People usually call out the page number before they start reading whichever antiphon it is that they are going to read, but they never give enough time to actually find the page. I think this is because the person reading the antiphon has a psychological urge to keep the pause shorter or equal to the antiphon itself. And antiphons, at least the particular ones I am writing about, are very short.
In similar circumstances, where the page number is called out for a song, for example, the leader usually gives everyone more time to get to the page. The length of the wait could have more to do with the amount of text we are going to go through rather than clear indications from everyone as to whether or not they've actually found the page. After all, there is always someone not bothering with the book, so you can't wait for everyone.
This would be an interesting study. Surely this is testable. Now, I just need to convince someone this would be a good science project!