Are attention spans actually shortening?

So a view I see a lot nowadays is that attention spans are getting shorter, especially when it comes to younger generations. And the growing success of short form content on Tiktok, Youtube and Twitter for example seems to support this claim. I have a friend in their early 20s who regularly checks their phone (sometimes scrolling Tiktok content) as we're watching a film. And an older colleague recently was pleased to see me reading a book, because he felt that anyone my age and younger was less likely to want to invest the time in reading.

But is this actually true on the whole? Does social media like Tiktok really mould our interests and alter our attention? In some respects I can see how it could change our expectations. If we've come to expect a webpage to load in seconds, it can be frustrating when we have to wait minutes. But to someone that was raised with dial-up, perhaps that wouldn't be as much of an issue. In the same way, if a piece of media doesn't capture someone in the first few minutes they may be more inclined to lose focus because they're so used to quick dopamine hits from short form content. Alternatively, maybe this whole argument is just a 'kids these days' fallacy. Obviously there are plenty of young adults that buck this trend.