[racinghamster]

The thing is, a hamster will walk into any toy or tube so nobody can tell whether they are voluntarily liking a ball or not. If they make it move they are doing so because they are moving, so the ball will move, but it can`t be nice for a poor sighted animal to bang into objects it can`t see. When they run in a wheel, the wheel is open sided, so they can choose to use it. A ball is enclosed, so the hamster has no choice buy to stay inside it. They could be running around inside it looking for a way out, rather than actually enjoying it, which is what a human perceives as `enjoying` because it looks fun to us. Which is why it is stated they should`nt be allowed to use a ball for more than 15 minutes as they could become stressed or anxious. I don`t personally feel they need this when a bit of time making a large run is a better option.