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

Do opposing secular trends on backwards and forwards digit span evidence the co-occurrence model? A comment on Gignac (2015)

“…Gignac's (2015) observations are important as they add to the list of rarely considered cognitive measures the secular trends for which seem to defy the Flynn effect. These include inspection time, which, like digit span, seems to show no secular trends (Nettelbeck & Wilson, 2004), simple visual reaction time, which seems to show quite pronounced secular declines (Silverman, 2010;Woodley, Madison, & Charlton, 2014a;Woodley of Menie, te Nijenhuis, & Murphy, 2015;Woodley, te Nijenhuis, & Murphy, 2013b, 2014b and also society-level indicators of cognitive capacity, such as per capita rates of macro-innovation and genius, which also indicate pronounced declines starting in the 19th century (Huebner, 2005;Murray, 2003;Simonton, 2013;Woodley, 2012;Woodley & Figueredo, 2013). Gignac (2014a) poses the following open question:…”

Using Score Equating and Measurement Invariance to Examine the Flynn Effect in the Wechsler Adult Intelligence Scale

“…As head size correlates primarily with g rather than group factors (Jensen, 1998), and head size correlates highly with brain size, it could be argued that the FE is unrelated to brain growth given that previous research suggests its effects are not on g. The FE is not associated with improvements in inspection time (Nettelbeck & Wilson, 2004) and appears to be inversely related to changes in reaction times (Woodley, te Nijenhuis, & Murphy, 2013). Thus, there is no evidence to suggest that the FE can be accounted for by changes in brain efficiency.…”

How fragile is our intellect? Estimating losses in general intelligence due to both selection and mutation accumulation

“…Potential evidence for this model has been found in the form of an apparent secular slowing of simple reaction time in several Western countries since the closing decades of the 19th century (Woodley, te Nijenhuis, & Murphy, 2013. These meta-analyses employed sample-type matched Western studies reporting simple reaction time means spanning the period 1888-2004.…”