make sure you change the materials or have several examples... ie. several different socks or pictures of socks.

Secondly your ABA consultant should work with you to discuss what the mastery criteria is. Generally you do not count prompted trials towards the 80-90% correct. If he's getting no trials correct without being prompted, then he does not have the skill.

I suggest you move back a step and go to matching these items to first determine if he can discrimated. Is he able to match a sock to a sock, a toothbrush to a toothbrush. Is so, then do sorting. then move to receptive trials but reduce the field to 3.

As always, make sure your reinforcement is REINFORCING to him. If you don't have good reinforcement, there's no point because you won't know if its lack of motivation or lack of understanding.

Ate you comfortable with the quality of your ABA provider? If you have another option in your area, you may want to give it a shot. There are lots of different ways to work through this (3D vs 2D labels, reducing the field, game playing, etc). So, if this is the first ABA provider you've tried, you may want to try another. I know from experience that there is a huge difference in results based on the therapist you have. My son currently has a team of 3 ABA therapists, and the results he "gives each one " varies - I wouldn't place the "blame" on the therapist necessarily, it's really dependent on the "match" with your son.

I meant decriminate.... ie. tell the difference of the different objects.

Thank you for all the advice. We have tried some of your suggestions like reducing the field,variable reinforcement and using the items in context. He is very good at figuring things out in context, it is a matter of does he understand "commands" with no gestures or contextual cues. The only way we were able to outsmart him with the task at hand was to have 3 different piles of items, with 3 different kinds of socks, spoons and trains. All 3 items were in each pile, since he memorized what we were asking for. This is where he started to get frustrated and we realized that he really didn't have labels for these items. I think we will need to go back to having him sort items, so that he can discriminate their distinct features. Reinforcement has been a big obstacle, we are constantly having to find new reinforcers.