Were the Victorians cleverer than us?

The answer to the question in the headline is "no". The line of argument used is extraordinarily tenuous: first it argues that reaction time is a good proxy for intelligence, then it collects different reaction-time studies, weights them by sample size, and computes a correlation. Unfortunately, if you look at the main graph of the paper, it looks like a trend-line drawn through noise. But! Because of the sample-size weighting, the data is dominated by a single study in 1889, which had 3410 participants (the largest out of 16) and an unusually fast reaction time (the fastest). They then use frequentist statistics to sneak in the assumption that reaction time varies only with different subjects and populations, and not with different test-apparatus and methodology, arriving at a "significant at p=.003" result which I have no confidence in.

We'll never know, because it's behind a pay wall. It's hard to consider the cause of the supposed effect without access to the methodology used.

How does this square with the Flynn Effect? Alas, I'm not clever to figure it out myself.

I'm not confident that you can really correlate simple reaction times with intelligence in general. But if our reaction times are indeed getting longer, that's interesting for other reasons.

Consider the relatively recent development of video games, many of which depend heavily on reaction time as a basic skill. We spend our childhoods immersed in these twitch-critical tasks: training the Victorians would have envied, if they had been all that concerned about simple reaction times. Yet our reaction times continue to go up, seemingly unabated. Why would that be the case? Shouldn't the extra practice at least slow the decline?

I think linking to journal articles is a good thing even when they are paywalled like this but please give some context and a summary of the results.

As a Republican and cultural relativist, I dislike the use of the term "Victorians" to refer to Industrial Revolution.

They may have been, but then they put lead in everything. Since then everyone has been dumb.

Well, they certainly might've had better grammar than us. “Cleverer” my foot.