just below STG in the above diagram) of neurologically healthy human participants. Since the OFA has been considered crucial for both facial identity (a “static” property) and expression (a biologically “dynamic” property) recognition , the authors hypothesized that stimulating the OFA would impair both types of recognition. The pSTS, in turn, was involved in perceiving biological motion , and the authors expected to see impaired recognition of facial (e)motion upon stimulation of participants’ pSTS.
As it turned out, dynamic faces became less recognizable (i.e. elicited less pSTS response in fMRI) when stimulation was applied (whereby pSTS was “inactivated”), but it happened regardless of whether the faces shown had non-neutral expressions—control runs with deadpan head-shakers (i.e. producing face movement without facial expressions) led to the same results as experimental runs with emoting face-movers. On the other hand, OFA stimulation did lead to reduced responses compared to baseline in runs with expressionless, immobile faces only, thus supporting the idea that a pathway dedicated to emotional recognition can indeed be separated from identity recognition in the early visual cortex. None of the results, however, detract from the possibility that emotional valence of faces can be a static property, especially since no controls with “emoting” but immobile faces had been run with OFA stimulation.
So, for the time being, whatever it is that we perceive from masks can still be reasonably called “emotional expressions”. In other words, just because most masks don’t move like a face, doesn’t mean they can’t scare you like a moving face could. Case in point:
Happy Halloween, face-movers.
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(b) The statues of the Four Heavenly Kings by Tsukumo Imamura
(c) reference , Figure 1
(d) reference , Figure 1