Feedback

Living systems hold themselves steady by watching their own output and reacting to it — that is feedback. In negative feedback, a change triggers a response that opposes the change, pushing the system back toward a set point. This is the loop that stabilizes: when body temperature drifts above 37 °C you sweat and cool down; when blood glucose climbs, insulin brings it back down. "Negative" does not mean bad — it names the direction of the correction, which is opposite to the disturbance. The result is a system that resists being pushed away from its target and keeps returning to it.

Positive feedback does the opposite: a change triggers a response that amplifies the same change, driving the system further from where it started. There is no set point to return to — the loop runs away from stability until an outside event stops it. Childbirth builds this way, each contraction releasing oxytocin that strengthens the next, and the spike of a nerve impulse works the same way. Positive feedback is not "good" any more than negative is "bad"; it is simply the loop that reinforces rather than corrects.

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The mistakes here come from reading the labels as value judgments instead of directions. One is hearing negative as "harmful" — when it actually names a correcting loop that stabilizes the system toward its set point, the very thing that keeps you alive. The other is confusing the two loops' direction — treating positive feedback as just "more of the same good thing," when its defining feature is that it amplifies away from the starting value with no set point to return to. Every scenario in this topic asks you to reason from does the response oppose or amplify the change to whether the system settles or runs away.