I haven't considered the research, I'm just talking about the positive changes I've seen in my life as a result of changing my mindset from "I can't do this because I'm not smart enough" to "this is hard, but I will learn it."
In the case of the former I was a non-starter. With the latter, everything becomes much more accessible.
I just object to this line in your comment: To briefly sum up the findings
On a macro level i.e. comparing people with vastly different circumstances/experiences/variables it does seem questionable, but on an individual level the change can be quite profound, going from a self-defeating to a more open/growth oriented mindset.
Also reminds me of one of my favorite quotes, by Henry Ford:
“Whether you think you can, or you think you can't--you're right.”