Michael A. Woodley of Vrije Universiteit in Brussels, Jan te Nijenhuisc of the University of Amsterdam and Raegan Murphy of the University College Cork in Ireland conducted a meta-analysis of the slowing of simple reaction time -- in indication of general intelligence.
"We tested the hypothesis that the Victorians were cleverer than modern populations, using high-quality instruments, namely measures of simple visual reaction time in a meta-analytic study," the researchers wrote in the study. "Simple reaction time measures correlate substantially with measures of general intelligence and are considered elementary measures of cognition."
The researchers used data of simple reaction time described in a meta-analysis of 14 age-matched studies from Western countries conducted from 1889 to 2004.
The study, published in the journal Intelligence, found a decline in general intelligence of 1.23 points per decade.
"These findings strongly indicate that with respect to general intelligence the Victorians were substantially cleverer than modern Western populations," the study authors said.
Previous research found in many Western countries women of higher intelligence had fewer children than women with lower intelligence.