DD9 still does this sometimes - not as much as she did when she was younger, however.
When we sat down with the people that were going to do the psychoeducational testing with her when she was 7 we tried to explain this to them. She had a habit of giving off the wall answers and do the grin thing and watch to see if anyone would catch it. If no one did she would just move on. I recall one question she told us about where they asked about something that was hot and dry during the day, but could get cold at night. We asked her what she answered and she told us she couldn't remember what she told the testers, but that the correct answer was a desert. She thought it was funny and laughed about it - much to our chagrin. We don't know if they caught her in the act or not and took that into consideration. The report we got didn't say anything about it.
