TABLE 1.
The specific meaning of each AU.
| Facial action units | Action description | Value range |
| JawOpen | Dropping of the chin without opening the mouth | (0, 1) |
| LipPucker | Pouting | (0, 1) |
| JawSlideRight | Slide the chin to the right (the negative number indicates a sliding of the chin to the right and then to the left) | (−1, 1) |
| LipStretcherRight | Stretch the right corners of mouth to the right | (0, 1) |
| LipStretcherLeft | Stretch the left corners of mouth to the left | (0, 1) |
| LipCornerPullerLeft | Pull the left corners of mouth to the upper left | (0, 1) |
| LipCornerPullerRight | Pull the right corners of mouth to the upper right | (0, 1) |
| LipCornerDepressorLeft | Pull the left corners of mouth to the left and down | (0, 1) |
| LipCornerDepressorRight | Pull the right corners of mouth to the right and down | (0, 1) |
| LeftcheekPuff | Puff up the left cheek | (0, 1) |
| RightcheekPuff | Puff up the right cheek | (0, 1) |
| LefteyeClosed | Close the left eye | (0, 1) |
| RighteyeClosed | Close the right eye | (0, 1) |
| RighteyebrowLower | Right eyebrow down (the negative number indicates a raised right eyebrow) | (−1, 1) |
| LefteyebrowLower | Left eyebrow down (the negative number means the left eyebrow is raised) | (0, 1) |
| LowerlipDepressorLeft | Pull the lower lip down to the left | (0, 1) |
| LowerlipDepressorRight | Pull the lower lip down to the right | (0, 1) |
The value represents the size of the facial action units’ movements in proportion to the resting state, usually 0.8 means a very large movement.