We're getting slower... and more dumberer.
sciencedirect.com
sciencedirect.com
Actual intelligence scores have risen each decade: http://en.wikipedia.org/wiki/Flynn_effect
Also, the "We" in these studies is no longer just a narrow range of middle to upper class white males. If you look at sub-groups, most likely everybody is rising even when the overall average might be declining.
This is what happened with SAT scores since the 60s: "SAT scores don’t decline because students get dumber; they go down because more students take them." http://www.washingtonmonthly.com/college_guide/blog/average_...
So the question is, have reaction times gotten slower because of more people being tested, or other factors? I'd imagine in decades past, participating in a psych experiment was a more "special" occasion warranting heightened attention and performance than it is today.
So the core of the paper is RT -> IQ correlation and then supporting their argument with measurements of RT over time. Let's examine them.
A) "Galton's measures indicated a simple visual RT mean of 183 milliseconds (ms) for a large sample of 2522 young adult males (aged between 18 and 30), along with a mean of 187 ms for a sample of 888 equivalently aged females."
B) "These means seem to be representative of the period as a 1911 review of various studies conducted in the last 19th and early 20th centuries (Ladd & Woodworth, 1911), which did not include Galton's measures, found an RT range of 151–200 ms (mean 192 ms), using different instrumentation to that employed by Galton (1889). Moreover, Silverman was also able to comprehensively rule out lack of socioeconomic diversity, as Galton's samples were diverse enough to be stratified into seven male and six female occupational groups (Johnson et al., 1985)... Twelve modern (post 1941) simple RT studies by contrast revealed considerably slower RTs for both males (mean 250 ms) and females (mean 277 ms) in a combined sample of 3836."
The key problem being "using different instrumentation to that employed by Galton", who they don't reveal, except by citation, was using some pendulum and string contraption to measure reaction time.[1] With a difference of only 67 milliseconds between the males of each group, and 90 milliseconds between the females you'd need to show an equivalence between Galton's method of measuring reaction time and later computer assisted measurement methods, which they don't appear to. They also make some adjustments to the times that they don't seem to detail fully, in favour of the effect they are looking for I think (I am just skimming the paper and doing a quick rebuttal here).
After the measurement problem there are other problems of control they don't deal with. They seem to control for occupations, but it's unclear what else they control for. For example one of the modern papers they use is from Australia where only people who responded to an invitation to take the study were included, and 20% or so of contemporary Australians are born overseas (often not from the UK) so it's not exactly directly comparable to 19th century UK. Then, as someone else has pointed out in this thread they don't defend against things that can change reaction time. It seems there can be a significant impact of diet on reaction time, in one caloric restriction study reaction time went down while word recall went up.[2] Circadian phase, hours awake and temperature all seem to also have huge effects.[3] So contrary to the headline not only are people today smarter and we are just talking about "genetic g" there is the potentially huge measurement error, diet, hours awake, circadian phase and temperature, so I think more than enough error to account for the 67-90 milliseconds they are talking about.
As we don't have even the beginnings of that kind of data from Galton, let alone even a reliable time measure, it's fairly pointless to try to use such a weak and contested proxy for intelligence in my opinion.
[1]http://galton.org/essays/1880-1889/galton-1889-rba-reaction-...
[2] page 18 http://www.uiteigenervaring.nl/Op_dieet/Tenslotte/Calorie_re...
[3] http://ajpregu.physiology.org/content/283/6/R1370.full.pdf+h...
"Reaction time (RT) Quickness of information processing would seem to be an advantage in early hominid survival and hence could be regarded as a Darwinian ‘fitness character’. Galton therefore included it in his battery of tests as another elemental indicator of general ability. But Galton’s own findings with RT looked unimpressive. Because of technical inadequacies in his method of measuring RT and the lack of any statistical method for determining the significance of his findings, his theory was discredited and abandoned during the first three-quarters of the 20th century.Recent research, however, has shown that Galton’s idea was right after all. We now know for sure that measures of reaction time in what are called elementary cognitive tasks (ECTs) do in fact reflect the g factor (Vernon, 1987; Jensen, 1998a)."
So Jensen says the theory of a correlation between IQ and RT was later shown to be right but there are "technical inadequacies in his method of measuring RT", as well as statistical techniques were unavailable. So a leading researcher in the field says that the measurement of those data points suffers "technical inadequacies". I think if you go back to the graph of the reaction times on page 5 of the paper (http://i.imgur.com/8TBnkNF.png) and remove the 19th century Galton data points there would seem to be no great change over time.
I get the feeling this is geared more for press and controversy than a real scientific conclusion.
http://en.wikipedia.org/wiki/Idiocracy
Jokes aside, I guess I will have to read the article, would this not been the case from the beginning? How drastic are changes in IQ averages over hundreds of years? Is it possible that there highest IQ holders were not a very slim strata of society, or are we to suppose over time that the margin and spread is getting wider?