[johnny]

That's an urban legend, actually. Humans use all of their brains, it's just that much of the brain is passive intelligence that is used to run things like the respiratory system, blood flow, all the automatic systems we do without thinking.

And, yeah, the horses at the camp were... pretty dumb. You had to be careful not to make any sudden movements or they'd freak out, even at the counselors who had been working with them for years and years. And one horse was afraid of gates. And another one was afraid of puddles of water. And whenever you groomed the horses or stood behind them, you had to have someone else in front of them patting their noses or necks because horses have a literal one-track mind and don't recognize two things happening to them at once.