HABIT, INSTINCT, AND INTELLIGENCE. 159 



EXPERIMENT WITH PIGEONS. 



Among many tests, take the simple one of removing the eggs to one side of the nest, 

 leaving them in full sight and within a few inches of the bird on the nest. The bird sees 

 the uncovered eggs, but shows no interest in them; she keeps her position, if she is a tame 

 bird, and after some moments begins to act as if the current of her feelings had been slightly 

 disturbed. At the most she only acts as if a little puzzled, as if she realized dimly a change 

 in feeling. She is accustomed to the eggs and now misses something, she knows not what. 

 Although she does not know or show any care for the eggs out of the nest, she does appear 

 to sense a difference between having and not having. 



There is, then, something akin to memory and discrimination, and little as this 

 implies, it can not mean less than some faint adumbration of intelligence. Now this 

 inkling of intelligence, or, if you prefer, this nadir of stupidity, so remote from the zenith 

 of intelligence, is not something independent of and foreign to instinct. It is instinct 

 itself just moved by a ripple of change in the environment. The usual adjustment is 

 slightly disturbed, and a little confusion in the currents of feeling arises which manife.-ts 

 itself in quasi-mental perplexity. That is about as near as I can get to the contents of 

 the pigeon mind without being able, by a sort of metempsychosis suggested by Bonnet, 

 to live some time in the head of the bird. 



In this feeble perplexity of the pigeon's instinct-mind, in this "nethermost abyss" 

 of stupidity, there is a glimmer of light, and nature's least is always suggestive of more. 

 The pigeon has no hope of graduating into a homo sapiens, but her little light may flicker 

 a little higher, and all we need to know is, how instinct behavior can take one step toward 

 mind behavior. This is the dark point on which I have nothing really new to offer, 

 although I hope not to make it darker. 



THE STEP FROM INSTINCT TO INTELLIGENCE. 



Some notion of what is involved in the step may be gathered by comparing wild with 

 semi-domesticated and fully domesticated species. These grades differ from each other 

 in respects that are highly suggestive. In the wild species the instincts are kept up to the 

 higher degrees of rigid invariability, while in species under domestication they are reduced 

 to various degrees of flexibility, and there is a correspondingly greater freedom of action, 

 with, of course, greater liability to irregularities and so-called "faults." These faults of 

 instinct, so far from indicating physical retrogression, are, I believe, the first signs of greater 

 plasticity in the congenital coordinations and, consequently, of greater facility in forming 

 those new combinations implied in choice of action. 



If we place the three grades of pigeons under the same conditions and test each in 

 turn in precisely the same way, we can best see how domestication lets down the bars to 

 choice and at the same time gives more opportunities for free action. The simplest exper- 

 iment is always the best. Let us take three species at the time of incubation and repeat 

 with each the experiment of removing the eggs to a distance of 2 inches outside the edge 

 of the nest. The three grades are well represented in the wild passenger-pigeon (Eclopistes), 

 the little ring-dove (Streptopelia risoria), and the common dove-cote pigeon (Columbn 

 livia domestica). The results will not, of course, always be the same, but the average will 

 be about as follows: 



(1) The passenger-pigeon. The passenger-pigeon leaves the nest when approached, 

 but returns soon after you leave. On returning she looks at the nest, steps into it, and 

 sits down as if nothing had happened. She soon finds out, not by sight, but by feeling, 

 that something is missing. Her instinct is keenly attuned and she acts quite promptly, 

 leaving the nest after a few minutes without heeding the egg. The conduct varies rela- 

 tively little in different individuals. 



(2) The ring-dove. The ring-dove is tame and sits on while you remove the eggs. After 

 a few moments she moves a little and perhaps puts her head down, as if to feel the missing 



