Picture this. We're in the woods when we meet a lively little dog. He wants to play chase. He runs up to George and then runs away. George chases him - for about 5 seconds, then he sits down. Little dog continues to run for a short time then goes back to George who chases him again for 5 seconds then sits. And so it goes on, little dog doing ten times as much running as George.
Now does this mean George is lazy - as I suspect - or very smart - as Younger Son insists? 'He knows the other dog will come back to him so why bother chasing?'
A third possibility has occurred to me.
Sometimes George and I play chase. He will come to me with a ball and I'll get up and get chase him - for about 5 seconds. Then I go and hide and wait for him to come looking for me when I'll leap out and say, 'BOO!'