Can you really tell if a kid is lying? | Kang Lee

Scientific concepts & discoveries / nature phenomena mentioned

Children’s lying as a typical developmental behavior

• Core finding: Lying emerges early and becomes common as children develop.

• Experimental/behavioral paradigm (prize/temptation game):

  • Children are asked to guess numbers on cards.
  • They’re told they can earn a large prize if they don’t peek.
  • The experimenter leaves the room with an excuse, telling children not to peek.
  • Hidden cameras monitor whether children peek.
  • Later, children are asked whether they peeked (confess vs. lie).

• Age-related rates of lying (approximate proportions reported):

  • Age 2: ~30% lie, 70% tell truth
  • Age 3: ~50% lie, 50% tell truth
  • Age 4: >80% lie
  • After age 4: most children lie

What makes some children better liars than others

• Two “ingredients” for more sophisticated lying:

  • Theory of mind (mind-reading): understanding that other people have different knowledge, and distinguishing what I know vs. what you know—supporting the logic of deception.
  • Self-control: regulating speech, facial expressions, and body language to produce a convincing lie.

• Associated developmental links:

  • Deficits in mind-reading and self-control are associated with ADHD and autism.

• Interpretation given: Early lying (e.g., around age 2) can signal a normal developmental milestone rather than a character flaw.

Difficulty of detecting children’s lies with ordinary observation

• Common claim tested: adults can detect children’s lying better than chance.

• Result: adults’ accuracy is about chance level (~50%).

• Groups mentioned as unable to reliably detect lying:

  • Undergraduates / law students
  • Social workers / child-protection lawyers
  • Judges / customs officers / police officers
  • Parents (including detecting their own children’s lies)

• Demonstration described: two example videos where participants often misidentify truth vs. lying.

Hidden emotions and physiological markers of deception

• Observation: Children often show neutral facial expressions when lying, while experiencing emotions such as:

  • fear, guilt, shame
  • possibly “liar’s delight”

• Mechanistic idea: emotion-related facial physiology changes are mediated by the autonomic nervous system (not under conscious control).

• Key physiological concept: facial blood flow (via blood vessels under facial skin) changes subtly with different emotions.

• Problem: these blood-flow changes are too subtle to see with the naked eye.

“Transdermal optical imaging” for detecting hidden emotions (and lying)

• Technology described:

  • Uses a regular video camera to record facial video while the subject experiences different hidden emotions.
  • Applies image processing to extract signals consistent with transdermal images of facial blood-flow changes.

• Performance claim: noninvasive, remote, inexpensive; ~85% accuracy, higher than chance.

• “Pinocchio effect” (physiological version):

  • When people lie:
    • cheek facial blood flow decreases
    • nose facial blood flow increases

Proposed and example applications of the technology

• Education:

  • Detect classroom anxiety (e.g., a mathematics teacher identifying an anxious student).

• Healthcare / remote monitoring:

  • During video calls (e.g., Skype with distant parents), monitor:
    • heart rate
    • stress level
    • mood
    • pain
  • Possible future risk estimation for heart attack and hypertension.

• Politics / debates:

  • Estimate heart rate, mood, stress, and possibly future deception likelihood from TV footage.

• Marketing research:

  • Assess whether people like products.

• Dating / interpersonal relationships:

  • Determine whether a smile reflects genuine liking or polite “being nice.”

Researchers or sources featured (named)

• Kang Lee (presenter)
• Richard Messina (elementary school principal, featured in a story)