This refusal to do a second time what has once had a disagreeable result is intelligent.

We now say that the chick "knows" that the worm is not good to eat.

The instinctive action of pecking at all worms is replaced by a refusal to peck at certain worms.

Again, taking the reverse case, we find that the chick which did not respond to the sight of drinking water instinctively, but had to see the mother drink first, acted intelligently, or through a state of consciousness, when it imitated the old hen, and afterward drank of its own accord.

It now "knows" that water is the thing to drink.
The further question which comes upon us here concerns the animal's acquisition of the action appropriate to carry out his knowledge.