To begin this newsletter I’d like preface this essay with a short story. This story starts on one fall morning where I had went to one of my undergraduate classes per usual. Towards the end of the class the professor had proposed a question for the class to answer for homework. The professor stood in the middle of the room and said “which of the two are more likely to predict success, luck or talent”.
It seemed that my peers thought it was a trivial question considering most of the class didn’t raise their hands. As someone who enjoys and reads up on current research in psychology, I felt the inclination to share my response. I told my professor that “I’d argue neither. According to the psychological data, the two highest predictors of success are IQ and conscientiousness”. My professor answered swiftly saying “IQ is a fad”.
He then proceeded to call on someone else. I sat there with a puzzled look on my face and I was rather confused. I felt I had scrupulously researched the data regarding IQ before and I felt I had knew it rather well. So I sat there wondering, was I wrong? What did he research to make him think that?
So I ended up devoting many more hours which then turned into weeks (and eventually a month) in additional research to try and have a better understanding of IQ and whether or not it is just some craze or if it has any credibility.
After taking the time to understand IQ and it’s history, I came to discover the contrary to my professor. Therefore, I will demonstrate in good faith how IQ is not a fad and how it actually does predict success (alongside conscientiousness) and much more.
Now before going any further I believe it’s important to first define IQ. The term IQ is actually an acronym that stands for Intelligence quotient. As defined by Oxford languages the term intelligence quotient is “a number representing a person's reasoning ability (measured using problem-solving tests) as compared to the statistical norm or average for their age, taken as 100”(google.com).
Therefore, IQ is a number that is measured by a standardized test that can and can not, deciding on what you choose, account for age. To add one’s intelligence quotient (IQ) score that is derived from the IQ test is a score that measure one’s general intelligence or g factor. British psychologist Charles Spearman developed a psychometric construct labeled the g factor, which refers to one’s general intelligence.
Given the brief introductory to what intelligence quotient means, how it’s obtained (via the IQ test), and what it’s supposed to measure (g factor or general intelligence), it is only appropriate to understand how psyshometricians and psychologists devised it and the history behind it.
The history of the intelligence quotient
The idea of testing for general Intelligence really started with two French psychologists Theodore Simon and Alfred Binet. These two men weren’t necessarily searching to discover how to test intelligence, that was, until the French government asked Binet to devise a way in which he could figure out which children would struggle more than others in school.
Binet and Simon had crated this questionnaire essentially to ask children and from there pick and choose which questions he sought fit at determining academic success. Binet Nd his colleague discovered that some students age ‘x’ were able to answer questions more efficiently than students who were age ‘x’ and vice versa. Therefore, with this information he concluded that there was a mental age.
Subsequently, the two psychologists developed what had came to be the first intelligence test called the Binet-Simon scale. This test devised by Binet and Simon is the basis of the current intelligence testing model we use as of today.
It took precisely three years later for word of the Binet-Simon scale to reach the west. This was done through the help of Henry Goddard who actually translated the Binet-Simon tests and from there had advised and did in fact use it in public schools.
Shortly thereafter German philosopher and psychologist, William Stern, had coined the term we all know and use today “intelligence quotient”. If this doesn’t sound familiar then maybe the acronym for it will. That being IQ. Not only did Stern coin the term IQ but he also worked upon Binet’s studies and proposed that we change the way we calculate intelligence. He suggested that instead of taking the difference between child’s mental age and chronological age that one would divide an individual’s mental age by their chronological age which would then equal a usable ratio.
Now Stern wasn’t the only academic who was trying to further the work upon the Binet-Simon scale. Another academic working off the Binet-Simon scale was American psychologist Lewis Terman. He was a professor at Stanford University. In 1916 Terman had developed the Stanford-Binet scale which is in fact the standard intelligence test used in the United States today (with revisions made since then). Now the intelligence test Terman had devised was different from Binet’s and Stern’s. He developed an equation akin to Stern’s, but with a minor change which allowed it to become more standardized. Terman did this by:
“Taking the IQ score and calculating it by dividing the test taker's mental age by his or her chronological age and then multiplying this number by 100.
For example, a child with a mental age of 12 and a chronological age of 10 would have an IQ of 120. 12/10 x 100 = 120 (verywellmind.com).”
Therefore, Terman had developed an equation that was unlike his predecessors because he multiplied the ratio by 100 at the end which helped standardize the test and more importantly it worked.
Soon after this test was devised and approved the U.S. army decided to utilize it to screen soldiers which helped decide who should and should not receive officer training. This was a pivotal moment for Terman’s IQ test because it helped the test accrue wide spread publicity and credibility. And ever since then, the west and other nations have used the same IQ test (with some revisions since) to measure cognitive ability and intelligence.
Now given the long history and research it took to develop an intelligence test, it’s important to know why we use it. Thus it is imperative that we not only understand the history and origins of the IQ test, but rather the data suggesting it’s accuracy and efficaciousness in determining intelligence.
Intelligence quotient data
Since one can’t review all of the available literature on IQ, I will be reviewing some of the more accredited studies that demonstrate general intelligence not only exists, but that it is effective in predicting general intelligence and how that effects other outcomes (i.e. job performance).
One of the most notable studies known of today that supports the validity of the IQ tests is actually a longitudinal study by nobody other than Lewis Terman himself. The study was called the Terman study of the gifted. Moreover, his successors have still carried on, even in recent times, with many more studies that still work off of his original study of the gifted.
Now this study of the gifted that was devised by Terman had began in 1921 when he decided to start tracking roughly 1500 kids who ranged from ages eight to twelve with genius level IQ's. This was all there really was to the longitudinal study. Simply track all of the kids lives individually and document their achievements (i.e. marriages, income, etcetera).
As time had passed Terman had eventually disclosed the data he had so far. The data showed that:
* “The average income of Terman's subjects in 1955 was an astounding $33,000 compared to a national average of $5,000”(verywellmind.com).
* “Two-thirds had earned college degrees, while a large number had gone on to attain post-graduate and professional degrees. Many of these had become doctors, lawyers, business executives, and scientists”(verywellmind.com).
Per the data it seems rather evident that those with higher IQ’s were more economically successful than those with lower IQ’s.
However, there are flaws to the study that do need to be taken into consideration. When reviewing the time period, critics claim that other external factors could have played a role in outcomes such as World War One, Two, and The Great Depression. Although this may be true, the study has been an accredited one and is truly groundbreaking for what it had demonstrated.
Another well known and accredited study was, once again, another longitudinal study by the national institutes of health (NIH). This study had actually tracked the correlation over a period of time between IQ and a humans survivability.
The test was rather simple. They had collected a subset of individuals IQ’s and ultimately tracked their lifespan. The data stated “In our cohort childhood IQ was a significant predictor of human survival”(ncbi.nlm.nih.gov). To add, the NIH had also reviewed for bias in the study. They had concluded also that the likelihood of any bias was unlikely.
Additionally, the NIH was not the only organization to try and test for this. The NIH had published data on a cohort study done in Sweden that had demonstrated a direct correlation between IQ and mortality. This study involved one million men. The data may bee seen in the chart below:
As seen in the graph above, men with an average IQ score of 1 had placed in-between 3.0 and 3.5 on the scale for ‘risk of death’. Meanwhile, men with the highest IQ score of 9 had placed in between 1.0 and 1.5 on the scale for ‘risk of death’.
Therefore, per the study, IQ is a significant marker for chances of mortality and actual mortality.
The last study I will review is an article posted by the NIH and the American psychological association (APA) that discusses the correlation between job performance and IQ. This study that was conducted in 2004 which really focuses on ones general mental ability (GMA) or ‘general intelligence’ which is argued to be what IQ tests for and therefore is relatively synonymous with another.
The article will be speaking about general intelligence which once again was devised by psychologist Charles Spearman and more commonly known as the g factor. To add, according to Spearman, the g factor actually included “multiple specific skills, including verbal, spatial, numerical and mechanical”(simplypsychology.org).
Nonetheless, the study provides clear evidence that
“GMA predicts both occupational level attained and performance within one's chosen occupation and does so better than any other ability, trait, or disposition and better than job experience.” (doi.apa.org)
The study was an extension off Spearman’s work and demonstrated that his original proposition of the “G Factor” can in fact predict ones economic status really and job performance reliably.
More importantly, not only is IQ able to predict job performance and economic status reliably, but more importantly it is able to predict them better than any other aptitude, trait, and even job experience.
Therefore, given the data listed above it seems rather evident that IQ is and can be a reliable psychometric tool that can accurately measure and test one’s general intelligence which helps predict numerous outcomes to some degree.
However, as there is over a century worth of evidence in support of IQ, it does not mean that there isn’t data suggesting the opposite because there in fact is. It seems only appropriate to now then review the data against IQ and where it actually may be unreliable or problematic.
Disclaimer: I understand how this may seem a bit repetitive by citing numerous studies by the same organization, however, the NIH is an extremely credible pro-science organization that is most certainly trust worthy and has been ranked with little to no bias.
Additionally If you are interested in reading the study above for yourself you can purchase it here for $14.95
The problem with the intelligence quotient
Now as there is an abundance of data supporting IQ there is also data suggesting the opposite. One study suggesting the opposite would be one by British Neuroscientist Adrian Owen who claims that IQ is unreliable and suggests that IQ does not demonstrate general intelligence at all.
Owen’s conducted a study of over 100,000 participants online whom all had completed 12 set cognitive tests that measured memory, reasoning, and attention.
Th study concluded that “there was not one single test or component that could accurately judge how well a person could perform mental and cognitive tasks”(cbsnews.com).
Owens and other researchers associated with the study discovered a variety of other results such as the notion that certain areas of the brain may control certain abilities a human performs.
Owen’s concluded the interview with CBC by saying “We have shown categorically that you cannot sum up the difference between people in terms of one number, and that is really what is important here”. He said this alongside the headline by CBC saying “IQ myth debunked by Canadian researchers”.
However, there are two issues with this study.
Firstly, when Owen’s says that his study ‘shows’ that you can’t sum up people’s intelligence with one number, I think that was a given. IQ was not designed to be a zero-sum measure in demonstrating someone’s intelligence and it never should be due to the fact that an individuals intelligence is much more convoluted than that. That is why we say IQ measures general intelligence, not the entire intelligence of an individual.
Additionally, the fact that CBC had allowed such a sensationalist title like “IQ myth debunked by Canadian researchers” is merely deplorable. You can’t prove IQ is some myth or ‘debunk’ it in one study. Although the study had in fact demonstrated that IQ was unreliable and that it may be a ‘myth’, that doesn’t mean that the study accounted for all variable and was perfect through and through.
Nonetheless, to give credit where credit is due, the study was thorough and seems to be adequate when providing evidence to make a case against IQ.
In addition to Owen’s study suggesting that IQ is unreliable and that IQ test scores don’t accurately represent one’s g factor, the NIH had devised what appears to really be a meta-analysis of IQ and it’s ability to prognosticate job performance.
Firstly the NIH speaks upon the validity of the IQ tests. They make the claim that the accredited Stanford-Binet and other tests are based on the cognitive tests prior to theirs which help provide plausibility for the tests. Now one may understand how this can be problematic because it’s based on the presupposition that the other tests are accurate and valid when, in due time, the data could become obsolete. Nonetheless it currently is not which helps maintain validity.
However, the NIH suggests that the mere fact that IQ tests are deigned to be based on the correlational data of prior IQ tests, that it actually lacks fundamental validity. The NIH goes onto explain why this is by providing a basic definition of the validity of a test that is testing for a function when it states “(a) the function exists and is well characterized; and (b) variations in the function demonstrably cause variation in the measurement outcomes”(ncbi.nlm.nih.gov). Therefore, by definition, the IQ tests can arguably not be categorized as a test that validly tests for a function.
The NIH continues to go on talking about other studies, potential errors, and diversity of tests. After touching upon all of the other variables, the article is concluded with an array of statements that essentially highlight the '“key” takeaways of the article. “Key” takeaways that seemed to succinctly highlight the most vital information included:
* Much in developmental theory, and psychology in general, depends upon the validity of IQ tests.
* Hundreds of studies prior to the 1970s reported low and/or inconsistent correlations between IQ and job performance.
* These correlations have been approximately doubled using corrections for supposed errors in primary results and combining them in meta-analyses. Such corrections have many strengths, theoretically, but are compromised in these cases by the often uncertain quality of the primary studies (ncbi.nlm.nih.gov).
It is imperative understand the first key takeaway as it is in fact true. Most of psychology in general depends upon the validity of IQ tests and therefore makes this conversation so much more complex. If you take the position that the IQ test is extraneous or is inaccurate, then you are also making a statement about the integrity of psychology as a social science in general.
Now the second key takeaway is essentially a direct attack on the first. There in fact have been hundreds of studies showing inconsistencies regarding correlation of IQ tests predicting job performance which is, to some degree, a factor of validity and therefore potentially lacking.
Alongside takeaway number two would be lastly the third one as the NIH essentially espouses the same critique it had prior in the article that I already covered which is the fact that the primary studies may in fact have flaws among their correlational data and therefore being based on the presupposition that the data is solid through and through can potentially decrease the IQ tests validity in predicting job performance and generally speaking.
Now there are more “key” takeaways, however, these were the ones that I deemed rather important or at least more important than the others. Nonetheless the key takeaways I had chosen had provided a relatively sufficient summary of the article in general and what one should takeaway from the article. And if you’re interested in viewing more key takeaways and studies in the article or just the article itself then click here.
To add, IQ’s controversies are not only limited to data interestingly enough. There is something rather more pernicious and even more contentious than studies and some data set’s which also makes IQ contentious. Therefore, once again, it only seems appropriate to review other additional material against the intelligence quotient.
In addition to the data and studies, another major issue around IQ is how we relay or define exactly what it is and what it measures. When talking about IQ we need to use precision with our speech because it’s a convoluted subject. The IQ test measures one’s cognitive ability and relays a reliable score that provides results on their general intelligence which would be their IQ score. Now IQ can predict certain outcomes and have other use cases but when it comes to defining it and how it measures general intelligence then that is it.
Therefore, IQ does not encompass every aspect of intelligence which then means that it is not always a reliable measure because it depends what you are measuring for.
An example of what the IQ tests lack to measure would be emotional intelligence (EQ). This is “The ability to understand, use, and manage your own emotions in positive ways to relieve stress, communicate effectively, empathize with others, overcome challenges and defuse conflict”(helpguied.org). Moreover, if you wanted to measure emotional intelligence, having someone take an IQ test would be inefficient because it doesn’t account for one’s ability to understand and perceive others emotions.
Not only does the IQ test lack to measure and/or examine emotional intelligence but it fails to measure a variety of other aptitudes like creativity or the idea of one’s will power; volition. All of this information is imperative in understanding IQ because this all demonstrates how IQ tests and scores are not absolute.
The notion of believing that IQ is and can be absolute when defining one’s intelligence has also caused IQ to attain a horrible reputation and become problematic.
This idea of IQ being absolute is more so a corollary to what I had initially said that a major problem with the intelligence quotient is the lack of transparency when defining it and how it should be used in real life through policy or etcetera. That is because when one believes that IQ is and can be an absolute measure of intelligence it can degenerate into a minacious philosophy known as eugenics.
Eugenics
The philosophy known as eugenics can be defined as “the study of how to arrange reproduction within a human population to increase the occurrence of heritable characteristics regarded as desirable”(Google.com).
Therefore, let’s say for example, you had a group of 10 people and there were a male and female who both had the genetic disorder Fragile X Syndrome. Assuming the other 8 people had believed in the philosophy of eugenics they would discourage or not allow those two people who had fragile x syndrome to reproduce because they may pass down undesirable traits to their children who then could do the same to the next generation.
As you could imagine this did not spawn out of thin air, but it was rather created. And that would be accurate to assume as the term eugenics was coined by British polymath and psychologist Francis Galton. Galton had also been the one who developed the philosophy of eugenics too so it mostly stems from him.
It wasn’t too long after Galton had developed the philosophy of eugenics until other leaders around the world had caught wind of his work. Shortly thereafter there were states and countries adopting the philosophy of eugenics and applying it to policy.
In the United States the rise of eugenics slowly began in the late 19th/early 20th century with Connecticut at the forefront. This law was passed in 1895 by the Connecticut state government which had forbid anyone who was “feebleminded” or epileptic from marrying one another.
After Connecticut it didn’t take long for the philosophy of eugenics to sweep across the U.S. ultimately resulting in roughly 30 states adopting eugenic policies and had sterilized over 60,000 people which was, in fact, required by law. The main catalyst for those who were sterilized was really just having undesirable traits like a hereditary illness or mental disability.
Now albeit the U.S. had almost a statewide compulsory sterilization campaign occurring, it actually got worse. And not in the states. The philosophy had also been adopted by the infamous Adolf Hitler before and around World War Two.
It really started after Germany was united by Nazi hegemony in the early to mid 1930’s. It wasn’t until July 14, 1933 when the German government had passed the Law for the Prevention of Offspring with Hereditary Diseases. The law itself is self-explanatory, but just to be clear, the law had declared that anyone who was deemed unfit or riddled with undesirable traits like a hereditary disability or illness were not allowed to procreate.
This law had a devastating effect for the next decade to come as Nazi Germany was able to forcefully sterilize an estimated 350,000 people who they deemed “feebleminded”.
Additionally, eugenics was also a core philosophy of Hitler’s as he spoke about it in mein kämpf and more notoriously when he had created the fallacy of Aryan’s being a superior race and his poor justifications for that.
It wasn’t until World War Two ended that eugenics really lost much of it’s following as many nations were left picking up after the mess Nazi Germany made.
To this day the fact that IQ can degenerate into such a minacious philosophy is still used as an argument against it (IQ) and rightfully so. However, it is important to have a transparent conversation about IQ and the discrepancies associated with it so we can have a meaningful discussion regarding that information.
With that being said, the flaws of IQ aren’t limited to just a few, however, they are not absolute either. As there is data suggesting that IQ is fallacious or that IQ is inaccurate there is always going to be data suggesting the opposite. With that being said, it seems as if this now leads to the question that was proposed by my professor: Is IQ just a fad? And therefore does it not predict long term success (alongside conscientiousness)?.
What IQ is and is not
I believe it is important to distinguish what I meant when I said IQ was able to predict long term “success” as I understand how the term may be vague, and therefore what I meant was social and economic success in which I also believe that is what my professor was insinuating too.
Nonetheless, when it comes to IQ’s predictive ability regarding long term (economic) success it is not only overwhelming, but rather highly replicable. After scouring the literature for one of the more rigorous and accredited studies I came across British professor and psychiatrist Ian Deary. He has worked closely with intelligence during his academic career and has published numerous articles with an astounding 133,000+ citations.
Now in this study Deary reviews the four group factors that were derived from the Wechsler Adult intelligence scale (which is in fact an acceptable IQ test akin to the Stanford-binet test) and their correlation to g or general intelligence. Among the 2450 subjects the correlation among group factors ranged from “0.63 and 0.83 with a mean of 0.76” (see in figure below) which Deary also goes on to conclude that “The fact that the group factors are so closely related to g means that most of the variance apparently arriving at the tests from the group factors actually comes from g”(scottbarrykaufman.com).
Therefore the data resulting from the study not only shows a high correlation between g and the group factors, but also the fact that the group factors being so closely related to g demonstrates it’s validity.
Deary goes on to discuss influences on IQ , however, he then goes on to discuss it’s predictive validity in which he states “in a review of thousands of reports over about 80 years, a general mental ability test emerged as one of the strongest predictors of job success. The correlations averaged about 0.5”(scottbarrykaufman.com). In addition to Deary’s findings, he also references a meta analysis of 85 years of research regarding IQ tests validity and it’s ability to predict long term success in which it states “this article presents the validity of 19 selection procedures for predicting job performance and training performance and the validity of paired combinations of general mental ability (GMA)… GMA plus a structured interview (mean validity of .63)”(psycnet.apa.org).
In regards to Deary’s high publicized and accredited findings, there is a 0.5 correlation between IQ and long term job success. And in addition to Deary’s work there was a meta analysis that was over 85 years of research published by the APA finding a .63 correlation between IQ/GMA with interview and job performance which in theory would then predict success since you’re paid based on performance. Therefore based on the data there seems to be a moderate correlation between job success/performance and IQ which, albeit it is a moderate correlation, IQ is still nonetheless the single highest predictor for job success/performance any psychometrician or psychologist has ever devised.
In addition to the data demonstrating how IQ predicts long term success, I also stated that conscientiousness does too.
Conscientiousness, unlike IQ, is a personality trait among the big five personality traits. It is the trait of being orderly and maintaining discipline. As I stated previously, conscientiousness also has the predictive validity regarding it’s ability to predict job success (and thus success generally speaking).
The data regarding conscientiousness’ ability to do so in fact is the single highest non cognitive predictor to do so. The data is highly replicable and attained accreditation from many respected psychologists and psyshometricians as well.
Nonetheless, the study that appears to sufficiently represent conscientiousness’ predictive validity is a meta analysis published in the proceedings of the national academy of sciences (PNAS). It was a study conducted by researcher Deniz Ones and colleague Michael Wilmot where they had reviewed 92 met analyses based on 175 variables that included over one million subjects and 2500 studies.
Deniz and Wilmot were conducting this study on whether or not conscientiousness has any predictive validity in regards to job success.
In figure two (see below) they calculated conscientiousness’ correlation between job success/performance among 8 occupations.
Deniz concluded based on the data derived from the 92 meta-analyses that “Effects range from ρ⎯⎯=0.13 to 0.33, with a mean of ρ⎯⎯=0.22 (SD = 0.06). Overall, C displays potent performance effects that generalize across available occupations; however, complexity moderates this relation”(pnas.org).
Therefore given the data there is a moderate mean correlation of 0.2 between job performance/success and conscientiousness. However, Deniz also suggests that conscientiousness has less predictive validity when it comes to more complex occupations. This would include positions like CFAs, CEOs, et cetera.
Nonetheless, the data in the meta-analyses is rigorous and demonstrates quite clearly how conscientiousness has relative predictive validity when it comes to predicting success/ job performance.
In light of all of the data and information it seems evident that conscientiousness and IQ can in fact predict long term success, the latter better than the former, which then makes neither a fad.
Moreover, considering that the data does demonstrate IQ’s and conscientiousness’ validity, it does not mean that we should use IQ and conscientiousness undoubtedly as measures of a human beings worth or intelligence overall.
I believe neuroscientist and philosopher Sam Harris conveys one of the much better nuanced discussions regarding IQ during his podcast with political scientist and author Charles Murray.
The discussion between the two mainly revolves around the controversial book Murray wrote called The Bell Curve. Murray writes about IQ and how it does in fact have predictive validity, how IQ scores vary among races, and it’s salience in society today.
Nevertheless, Harris sums up the robust scientific case regarding IQ (plus IQ tests) and it’s predictive validity when he states during the podcast (2:30):
Now for better or worse, these are all facts (regarding data regarding IQ and claims in Murrays book). In fact there is almost nothing in psychological science for which there is more evidence than these claims about IQ, about the validity for testing for it, about it's importance in the real world, about its heritability, and about it’s differential expression in different populations. Again, this is what a dispassionate look at decades of research suggests.
And with that being said, I too agree with Sam Harris as what he has said about IQ is in fact in accordance with decades of empirical data and virtually everything I had outlined in this essay.
(Some) Sources: Painting of Francis Galton (science.howstuffworks.com)
Deary, I., Penke, L. & Johnson, W. The neuroscience of human intelligence differences. Nat Rev Neurosci 11, 201–211 (2010). https://doi.org/10.1038/nrn2793
(other sources may been seen by clicking on underlined words or hyperlinks)
Extra
In addition to all of the empirical data that I had reviewed, I also felt the inclination to add a minor segment that also supports the paper as well which is the book Charles Murray wrote, The Bell Curve, which I referenced above.
Now albeit Murray made idiosyncratic remarks regarding the data, the empirical evidence in The Bell Curve does accurately outline the fact that IQ exists, tests relatively accurately for general intelligence or g, and has predictive validity. All of the this data outlined in the book (like IQ having predictive validity) was immensely contentious among many pundits and others in the media.
However, the data in the book was accurate and for anyone who disagrees with that and feels as if the data was misinterpreted or falsely presented I implore you to read and review this accredited study and article published in the American Psychological Associationwebsite called, Intelligence: Knowns and Unknowns, which is a report issued in 1995 by a task force created by the Board of Scientific Affairs of the American Psychological Association. The study had confirmed virtually everything The Bell Curve claims which, at the time of publishing the book, it was and still is mainstream science.
To add, almost all of the data that was in The Bell Curve and confirmed from the Knowns and Unknowns study is still scientifically accurate today with very few bits of the data still being highly contestable or no longer mostly accurate.
