Sometimes autism symptoms are confused with signs of co-occurring disorders. These include flapping or other self stimulating behaviors, self destructive behavior, oversensitivity to sounds and other stimuli, and irrational fears.
Why not talk about core deficits instead? They are the difficulties children with autism, Asperger's Syndrome, or Pervasive Developmental Disorder all have in common.
Declarative communication: They may be able to point to what they want (instrumental communication), but they cannot share their experiences with you.
Referencing: No matter if they learn to recognize and label facial expressions, or learn "eye contact," they cannot "borrow your perspective" to help them resolve situations of confusion.
Regulating: They may be able to follow a script in certain prescribed settings, but they cannot follow your spontaneous or unpredictable interactions.
Episodic memory: Rote memory is usually not a problem--in fact, it can be quite good. What is difficult is for them to reflect on the past and to use their memories to plan for the future.
Flexible thinking: Not to be confused with rule-based thinking, this deficit prevents them from being able to determine when something is good enough or to see shades of gray when evaluating solutions to problems.