Neuroimaging of Mood Disorders

The Keys to Measuring Intelligence: Thinking Versus Knowing

Why do we measure intelligence?

We administer tests of intelligence to inform us about how well a student can think to learn. Once we determine tasks in which a student thinks well and where the student’s thinking is disrupted, then we can better understand the corresponding strengths and weaknesses in academic performance. T

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 using an intelligence test is not confounded by what they know. A simple way to determine is to apply this rule: “What does the student need to know to answer the question, and how does the student have to think?”

Measuring Thinking vs Knowing

Thinking should be measured using 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, IQ tests typically measure a person’s vocabulary and general information.

These tests questions cannot be answered by thinking. Only those who have learned the meaning of the word are able to articulate a response. Unfortunately, we have used tests that demand knowledge since 1920 when the U.S. Army developed the Alpha and Beta Tests (Yoakum & Yerkes, 1920) to measure intelligence using verbal and nonverbal test questions, respectively.

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

To measure thinking (i.e., intelligence) without the confounding effect of knowledge,we should start with a theory of intelligence defined by brain function. The best way to do that is to measure thinking defined as cognitive processes associated with different parts of the brain.

For example, it is well established that the base of the brain is responsible for selective attention and resistance to distraction; the back of the brain for understanding inter-relationship among things; the sides of the brain are used whenever sequencing is required and; 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.

The brain areas and activities I have described are commonly referred to as Planning, Attention, Simultaneous and Successive theory of intelligence (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 upon the kind of thinking required for each task.

How to Measure Knowing

Educators and 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 important to measure 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.  If so, it may suggest the existence of a specific learning disability.

The Fix

Traditional IQ tests greatly limit the measurement of intelligence because they demand too much knowledge. Only by measuring thinking without the influence of knowledge can we more accurately assess intelligence. When our intelligence test measures thinking not knowing, we can help teachers, parents and most importantly the student, have an accurate understanding of their intellectual strengths and weaknesses and a path to life success.


AERA, APA, NCME (2014). Standards for Educational and Psychological Testing. Washington, DC: AERA

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

Yoakum, C. & Yerkes, R. M. (1920).  Amy Mental Tests. New York: Holt and Company.



The Keys to Measuring Intelligence: Thinking Versus Knowing


APA Reference
Naglieri,, J. (2020). The Keys to Measuring Intelligence: Thinking Versus Knowing. Psych Central. Retrieved on September 18, 2020, from


Scientifically Reviewed
Last updated: 16 May 2020
Last reviewed: By John M. Grohol, Psy.D. on 16 May 2020
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