When the will attains control over expression we may not merely repress the impulse to expression when we feel strongly, but having no feeling of a given kind we may voluntarily adopt its expression, and this adoption of the expression very often leads by association to the real feeling. Again, when experiencing a feeling we may simulate the expression of another or even opposite feeling. It is often advantageous in the struggle for existence to throw others off their guard by deceiving them as to the real emotional state; hence, craft and guile have from a tolerably early stage in evolution played a part in the history of life. Animals and men alike soon appreciate the distinction between appearance and reality, that a kind and pleasant expression is often but the lure of malice and hostility, that injury is often meant where there is the show of benefit. Plants, as well as animals, often are quite other than they appear, both for offence and defence; and there is the wide field of mimetic protection which cannot, however, at present be brought under our subject. Simulation of expression probably arose as an economical makeshift; a mere show which costs the organism little often attains ends which would otherwise require a vast deal of mental force. Thus we see children scared into desired behaviour by assumed anger, grief, etc.; and even animals, as I have noticed with dogs, likewise frequently affect expressions which have no support in real emotion. The unsophisticated, however, learn with great rapidity to distinguish between assumed and real emotion. Any one who has made a pretence of crying before little children must have remarked this. Simulation of expression in order to easily reach desired ends is thus rather limited, but still has a real value and a considerable place under natural selection.