Why was Arithmetic dropped as a Core subtest?
Arithmetic was dropped because of the significant maths load that confounded the meaning of the result. However, it was retained as a Supplemental subtest because it is an excellent measure of Working Memory. Working Memory must be assessed with some content load. For children with grade appropriate maths skills, Arithmetic is an excellent measure of Working Memory. However, results are difficult to interpret for children weak in maths skills. Mental arithmetic is a task with considerable ecological validity because it is something many people are frequently called upon to do in real life.
