When does the brain distinguish between genuine and ambiguous smiles? An ERP study

Area of Science:

• Cognitive Neuroscience
• Social Psychology
• Neuroscience

Background:

• Facial expressions convey crucial social information.
• Ambiguous expressions, like a smile with non-happy eyes, pose challenges for social perception.
• Understanding the neural basis of processing these expressions is key.

Purpose of the Study:

• To investigate the temporal dynamics of processing ambiguous facial expressions using event-related potentials (ERPs).
• To compare the neural processing of genuinely happy, ambiguous, and non-happy faces.
• To determine when emotional valence and ambiguity are detected in the brain.

Main Methods:

• Recorded electroencephalography (EEG) from 64 scalp electrodes.
• Presented participants with various facial expressions (happy, ambiguous, non-happy).
• Analyzed event-related potentials (ERPs), specifically P200, EPN, and LPP components.

Main Results:

• Early ERP components (P200, EPN) differentiated emotional valence (positive vs. neutral/negative).
• Later ERP components (LPP) were sensitive to expression ambiguity (genuine vs. ambiguous).
• Emotional discrimination occurred from 180-430ms, while ambiguity resolution took 470-720ms.

Conclusions:

• The brain processes basic emotional valence earlier than resolving facial expression ambiguity.
• Ambiguous expressions with fearful or neutral eyes alongside a smile are poorly discriminated from genuinely happy faces early on.
• Neural sensitivity to ambiguity emerges significantly later than initial emotional valence detection.