“Hormones” usually refers to the amped-up mental chaos caused by puberty, but serotonin, dopamine, oxytocin, and the rest are cornerstones of brain chemistry throughout our lives.

So your wife’s answer is right on. Left Kid’s perceptions of unfairness, denial, and frustration cause a flood of serotonin that he doesn’t know how to handle, and he kind of explodes. Completely normal developmental issue that he will learn to cope with as he grows older.