I've been able to do the same with my two Roos. I've held them a lot ever since they were young, and so now, (they're 2 months old), they can sit on me for hours without pooing. They'll only go when I put them down. I haven't figured out how to make them "go outside" but yes, evidently, they can certainly hold it in when they want to. I'm not sure either what causes them to do this.