Fig 7. AU12, lip corner puller, without AU113, sharp lip puller, (A) and AU12 with AU113 (B).

Note the difference in the shape at the corner of the mouth. AU12 produces a curvature at the mouth corner; however, when AU113 is applied with AU12 the mouth has an angular appearance at the top corner, with corresponding wrinkles in the skin surrounding the mouth. See S15 Video for a demonstration of these actions acting simultaneously.