Maximize Emotional Impact
KEY CONCEPT: The shape of the mouth region is a key signifier of emotion.
Figure 1. | The human face is the most mobile in the animal kingdom, infiltrated with a more complex network of muscles and nerves than any other creature, by far. The repertory of movements that we can create is endless including, for some, wiggling the ears. However, only a very small subset of these movements is significant in the facial expressions of emotion, and even here all of the facial changes that accompany, say, smiling or frowning are not equally important for recognition. Most of our attention is focused on two tiny regions of the face we are pre-programmed to notice – the “Hot Spots” of the eye and mouth. |
The mouth is a bit more complicated than the eye, in that it can be expressive either opened or closed, with certain details being more heavily weighted than others. (see Figures 2 & 3) In the case of the Open Mouth, important in the expressions of surprise, anger, disgust, joy, sadness, and fear, the most significant element is the shape of the mouth opening itself. Although the lips are highly stretched and modified in many of these expressions (see Figure 1), and the teeth are exposed in different manners, the Open Mouth shape alone can effectively communicate the expression in progress. This is why, for example, Mickey Mouse can smile so brightly without the accompaniment of teeth (although this is anatomically impossible.)
Figure 2. | Figure 3. | In Figure 2 the Open Mouth "hot spot" is expresssed through the shope of the mouth opening which carries the most expressive weight. In Figure 3, the Closed Mouth "hot spot" is expressed through the outside corners of the mouth which, similarly, carries the most expressive weight. |
Figure 7. | Figure 8. | Note that Figure 5 appears identical in effect to Fig. 7,, and Figure 8 to Figure 6, in spite of the jaw drop being eliminated in the lower two images. The upper images for Open Mouths are anatomically correct and the lower ones are impossible, but we focus on the "hot spot" (shape of mouth opening) to read the facial expression, and we ignore the discrepancy. |
The mouth shape is the key element in the expression, and what’s critical here for surprise to be clear (and not be confused with fear), is that the mouth has to open in a totally relaxed fashion. When that occurs, the resulting shape of the mouth opening is taller than it is wide, with no sharp or abrupt angles. We are very sensitive to both the proportion and the “softness” of the shape, and even a small discrepancy can throw off the expression. | Figure 9. | Figure 10. |
Artists can use the principle of the" hot spot" to help determine what to leave in and leave out in more radical character designs. A robot mouth can be surrounded by a rigid box, for example, where the mouth can open, close and stretch without needing any modification to the box itself. But non-human character design can come with certain limits. In the case of Donald, the rigidity of the beak means that there is no effective way to distinguish open-mouthed surprise (where the mouth opens in a simple oval, as in Figure 13) from fear (where the mouth is stretched sideways, as in Figure 14) since the shape of the mouth opening itself cannot be altered.