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.