Discrepancy in WISC IV Scores

Q: My daughter is 11 and was recently tested using WISC IV Australian. She scored Superior in PRI and PSI, average in WMI and VCI. In WIAT-II Australian her Mathematics Composite score & Written Expression Skills were at the 75th percentile. Reading Comprehension 70th, yet Word Reading Accuracy 42nd and Spelling 25th. She also plays the piano at AMEB level 7.

We had her tested because she is in the lowest English and Math classes at school and we felt she was capable of more. We are now confused about what these results demonstrate. Can you explain this to us?

A: It is important to understand what the various indexes indicate. The following shows the four main indexes of the WISC-IV and what they measure:

Verbal Comprehension Index (VCI)	Measure: Verbal concept formation. It assesses children's ability to listen to a question, draw upon learned information from both formal and informal education, reason through an answer, and express their thoughts aloud. It can tap preferences for verbal information, a difficulty with novel and unexpected situations, or a desire for more time to process information rather than decide "on the spot." Note: This index is a good predictor of readiness for school and achievement orientation, but can be influenced by background, education, and cultural opportunities.
Perceptual Reasoning Index (PRI)	Measure: Non-verbal and fluid reasoning. It assesses children's ability to examine a problem, draw upon visual-motor and visual-spatial skills, organize their thoughts, create solutions, and then test them. It can also tap preferences for visual information, comfort with novel and unexpected situations, or a preference to learn by doing.
Working Memory Index (WMI)	Measure: Working memory. It assesses children's ability to memorize new information, hold it in short-term memory, concentrate, and manipulate that information to produce some result or reasoning processes. It is important in higher-order thinking, learning, and achievement. It can tap concentration, planning ability, cognitive flexibility, and sequencing skill, but is sensitive to anxiety too. It is an important component of learning and achievement, and ability to self-monitor.
Processing Speed Index (PSI)	Measure: Processing speed. It assesses children's abilities to focus attention and quickly scan, discriminate between, and sequentially order visual information. It requires persistence and planning ability, but is sensitive to motivation, difficulty working under a time pressure, and motor coordination too. Cultural factors seem to have little impact on it. It is related to reading performance and development too. It is related to Working Memory in that increased processing speed can decrease the load placed on working memory, while decreased processing speed can impair the effectiveness of working memory.

It appears that your daughter scored in the superior range in PRI (for non verbal and fluid reasoning) and PSI (for processing speed). The average scores on VCI and WMI shows average ability in forming verbal concept and holding and manipulating new information. With the limited information given on the scores, what I suspect here is a probable learning disability that may have gone undetected all this time. The WISC can be used to detect a learning disability as it provides a comprehensive diagnostic assessment of a child's educational and cognitive strengths and weaknesses.

For VCI, it is more rewarding for a more responsive child so if your child is not very responsive, she may lose a little here. The lower scores are average and not extremely low, therefore it is best to see the psychologist who did the testing to check the detailed scores and determine the sub-areas that brought down the scores for a better indication of extremities. It has been suggested that a 19 point discrepancy in the VCI (or PRI) composites may warrant further investigation. Again, detailed scores are required to determine any further assessment. Please speak to the tester or see a psychologist who is familiar with WISC IV with the detailed report. Good luck!