DS2.6 won't sort things for me. No interest. I tried to interest him in a "game" of putting away the clean forks/spoons etc the other day. He just flies them through the air and says random things like, "the little mommy laughed to see such sport and the fork ran away with the spoon".
On the other hand he's quite capable of sorting when he initiates it, for example not too long ago we came home from the pet store and he gathered up every stuffed "pet" put them on one chair to make a pet store. He kept wanting more and I suggested his dinosaurs and he didn't want them, he said they didn't go. Similarly he didn't want a toy turkey/sheep/horse, presumably because those belong on a farm.
DS is lacking in obedience rather than ability (and I'm not complaining, I'm perfectly happy with his interest in self-direction, he'll need that later on). He doesn't test well though. The few times I've lost it and yelled at him he does an about face. (For example the other day he intentionally spilled out a whole jar of coins while looking for a penny and then flat out refused to help pick them up, for the second day in a row).
DS failed a early intervention exam (for speech issues now resolved) item for turn-taking, because he would not play ball. He's just not into balls. Back at the time of the evaluation he took turns just fine for eating yummy things that we were all sharing, pass around a spoon for ice cream for example he knew exactly who's turn it was.
Does identifying the rotational motions of a dishwasher, helicopter and lawnmower have at its base the same thinking as sorting? Seems like it is also an ability to see a similarity between items that are otherwise different, missing the motor aspect of physically putting them in one pile.
As far as milestones to do that, I like the pbs website, it lists classification by function (their example is noticing that two objects are used for transportation) as a 3-4 year old thing.
http://www.education.com/reference/article/Ref_Tracker_Science_3_4/ Here is also the link for the website as a whole:
http://www.pbs.org/parents/childdevelopmenttracker/Polly
