You’ve probably heard that fidgeting, avoiding eye contact, or doing certain hand movements signals dishonesty. Yet, these are often misleading distractions. The true indicator is not an isolated gesture but a sudden deviation from someone’s typical behavior pattern.

Body language expert Chase Hughes, founder of Applied Behavior Research, emphasizes that deception emerges through inconsistencies in overall conduct rather than particular actions. Here, we’ll explore how to detect subtle behavioral cracks, understand why context is crucial, and identify additional nonverbal cues, such as changes in blinking patterns, that can show us when someone is lying.

Sudden behavior shifts: the real lie detector

The most reliable sign of dishonesty is a departure from an individual’s normal baseline. According to Hughes, when someone lies, the automatic, natural patterns they typically exhibit are disrupted. For example, a person who is usually relaxed and expressive might suddenly tense their muscles, rigidify their posture, and lose the fluidity of their gestures. Their tone may shift from a warm, varied cadence to a flat, monotone delivery as they struggle to maintain control while fabricating a story.

Consider a colleague who normally engages in animated conversation with lively gestures and an engaging tone. When the subject turns sensitive, they become unusually still, their face loses its natural expressiveness, and their voice becomes monotonous. Such rigidity suggests that they’re consciously curbing their typical behaviors to mask the truth.

4 subtle signals that back up your suspicion

Shifts in behavior become much more telling when accompanied by other nonverbal cues, such as the following four.

Blinking extremes: Rapid blinking often signals stress, a common reaction when hiding information, whereas an unusually prolonged gaze with minimal blinking suggests an effort to control one’s nonverbal expression.
Words and gestures discrepancies: For example, nodding “yes” while verbally saying “no” can reveal a liar. The body frequently shows falsehoods before the conscious mind can filter them.
Overly polished or vague stories: Deceptive narratives typically fall into two extremes, either they are laden with unnecessary details (“The waiter wore a striped apron and hummed ‘Happy Birthday’…”) or they are frustratingly vague (“I just… did stuff”). Both approaches can aim to manipulate your perception and lend false credibility.
Microexpressions of discomfort: A fleeting grimace, tightening of the lips, or a slight wrinkle of the nose can indicate inner guilt. Even skilled liars often struggle to completely suppress these involuntary expressions.

Keep in mind that no single behavior guarantees deception. Someone might blink rapidly because of dry eyes or freeze due to shyness. Focus on clusters of uncommon behaviors that emerge during specific topics. For example, if your partner usually laughs easily but becomes rigid and avoids eye contact when discussing their weekend plans, probe deeper. Combine that observation with other cues, such as a mismatched head nod, to assess their credibility.

Detecting deception requires careful attention and mental effort. The more you observe subtle shifts in overall behavior rather than isolated gestures, the harder it will be for someone to hide the truth. Stay curious rather than accusatory, and let consistent patterns guide your judgment.