arms. Many responses of organisms are modified in a similar way, not only by artificial limitations, but also by natural ones.
(c) Responses which have become fixed and constant through natural selection or other means of limitation may become more varied and general when the compulsory limitation is relaxed. Behavior in the former case is fixed and instinctive, in the latter more varied and plastic. Thus Whitman found that the behavior of domesticated pigeons is more variable and their instincts less rigidly fixed than in wild species. If the eggs are removed to a little distance from the nest the wild passenger pigeon returns to the nest and sits down as if nothing had happened. She soon finds out, not by sight but by feeling, that something is missing, and she leaves the nest after a few minutes without heeding the eggs. The ring-neck pigeon also misses the eggs and sometimes rolls one of them back into the nest, but never attempts to recover more than one. The dove-cote pigeon generally tries to recover both eggs.
In these three grades the advance is from extreme blind uniformity of action, with little or no choice, to a stage of less rigid uniformity. . . . Under conditions of domestication the action of natural selection has been relaxed, with the result that the rigor of instinctive coordination, which bars alternative action, is more or less reduced. Not only is the door to choice thus unlocked, but more varied opportunities and provocations arise, and thus the internal mechanism and the external conditions and stimuli work both in the same direction to favor greater freedom of action. When choice thus enters no new factor is introduced. There is greater plasticity within and more provocation without, and hence the same bird, without the addition or loss of a single nerve cell, becomes capable of higher action and is encouraged and even constrained by circumstances to learn to use its privileges of choice. Choice, as I conceive it, is not introduced as a little deity encapsuled in the brain. . . . But increased plasticity invites greater interaction of stimuli and gives more even chances for conflicting impulses.
(d) Finally in all animals behavior is modified though previous experience, just as structure is also. Where several responses to a stimulus are possible and where experience has taught that one response is more satisfactory than another, action may be limited to this particular response, not by external compulsion, but by the internal impulse of experience and intelligence. This is what we know as conscious choice or will. Whitman says:
Choice runs on blindly at first and ceases to be blind only in proportion as the animal learns through nature's system of compulsory education. The teleological alterations are organically provided; one is taken and fails to give satisfaction; another is tried and gives contentment. This little freedom is the dawning grace of a new dispensation, in which education by experience comes in as an amelioration of the law of elimination. . . . Intelligence implies varying degrees of freedom of choice, but never complete emancipation from automatism.
Freedom of action does not mean action without stimuli, but rather the introduction of the results of experience and intelligence as addi-
