The theory that people's attention spans keep getting shorter and people can't watch longer videos anymore doesn't match up with the trends on Youtube.

well... there's a few things about that. Within youtube itself there are different incentives than there might be on other platforms, and changes in rules, recommendation algorithms, and advertising methods have all contributed to shaping what kind of content does well as much or more than people's attention spans or preferences. There was a time when short videos were king, but changes to monetization and such shifted away from that.

But if you look industry wide there has been an explosion in the short form stuff. it's not prima facie evidence of declining attention spans but it is a real trend that has probably brought the average down.

IMO it's just two different ways to retain attention: a long drawn out explanation or story with the promise of some payoff where it all comes together or builds to a big moment (often lacking), versus rapid fire content coming at you so fast it doesn't even really matter if its that good as long as its stimulation.

the "declining attention span" thing feels real in other ways though. Most people I know couldn't sit down and read a book for any length of time if they tried.