Facial Muscles and Action Units
AU Illustration List
| AU | Video | Action Description (FACS) | Common Emotional Associations |
|---|---|---|---|
| 1 |
1.0x
|
Inner Brow Raiser | Disgust, Surprise, Happiness, Fear、Sadness |
| 2 |
1.0x
|
Outer Brow Raiser | Surprise |
| 4 |
1.0x
|
Brow Lowerer | Sadness, Fear, Anger, Disgust |
| 5 |
1.0x
|
Upper Lid Raiser | Anger, Surprise, Fear |
| 6 |
1.0x
|
Cheek Raiser | Happiness |
| 7 |
1.0x
|
Lid Tightener | Disgust |
| 9 |
1.0x
|
Nose Wrinkler | Disgust, Anger |
| 10 |
1.0x
|
Upper Lip Raiser | Disgust, Anger |
| 11 |
1.0x
|
Nasolabial Deepener | |
| 12 |
1.0x
|
Lip Corner Puller | Happiness |
| 13 |
1.0x
|
Cheek Puffer | |
| 14 |
1.0x
|
Dimpler | Disgust,Happiness, Sadness |
| 15 |
1.0x
|
Lip Corner Depressor | Sadness, Disgust |
| 16 |
1.0x
|
Lower Lip Depressor | Anger |
| 17 |
1.0x
|
Chin Raiser | Disgust |
| 18 |
1.0x
|
Lip Puckerer | |
| 20 |
1.0x
|
Lip stretcher | Fear |
| 22 |
1.0x
> |
Lip Funneler | Anger |
| 23 |
1.0x
|
Lip Tightener | Anger |
| 24 |
1.0x
|
Lip Pressor | Digust |
| 25 |
1.0x
|
Lips part | Fear, Surprise, Disgust |
| 26 |
1.0x
|
Jaw Drop | Surprise, Happiness |
| 27 |
1.0x
|
Mouth Stretch | Surprise, Happiness |
| 28 |
1.0x
|
Lip Suck | Happiness |
| 41 |
1.0x
|
Lid droop | |
| 42 |
1.0x
|
Slit | |
| 43 |
1.0x
|
Eyes Closed | Sadness |
| 44 |
1.0x
|
Squint | |
| 45 |
1.0x
|
Blink | |
| 46 |
1.0x
|
Wink |
Basic Coding Guidelines for micro-expression
- When corners of lips pulled up (AU12) appears, it can be coded as a positive emotion, i.e., happy; In addition, cheek rise (AU6), lip suck (AU28) are both happy specific action units and can also be coded as positive emotions;
- When brow rise (AU2) is present, it can be coded as surprise;
- When frown (AU4) is present, it can be coded as a negative emotion;
- It can be coded as anger when gnashing (AU16, AU22 or AU23), which only occur in the specific action units, appear;
- When movements of the eyebrows (AU1 and AU4), eyes (AU5) and mouth (AU25) are present simultaneously, they can be coded as fear;
- It can be coded as disgusted when the specific action unit of disgust, lower eyelid rise (AU7), mouth tightly closed (AU24), is present;
- It can be coded as sad when frown (AU4) and eyes wide open (AU5) are present at the same time; eyes closed (AU43) is the specific action unit for sadness and can also be coded as sadness.
References
Dong, Z., Wang, G., Lu, S., Li, J., Yan, W., & Wang, S. J. (2022). Spontaneous Facial Expressions and Micro-expressions Coding: From Brain to Face. Frontiers in Psychology, 5808.