Information - fund of general knowledge; long-term memory; recall
The Information subtest reflects two factors in the child's development of language and knowledge: 1) The richness of the child's verbal environment during his development is reflected in the fund of knowledge. 2) The ability to store that knowledge in long-term memory, recall it, and verbally express it is an individual ability that is measured by the Information subtest.
Similarities - Verbal categories and concepts; abstract verbal reasoning
In order to store language and information in long-term memory, humans use a process of categorization and conceptualization that develops from the concrete to the abstract. The Similarities subtest captures the child's ability to mentally process verbal information, categorizing and conceptualizing information in the long-term memory store. Over the course of the child's development, their conceptual skills progress from concrete to abstract reasoning, a process that is reflected in the Similarities subtest.
Arithmetic - Numerical reasoning; attention and concentration
The numerical tasks of the Arithmetic subtest are worked out "in the child's head". She must have the ability to attend to the verbally presented problem and concentrate on working out the answer in her short-term memory. The Arithmetic subtest requires a level of freedom from distractibility that is considered a factor in overall intelligence. Performance on Arithmetic also requires a mastery of the mathematical operations required by each item, and therefore reveals information on the child's achievement in arithmetic learning.
Vocabulary - Language development; word knowledge; verbal fluency
The Vocabulary subtest reflects both the child's knowledge of words and a higher order ability to categorize words by their meanings, to retrieve that information, and express it with verbal fluency. Quite an advanced task that again demonstrates both the richness of the child's language environment and his natural ability to process that language.
Comprehension - Understanding social rules and ethics; common sense and judgment
The Comprehension subtest is based on social comprehension, a skill that is deficient in many LD and ADHD children. The social understanding that underlies the Comprehension subtest is greatly influenced by environment. Ethical judgment may be lacking for a variety of reasons - intellectual, environmental, and emotional. For children with significantly weak comprehension subtest scores, direct instruction in social skills may be required. Again, the Comprehension subtest performance is related to the child's ability to express himself verbally.
Digit Span - Short-term auditory memory; concentration and attention
The Digit Span subtest is often excluded from the WISC-III administration and is not required to obtain the IQ scores. It is included in an assessment of the factor known as Freedom from Distractibility. An examiner may use the Digit Span subtest to suggest a possible ADD/ADHD diagnosis, particularly if it correlates with the other Freedom from Distractibility subtests - Arithmetic and Coding. High Digit Span scores suggest a superior ability to concentrate and memorize orally presented information.*Note - In the WICS-IV, Digit Span is included in the Full Scale IQ in the Working Memory Scale with a new subtest called Letter-Number Sequencing.