I work on a mobile app (ecommerce) which during the purchase path has persistent buttons that are always to the bottom of the screen, regardless of where the view is scrolled, in order to move the user through to the next step.
For example it would be the equivalent to the Amazon app always having a "Buy Now" button stuck to the bottom of the screen no matter where you were scrolled on their product view. Or on the eBay app, having a "Bid" button always showing when you view an item rather than having to scroll to that point in the view.
What I'm wondering is, has there been any research around this type of persistence in actions? My theory is that while it may maximize the number of people who tap the button and go on to the next step since it is always visible, the button always being there may also decrease engagement with the content of the view itself. Haven't been able to find any research on the soundness of this kind of approach.