>>> Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials
Abstract Objectives To determine whether parachutes are effective in preventing major trauma related to gravitational challenge.
Design Systematic review of randomised controlled trials.
...
Study selection: Studies showing the effects of using a parachute during free fall.
Results: We were unable to identify any randomised controlled trials of parachute intervention.
Conclusions: As with many interventions intended to prevent ill health, the effectiveness of parachutes has not been subjected to rigorous evaluation by using randomised controlled trials. Advocates of evidence based medicine have criticised the adoption of interventions evaluated by using only observational data. We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute. <<<
If mine wasn't clear to you, the article starts with a claim that this 'word gap' is the cause of effects observed later in life. It's easy to see the attraction of this, simply talk to kids more, then better adults right?
This is hardly cutting edge research, this has been floating around for some time, long enough for people to do some 'interventions,' of talking to kids more and the like, what did they find? Not much difference.
Back to the drawing board then right? Nope, not in social science, in social science if the results don't match our desires, we keep trying to beat the square peg into the round hole until they do!
What makes this shoddy science is that they assert the 'word gap' to be the cause with no evidence of it being so, and ignore other explanations, things like perhaps there are heritable 'psychological proclivities' that lead to parents raising a child in a particular way, the child inherits some portion and arrangement of these 'psychological proclivities' from the parent, these same 'psychological proclivities' then have an effect on the things observed later in life.
So if the social scientists want to do something productive instead of ignoring or bemoaning the fact that there are genuine differences among people, they could explore ways of structuring societies and institutions such that better results for people of all 'psychological proclivities' can be achieved.
I would say that many scientists are good at acknowledging this, though they may get over eager and forget to emphasize the point once they get to their discussion (or when an article is summarizing a piece of research).
Whenever I read observational research, I just mentally insert "under a set of structural assumptions about the world" before every statement like the one you listed above, and everything is okay again :).
Some of the other data points that would be interesting to know would be:
1) whether or not the child has a parent or full-time caretaker in the home
2) does the child attend preschool
3) how much television/videos does the child watch
4) how regularly the child is read to
There's tons of evidence around stereotype threat/self-talk and performance[0] so there's a strong argument that being exposed to fewer words, and far more negative words, won't help these people be successful.
That's quite a leap to say "this caused that," rather than them both just being a side-effect/characteristic of something else.
It is the height of shoddy science to look at correlated data points and proclaim a conclusion. But of course, much of what falls under 'social science' especially these days is shoddy.