General intelligence, IQ


The first idea for many people regarding genius is IQ. So I will look at it briefly to help to understand what it is measuring and how is it connected to geniuses.

Sir Francis Galton tried first to measure the personal differences in intelligence. In 1884 at the International Health Exhibition in London he presented his views. He collected data from almost 10 thousand people within one year. He measured head size, arm span, standing height, weight, breathing capacity, reaction time, visual acuity, and similar things.

‘oh sir galtpn. Are you sure you need to measure that to get to know my integence? You silly boy…

Based on the principles of Sir Galton, James McKeen Cattel created the first mental test in the world, which mostly measured reaction time. One of the students of Cattel demonstrated soon, that there was no statistical relationship between scores on Cattell's tests and academic performance and there was no correlation between each tasks, so if any question was measuring intelligence, the whole test is not good for this goal.

One of the first intelligence test similar to those what we use today, was created by Alfred Binet. His major drive was a very practical problem. The French educational system faced a challenge after the French law made mandatory for children ages six to fourteen to attend school. His job was to identify those children who are not able to keep pace with the other children.

After the law came into effect, they created soon classes for children with the worst performances, who need an alternative education.

Children at first were selected by their teachers to these classes.

However, Binet created a simple test to help to identify these children.

He applied questions connected to our every-day life.

Children had to point out body parts, repeat some digits, define simple words like house, reproduce drawings from memory, etc.

So, in 1905 the first intelligence test was created.

Binet was successful in predicting school performance and intelligence and identified an important factor, the age of the child.

 Elder children outrank younger children in mental development.

He analyzed which tasks could be solved by children in different ages.

So his tasks were connected to performance in different ages.

He called this performance the mental age of the child.

So, if a child can solve tasks, what 8 years old children can, but can’t solve, what 9 years old children can, then he’s mental age is 8 years old.

After that he compared the mental age of the child to his chronological age, to identify children who outperform, and those who underperform their peers.

 And if an 8 years old child can only solve the tasks what an average 6 years old child can, unfortunately he drops behind with two years.

Binet’s method had one mistake, which was later corrected by Wilhelm Stern.

Let’s compare two children based on the knowledge what Binet had:

If ‘A’ child is 6 years old, and can solve tasks, what generally 4 years old children can, then he drops behind with 2 years.

If ‘B’ child is 8 years old, and can solve tasks, what generally 6 years old children can, then he drops behind with 2 years.

We found the same difference.

However, based on experiences, in the early age this difference proved to be much bigger. So Wilhelm Stern showed that we will get a more accurate result, if we divide these two numbers.

That is the moment, when the term intelligent quotient was born.

If we apply now this to the earlier mentioned two children.

The IQ of the A child is 4/6=0,67, and the IQ of the ‘B’ child is 8/10 = 0,8.

The next important step came from the Unites States.

Lewis Terman adapted this test to English, improved it, and multiplied it with 100

to better understand it.

So IQ can be calculated as mental age / chronological age *100. However, I have to warn you that this method can’t be applied for adults.

The first IQ test for adults and the concept of IQ deviation was created by Donald Wechsler. We will look at it in the next video!

Előd Szabó
Előd Szabó