Facial expression. 1. A gesture produced by compressing, in-rolling, and narrowing the lips to a thin line. 2. A position of the mouth in which the lips are visibly tightened and pressed together through contraction of the lip and jaw muscles.
Usage: The lips are our most emotionally expressive bodily features. Lip and jaw tension clearly reflects anxious feelings, nervousness, and emotional concerns. Thus a tense-mouth precisely marks the onset of a mood shift, a novel thought, or a sudden change of heart.
Meaning. The tense-mouth has been observed as a sign a. of anger, frustration, and threat; b. of determination; c. of sympathy; and d. of cognitive processing (e.g., while pondering, thinking, or feeling uncertain). The face may show obvious muscular tension (i.e., with the lips held tightly together) or less noticeable tension (i.e., with the lips parted and slightly tightened).
Observations. 1. Subliminal (i.e., barely noticeable) tension in a wife's lips prompts her husband to ask, "What's wrong?" 2. A CEO's tense-mouth face greets staff as they enter the conference room, creating a guarded atmosphere in which nobody speaks. 3. "Nothing's the matter," a boyfriend says. But his mouth's unusually thin line belies the point. His girlfriend asks, "Is there something we should talk about?"
U.S. politics. 1. The lips of a chronically angry, anxious, or intense person may "freeze" in a permanently tight-lipped expression, as shown, e.g., in 1960s photos of FBI director, J. Edgar Hoover. 2. The tense-mouth is visible in AP photos of President William Jefferson Clinton, sitting in the Map Room of the White House on August 17, 1998, minutes before making a televised statement to the American people: "Indeed, I did have a relationship with Ms. Lewinsky that was not appropriate."
RESEARCH REPORTS: 1. In Old World monkeys and apes, tense-mouth expressions convey threat and dominance (Van Hooff 1967). 2. Rolling the lips in is a socially avoidant cue in children (McGrew 1972). 3. In children, smiles in threatening situations are combined with tightening and compressing the lips (Stern and Bender 1974). 4. Monkeys and apes perform the tense-mouth with lips closed or nearly closed, mouth narrowed to a slit, and jaws tightly closed prior to an attack (Givens 1976). 5. In babies, lip-compression and brow-lowering (combined in the pucker face) appear when mothers persist in playing or feeding beyond an infant's tolerance (Givens 1978C). 6. Lip-compression (lips pressed tightly together and rolled inward) often appears in the company of strangers, where it correlates with gaze avoidance, non-contact, and distancing between individuals (Givens 1978D). 7. "You glance toward Mom at the other end of the table. You notice that her eyes are focused on Dad, and her lips are pressed tightly together. You brace yourself. You are about to get it. That look always means 'you're in hot water now!'"(Richmond et al. 1991:75). 8.The lip bite means "I am angry." The angry gesturer "bites his own lower lip with his teeth, shaking his head from side to side vigorously as he does so" (Morris 1994:154).9. The tense-mouth is an aggressive sign in our nearest primate relative, the pygmy chimpanzee or bonobo (Waal 1997).
Anatomy. In the tense-mouth, our lips' orbicularis oris muscles contract. Their rubber-band-like fibers tighten to produce visible compression, in-rolling, and narrowing. Tension may be accented by contracting the masseter and temporalis muscles used in biting.
Neuro-notes. A gestural fossil, the tense-mouth is innervated by special visceral nerves originally designed for feeding. The expression is emotionally responsive today as it reflects visceral sensations (i.e., "gut feelings") aroused, e.g., by aggression and anger. In effect, we tighten our lips to seal off our mouth opening--a form of "nonverbal lock-down." Emotional stimuli pass from higher brain centers to brain-stem nuclei below, where the trigeminal (cranial V) and facial nerves (VII) arise in a special visceral motor column of the pons. From deep within the brain stem, the facial nerve travels out of the skull, branches, and links to the sphincter-like orbicularis oris muscles which tighten, compress, and in-roll our lips.
U.S. President George H.W. Bush disagreeing [note extended index finger, palm-down hand, and directed gaze] with aid [compressed-lips, averted gaze (downcast eyes)] (copyright 1992 byWahington Post)