WAYS OF NATURE 
shallow its wit. When a cat or a dog, or a horse or 
a cow, learns to open a gate or a door, it shows a 
degree of intelligence — power to imitate, to profit 
by experience. A machine could not learn to do 
this. If the animal were to close the door or gate be- 
hind it, that would be another step in intelligence. 
But its direct wants have no relation to the closing 
of the door, only to the opening of it. To close the 
door involves an after-thought that an animal is not 
capable of. A horse will hesitate to go upon thin ice 
or upon a frail bridge, even though it has never had 
any experience with thin ice or frail bridges. This, 
no doubt, is an inherited instinct, which has arisen 
in its ancestors from their fund of general experience 
with the world. How much with them has depended 
upon a secure footing! A pair of house wrens had 
a nest in my well-curb; when the young were partly 
grown and heard any one come to the curb, they 
would set up a clamorous calling for food. When I 
scratched against the sides of the curb beneath them 
like some animal trying to climb up, their voices 
instantly hushed; the instinct of fear promptly 
overcame the instinct of hunger. Instinct is intelli- 
gent, but it is not the same as acquired individual 
intelligence; it is untaught. 
When the nuthatch carries a fragment of a hick- 
ory-nut to a tree and wedges it into a crevice in the 
bark, the bird is not showing an individual act of 
intelligence : all nuthatches do this; it is a race 
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