vn ASSIMILATION AND READJUSTMENT 115 



response is itself modified by the result, in which, that is 

 to say, an object to which we begin by reacting in a certain 

 fashion, which we may call positive, yields some further 

 stimulus which checks that reaction, and in which this 

 effect persists so that we no longer react positively to an 

 object of the same kind. With these we may class, con- 

 versely, cases in which an object, to which we are at first 

 indifferent, becomes, as the result of experience, a stimulus 

 to reaction, which is confirmed every time it is repeated. 

 This operation of experience, in its simplest and also its 

 completest form, is beautifully illustrated by Mr. Lloyd 

 Morgan's observations on young chickens. 



" With regard to the objects at which domestic chicks peck, in 

 the absence of any parental guidance, one may say that they 

 strike at first with perfect impartiality at anything of suitable 

 size : grain, small stones, bread-crumbs, chopped-up wax matches, 

 currants, bits of paper, buttons, beads, cigarette-ash and ends, 

 their own toes and those of their companions, maggots, bits of 

 thread, specks on the floor, their neighbours' eyes anything and 

 everything, not too large, that can or cannot be seized is pecked 

 at, and, if possible, tested in the bill. . . . There does not seem 

 to be any congenital discrimination between nutritious and in- 

 nutritious objects, or between those which are nice and those 

 which are nasty. This is a matter of individual acquisition. 

 They soon learn, however, what is good for eating, and what is 

 unpleasant, and rapidly associate the appearance with the taste. 

 A young chick two days old, for example, had learnt to pick out 

 pieces of yolk from others of white of egg. I cut little bits of 

 orange-peel of about the same size as the pieces of yolk, and one 

 of these was soon seized, but at once relinquished, the chick 

 shaking his head. Seizing another, he held it for a moment in 

 the bill, but then dropped it and scratched at the base of its beak. 

 That was enough ; he could not again be induced to seize a piece 

 of orange-peel. The obnoxious material was now removed, and 

 pieces of yolk of egg substituted, but they were left untouched, 

 being probably taken for orange-peel. Subsequently, he looked 

 at the yolk with hesitation, but presently pecked doubtfully, not 

 seizing, but merely touching. Then he pecked again, seized, 

 and swallowed. 



"To some other chicks I threw cinnabar larvae, distasteful 

 caterpillars, conspicuous by alternate rings of black and golden- 

 yellow. They were seized at once, but dropped uninjured ; the 

 chicks wiped their bills a sign of distaste and seldom touched 

 the caterpillars a second time. The cinnabar larvse were then 



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