From a great NYT feature on geniuses as children:
After the English lawyer Daines Barrington examined the 8-year-old Mozart in 1764, he wrote: “He had a thorough knowledge of the fundamental principles of composition. He was also a great master of modulation, and his transitions from one key to another were excessively natural and judicious.” Yet, Mozart was also clearly a child. “Whilst he was playing to me, a favorite cat came in, upon which he immediately left his harpsichord, nor could we bring him back for a considerable time. He would also sometimes run about the room with a stick between his legs by way of horse.”