Originally Posted By: jimmyy
Hi all, just discovered this forum a few days ago. May I ask a question on how to interpret low digit span score from my son's WISC IV test?

My son is 9 yr old. He did WISC IV test this past weekend and got the following score:
VCI: 146
Similarities: 18
Vocabulary: 18
Comprehension:17
PRI: 143
Block Design: 17
Picture Concepts: 17
Matrix Reasoning: 17
WMI: 129
Arithmetic: 17
Digit Span: 9
Letter-Number Seq: 13
PSI: 128
Coding: 15
Symbol Search: 15

FSIQ: 148

It seems Digit Span score is real low. How to interpret this? What is the symptom/consequence of this? Anything needs
to be concerned? The testing school psychologist said nothing
to be worried. But still I am wondering if the experienced parents may have seen this kind of "pattern"? Thanks very much.


There is indeed nothing to worry about; a test's "g-loading" is its correlation with full-scale IQ (the extent to which the test taps into the general intelligence factor). Forward digit-span only has a g-loading of about 0.30, meaning that only 9% of the variance in scores on forward digit-span are attributable to differences in g. There is no reason to assume that because a child has a high IQ, such as your son, that he or she would perform in the superior range on forward digit-span.

Backward digit-span is a much more g-loaded task, with a correlation with full-scale IQ of about 0.40 (i.e., 16% of the variance in performance on backward digit-span is attributable to full-scale IQ). However, a person's performance on this task is hindered by his or her forward digit-span; in other words, a child cannot recall a certain number of digits backwards if he or she cannot first recall the digits forward. (There are of course exceptions to this rule, and they reveal valuable clinical information on the momentary psychological and physiological state of the examinee).

When one combines the forward digit-span and backward digit-span tasks, one yields the digit span task utilized on the WISC-IV and WAIS-III, which has a g-loading of about 0.57 (about 32% of the variance on this task is explained by differences in g). This is still a fairly poor g-loading. In a sample of 148 gifted children, the average group performance on digit span was 13.5, with a maximum of 21 and a minimum of 6. In comparison, the group's average performance on vocabulary was 16.1, with a minimum of 12 and a maximum of 28. (Vocabulary has a g-loading of 0.83).

In conclusion, the results are not at all inconsistent; a very high IQ in no way mandates very superior or even superior performance on the digit-span task because it is a poorly g-loaded test.


Edited by Frank22 (08/06/14 01:03 AM)