BUT it has become the mantra of distance education. They need to be awake to learn - we have research on this for sure. Gagne's Nine Events of Instruction suggests we have to have the learner's attention if they are to assimilate any information into their short term, working or long term memories. Similarly talking heads aren't much better - you can see and hear but you can still fall asleep. Add audiographics and the same holds true - 100 Power Point slides may keep you awake but then again, maybe not.
Students lose their initial interest and attention levels continue to drop as a lecture proceeds.
We add interaction. If we encourage passive learners working at the very surface level of simply 'getting' the content to accomplish some learning task, like take the test, be present at the training, we end up with very little learning actually taking place and minimal retention over time - the psychology course I noted above is an example. I rest my case. If we want learners to gain a thorough understanding of the content area and construct knowledge, we need to encourage deep learning and we can through four interventions according to research. Interaction to assess needs, encourage learner to establish and share learning goals, etc.