Historical Comparison

Were the Victorians cleverer than us? The decline in general intelligence estimated from a meta-analysis of the slowing of simple reaction time 

Using psychometric meta-analysis we computed the true correlation between simple reaction time and g, yielding a decline of − 1.23 IQ points per decade or fourteen IQ points since Victorian times. These findings strongly indicate that with respect to g the Victorians were substantially cleverer than modern Western populations.

http://www.sciencedirect.com/science/article/pii/S0160289613000470