Intelligence testing is used in many selection processes, but its use has long been questioned for many reasons. The first questionings were based on the concern to discriminate in case the test favors or disfavors people with a characteristic that should not be a deciding factor. For example, imagine that while in India a foreigner applies for a Java developer job and encounters the question “Judge is to Laws as Brahman is to ____”.
The aim of this question should be to measure the ability to understand the abstract relationship between concepts. But, for a person who does not know Indian culture, it would be difficult to answer. This question could, therefore, be discriminating against people who do not know Indian culture even though this has no relation to the performance of a Java developer.
It is important to ensure that the intelligence tests to be used do not discriminate based on factors other than intelligence and, above all, that they do not discriminate based on factors for which discrimination is not permitted, in which case we might even have legal connotations.
The second factor to consider is whether the intelligence test or IQ test correlates with the person’s future performance in the position. In general, for a large number of jobs, there is a correlation. In my particular experience with IT professionals, I have noticed a clear, but not absolute correlation. Intelligent people tend to learn faster and be good at solving logical problems. Thus, a large part of professional jobs is going to correlate positively with a favorable result in an intelligence test. But…
First of all, in many jobs, slightly higher than average intelligence is enough, while only some jobs require higher intelligence. It is important to be clear about this so you would not filter out candidates who could do a good job just because they are not geniuses.
Second, intelligence tests measure what we call fluid intelligence, which is the ability we have to solve problems without requiring a knowledge base. The other intelligence, crystallized intelligence, has to do with our ability to solve problems using our knowledge and experience.
Therefore, my recommendation, based on my experience rather than on scientific studies, is as follows:
For junior positions in jobs where you need to learn a lot and potential is sought, intelligence tests are very useful and should have an important weight in the decision. In the IT area, when looking for junior developers, intelligence testing is an excellent predictor of performance. The only thing better to evaluate a junior developer than an intelligence test is Evalart programming tests (excuse me for the publicity).
For more senior profiles, intelligence is no longer the predominant factor, but it remains important. In these cases, structured interviews and knowledge tests are a good complement to obtain a more complete profile. Here, it is important to verify not only fluid intelligence but also crystallized intelligence. Questions such as “what was the most complex work problem you had to solve and how did you solve it?” help to discern this.
Which positions require higher levels of intelligence? According to my own “meta-study”, these positions would be the following: scientist, professor of higher education, doctor, lawyer, accountant, finance, engineer (civil, electrical, industrial, computer), and sales (yes, although some might think not, for complex B2B sales you need some additional horsepower in the mental department). In these professions, in general, the smarter the better.
Then in second place, we have a group where intelligence is welcome and important, but geniuses are not needed. These positions are the following: entry-level teachers, customer service, administrative staff, technicians, and managers (yes, you read right, managers).
And finally, areas where intelligence is not a determining factor for the job: operators, drivers, carpenters, construction workers, cleaners, mechanics and plumbers.
It is important to emphasize that the intelligence ranks for each position are wide and in all intelligence adds, not subtracts. Yet, some jobs are practically impossible to do well without a high level of intelligence (such as the engineer who has to build a nuclear reactor) and others where other skills determine success (such as the creativity and drawing ability of a designer or the strength and precision of a blacksmith).