Aidan turned six on Saturday. To celebrate his “birthday eve,” we invited his cousin, Kiley, to come spend the night on Friday night.

After pizza and the usual period of indiscriminately tearing around the house, everyone settled down for popcorn and a movie. The evening’s feature presentation was Earth, Disney’s recent nature documentary. It didn’t have any sarcastic superheroes or talking rodents, but it managed to keep the kids’ attention nonetheless.

As usual with nature documentaries, this one eventually showed a high-tension chase, with a speedy predator going after something slower and doomed. In this case it was a cheetah and a Thompson’s gazelle.

Everyone had a different reaction to the thrilling sequence. Each, I think, demonstrates well the way our brains work at different ages.

Thirty-somethings Byron and I wondered how they managed to get these shots. How long do these people have to sit still, in the jungle or on the tundra, waiting for the chase to happen? Can they bring a book or an iPod? Wow, think of the peace and quiet. And what kind of cameras do they use? The clarity is amazing. It’s crazy how technology keeps advancing.

Elementary-school-age Mack, Kiley and Aidan were yelling, “Is the cheetah going to catch him? The gazelle is pretty fast! Is the gazelle going to get away? What is the cheetah going to do to him? He’s going to eat him, isn’t he! Gross! Is there going to be blood? Will we see the blood? How much blood?”

Three-year-old Reid said nothing through the whole chase. He seemed riveted by the action, deep in thought. Then he turned to us and said, “I wish I had a tail.”