Increasing simple reaction times demonstrate decreasing genetic intelligence in Scotland and Sweden
There is a paradox in that although more intelligent people tend to have fewer children than less intelligent people, more recent generations tend to perform better on tests of psychometric intelligence. Since intelligence is highly heritable, this differential fertility would predict a decrease in IQ in the general population. The apparent IQ increase, known as the Flynn effect, is assumed to have environmental causes, such as schooling and the focus on abstract categorization prevalent in an information society. In other words, two different processes are simultaneously working in opposite directions, and it is then impossible to separate them when measured with the same instruments, typically paper-and-pencil matrix reasoning tests. Here, we show that change in genetic intelligence can be estimated, independently of the Flynn effect, by way of simple reaction time (RT). Data from three studies with different samples from Sweden, UK, and USA converge at an RT increase of 0.7-0.9 ms per year, which corresponds to a decrease in intelligence of between 4 and 5 IQ points per generation, or 1.3-1.7 points per decade in these countries.
This will have implications for educational attainment