THE LEVEL OF INTERACTION in Distance Education is affected by the choice of synchronous or asynchronous delivery. If the medium is synchronous, then the interaction that occurs takes place in real time. Delayed, or asynchronous, communication is any transfer of information that is stored or archived and then later accessed. It is important to determine the most effective delivery mode since it directly impacts the level of interaction.(Steiner, 1996)

Simply put, this is the transfer of information without delay. Traditional stand up teaching would be considered totally synchronous. In distance education examples would include audio and/or video transmitted "live" among instructors and students via TV, Internet or radio.

It is desirable to have some level of synchronous communication between the actors (instructor and students) since this creates the most spontaneous interaction. This enables the instructor to adapt and respond to questions without delay.

There are several advantages to synchronous delivery, including:

• Motivation -- focuses the energy of group and encourages students to keep up with their peers and continue with study
• Telepresence -- helps create a feeling of community and classroom cohesion
• Feedback -- rapid feedback foster consensus-building in group activities
• Pacing -- helps keep students up-to-date with the course (Mason, R.D)

All archived and stored material belongs in this category, including media such as CD-ROM, web pages, email, fax, videotape, and so forth.

There are several advantages to this type of delivery system, including:

• Flexibility -- access to the teaching material can take place at any time.
• Time to reflect -- rather than having to react instantly, it allows the learner to reflect over ideas, check references and take time to prepare a reply. If the teaching session is recorded and archived then students can go back and review the lesson.
• Situated learning -- the technology allows access from home or work, learner may have opportunities to integrate ideas being discussed on the course.
• Cost effective -- text based systems require little bandwidth and low end computers to operate, making access more equitable. (Mason, R.D)

When designing a distance education course the instructional designer should take into consideration both types of delivery. Selection of delivery systems depends upon the needs of the students and the type of subject matter. Some instruction can be entirely of one delivery type or another. But this is rare.

Both have their advantages and, conversely, their disadvantages are addressed by the opposite delivery system. A combination of the two provides an interactive learning environment. For more information on this combined approach look at the article:

A Hybrid Synchronous / Asynchronous Approach.

Here are some examples of institutions that use a combination of both delivery methods.

• OnLine Education, University of Paisley, Scotland.
• George Washington University, Washington D.C.
• Nova Southeastern, Florida.
• University of Twente, Netherlands.

Harley Bergsma ，Graduate Student ，SDSU Educational Technology