From Plato's Academy to the modern university, knowledge has been transmitted orally for over 2000 years. Although the original Socratic method required a dialogue between teacher and student, the lecture, as it was developed in the medieval university, did not. Originally, lecturing was the only way that the knowledge stored in books could be transmitted to a large number of students; the word "lecture" is derived from the Latin legere, "to read." Many centuries after the invention of movable type and other significant advances in technology, lectures continue to be the primary mode of instruction in higher education. The reasons for their popularity are not hard to adduce: lectures are cheap, since a single teacher can lecture to an auditorium full of students; they are easily changed and updated; and they are efficient in covering material quickly. Finally, and perhaps most important, the method is familiar to students and teachers alike, and their roles are clearly defined.

“ I can't imagine teaching without the lecture method. There are certain things that I must cover in class; I organize the lecture material in a way that provides a conceptual overview that allows us then to ask for the implications of a bit of knowledge.”   Speech Communications professor

Lectures are appropriate for presenting material not otherwise available to students, or material that is too complex for students to grasp on their own. They are also an excellent way to provide overviews or summarizations of course material, to draw together diverse elements and to show connections between concepts. If the teacher is an effective speaker, lectures can also communicate the teacher's enthusiasm and interest in the subject matter and thereby stimulate students to want to learn more.

However, the traditional lecture method, in which the instructor does all or most of the talking, has a number of drawbacks. Lectures of this sort are based on "learning by listening," which is a disadvantage for students who prefer to learn by reading, or by doing, or by some other method. Although the traditional lecture conveys factual information very well, it is not well-suited to the higher levels of learning; critical thinking, analysis, and problem-solving must be learned by doing. In a traditional lecture class, the student is passive, has little control over the flow of information, and is reduced to playing a stenographic role. Moreover, research has shown rather that students frequently forget, or never learn, much of the material taught through lectures.

How can we exploit the strengths of the lecture method and avoid its weaknesses? Effective teachers seem to share many of the same lecture techniques (even though their styles may differ considerably), and these techniques reflect principles grounded in cognitive psychology. By paying attention to a few of these basic principles, we can refine our lecture techniques and make our lectures as effective as possible.

Several studies have shown that the attention span for uninvolved listeners is roughly 15 to 20 minutes. After 15 minutes students begin to tune out and, although some may continue to take notes, they are no longer processing the information they receive. Since passive listeners have short attention spans, the way to overcome the problem is to involve them in some way.

Some teachers at UNC have discovered that a highly interactive, question-and-answer lecture style will keep students actively engaged for the entire class period. Instead of providing information, the teacher tries to elicit much of it from the students through "unfinished statements" and direct questions.  Another approach teachers use to overcome the attention span problem is to divide the class period into 15 or 20 minute blocks of time, alternating lecture with discussion or some other activity that requires student participation.

Another problem with audience attention has to do with the way they process the information they receive aurally. It is difficult for students to discriminate between the more important and less important material in a lecture unless they are given appropriate cues. Although most teachers give oral signals during a lecture-- "Now, this is important"--students also need to understand the overall structure and organization of the lecture so they can focus their attention on the more important concepts and the way these elements fit together. Many professors regularly provide topical outlines on transparencies, handouts, or the blackboard, that reveal the organization of the lecture and give students clues to its most significant elements. Some teachers include a unit-by-unit outline of their lectures in the syllabus for the course. The basic principle is that students will filter out nonessential information if they are told, in various ways, what is essential.

One-way communication, as in the traditional lecture, can also cause problems with audience perceptions of the message being sent. For example, we know that humans screen messages through a variety of sensory and cognitive filters. Children in grade school saying the Pledge of Allegiance often recite "and to the Republic for Richard Stands," because they think that is what the teacher said. Our perceptions are shaped by a variety of personal factors--our backgrounds and experiences, our individual learning styles, and the way we encode information. The Rorschach Test is based on this principle; it would not work if everyone saw exactly the same images in the inkblots. When lecturing, however, we want everyone to receive the information in the same way, accurately.

Most teachers pay attention to the facial expressions of their students in order to gauge roughly whether they are puzzled, amused, alert, or bored. But in order to verify (with any degree of precision) that they are getting the point, the teacher needs to establish two-way communication--to ask them questions, to test their perceptions in a dialogue of some sort. This kind of verification requires directing questions about the subject matter to individual students. Periodically posing questions to the entire class does not usually work because only the best students will respond, and they are least likely to have difficulties with perception of your message. Nor is it sufficient to ask, in a general way, "Are there any questions about these points?" since this type of question does not require students to test their perceptions against yours.

Yet another problem related to perception is the difficulty students have in learning new information unrelated to any former learning or experience (and for the average freshman, there is great deal of information that falls in this category). There is some evidence that we tend to learn by subsuming new ideas and information under pre-existing categories in our cognitive structure--in other words, perceptions are related to specific fields of memory. The implications of this principle are clear: new terminology and ideas should be linked to previous experiences or associations. This exercise can be as simple as showing students a mnemonic device to help them remember the elements of a chemical processor as complex as finding elegant metaphors for the most difficult concepts in your field. One researcher has suggested that one trait that effective teachers seem to share is the ability to construct metaphors that immediately connect with the minds of their students. One history professor explains eighteenth century imperialism in terms of pancake sales. A literature professor uses television soap opera characters to draw parallels with characters in novels and short stories. Perhaps one of the most famous practitioners of this technique is Jaime Escalante, the brilliant math teacher profiled in the movie "Stand and Deliver." He has developed a variety of metaphors that help his students understand and remember concepts in mathematics.

In addition to relating new information to pre-existing fields of memory, one must also provide many concrete examples in order to help students form new concepts and understand new processes. Although examples can be given orally, they might also take the form of pictures, diagrams, illustrations, or even exercises that the students perform. A professor of business law illustrates case studies in the course with a series of overhead transparencies that show, in cartoon format, the figures and the issues involved in each case. A psychology professor illustrates the Freudian concepts of superego, ego, and id through conceptual diagrams, thereby creating concrete examples of theoretical constructs that students have difficulty grasping.

Lecturers must also be aware of the limitations on learning imposed by the way humans encode and retrieve information. As we receive bits of information, they are first sent to short-term memory where they are encoded before being sent for storage in long-term memory. Most individuals can hold about seven chunks of information in short-term memory (which is why our telephone numbers are in seven digits), and if more new information is received before the encoding process can take place, some chunks will inevitably be lost. When students receive a long, unbroken stream of new information in a lecture, they don't have time to encode it for long-term storage--they can only try to record it in their notes.

In order for students to learn from a lecture, they need blank time in which no new information is being presented to interrupt the encoding process. Some professors pattern their lectures so that, after introducing a series of new ideas, they always provide subordinate, illustrative, or anecdotal material which is not new, but is related to the new information in some way. Frequent internal summaries in a lecture also provide blank time for processing the new information.

I've found that the optimal approach for me is to do mini-lectures. They never run more than half the class period so I have time to do some kind of experiential exercise. The mini-lecture can introduce material needed for the exercise, or summarize the exercise, or both.--Speech Communications professor

One thing that is valuable to do is that when a student asks a question to have other students answer it, rather than answer it myself.--Statistics professor

I try to draw the students in by asking them to apply the theorist's ideas to their own lives. For example, I might say "Have you been in situations where you would believe that Hobbes was right about life being `solitary, poor, nasty, brutish, and short?'"--Political Science professor

You can hit them with dates and facts and dates and facts and it boggles the mind after about 15 minutes. So I use a current event that makes the facts come alive. Student interest picks up when there's something in the lecture that they may have just read or seen in the news.--Physical Education professor

I don't stay in one position at the front of the class; I'll walk around between rows or I'll walk right up to a student and say "Now, if you were in Hamlet's circumstances what would you do?" I look them eyeball to eyeball--that contact is important--it creates a liveliness and keeps students on their toes.--English professor

I want students to do more thinking, not just be stenographers. At a point in the lecture where I want them to think, I have them put their pencils and pens down and just listen. It makes them a little uncomfortable at first, but it helps them think about what they are hearing.--Psychology professor

Every time I come to a spot where I think they should know something, I ask them for it. That allows them to participate and it reinforces what I taught earlier. If no one answers, I know I've got to back up and rebuild that information. --Chemistry professor

I have students remember a subject from their own lives, or imagine a scenario, or tell them an anecdote that gets them into the content.--Psychology professor