Behavioral and electctrophysiological evidence for enhanced sensitivity to subtle variations of pain expressions of same-race than other-race faces.

Recent research has shown enhanced brain activity in responses to pain expression of same-race than other-race faces. However, due to the stimuli used in electctrophysiological (EEG) research (i.e., photos of static pain expressions) and low temporal resolutions of neural activity reported in functional magnetic resonance imaging (MRI) studies, it remains unclear how dynamic neural responses to subtle variations of pain expressions are shaped by perceived race in the first few hundreds of milliseconds after face onset. We tested the hypothesis of greater sensitivity to subtle variations of pain expressions of same-race than other-race faces by integrating psychophysical and EEG responses to increasing amount of pixels of pain expressions applied to neutral faces. Experiment 1 found that adults required fewer painful pixels to perceive pain expression of same-race than other-race faces. Experiment 2 showed that the amplitude of a positivity activity at 140-190 ms over the frontal/central electrodes (P2) increased faster in response to the increasing amount of painful pixels of same-race than other-race faces. These results provide evidence for enhanced sensitivity of both subjective feelings and neural responses pertaining to subtle variations of pain expressions of same-race than other-race faces.