A Closer Look

Thinking Versus Knowing: The Key to Measuring Intelligence

Why We Measure Intelligence

We administer tests of intelligence to inform us about how well a student can think. Once we determine tasks in which a student thinks well and where the student’s thinking is disrupted, we can better understand the corresponding strengths and weaknesses in academic performance. The pattern of strengths and weaknesses in a student’s thinking and knowing gives us information about eligibility (perhaps a specific learning disability) and direction for intervention. It is, however, critical that the way we measure how well a student thinks is not confounded by what they know. That is why you should always interpret any test score by asking the questions “What does the student need to know to answer the question, and how does the student have to think?”

Measuring Thinking Versus Knowing

Thinking should be measured by an intelligence test and knowing by an achievement test. But that assumes that the intelligence test is as free from knowledge as possible. For example, a test like block design measures thinking, but a test of vocabulary measures knowing because a student can’t answer the question just by thinking; they have to have learned the meaning of the word and be able to articulate a response. Unfortunately, we have been taught that tests that demand knowledge (e.g., subtests that require knowledge of arithmetic, word knowledge, and general learned information about the world) can be used to measure intelligence. However, according to the Standards for Educational and Psychological Testing (AERA, APA, & NCME, 2014), a test may be considered unfair if it penalizes students for not having learned the content in a test of intelligence.

How to Measure Thinking

If our desire is to measure thinking (i.e., intelligence) without the confounding effect of knowledge, we first should define what we mean by thinking. The best way to do that is to measure cognitive processes associated with different parts of the brain. For example:

  • The base of the brain is responsible for selective attention and resistance to distraction, and it helps students focus on the teacher’s instructions and resist distractions in the room as well as one’s own thoughts.
  • The back of the brain is responsible for understanding the interrelationship among things and is used when the teacher requires the student to understand relationships between words and ideas (e.g., comprehending the meaning of text or a math story problem).
  • The sides of the brain are used whenever sequencing is required and are responsible for managing reading decoding tasks which depend upon sequencing of sounds.
  • Perhaps most importantly, the front part of the brain is used to manage the whole brain so that a person can do whatever they intend to do, such as writing a story, calculating math, and planning how to get things done on time.

These brain areas and activities are commonly referred to as Planning, Attention, Simultaneous, and Successive cognitive processes (PASS; Naglieri & Otero, 2017). All four of these ways of thinking are necessary for a person to learn. Some of the PASS processes are involved in learning more than others depending on the kind of thinking required for each task. These four types of thinking, also referred to as cognitive processes, give a road map for what a test of thinking (i.e., intelligence) could measure.

How to Measure Knowing

School psychologists get information about how much a student has learned from school grades and the wide variety of published achievement tests. These tools are explicitly designed to measure what a student knows in a variety of content areas. It is certainly important for us to calibrate how well a student has benefited from their educational experiences and the relationship between academic skills and ability to think. What we strive to understand is if acquisition of specific academic skills has been limited by a weakness in thinking abilities. If so, it may suggest the existence of a specific learning disability.

Our Ultimate Goal

We all want to use tools that help us know how well a student can think and learn. We also want measures that are socially just, are sensitive to learning strengths and weaknesses, and are easy to explain to parents, teachers, and students. We want tools that provide a direct path to relevant and effective intervention and instructional design. After all, one of the most important tasks we have as school psychologists is to provide information about the intellectual status of a student, how that relates to current academic performance, and what interventions are needed to help the student achieve. When our intelligence tests measure thinking not knowing, we achieve our ultimate goal of helping teachers, parents, and (most importantly) the student, have an accurate understanding of their intellectual strengths and weaknesses.


American Educational Research Association, American Psychological Association, & the National Council on Measurement in Education. (2014). Standards for Educational and Psychological Testing. American Educational Research Association.


Feifer, S. G., & Gerhardstein, R. N. (2015). Feifer Assessment of Reading (FAR). PAR.


Naglieri, J. A., & Otero, T. M. (2017). Essentials of CAS2 Assessment. Wiley.

About the Author

necessary Jack A. Naglieri, PhD
Jack A. Naglieri, PhD is a Research Professor at the University of Virginia, Senior Research Scientist at the Devereux Center for Resilient Children, and Emeritus Professor of Psychology at George Mason University.