Rather than giving our undivided attention, it's usually demanded of us. Even if it's not for particularly lengthy stretches of time, undivided attention isn't something we decide upon, but instead something that happens, something that, after the fact, we realize was taking place. When it's required of us, what we ordinarily do is attempt to stare straight ahead in a culturally accepted pose that we expect will be understood as the desired attention. What's actually taking place in our minds at that time is often something very different.