A sure sign of a poor actor is one who over-uses his/her forehead. This is true whether they are using the entire forehead or seen in the context of a central forehead contraction (usually elevated, aka an "Elevated CFC"). The central forehead contraction is often clustered with some semblance of a mouth smile. Such "smiles" are false smiles though - and thus never sincere.
This CFC-pseudo mouth smile combination is often seen very commonly displayed by news reporters, attorneys, sales professionals, politicians, etc. - and other professions where there is low-to-medium quality acting. Said another way, these other professions require a degree and frequency of pretending one thing when another is felt - yet Daniel Day Lewis or Meryl Streep they are not.
Good actors and sincere people don't over-use their forehead muscles - and when they are contracted, the CFC seen in concert with congruent verbal and paralanguage.
Another setting where the forehead muscles are over-used is within the context of sociopathic behavior. These individuals are also chronically insincere. In fact - chronic insincerity is one of the cornerstones of a sociopath (What are its other key characteristics). Sociopaths are usually modest actors - but rarely great.
Below are three images from Jurassic World - a film which premiered in North American theaters today. One of these photos is captured from the video/trailer above. Chris Pratt dramatically over uses his forehead. He relies on his looks to carry his roles. His acting is sophomoric.
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