i happily left my son playing on his own sometimes while i had a bath from about the age of 18mths but we live in a flat so i was not far away. I would always give him something to keep him occupied. But what i said before its not because of not leaving him alone, its just i think that young children learn and develop mostly from watching their parents, talking to them and being involved with everything happening in their home. Its positive attention for them, enjoyable for mum/dad and teaches them so much.