My 3.5 year old hound mix doesn't play. Not with toys, anyhow. He will chase us, and jump up on us, but he won't play with any toy or ball. He plays with other dogs, he will wrestle with us in the bed, but no toys.

In comparison, my sister's 9 year old chocolate lab? That boy plays all the time, he has something in his mouth 99% of the time, unless he is asleep.