The smile is one of the most powerful non-verbal tools humans possess, capable of communicating a vast range of emotion. While a symmetrical smile is recognized as an expression of genuine joy, the canted smile offers a more ambiguous signal. This distinctive facial expression, sometimes called a lopsided or asymmetrical grin, is characterized by a noticeable difference in the height of the two corners of the mouth, where one side of the upper lip is pulled distinctly higher than the other.
Defining the Asymmetrical Expression
The canted smile is a visually arresting phenomenon where the horizontal plane of the mouth appears slanted or diagonal across the face. Instead of the gentle, even curve of a symmetrical expression, one side of the mouth is markedly elevated toward the cheekbone. This elevation results in an uneven exposure of the upper teeth and gums.
This asymmetry extends beyond the mouth, creating differences in surrounding facial features. The cheek on the higher side typically appears more bunched, and the nasolabial fold—the line running from the side of the nose to the corner of the mouth—is often deeper and more pronounced. Conversely, the lower side may appear flatter, with the lip corner remaining closer to its resting position.
The Underlying Musculature and Mechanics
The physical mechanics of the canted smile are rooted in the differential action of the paired facial muscles of expression. The primary muscles responsible for lifting the corners of the mouth upward and outward are the zygomaticus major and zygomaticus minor. These muscles originate on the cheekbone and act as the main elevators for the upper lip and lip corner during a smile.
A canted smile occurs when the corresponding muscles on the left and right sides of the face exhibit an uneven level of activation or tonicity. If the right-side zygomaticus major contracts more forcefully or earlier than its left-side counterpart, the right corner of the mouth will be pulled higher. The movement of these facial muscles is governed by the facial nerve, the seventh cranial nerve (CN VII).
This nerve branches out to supply motor control to the muscles of the face, and a difference in the strength of the neural signal to one side’s muscles can result in the asymmetrical pull. While the structural alignment of the jaw or teeth can contribute to the visual perception of a cant, the dynamic canted smile is fundamentally a result of this muscular imbalance. This neurological and muscular coordination dictates the degree and direction of the tilt.
Natural Variation Versus Neurological Factors
The causes of a canted smile can be broadly divided into natural variations and those stemming from underlying neurological or structural issues. Many people exhibit a natural degree of facial asymmetry, meaning their paired facial muscles are not perfectly equal in tone or strength. This inherent difference often results in a smile that naturally favors one side, especially during spontaneous expressions.
In other cases, the asymmetry can be a learned, functional pattern, perhaps related to dominant-side use or a practiced expression. However, a canted smile that appears suddenly or worsens may indicate a neurological concern. Conditions like Bell’s Palsy, which causes temporary facial nerve weakness, or a minor stroke (Transient Ischemic Attack) can impair the function of the facial nerve, leading to significant one-sided muscle weakness. This nerve damage prevents the muscles on the affected side from contracting fully, causing the mouth corner to droop or fail to lift symmetrically.
Social and Psychological Interpretation
The asymmetrical nature of the canted smile gives it a different communicative function than a fully symmetrical, genuine expression, known as the Duchenne smile. The Duchenne smile, which involves muscle contraction around the eyes, is associated with true enjoyment and is perceived as trustworthy. The lopsided grin, in contrast, is frequently interpreted as conveying conflicting or nuanced emotions.
Psychologically, the canted smile often signals suppressed amusement, irony, or skepticism, suggesting an incomplete commitment to the emotion being displayed. This expression can also be perceived as a mild form of contempt, signaling disapproval mixed with disgust, often referred to as a smirk. Studies suggest that asymmetrical smiles are less likely to induce cooperation, as they are viewed as less reliable indicators of genuine intent.