The psych that tested DD did it and just indicated on the report that she substituted. I think the NACG suggests that gifted kids tend to do better on arithmetic than digit span because arithmetic is more interesting/meaningful. It would be interesting to see how DS would do on arithmetic. It could be why DD's working memory score is so much better than DS's although if the psych had done digit span on her instead of arithmetic, I think she would have done fine. She can repeat about 5 numbers backwards. DS seems to have more trouble with it.
