Parakinetic stereotyped acts are of common occurrence, and embrace every variety of movement or gesture.
A former acrobat leaps staircases, climbs railings, exercises his arms rhythmically and regularly, etc.
A patient promenades untiringly in the same corner and at the same pace.
An old engraver, now a dement, passes the day in reproducing in a more or less modified form certain actions associated with his former profession.
Alike in tics and in stereotyped acts, a time comes when the motor habit establishes itself, for no apparent reason or purpose; hence the co-existence of the two classes in chronic delusional insanity, in dementia precox, in catatonic states, in systematised mental disease of other forms, and in general paralysis.
Stereotyped acts may be the embodiment of ideas of persecution and of grandeur, or the outcome of mystical, hypochondriacal, and other states. A patient with delusions of persecution writhes because he is being "electrified." A hypochondriac rests motionless because he believes himself made of glass. A mystic maintains an attitude of genuflexion for hours at a time.
Obsessions also play a part in the genesis of the acts we have under consideration, but of all delusional ideas those of defence are the most fertile in this respect.
A patient under the care of A. Marie used to carry a fragment of glass between his teeth and other pieces beneath the soles of his feet, the idea being that they formed insulating cushions whereby to protect himself from the electricity of his enemies.
The suggestion was thrown out by Bresler that the movements of tic are often of a defensive character—that the disease, in fact, is a sort of "defence neurosis" linked to hyperexcitability of psychomotor centres. This theory is not unlike the view of hysteria taken by Brener and Freud, and as the movements themselves are usually of the nature of mimicry, Bresler has proposed the term mimische Krampfneurose.
In some cases of mental torticollis, the attitude assumed may be considered as a stereotyped act. Martin has recorded an example of torticollis in relation to melancholia. Another of his patients suffered from rotation of the head to the left, a position which could easily be rectified by asking the man to make the sign of the cross. The moment he put his finger on his forehead the displacement of the head was corrected. If, however, he were requested to look straight in front of him, he remained incapable of altering the vicious attitude, the reason he advanced being that he could no longer see the sun.