There is a significant disconnect between our internal emotional state, our physical motor patterns, and the language we use to describe our feelings. These three streams of behavior only correlate at about 0.2, meaning what someone says they feel often doesn't align with their body language.

A lack of contagious yawning can be a subtle sign of psychopathic traits. This reflects a diminished capacity for "automatic empathy," or catching others' emotions, even though their cognitive understanding of emotions may be intact.

People with dark personality traits often self-report them honestly on questionnaires. They don't see being callous, manipulative, or superior as negative characteristics, so they feel no shame or remorse in admitting to them.

Research shows the key to a trustworthy smile isn't showing teeth but engaging upper cheek muscles, creating eye crinkles. This “real smile” is contagious, making others feel happier, whereas a fake smile evokes no emotional change. This is crucial for profile photos or first impressions.

The guest uses the metaphor of a glass wall to describe her internal state: she can observe, study, and perfectly emulate human behavior and emotion, but can never truly feel or connect with it herself.

A key nonverbal cue for psychopathy is an inappropriate combination of verbal and nonverbal emotional displays. For example, using angry, hostile words while making a big, broad smile can be a red flag that people subconsciously detect.

Your internal emotional state is transmitted to others, even when you try to hide it. Behavioral investigator Vanessa Van Edwards found that subtle micro-expressions induce the same feelings in others, causing them to form a negative or positive opinion about you within the first few seconds of an interaction.

A key facial indicator of potential volatility is an incongruous expression. Specifically, when someone holds the 'fear' expression in their upper face (eyelids pulled back) while the lower face shows joy or arousal (a smile), it creates a deeply unsettling effect. This mismatch is a significant red flag.

The 'successful psychopath' trope is a myth. Research on government officials and hedge fund managers found that higher levels of psychopathy were associated with less influence and lower earnings. They may seem confident but are typically terrible managers who hurt team performance.