Is the relationship between IQ and brain processing speed/power linear, logarithmic or other?

For example lets say you two groups:

  1. Random group of 25 people each with an IQ close to a 100 IQ (95 - 105 ... 5% difference).

  2. Random group of 25 people each with an IQ close to a 150 IQ (142.5 - 157.5 ... 5% difference).

The individuals in each group have to solve one or more problems ... enough time required such that the testing time isn't so small as to introduce significant measurement error.

Lets say the problems are such that there is confidence all participants can solve them.

If we average the time to complete the task of the 100IQ group vs the 150IQ group, sans outliers, would that average time more likely be:

1) Linear, 50% faster (150 = 100 x 1.5) 2) logarithmic, 217% faster (log 150; base 10) = 2.71) 3) Other

  • 1
    $\begingroup$ So, you implicitely seem to define task completion time or performance as 'brain processing speed/power'. I believe it is better to stick to the metric you are interested in and not open the can of worms on using an ill-defined concept and whether or not one is related to the other. $\endgroup$
    – Steven Jeuris
    Mar 6, 2019 at 8:28
  • $\begingroup$ @StevenJeuris Why is time an ill-defined metric? $\endgroup$ Mar 6, 2019 at 16:47
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    $\begingroup$ I was talking about 'brain processing speed/power'. I suggested to stick with your 'time' definition and leave 'brain processing speed/power' out of it. $\endgroup$
    – Steven Jeuris
    Mar 6, 2019 at 17:02
  • $\begingroup$ This is a fairly interesting question, but might not be well posed because accuracy (getting the right answer as opposed to a wrong one) matters more than speed in IQ tests. In other words: what's the speed of a wrong answer? $\endgroup$ Mar 6, 2019 at 22:55
  • $\begingroup$ @StevenJeuris Are you saying time to solve a problem is not a measure of brain speed/performance? $\endgroup$ Mar 6, 2019 at 23:53


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