But maybe in the days of phrenology, people thought a hooked nose* had a plausible connection to personality as well?
Weird to think about.
*Sorry, this is physiognomy not phrenology. The same basic point stands though.
If our society needs 1% of the population to be accountants (to pick an example) but only 0.1% of the population either have incredible focus abilities or don't find accounting brain-meltingly dull, then at least 90% of accountants are going to feel like they have a lot of trouble focusing at work. Once enough start medicating (legally or otherwise) it's gonna feel to others like they really do have a condition that most don't, but they both kinda do (in a practical sense, they do need to focus better to keep up with their peers) and kinda don't (in that it's sort of our society that's sick, not them—they're just acting like most people would, in that situation).
The marshmallow test was so appealing because it was incredibly easy to perform and seemed like it was pretty close to a measure of the kind of self-control and discipline that's needed to succeed in a variety of life's most important challenges.
Phrenology is bumps on the head right? I think hook nose would be physiognomy. But yes, the idea was that your behavior was due to your brain and your brain was composed of many different parts that each controlled different propensities or abilities. Then it was just a matter of identifying where those propensities lived, in relation to the head and then you could feel for the differences from person to person across the surface of the head. From the naive viewpoint it is plausible, oh, you say the back right section of my head, above the ear is a bit larger so the self-control portion of my brain is well developed? I've always thought so!
Setting aside the marshmallow test, you can easily see how scientific theories about this sort of thing, both right and wrong, easily integrate.