The involuntary brushing a fly from the face, or the attempt to move away from an annoyance when tickled with a feather are examples. The nervous impulse comes from the outside and returned, is acted upon without going to the cerebrum. As it were, the message is short-circuited back to the surface by motor nerves, without having reached the thinking centers. Automatic acts are accomplished without thinking. By training the acts have become automatic.
Habits are really acquired reflex actions.
Habit trains certain nerve centers. The amount of function depends upon the renitency, the impulsive force obtained by the bounding back, the reflex action. A reflex center is any ganglionic center where a sensory impression is changed into a motor impulse. Sneezing and the involuntary sniffing of an odor, whether pleasant or unpleasant, are reflex actions. Coughing and choking may be produced by tickling the pharynx, reflex actions, the performances of functions by the controlling intelligence without using the encephalon.