Scientists discover the brain chemical that helps you break bad habits

Scientists have uncovered a key brain signal that helps us break old habits and adapt when circumstances suddenly change. By watching mice navigate a virtual maze, researchers found that disappointment—when an expected reward failed to appear—triggered a surge of the neurotransmitter acetylcholine, making the animals more likely to try a new strategy. When acetylcholine was blocked, the mice became less flexible and were more likely to stick with outdated choices.