Guilford (1967) maintains that many aspects of intelligence tend to be ignored when items are lumped together to form tests. An item used as a test of verbal ability is distinguished from one that is nonverbal on the basis of its content-words as opposed to pictorial material.
But what one does with content of the test item (e.g., memorizes it or uses it to engage in a reasoning process) will depend n the nature of the task and may be relatively independent of the content. Guilford maintains that intelligence test items should not be distinguished in terms of content alone, (also in terms of the operations performed upon.