Table 1.

Single action units in the facial action code Ekman et al., 2002.

AU number	Name of action	Muscle(s) activated
1	Inner brow raiser	Frontalis (pars medialis)
2	Outer brow raiser	Frontalis (pars lateralis)
4	Brow lowerer	Depressor glabellae, depressor supercilii, corrugator supercilli
5	Upper lid raiser	Levator palpebrae superioris, superior tarsal muscle
6	Cheek raiser	Orbicularis oculi (pars orbitalis)
7	Lid tightener	Orbicularis oculi (pars palpebralis)
8	Lips toward each other	Orbicularis oris
9	Nose wrinkler	Levator labii superioris alaeque nasi
10	Upper lid raiser	Levator labii superioris, caput infraorbitalis
11	Nasolabial deepener	Zygomaticus minor
12	Lip corner puller	Zygomaticus major
13	Sharp lip puller	Levator anguli oris (i.e., caninus)
14	Dimpler	Buccinnator
15	Lip corner depressor	Depressor anguli oris (i.e., triangularis)
16	Lower lip depressor	Depressor labii inferioris
17	Chin raiser	Mentalis
18	Lip pucker	Incisivii labii superioris and incisivii labii inferioris
19	Tongue Show
20	Lip stretcher	Risorius with platysma
21	Neck tightener	Platysma
22	Lip funneler	Orbicularis oris
23	Lip tightener	Orbicularis oris
24	Lip pressor	Orbicularis oris
25	Lips part	Depressor labii inferioris or relaxation of mentalis, or orbicularis oris
26	Jaw drop	Masetter; relaxed temporalis and internal pterygoid
27	Mouth stretch	Pterygoids, digastric
28	Lip suck	Orbicularis oris
41	Lid droop	Relaxation of levator palpebrae superioris
42	Slit	Orbicularis oculi (pars palpebralis)
43	Eyes closed	Relaxation of levator palpebrae superioris, orbicularis oculi (pars palpebralis)
44	Squint	Orbicularis oculi (pars palpebralis)
45	Blink	Relaxation of levator palpebrae superioris, orbicularis oculi (pars palpebralis)
46	Wink	Relaxation of levator palpebrae superioris, orbicularis oculi (pars palpebralis)

The coded numbers are arbitrary and do not correspond to any significant value.