100 INSTINCT 
objects, although without a knowledge of the end they sub- 
serve. There is so complete a gradation of responses 
between simple reflexes and complex instincts that it be- 
comes an arbitrary matter where the line is drawn between 
them. In ourselves coughing, sneezing, winking, hiccough- 
ing, swallowing, vomiting, jerking back when tickled or 
painfully stimulated are commonly set down as reflexes. 
Sucking, biting, chewing, spitting out, making a face over 
disagreeable objects, grasping with fingers and toes, carrying 
objects to the mouth, etc., are usually classed as human 
instincts (Preyer). These acts are manifested by the human 
infant at a very early period and in much the same way by 
different individuals, and there can be no doubt that their 
relation to the inherited organization is the same as in the 
lower animals. Chewing, spitting out and making a face 
over a disagreeable taste are little more complex than the 
reflexes of swallowing and coughing. If not performed 
involuntarily, there is at least a strong involuntary pro- 
clivity to their performance which would express itself in 
action if not suppressed by an effort of the will. Swallowing, 
coughing and sneezing are likewise capable of voluntary 
suppression, so that we cannot separate these activities 
sharply on the basis of their relation to the will any more 
than on the ground of complexity. 
In man the gradation from the simple to the more com- 
plex manifestations of instinct is not so obvious owing to the 
fact that human instincts are so closely interwoven with 
habits and the workings of intelligence; but in lower forms 
where intelligence is reduced to a minimum the relation is 
shown very clearly. In an animal such as the crayfish the 
relation of instinct and reflex action may be studied very 
advantageously by the experimental method. The cray- 
fish has a number of well defined instinctive reactions such 
