FACIAL EXPRESSIONS | Sad

The Subtle Signs of SADNESS 

Fig. 1 - Sad face expressed through
​subtle facial cues.

Fig. 2 - Sad face bordering on grief. 

It doesn't take much to look sad.  Of all the emotions, sadness can be portrayed with the least facial movement.  ​I found a particularly good photograph of slight sadness in a newspaper recently, and I decided it would make a great subject for this month's blog.

The face of the young woman in Fig. 1 is obviously sad, but the marks of sadness on her face are slight enough to be reckoned in movements of a fraction of an inch.  She tugs at our heartstrings, but with so little actually going on!

The woman in Fig. 2, by contrast, has a face that is much more contorted in sorrow - the eyes, forehead, cheeks, mouth, and chin are all dramatically distorted and reconfigured; it's the way someone looks just short of weeping.  It is hardly surprising, when comparing the emotional intensity of the two women, that 100% of test-takers agreed that the woman in Fig. 2 appears more sad than Fig. 1.  100% results are not that uncommon with really strong expressions.  

Occasionally, however, subtle expressions can also receive unanimous results from test takers. Case in point, the unhappy woman in Fig. 1 tested as clearly and unambiguously as her near-crying counterpart, with 50 out of 50 random participants agreeing she was sad.  

I was naturally curious: how can the sad young woman in Fig. 1, with such slight cues visible on her face, communicate such a clear message?  I examined her subtly sad face alongside her neutral face (see Figures 3 and 4 below), and here's what I noted:

Fig. 3 - Young woman with sad face.

​Fig. 4 - Young woman with neutral face.

1. The most obvious difference between the two photos is her eyebrows, which in Fig. 3 slant obliquely upwards. the classic sadness configuration.
2. The mouth shape has changed -  barely - with the outer corners of her mouth slightly lower in her sad face than her neutral one, with small facial bulges and creases nearby. 

​After extensive testing, I determined that the subtle bulges and creases around her mouth were much more important in communicating her emotion than I had, at first, suspected. ​To verify this, I created two slightly different images of her sad face.  In both images, her upper face has been edited to have no expression.  Her lower face, with its sad mouth, is also the same, except that in Figure 6, I have smoothed out all the bulges and creases surrounding her mouth.

Fig. 5 -  Same sad woman as in Fig. 3, but with her eyebrows relaxed to "neutral" by the author

Fig. 6 -  Same sad woman as in Fig. 5,  but with chin bulge, and creases under lower lip and terminating her cheeks removed by the author. 

The facial creases (under her lip and descending from her nose) and chin bulge that are present in Figure 5, but not Figure 6, are created by the three muscles that contract in the expression of grief: the Zygomatic Minor, the Mentalis, and the Depressor Anguli Oris (for further details, see my book).  What’s important is that the removal of these very subtle elements decreased the look of sadness in this woman's face by 60%. That's pretty impressive for such small movements.

How can such tiny changes on the face be so critical to our reading of sadness in Figure 5?  There are several reasons:
​

1. Of all the facial expressions, sadness is the most communicative at low levels of facial activity.  This makes sense, since sadness is, by its nature, a withdrawal into oneself; it is low-energy compared to anger, joy, surprise, or fear, and the small amount of face in movement reflects that;
2. We can recognize sadness from either the mouth alone, if we have enough clues with the "active" sad mouth and lower face, or with the brows/eyes;
3. In my testing, sadness has been the easiest expression to pose, and it is also the most common “noise” in appraising neutral faces.  People are more likely to see sadness than any other emotion when the face is still;
4. Since the activity of the mouth alone in Fig. 5 is so slight (and the upper face is neutral), adding the lower-face changes which ONLY occur in sadness dramatically clarifies the emotional message.

This fine-tuning of sadness is too subtle for most animation applications.  CG faces are not rigged to produce the accessory changes so critical to the slightly sad face (chin bulging, lip and cheek creasing).  To compensate, animators rely on a more obvious frowning mouth (see Figs. 7 & 8) where we don't need the surrounding bulges and creases to recognize the expression.

Still, I wonder if the day is not far off when CG characters will be built to sustain a more fine-tuned level of facial performance.  With an expression like sadness, you can do so much with so little. Perhaps someday our digital creatures will be capable of communicating  more of the nuances of real faces, particularly with low-intensity expressions.

Figures 7 & 8 - Here are two examples of faces where the downward mouth movement is
obvious so the more subtle creases and chin bulge are not necessary to be read as "sad."

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Credits: Figures 1, 3, 4, 5 & 6 -- Brandy Landauer, sister of kidnapped 15-year old, interviewed by Jessica Jaglois in "'She’s a smart girl’: Elizabeth Thomas’ sister believes she ran away," and aired on  News 2 WKRN-TV on March 21, 2017; Figure 2 -- Ikea Coney, photographed by Andrew Renneisen for New York Times article, "On Staten Island, Thousands Protest Police Tactics" by J. David Goodman, published on August 23, 2014; Figure 7 -- 3D modeling rig created by "Frankie" at https://franklyfrankie.wordpress.com; Figure 8 - Ink drawing by author, 2017.

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