TABLE 1.

Characteristics of the Wechsler Intelligence Scale for Children Subtests^a

Subtest	Description
Information	This is a test of general knowledge. It reflects the ability to acquire and store knowledge in long-term memory, to access it, and to express it verbally. Test items include questions about knowledge in history, geography, and art and are arranged in order of difficulty from the simplest to most difficult.
Similarities	This is a test of verbal concept formation and reasoning. It captures the ability to categorize and conceptualize information available in semantic memory (a form of long-term memory). The similarities subtest asks the child to explain what a pair of words has in common (e.g., that apples and oranges are both fruits), with word-pairs ranging in difficulty from concrete relations to abstract ones.
Vocabulary	This is a test of language skills and includes questions about the meaning of words (e.g., What does winter mean?). It captures language processes such as the ability to acquire word meaning, recall it, and effectively express it.
Block Design	This is a test of visual-spatial organization, executive planning, and problem solving skills. The child is required to put together two, four, or nine red and white blocks in a pattern according to specific designs being displayed. Test items are presented with increasing difficulty. Higher scores reflect both accuracy and speeded responses.
Object Assembly	This is a test of visual perception and construction ability. This test contains cut-up cardboard figures of familiar objects (puzzles), which are given in order of increasing difficulty. The child must analyze the object and construct the whole visual object from its parts within time constraints. Responses are scored for both accuracy and speed.
Picture Completion	This is a test of visual discrimination and reasoning. It requires knowledge of a variety of common objects and scenes. Children are shown incomplete pictures of human features, familiar objects, or scenes arranged in order of difficulty and are asked to identify the missing part by pointing to it and/or naming it. The child must look at the visual whole presented and analyze its parts to identify what is missing.
Arithmetic	This is a test that requires working memory processes to be applied to the manipulation of orally presented verbal information. It involves numerical knowledge, short-term memory, attention, and concentration. Children are presented with arithmetic problems in story format (e.g., Four men can finish a job in eight hours. How many men will be needed to finish it in one-half hour?). Performance requires holding information in short-term memory, accessing long-term memory to retrieve numerical rules of mathematical operation, and using the rules to manipulate the stored data. Items are arranged according to the level of difficulty and have time limits.
Digit Symbol	This is a test of psychomotor speed and coordination and attention/concentration. Better performance also depends on incidental learning. A key that pairs symbols and numbers is presented. Within a time constraint, the child is requested to fill in rows containing blank squares (each with a randomly assigned number above it) using the key.

^aData described previously (28).