Multimedia is the integration, control, and manipulation of text, art and graphics, photography, animation, audio and video for presentations. In schools, multimedia is primarily used for research, presentation and interactive tutorials (Berry, 1996). Most research involved with multimedia focuses on a constructivist approach to learning (Toomey & Ketterer, 1995). When multimedia is used, there appears to be a decrease in teacher-led instruction (Collins, 1991). Among the major findings regarding multimedia applications is that they provide better problem solving, language development, creativity and communication (Char, Hawkins, Wotten,, Sheingold, & Roberts, 1983). Moreover, there are many advantages to using multimedia for learning. These advantages include an improved learning effectiveness, an increase in retention rate, an increase in interest and motivation, and, an increase in the amount of information that can be covered. The educational potential is that multimedia is data-rich. Moreover, the data is interrelated and the students can access by creating their own knowledge paths (Toomey, 1995). Furthermore, students need to construct knowledge for themselves (Toomey, 1995, p. 472) and students need to be better able to compile knowledge for themselves.

Some of the most significant work done on the effectiveness of multimedia as an instructional medium centers on the theory of multiple-channel communication. This theory promotes the synchronous presentation of information "...through different sensory channels which will provide additional stimuli reinforcement" (Dwyer, 1978, p. 22). However, Smith (1992) stated that in 1985 no multimedia products were suitable for educational use because they were not designed to elicit increase understanding from visuals. Severin's (1967) cue summation theory asserts that learning will be increased when stimuli that share information are presented because they reinforce each other. But, the criticism of this is multimedia productions may create sensory overload (Seels, 1994).

Moreover, Clark (1983) contends that research that showed a change in achievement because of the use of media was a result of a change in instruction techniques, not because media was used. "It was not the medium that caused the change but rather a curricular reform that accompanied the change. ...Basically, the choice of vehicle might influence the kind or distributing instruction, but only the content of the vehicle can influence achievement" (p.445). Clark further contends that many things confounded media research. For example, uncontrolled variables like instructional method or content difference between treatments and the novelty of new media caused the greatest change. But if these variables were controlled, the results would show that all media have the same effect. "It seems reasonable to assume, therefore, that media are delivery vehicles for instruction and do not directly influence learning. However, certain elements of different media, such as animated motion or zooming, might serve as sufficient conditions to facilitate learning of students who lack the skill being modeled" (p.453). Moreover, Clark would argue that individuals learn to prefer some media to others and individual preference might influence relevant outcomes. "Students incorrectly assess the extent to which the instructional method carried by the medium will allow them the most efficient use of their effort." (p.455).

Kozma (1991) argues against Clark (1983), supporting the influence of media on learning.

"Media can be defined by its technology, symbol system, and processing capabilities. The most obvious characteristic of a medium is its technology; the mechanical and electronic aspects that determine its function and, to some extent its shape and other physical features." É "Whether or not a mediumÕs capabilities make a difference in learning depends on how they correspond to the particular learning situation - the tasks and learners involved - and the way the mediumÕs capabilities are used by the instructional design. Tasks vary in their situational characteristics and in the demands they place on the learner to create mental representations of certain information and to operate on that information in certain ways. Learners vary in their processing capabilities, the information and procedures that they have stored in long term memory, their motivations and purposes for learning, and their metacognitive knowledge of when and how to use these procedures and information. Many learners, perhaps most, can and frequently do supply useful representations and operations for themselves from the information externally available, regardless of the medium used. But learners will benefit most from the use of a particular medium with certain capabilities -if the capabilities are employed by the instructional method to provide certain representations or perform or model certain cognitive operations that are salient to the task and situation and that the learners cannot or do not perform or provide for themselves. These representations and operations, in turn, influence problem solving and the ability to generate and use representations in subsequently encountered situations" (Kozma, 1991, pp. 180-182).

However, these researchers agree on the specific influence each medium contributes to the learning process. Research regarding each medium is briefly illustrated below.

Learning with books

Separately, each media that encompasses multimedia has its own effect on the learning process. Clark (1983) proposes that learning with books is effective because the stability of the printed work helps the information to be processed. Moreover, the stability of text is what makes it flexible, since student can always go back to it and find it in the exact same way. This is clearly different from the transient nature of audio or video. Considering pictures in the text, good readers look at pictures first to establish a setting and then rarely look back at them while poor readers constantly go back and forth, not able to focus on one or the other . "It seems that the text carries the primary semantic message while the pictures are used to map this information on to this preliminary mental model É however, too often in school learning these mental objects or operations have little correspondence to real-world objects, events, and their abstractions and map only onto the symbolic domains from which they were derived. ... for some learners, the use of pictures, in addition to text, may provide information needed to map mental representations derived from the text onto mental representations of the real-world" (Clark, 1983, pp.186- 188). Furthermore, if students are encouraged to create mental images of what they are reading they will remember just as much as if pictures were used. The reader must translate/interpret the text by creating some sort of mental model. "The situation model is connected to and constructed from information in the text base and from knowledge structures evoked from long-term memory by information appearing early in the text or information activated by the reader's purpose" (Clark, 1983, p.183).

Learning with television

In trying to understand learning with television, much focus is given to visual attention. Formal features such as types of voices influence visual attention. Studies on television influences suggest that "perceptions students have about a medium and the purposes they have for viewing influence the amount of effort that they put into the processing of the message and consequently, the depth of their understanding of the story" (Clark, 1983, p. 189). Whereas with reading the information is chunked by the reader at his/her own pace, with television where the pace is directed by others (Kozma, 1991, p. 193). Moreover, when considering learning from television, research must look at the processing two symbols, video and audio. Currently, there are two hypotheses: 1) the simultaneous presentation of audio and visual compete for cognitive resources which reduces comprehension, and, 2) information given in both media work together to increase comprehension.

Learning with computers

Students have trouble connecting things on computers with things in the real-world. But, when used appropriately, computers can model information which otherwise would never be seen or heard (Clark, 1983, p.199).

In essence, learning with multimedia is influenced by the point of view of the programmer and the designer as well as the hypertext abilities. However, multimedia applications tend to make better connections with the real-world, especially because of their hypertext/hypermedia abilities. However, Charney (1994) considers the suitability of hypertext for transmitting information. He argues that "hypertext may hinder the needs of the learners who depend on linearity to sequence the flow of ideas through focal attention." Print as does standard video production provides a linear foundation that gives the readers a logical sequence, albeit a singular sequence, by which to acquire knowledge. The trouble is that often concepts or ideas do not lend themselves well to a linear flow. True interconnectedness cannot be achieved except through the links of related ideas. The linear presentation style assumes interconnectedness based on proximity and this often leads to misconceptions. Hence, the non-linear format of a hypertext system is a considered a positive consequence because it does not fix the learner into one specific frame of reference for the knowledge.