The expressive mask of Parkinson's disease, a reduced spontaneity, intensity, and fluidity of facial, bodily, and vocal expression, jeopardizes interpersonal interaction and quality of life. Observers have difficulty perceiving the "real" person behind the mask, leading to failed communication and misunderstanding. A social ecological explanation of this difficulty is that observers have learned in their daily social lives, and quite appropriately so, that expressive behavior reveals meaningful information about character. The premise of this study was that health practitioners, especially novices, would bring into the clinic their everyday perceptual tendencies related to deciphering character. The study examined novice and expert practitioners' impressions of the personality of patients with Parkinson's disease who were videotaped during a healthcare interview. It was found that practitioners, especially novices, appeared to be overly sensitive to expressive masking when forming impressions about patient extraversion. They incorrectly perceived patients with more masking to be less extraverted than patients with less masking. Novice practitioners were particularly inaccurate in their impressions of neuroticism compared to experts. Novices incorrectly perceived patients with more masking as being more neurotic, whereas experts tended to be sensitive to valid cues of neuroticism. Practitioners' impressions of patient conscientiousness were not sensitive to masking and were highly accurate.