If they do a thing once, they will do it again.

When she came to us, she had a trick of biting at a person who gave her oats.

She would do it without fail, so father put a little stick under his arm, and every time she would bite he would give her a rap over the nose.

She soon got tired of biting, and gave it up.

Sometimes now, you'll see her make a snap at father as if she was going to bite, and then look under his arm to see if the stick is there.