Why is it so hard to spot a liar? The psychology of deception

Can you tell when someone is lying?

Not as well as you would think. Research consistently shows that most people perform only slightly better than chance when detecting lies.

We often rely on stereotypes, such as avoiding eye contact or appearing nervous, but these are poor indicators of deception.

Our capacity to empathise can shape how well we can understand and interpret others' intentions and behaviour, sometimes allowing us to detect their lies.

Likewise, our capacity to take another person’s perspective allows us to lie or manipulate others.

Some personality traits (such as schizotypy, neuroticism or low agreeableness) also shape how we interpret others' behaviour and can bias our perceptions leading us to see deception where none exists and be more distrusting of people.

In my own research, dark personality traits such as psychopathy or Machiavellianism are associated with increased deception and interpersonal manipulation.

Why do we suspect the wrong person?

In groups, a compelling narrative can become more influential than objective evidence itself, and we may stop to look for counter-evidence.

Once we detect some inconsistencies and suspicion takes hold, people tend to seek evidence that confirms their beliefs and overlook evidence that contradicts them (it's called confirmation bias).

We often judge people based on how well their behaviour fits (and confirms) our expectations (which might be further biased by our stereotypes or manipulated through spreading of misinformation) rather than whether they are actually guilty.

Why does suspicion spread through a group?

Suspicion is highly contagious. Humans are social learners, so when several people express doubt about someone, the power of perceived consensus kicks in, and others begin to reassess that person through the same lens.

Group discussions can amplify suspicions, creating a snowball effect where confidence in a judgment grows even when evidence does not.

Moreover, "groupthink" is a psychological phenomenon in which the desire for harmony, agreement, or cohesion within a group overrides critical thinking and objective evaluation of alternatives.

Members may suppress doubts, avoid dissent for fear of attracting suspicion or being excluded, and conform to the emerging group consensus, even when that consensus is flawed.

To top this, groupthink leads to overconfidence - groups can develop an illusion of certainty, believing their decisions are more accurate than they really are, leading to poor decisions, misjudgements, and collective errors, even catastrophic failures.

In contexts such as The Traitors, once a group becomes convinced that someone is suspicious, members may reinforce each other's beliefs and overlook evidence of innocence, leading to the banishment of faithful players.

This illustrates how social influence can sometimes be a stronger driver of judgement than objective evidence.

Why do some people seem more trustworthy?

Trust is often built through warmth, confidence, and social connection rather than factual honesty.

Individuals who are socially skilled, emotionally intelligent, or high in certain dark personality traits can be particularly effective at managing impressions.

For example, being particularly charming and persuasive would certainly help to manipulate others.

They understand what others want to hear and how to present themselves as trustworthy, regardless of whether they are telling the truth.

It may take some time to pick up on the inconsistencies and become suspicious of their behaviour.

Why do innocent people sometimes look guilty?

Stress, anxiety, and being falsely accused can produce behaviours that people mistakenly associate with deception.

An innocent person may appear nervous, defensive, or inconsistent simply because they are under pressure.

They might become incoherent in their search for explanations leading to inconsistencies and increasing suspicion of them.

Thus, ironically, the psychological burden of being suspected can sometimes make innocent people appear more suspicious than actual deceivers.

Coming back to our dark personalities, these individuals are better at staying cool, calm and collected... as such avoiding suspicion - at least initially.

What can The Traitors teach us about spotting deception?

Perhaps the biggest lesson is how difficult deception detection really is.

Success often depends less on identifying lies and more on understanding social dynamics, group influence, and cognitive biases.

The show demonstrates that people frequently make judgments based on trust, familiarity, confidence, and emotion rather than reliable evidence.

In that sense, it reveals as much about human psychology and our flawed biases as it does about deception itself.

Dr Nadja Heym, Associate Professor in Personality Psychology and Psychopathology, and co-chair of the Affect, Personality and the Embodied Brain (APE) research group at NTU.

More from Dr Nadja Heym:

'Dark empaths' - how dangerous are psychopaths and narcissists with empathy?, The Conversation

5 things you didn’t know about Psychopathy, The Conversation

On psychopathy and Dark Empaths, People Who Read People podcast

Psychology of Dark Empaths, podcast with Jacob J. Watson-Howland

What is a dark empath?, Psychologies magazine

Empathy at the Heart of Darkness, Frontiers in Psychiatry