IQ and age (part III)

IQ and age - declines are inevitable
IQ and age – Fluid IQ diminishes as we enter into middle age

This is my third posting on the interesting topic of the interplay between IQ and age. As discussed in my last posting, our fluid intelligence (that is, our ability to solve novel problems) will expand during childhood, slow down after the age of 16 and peak at 25, before beginning a gradual decline thereafter. That’s right, our fluid IQ and fluid intelligence will decline into adulthood.

So what does this mean? Fluid IQ and age are positively correlated between the ages of 0-25, and negatively correlated from the age of 25 until we die. In absolute terms, our raw intelligence (as measured by fluid IQ) will increase from birth until our mid 20s, before declining thereafter.

But when one thinks about IQ measurement, is it important to consider both absolute and relative elements of the IQ score. This is so because in absolute terms, most 25 year olds will be more intelligence than children under the age of 10, although in relative terms the comparison of intellectual abilities between the two groups requires a relative dimension.

That is, a 10-year old who is able to think and process information like a 16 year old would be exceptional for her age – and this would be reflected in an exceptional IQ score. In absolute terms, this child would perhaps not be as clever as a bright 25 year old college graduate, but in relative terms, would be leaps and bounds more advanced than her age-related peers and probably a significant proportion of 25 year olds.

Conversely, a 25 year old who failed to complete high school because he struggled with the difficulty of the material would most likely be found to have a low IQ score, both in absolute and relative terms.

High IQ societies such as Mensa will typically make adjustments for the age of the test taker, but in childhood through to early adolescence only.  That is, the bar for achieving a score in the top 2% of IQ will be lower for the 12 year old taking the test, relative to the 25 year old. In fact, after the age of 16, test takers are measured on the ‘adult’ IQ scale.

IQ and age – relative and absolute scores needed

The problem is that this age-correction does not take place past the age of 25, which means that new joiners to Mensa who are not supplying ‘prior evidence’, which means proof of a score in the top 2% at some point in that individual’s lifetime, are much less likely to be in their late or early 40s than say, early 20s.

So in fact, middle aged people taking a fluid IQ test will be measured against the population in absolute terms (and thus against peak adults) and will get no insight as to how well they have maintained their fluid IQ relative to their age-related peers.

At, we are working on establishing a scale which would provide this level of color. We expect to be able to publish the results of this study by early 2015. That is, we hope to be able to give middle aged and golden aged individuals both a relative picture as well as the absolute picture of how well they are fairing when it comes to IQ and age.

In the meantime, you can test your absolute IQ score HERE,