I commented on this last year — so I really don’t have anything to add.
Woodley, M.A.,et al., Were the Victorians cleverer than us? The decline in general intelligence estimated
from a meta-analysis of the slowing of simple Intelligence (2013), http://dx.doi.org/10.1016/j.intell.2013.04.00
Simple RT = −1142.9659 + 0.7078 x year