• One of the most obscure AUs to find references for.
• Generally, tech companies don’t even bother tracking 11, because 11 is so poorly understood and difficult to gather data for.
• Part of this difficulty comes from that fact that 11 is so challenging to perform voluntarily.
• Due to the poor understanding of what 11 even is, sadly, 11 often gets lumped in with 10.
• As mentioned in the AU10 section above, see my Instagram post to view a more detailed comparison of 10 vs. 11.
• Despite many tech companies’ decisions to ignore 11, it is paramount in many variations of sadness prototypes.
• If you watch any of the crying videos I’ve posted on my social media accounts, you will see very strong 11s.

• Most people know 12 as the “smile.”
• 12 is required in all happiness prototypes.
• It is easily confused with 13 or 14 – especially when weak.
• Differs from 13 and 14 in that it pulls the lips more laterally & diagonally, creating a wider mouth shape.
• When 12 is at high intensities, it separates the lips, exposing teeth. Contrary to common expression building techniques, the separation of the lips for 12 CANNOT BE REPLICATED BY ADDING 10 AND 16. See post on building smiles the right way.

• Most often confused with 12, because 12 is the more popular and recognizable action between the two.
• Because 13 is so similar to 12, most machine learning-based trackers will almost certainly confuse 13 with 12. If you are labeling data and wish to distinguish 13 from 12, training novice (or even advanced) expression labelers will be difficult.
• When comparing 12 and 13, 13 pulls the lip corners at a more drastic angle than 12 – hence its name, “sharp lip puller.”
• Commonly left out of expression shape sets.

• 14 is the lip corners compressing and pinching against the teeth.
• A unilateral 14 can be considered one of the contempt expressions.
• From personal observation, people do (bilateral) 14 when uncomfortable or dissatisfied. Individuals high on the anxiety spectrum make tons of 14s. When I was in sales, every time someone did a 14, I eventually learned I wouldn’t  be able to close them.

• Yet another difficult action for people to perform voluntarily.
• Commonly confused with or unintentionally combined with 17. This confusion is largely due to the lip corner lowering illusion that occurs when 17 pushes up the center of the lower lip.
• Many online and in-print FACS references have incorrect 15 examples contaminated with 17.
• 15 is seen in many of the sadness prototypes.

• Makes an appearance in some disgust prototypes.
• Often mistakenly added to open-lipped smiles to create shapes showing the teeth. As mentioned in the AU 12 section, this method should not be applied to smiling.

• An action present in some sadness and disgust prototypes.
• Co-occurs with 15 to create “facial shrug.”
• I see many art and tech companies creating a “facial shrug” shape despite already containing shapes for 15 and 17 in their sets. (ARKit is one of them.) Because 15 and 17 combine so logically, it is probably unnecessary and a bit redundant to build an entire additional shape combo for 15+17. I would only recommend building a 15+17 shape for groups who wish to swap out individual shapes for 15 and 17 and reduce them to one singular combo shape.

• Many people confuse 18 with 22. Please see my demonstrations highlighting the differences here.

• Important action in fear expressions.
• In some people, 20 stretches across the face in a straight line. In others (including myself), the lip corners can be pulled and angled down. In the case that the lip corners are angled and stretched downward, 20 can easily be confused with 15. I have observed tech companies commonly mis-tracking 20 as 15. It is important to properly distinguish 15 from 20, because both are key players in different emotions (sadness and fear, respectively).

NOTE: There is a bit of 17 creeping into my 20 in this GIF. You can see the 17 by the dimpling on my chin from mentalis.

• Commonly confused with 18 – but very different. Again, see my demonstration here on how to tell 18 and 22 apart.
• Present in some anger prototypes.
• Important in the creation of “sh” and “ch” sounds.

• Even more misunderstood than 11!
• The internet and many textbooks are full of incorrect 23 references. Please read my post on how to observe a proper 23.
• Important action in many anger prototypes.

• Another anger prototype action.
• Easily confused with 23 when 23 is done with closed lips.

• Literally just means the lips are parted and not closed.
• 25 is not an anatomical description. It is a state: open or closed.
• Any action in this document that has the lips open, in FACS, should technically be labeled as having a 25.
  • For example, in the AU23 section, the lips are parted; therefore, 25 is also present. I have opted out from including 25 in the AU sections with open lips. I made this decision to reduce excess text and prevent possible confusion Labeling. 25 is mostly important in academic labeling.

• Jaws parting to a certain intensity.
• The parting must be relaxed to quality as AU25 – meaning it is lowered not due to forced action.
• When the jaw is stretched down or lowered with force at maximum intensity levels, the jaw drop turns into 27. (See next tab.)

• Jaw intentionally lowered, not due to relaxation.
• Creates a pop in the pterygoid area at maximum intensity.

• Sometimes referred to as “lip roll.”
• Lips curled into mouth.
• Almost always requires slight jaw dropping – but because this is done with closed lips, many do not consider the presence of jaw dropping.
• Can be confused with 23 or 24 in tracking tech due to the effect of the flesh part of the lips being narrowed from being sucked in.