As used in this passage, the phrase "feed into" most nearly means:

As used in the passage, the phrase feed into most nearly means to encourage. In the context of the paragraph, therapists advise parents not to react emotionally or engage in power struggles with children exhibiting oppositional behavior. Instead, they are encouraged to praise positive behaviors and discourage negative behaviors through the use of timeouts rather than harsh discipline. The phrase implies that parents should not contribute to or reinforce oppositional behavior but rather take steps to promote more positive behavior.