Duke TIP

Nonverbal Assessment of Ability: What Is It?

August 28, 2006

Many people assume that intelligence comes in two kinds—verbal and nonverbal. What they do not understand is that the verbal-nonverbal distinction refers to the content of the items on an intelligence test, not to the type of thinking, or intelligence, required. Verbal and nonverbal tests are two different ways of measuring general ability.

What Is General Ability?

David Wechsler, who developed the Wechsler Intelligence Scale for Children (WISC), defined general ability as “the aggregate or global capacity of the individual to act purposefully, to think rationally, and to deal effectively with his environment.” The psychologist Rudolph Pintner explained, “We did not start with a clear definition of general intelligence . . . [but] borrowed from everyday life a vague term implying all-round ability and knowledge, and . . . we [are] still attempting to define it more sharply and endow it with a stricter scientific connotation.” So there is little reason to assume that those who invented tests of general ability conceptualized verbal and nonverbal types of intelligence. General-intelligence tests with verbal and nonverbal content measure the same construct of general ability as tests that are all nonverbal; therefore they are more useful across cultures. The verbal-nonverbal distinction is a practical rather than a theoretical one, coming into play especially when diverse populations are tested.

For persons whose first language is not English, the use of verbal tests in America creates an obstacle because, quite simply, such persons sometimes don’t know enough English. Logic and empirical research support the conclusion that they do poorly on English measures of general intelligence that contain verbal tests because of their limited English-language skills, not because of low intelligence.

What Does a Nonverbal Test Look Like?

A typical nonverbal test item from the Naglieri Nonverbal Ability Test (NNAT) is shown in the figure. A student must see the patterns formed by the shapes organized into groups, then choose an answer that completes the pattern. Actual test items use blue, white, and yellow because these colors are most easily perceived by those with color-impaired vision. In this example, the child has to understand that the three shapes form a pattern throughout the three-by-three matrix. The circle forms a diagonal line from the bottom right to the top left. The triangles and the squares form their own alternating pattern; once the child understands it, he or she can choose the correct option (no. 2).

Image: Naglieri Nonverbal Ability Test item

Many academic tasks, regardless of content, call for the same basic intellectual activity required to solve this problem. For example, understanding a written paragraph requires a child to “see” how various pieces of information are interrelated. Learning to spell often involves seeing patterns in a sequence of letters. Many aspects of math involve recognizing the patterns and relationships among concepts and numbers. Because a nonverbal test measures a basic and essential way of thinking, it helps us understand how smart a child is and how likely that child is to do well in school. Because the test items do not require knowledge of words, they permit a fair evaluation of children from different cultural and linguistic groups.

Who Is a Good Candidate for a Nonverbal Test?

Although nonverbal tests are especially useful for children with limited English-language skills, their value is not limited to that group. For example, children whose economic or social circumstances have limited their acquisition of knowledge and verbal skills may best be able to display their knowledge through such a test. They should and will earn good scores on tests of general ability. Taking nonverbal tests of ability will afford them the same opportunity to succeed as other children. Nonverbal tests are also useful for evaluating those with impaired hearing.

In summary, nonverbal tests provide a valid way to measure general ability for all children. Researchers have found that they identify similar proportions of black, white, and Hispanic children as gifted. This suggests that the problem of underrepresentation of minority children in classes for the gifted may be addressed by using such tests. Using nonverbal tests of general ability gives all children an equal opportunity to succeed.
Jack A. Naglieri, PhD

Jack A. Naglieri is professor of psychology at George Mason University. He has published many scholarly papers, chapters, books, and tests, including the Naglieri Nonverbal Ability Test.