Ohio Buckeye or Horse Chestnut?

When I was studying horticulture, my oldest son was a toddler. Quite frequently, we carried him about in a backpack. When I took my trees class in the fall, I went to a nearby park with him and was learning to tell various trees apart. Because I talked to him all the time about whatever I was doing, I showed him the trees and their leaves and told him the names. He got so he was better at that age at telling certain thing, such as distinguishing Ohio buckeye from horse chestnut. To this day, he can still tell them apart with more certainty than I, both from a distance and up close. And he claims to remember those rides around the park learning about trees, though he was barely 3 at the time. Oh, this one is Ohio buckeye. He is certain of that.