Lectures as social events
As well as being spoken communications, lectures are properly delivered by an actually-present individual. This creates a here-and-now social situation which unfolds in real time. Humans are social animals, who are naturally more alert and vigilant in social situations.
What makes the lecture a social situation is the potential for two-way communication - mainly a visual link of eye-contact between lecturer and audience. This situation of social communication is what makes lectures easier to attend and remember than written material, because failure to pay attention or an apparent failure to comprehend material can be seen by the lecturer. This need for direct communication sets a size limit to effective lectures (although this size can be increased by good design of auditoria).
In a very large lecture auditorium – even more so when electronic media are used to transmit a lecture remotely - the lecturer cannot maintain eye-contact with all members of the audience. This has two bad effects: firstly that the lecturer cannot monitor the response to his words on the whole audience, secondly (and more importantly) that remote parts of the classroom become cut-off from the lecturer because the students instinctively recognize that they are not being visually monitored. The remote students lose the possibility of participating in the here-and-now social event, in effect they are excluded from the lecture situation.
A properly-conducted lecture also exploits another spontaneous psychological disposition: the tendency to attend to persons of authority. In effect, the formal lecture is a mutually beneficial 'collusion' between class and lecturer. The structure of a lecture creates a situation in which a group’s attention is focused on the lecturer. This artificially generates authority in the lecturer which creates a receptive psychological state conducive to learning. The collusion is that a class of students implicitly, by their silent attention, awards temporary authority to the lecturer (authority which happens to be gratifying for the lecturer) for the purpose of making learning more effective (which is gratifying for the students – and is the aim of the exercise).
To enable lectures to be effective for learning, the process of communication therefore needs to be controlled by the lecturer. If communications from the audience are too frequent or uncontrolled, for example too many questions or discussions interrupting the flow of discourse, then this will sabotage the necessary authority structure in a way that will undermine learning. ‘Hecklers’ understand this very well.
A further aspect is that my experience strongly suggests that lectures should where possible be given as a whole course – not as one-off events – and by a single lecturer – rather than by a team. This seems to work better because it needs repeated interactions for a relationship of trust to build up between lecturer and class – and only when trust is established (if it is established) will students learn effectively.
It is precisely because the authority structure of a formal lecture is so powerful and instrument for focusing attention and improving learning that the lecture medium can be abused for propaganda purposes. Because they so effectively exploit human psychology, lectures are intrinsically a form of imposition by one upon the many, and there need to be safeguards to prevent this situation being used for inappropriate purposes.