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Introduction

Psychological traits are a central focus of research in psychology and other social sciences. Unlike physical measures like height, weight, or blood pressure which have specified measured objects, objects of measurement and measurement units, psychological traits are inherently more complex and abstract, which makes their measurement and assessment challenging and, as I will argue impossible due to non-identity between psychological traits and physical objects. I will explore the fundamental dissimilarity between psychological traits and physical measures, while highlighting the unique features of psychological traits that make them immeasurable.

Measurement is elusive for psychometrics. This is because there is no specified measured object, object of measurement or measurement unit for any psychological trait. There is no specified measured object, object of measurement and measurement unit for any psychological trait since they are not physical; only physical things can be measured. This is a line of argument I’ve been making for years against the possibility of the measurement of the mind (human psychology). Although some have attempted to provide the specified measured object, object of measurement and measurement unit for IQ, they have failed. Still others have attempted “gotchas” on me by saying “what about earthquakes or UV waves?” The basic criteria for measurement exists for those things. In this article, I will give examples of the specified measured object, object of measurement and measurement unit for many different things, and this analogy will show why the so-called underpinnings for psychometrics fail and why the mind (human psychology) cannot be measured.

What is a specified measured object, object of measurement and measurement unit?

A specified measured object refers to a physical entity or property which is measured; a thing or phenomenon to measure or observe. This specified measured object needs to be define clearly and precisely which involves specifying size, shape, behavior, and specifying the conditions in which the measurement will be made. Quite clearly, a specified measured object needs to be physical—meaning it needs to be observable.

The object of measurement refers to the specific property or characteristic of the specified measured object in which we are interested in quantifying. It’s an attribute, characteristic, or property to be quantified or evaluated. So this property will help us better understand the specified measured object.

A measurement unit is a standard quantity or physical property used to express the measurement of the object of measurement—it is a standard quantity or magnitude. It provides a standardized way of quantifying the object of measurement and making it able to be compared to other measures. But before we even begin to think about a measurement unit, we need to know what we are measuring and if we can even measure it at all.

Now that the terms have been defined, clearly if one says that X is a measure, then X must have a specified measured object, object of measurement and measurement unit. So now the proposition is: For X to have a specified measured object, object of measurement and measurement unit, X must be physical. X must be physical since the above definitions refer to physical things. They can be expressed using physical vocabulary. The mental, however, cannot be expressed and described in material terms that only refer to material properties, and facts about the mind cannot be stated using a physical vocabulary. So all of this being said, we now come to “IQ”—if IQ doesn’t meet the above requirements, then it is not a measure of anything. Although IQ-ists like Eysenck and Jensen have tried, they were unsuccessful in arguing that IQ is similar to temperature. Measurement cannot be by fiat, but only based on the actual nature of the object of measurement. So if there is no object of measurement, then no measurement can take place.

Specified measured objects, objects of measurement, and measurement units for different things

UV radiation

Specified measured object – amount of electromagnetic radiation that falls within the UV range of the electromagnetic spectrum

Object of measurement – intensity or wavelength of the UV radiation

Measurement unit – nanometer, microwatts/millowats per square cm

A UV index is a measure of strength from the sun and it takes into account the time of day and the season. It ranges from 0 to 11 with higher numbers indicating higher levels of UV radiation.

Earthquakes

Specified measured object – the movement and vibrations of the earth’s crust caused by seismic waves

Object of measurement – magnitude of the quake, numerical measure of released energy

Measurement unit – Richter scale which measures amplitude of seismic waves and moment-magnitude scale which is based on total energy released by the earthquake

Volume of a container

Specified measured object – a container

Object of measurement – amount of space the container can hold

Measurement unit – liters or cubic meters

Brightness

Specified measured object – a light source

Object of measurement – amount of light energy emitted by the source per unit time and per unit area

Measurement unit – watts per square meter and lumens

Blood pressure (with a sphygmomanometer)

Specified measured object – force exerted by blood against the walls of the arteries as it flows through the circulatory system

Object of measurement – the actual force of blood against the walls of the arteries at a particular moment in time

Measurement unit – mmHG which is then reported as systolic over diastolic pressure

Internal infection (white blood cells)

Specified measured object – number of white blood cells in a blood sample

Object of measurement – presence and quantity of white blood cells in the blood which can indicate an immune response to internal infection

Measurement unit – cells per microliter

Blood alcohol content (with breathalyzer)

Specified measured object – breath alcohol content

Object of measurement – concentration of alcohol in the breath

Measurement unit – percentage of alcohol in the breath by volume, eg 0.08% breath alcohol content

Speed

Specified measured object – the rate at which an object is moving

Object of measurement – the velocity of the object

Measurement unit – meters per second, miles per hour, and feet per second

Time

Specified measured object – duration or interval between two events or the duration of a physical process

Object of measurement – amount of time that had elapsed between two events or the duration of physical processes

Measurement unit – seconds, minutes, hours, days, weeks, months, years

What this means for psychological traits like IQ

Quite obviously, this has stark—and unwanted—implications for psychological traits, like IQ. For if the above examples are of physical objects and processes, and the main aspect of IQ test-taking is thinking which is immaterial, then it can’t be measured.

Russel Warne, in In the Know (2020) states that “Just as kilograms and pounds are measures of weight, IQ is a measure of intelligence.” Warne (2020) also claims that “As long as a test requires mental effort, judgment, reasoning, or decision making, it measures intelligence.” This is outright wrong. Even Haier (2014, 2018) stated that IQ test scores are not like inches, liters, or grams. The fact of the matter is this—if IQ tests are measurement tools, then what is the property that IQ tests measure? In lieu of an answer to this question, the claim that intelligence is measurable with IQ tests is false, since there is no specified measured object nor even a measurement unit, as admitted by Haier. IQ points aren’t measurement units.

The fact of the matter is, the purpose of measurement is to object of measurement find out that what we designate as the specified measured object even allows the possibility of measurement. Objects of measurement have to be definite processes or objects, with definite properties. When it comes to psychometry, the object of measurement is conceptualized as a concept or construct. Since concepts can’t be measured since they aren’t empirical, then psychometrics isn’t measurement. Psychologists need to show that their attribute is quantitative, and construct procedures for numerically estimating magnitudes, bur since psychologists have their “own, special definition of measurement” (Michell, 2007), they think they can get around the measurement objection and the fact that IQ isn’t like the actual measures given above.

Since psychometricians render “mere application of number systems to objects” (Garrison, 2004: 63), they just assume that their desired object of measurement is quantitative, basically ignoring Michell’s challenge. So since standardized tests “exist to assess social function” (Garrison, 2009: 5), and they aren’t measuring psychological processes, they are merely legitimizing hierarchy “via the assessment of social value“, and so it “it may be more useful in analyzing psychometry to view it as a political theory, as a formal justification for a system” (Garrison, 2004). This is the only conclusion to take from the fact that they have no specified measured object, object of measurement and measurement unit for any psychological trait, including IQ. The fact of the matter for IQ is this: IQ tests aren’t valid measures like other unseen functions of bodily processes (Richardson and Norgate, 2015), nor is IQ like any physiological measurement (Richardson, 2017: 163-167).

Looking at actual physical measurements using actual physical tools to ascertain these measurements that have actual theories and definitions of them shows that IQ isn’t like them, and so if IQ isn’t like them then IQ isn’t a measure at all. Michell (2003) is led to conclude that “the definition of measurement usually given in psychology is incorrect and that psychologists’ claims about being able to already measure psychological attributes must be seriously questioned.” Furthermore, “conceptual analysis, realistically construed and applied to mental concepts, may show that they exclude quantitative structure” (Michell, 2022). The reducibility of the mental to the physical isn’t an empirical issue, it is a conceptual one, and conceptual arguments dispense with the claim that psychological traits are measurable. But the issue of psychological measurement is empirical and conceptual. Michell (2022) concludes something I’ve argued for similarity in the past:

Based upon logic, conceptual arguments regarding the measurability of mental states will have merit and I have used them¹⁹ to show that current conceptualisations of mental states, while permitting relations of greater than and less than between levels,²⁰ do not sustain quantitative speculations, much less support the presupposition that mental states are measurable.

From the way IQ-ists talk about intelligence, it’s posited as a psychological trait, a concept or construct. Since these are immeasurable, then IQ-ism fails, and there can’t be a science of the mind. Nash (1990: 144-146) has some very insightful commentary on this matter:

In first constructing its scales and only then proceeding to induce what they ‘measure’ from correlational studies psychometry has got into the habit of trying to doing what cannot be done and doing it the wrong way round anyway. (133)

If we begin to think about psychometric test practices following Berka’s analysis it is clear that the expression ‘measurement of an ability construct’ in preference to ‘measurement of ability’ is intended to signal the object of measurement as a special kind of theoretical object. ‘Ability’ might simply mean something that can be done but in psychometry an ‘ability construct’ is pre-theorised as a normally distributed functional ability in a particular area of performance. The analysis I gave of construct validity described how psychologists came to refer to ‘ability constructs’ as ‘hypothetical concepts’ or as ‘theoretical constructs’, and criticised the philosophy of science from which this thinking is derived. Attempts to justify the discourse of ‘theoretical constructs’ can be found occasionally but attempts to discuss the theoretical basis of their measurement are very rare. It is usually just taken for granted that the ‘measurement of constructs’ is a highly scientific and acceptable practice: nothing could be further from the truth.

What we get from a mental test is actually a clinical or pedagogic classification expressed in norm-referenced levels by some more or less obscure properties of the cognitive capabilities people actually possess. This classification is given an illegitimate metrical form by the pseudo-measurement practices of psychometrics. That psychometry is unable to provide a clearly specified object of measurement or, consequently, to construct a measurement unit, means that the necessary conditions of measurement do not exist. ‘Ability’, whether understood in the realist sense of Reid as a functional and explanatory capacity or in the behaviourist sense of Quine as a disposition, cannot be expressed in a metric concept and will only permit classification. Once these ideas are clear the unhappy history of attempts to treat intelligence as a ‘concept’ like temperature becomes much easier to appreciate.

…

Yet we have learned that intelligence cannot be expressed legitimately in a metric concept (no matter what sensible meaning is given to the word ‘intelligence’) but is a process which allows only the relations less than, equal to, and greater than, to be made. The psychometric literature is full of plaintive appeals that despite all the theoretical difficulties IQ tests must measure something, but we have seen that this is an error. No precise specification of the measured object, no object of measurement, and no measurement unit, means that the necessary conditions for metrication do not exist. Certain processes of cognition are formally necessary to the solution of IQ test items and to the comprehension of academic knowledge and that trivial fact is reflected, as it must be, in the correlations observed between IQ scores and attainment scores. But such findings establish no secure foundation for the construction of worthwhile theory of mental measurement.

We may conclude that our species common cognitive capacities should not be referred to vaguely as ‘underlying abilities’; should not be conceptualised by means of a so-called ‘hypothetical’ normally distributed construct of intelligence (or scholastic abilities); should not be identified with the first principle component on a factor analysis of cognitive tasks and, most importantly, should not be regarded as properly expressed by a metric construct, something measurable by a privileged test instrument. A Binet-type test will give a broad classification reflecting some crudely understood aspects of mental development, which still lacks expression in an appropriate concept, but it does not measure anything. (144-146)

This is just like what Howe (1997: 6) states:

A psychological test score is no more than an indication of how well someone has performed at a number of questions that have been chosen for largely practical reasons. Nothing is genuinely being measured.

This prompts Richardson (1998: 127) to conclude:

The most reasonable answer to the question “What is being measured?”, then, is ‘degree of cultural affiliation’: to the culture of test constructors, school teachers and school curricula.

Conclusion

Thus, the fundamental dissimilarity between psychological traits and physical measures has significant implications for so-called psychological measurement in psychology and other social sciences. Physical measures are relatively straightforward due to their objective and quantifiable nature (we can come to similar measurements on a piece of wood for example), while psychological traits are immaterial and and subjective, this means that science can’t study first-personal subjective states.

From the discussion of what a specified measured object, object of measurement and measurement unit are to examples of actual physical measurements that meet these criteria, it is quite clear that IQ—nor any psychological trait—is like a physical measure. While IQ tests are said to be measurement devices, the claim fails upon closer conceptual analysis, since there are no measurement units, and since even before a measurement unit is presented, it must be know whether or not it is possible to measure what one desires to. Psychological traits aren’t actually quantitative since they lack a specified measured object, object of measurement and measurement unit.

If psychometricians have the ability to measure psychological traits using psychological tests, then there must be a specified measured object, object of measurement and measurement unit. There is no specified measured object, object of measurement and measurement unit for any psychological trait. Therefore, psychometricians don’t have the ability to measure psychological traits, and so psychometrics isn’t measurement. Not even the hypothetical construct g (“general intelligence“) will save psychometry. If psychological traits can be measured, then they are similar to physical measures that have a specified measured object, object of measurement and measurement unit. Psychological traits are not similar to physical traits that have a specified measured object, object of measurement and measurement unit. Therfore, psychological traits are immaterial and and so immeasurable.

Nothing is genuinely being measured by IQ test, if we take measurement to be the process of quantitatively determining the value or magnitude of a physical, chemical or other property of a physical object or phenomena, since psychological traits aren’t physical, they are immaterial. And since they are immaterial, then they are immeasurable. Therefore there can’t be a science of the mind. So the claim that IQ tests measure something is false, since there is no specified measured object, object of measurement and measurement unit for IQ. And so, the quest for a scientific foundation for psychology is impossible, most importantly since the mental is irreducible to the physical.