> humans are worst at discerning faces today because we need to discern letters and words and dedicate brain power for that.

I have absolutely nothing to back this up, but my gut tells me this risks being one of those bold claims that grows legs and runs for a while until we debunk it.

Yeah, has that Malcolm Gladwell knowledge porn vibe. A book that empowers its reader with secret knowledge of explanation that all fits together a little too neatly and loses nuance or is often just plain wrong.

After finding out even Think Fast, Slow (a book from a very creditable researcher and nobel laureate) is full of replication crisis, I approach pop-sci as entertainment instead of self-education.

It's not completely insane, the part of the brain that gets used for recognising words is very close to the part of the brain that recognises faces. The brain likely cannibalises the part of the cortex that's used to recognise faces to recognise words and letters instead. See this study[1] where the visual word form area reacts much more strongly to faces in illiterates than in people who have learnt to read.

[1] https://www.unicog.org/publications/1-s2.0-S1364661311000738...

https://en.wikipedia.org/wiki/Visual_word_form_area

https://en.wikipedia.org/wiki/Fusiform_face_area

There are people who have face-blindness (inability to discern faces) or dyslexia (visual processing disorder that leads to severe difficulties with reading). The two aren't strongly correlated.

Dyslexia seems to be tied to some broader visual processing issues, which impair the ability to discriminate faces somewhat. But not the other way around.

If the two skills were strongly related, you'd expect a very strong and obvious link. Maybe in form of both performing poorly, if damage to the same pathways impairs both. Or as one performing poorly while another performs unusually well (super-recognizers? children who learn reading at 2?) - if the two skills compete for brain real estate and create a performance tradeoff, as claimed.

It's the one that immediately set off my alarm bell. I always try to put myself in the shoes of a scientist and imagine how it would be possible to design a study to test a claim. To me, this one implies humans of today are worse at recognizing faces compared to humans of the past who did not read as much or at all. That one cannot possibly be tested because you cannot test the cognitive capabilities of people of the past who no longer exist.

On the more productive side, this suggests we might develop standardized tests of human capabilities and limits that would allow people of the future to compare themselves to us.

I'm struggling to think of any way to test the hypothesis which is (A) practical and (B) accurate.

For example, suppose you sampled a group today and found an inverse-correlation between "good at recognizing many faces" and "good at recognizing written text"... That still wouldn't show that one facility grew causing the other to shrink, because maybe people are just born (or early-development-ed) with a certain bias.

It seems that there is an study in which the part of the brain used to recognize words is also used for recognizing letters, and when one increases taking more space the other shrink. That study used brain scanners to measure and detect brain activity.

Or perhaps something that it's true even after we "debunked" it