The actor really experiences something of the inner excitement which he imitates and with the excitement the automatic reactions appear.

Yet only a few can actually shed tears, however much they move the muscles of the face into the semblance of crying.

The pupil of the eye is somewhat more obedient, as the involuntary muscles of the iris respond to the cue which a strong imagination can give, and the mimic presentation of terror or astonishment or hatred may actually lead to the enlargement or contraction of the pupil, which the close-up may show.

Yet there remains too much which mere art cannot render and which life alone produces, because the consciousness of the unreality of the situation works as a psychological inhibition on the automatic instinctive responses.

The actor may artificially tremble, or breathe heavily, but the strong pulsation of the carotid artery or the moistness of the skin from perspiration will not come with an imitated emotion.