What is intelligence and how IQ tests work

Today, there is no unanimous opinion of the scientific community on the definition of intelligence. In general, we could say that it is the ability to adapt one’s thinking in the face of changing circumstances, in order to achieve certain objectives. A promising theoretical model is that of Cattell which distinguishes fluid intelligence and crystallized intelligence of albert einstine .

Let’s talk today about a concept widely used in everyday life and let’s start doing it starting from its meaning: intelligence and IQ

Several theories

Do we really know what it is? We can answer with a simple no. Because? Trivially, because in the scientific community  there is no definition of intelligence on which there is common agreement. Despite this, we all (some more, some less) have an idea of ​​the concept of intelligence, at least on an intuitive level.

In the scientific field we have tried to give many descriptions and here we try to provide a simple explanation that attempts to enclose the common elements of the various definitions: intelligence is the ability to adapt one’s thinking in the face of changing circumstances, in order to to achieve certain goals.

To many this definition will have seemed very vague, to the point of including almost every skill in this concept. And so it happened! Just think  of Gardner’s theory of multiple intelligences  which also considers motor skills as a form of intelligence.

A theoretical model that is often referred to is that of  Cattell  which divides intelligence into  fluid intelligence and  crystallized intelligence . The first refers to the ability to face and solve problems whose solution  does not depend on previous knowledge , the second instead is identified with the ability to use skills and knowledge acquired with experience .

Other theories on intelligence have also been formulated but, apart from Salovey and Mayer’s emotional intelligence, they have had little practical impact.

Instead, it is important to keep in mind the theoretical model of fluid intelligence and crystallized intelligence to try to understand the meaning of the IQ tests we are about to talk about.

IQ tests are tests that attempt to estimate an individual’s intelligence based on the answers provided. Their biggest problem is that, lacking a clear definition of intelligence, no one really knows what they measure and in fact many have been built without real theoretical assumptions. Despite everything, they continue to be widely used for their so-called  predictive validity , that is, for their ability to predict (at least in part) the future success of people in study and work (on average 20-25% of future results).

Many parents, when taking their child for a neuropsychological assessment (usually for learning difficulties), are curious or frightened by the idea that the latter is subjected to intelligence tests. It is not uncommon for them to ask who has been through this first what it is, what the IQ score means, when it is considered high and when it is low, etc.

Let’s try to clarify.

What is IQ?

It is a very simple concept: it is a score that tells us how far a performance is from the average . It may sound complicated but now it will look simpler. The IQ has an average of 100, that is, if we placed people on a scale from 1 to 100, individuals at the 50th step would have an IQ of 100 (50th percentile). This means that with a score above 100 you will have an above average performance and below the opposite. Usually  we consider normal IQ between 85 and 115  (within which falls about 68% of the population) and we consider intellectual deficit performance scores  below 70 .

How is IQ measured?

The most used intelligence tests can be traced (albeit with some forcing) to the aforementioned concept of fluid intelligence and crystallized intelligence.

The most used are the  Progressive Raven Matrices  (usually the PM 38 and the PM 47) and the  Wechsler scales  (in Italy the most recent are WPPSI-III, WISC-IV and WAIS-IV).

In the first case, reference is made to the concept of fluid intelligence and consequently the tests consist in solving problems that do not require previous knowledge to be solved (at least in theory they are independent from the cultural level of the person being examined). These are incomplete figures that are missing a piece to be completed. The subject’s task is precisely to choose the missing piece.

In the second case, these are tests that measure in part fluid intelligence (usually with tasks similar to the one just described and other types of tasks, such as the reproduction of images through colored cubes) and in part crystallized intelligence (tasks of verbal type in which we rely on the knowledge of school notions and the ability to elaborate them verbally). 

There are also other tests that make up these tests, which can be traced to  the processing  speed (speed with which the brain would be able to process information) and  working memory. (ability to keep information in memory and perform processing with them). 

This aspect is very interesting because according to many studies, the results obtained in the tests of working memory and processing speed seem to be able to explain most of the results in the tests of fluid intelligence.

Although many scholars now consider IQ an outdated concept, this remains a cornerstone in the definition of some disorders and therefore its measurement remains  essential for diagnostic purposes . It also continues to be a tool that can give important information, albeit to be used with caution given the enormous theoretical limits.

To sum up we could say that the IQ tests are tests that try to  place people on a scale of intellectual functioning whose performance range is defined in relation (deviation) to the average (100) . Despite their great limitations, these scores continue to be used because they allow in part to estimate the degree to which a person will be able to cope with study and work commitments .

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