The advent of computer technology has enabled an explosion in the availability of visual ways of presenting material, including large libraries of static images as well as compelling dynamic images in the form of animation and video. Teachers have the option of choosing from a variety of prepared multimedia software packages and/or creating their own multimedia presentations through the use of graphic-oriented and presentation software (e.g. Paint, Power Point, etc.). Not all multimedia instruction, however, enhances student learning. On what basis should teachers select multimedia software or construct their own multimedia presentations in order to improve instruction?
The goal of this article is to examine principles for learner-centered design of multimedia learning environments that meet three criteria: (1) intelligibility – that the principles are derived from a cognitive theory of multimedia learning; (2) plausibility – that the principles are consistent with empirical research on multimedia learning; (3) applicability – that the principles can be applied to new multimedia learning situations.
The Case for Multimedia Learning
An instructional message is a communication that is intended to foster learning. In presenting an instructional message to learners, designers have two formats available – words and pictures. Words include speech and printed texts; pictures include static graphics (such as illustrations and photos) and dynamic graphics (such as animation and video). For hundreds of years, the major format for presenting instructional messages have been words, including lectures and books. In short, verbal modes of presentation have dominated the way we convey explanations to one another, and verbal learning has dominated education. Similarly, verbal learning has been the major focus of educational research.
In light of the power of computer graphics, it may be useful to ask whether it is time to expand instructional messages beyond the purely verbal. What are the consequences of adding pictures to words? What happens when instructional messages involve both verbal and visual modes of learning? What affects the way that people learn from words and pictures? In short, how can multimedia presentations foster meaningful learning?
A Cognitive Theory of Multimedia Learning
The case for multimedia learning is based on the idea that instructional messages should be designed in light of how the human mind works. A cognitive theory of multimedia learning assumes that the human information processing system includes dual channels for visual/pictorial and auditory/verbal processing, that each channel has limited capacity for processing, and that active learning entails carrying out a coordinated set of cognitive processes during learning.
1. The Dual Channel Assumption
Let’s assume that humans have two information processing systems- one for verbal material and one for visual material. Let’s also acknowledge, that the major format for presenting instructional material is verbal. The rationale for multimedia presentations – that is, presenting material in word and pictures – is that it takes advantage of the full capacity of humans for processing information. When we present material only in the verbal mode, we are ignoring the potential contribution of our capacity to also process material in the visual mode.
Why might two channels be better than one? Two explanations are the quantitive rationale and qualititive rationale. The quantitave rationale is that more material can be presented on two channels than on one channel – just like more traffic can travel over two lanes than one lane. In contrast, the qualitative rationale is that words and pictures, although qualitatively different, can complement one another and that human understanding occurs when learners are able to mentally integrate visual and verbal representations. As you can see, the qualitative rationale assumes that the two channels are not equivalent; words are useful for presenting other kinds of material – perhaps more intuitive, more natural representations.
The most intriguing aspect of the qualitative rationale is that understanding occurs when learners are able to build meaningful connections between visual and verbal representations – such as being able to see how the words the piston moves forward in the master cylinder relates to the forward motion of a piston in master cylinder in an animation of a car’s braking system. In the process of trying to build connections between words and pictures, learners are able to create a deeper understanding than from words or pictures alone. This idea is at the heart of the cognitive theory of multimedia learning.
2. The Limited-Capacity Assumption
The second assumption is that humans are limited in the amount of information that can be processed in each channel at one time. When an illustration or animation is presented, the learner is able to hold only a few images in working memory at any one time. Similarly, when a narration is presented, the learner is able to hold only a few words in working memory at any one time. These images reflect portions of the presented material rather than an exact copy or recording of presented material.
Sweller and Chandler (1994) and Sweller (1994) have distinguished between intrinsic and extraneous sources of cognitive load during learning. Intrinsic cognitive load depends on the inherent difficulty of the material – how many elements there are and how they interact with each other. When there are many elements in the material and they are related to one another in complex ways, intrinsic cognitive load is high. In contrast, intrinsic cognitive load is low when the material is not complicated, such as when each element in the material can be learned separately. Extraneous cognitive load depends on the way the instructional message is designed – that is, on the way material is organized and presented. When the message is poorly designed, learners must engage in irrelevant or inefficient cognitive processing; when it is well designed, extraneous cognitive load is minimized.
3. The Active-Processing Assumption
The third assumption is that humans actively engage in cognitive processing to construct a coherent mental representation of their experiences. These active cognitive processes include paying attention, organizing incoming information, and integrating incoming information with other knowledge. In short, humans are active processors who seek to make sense of multimedia presentations. This view of humans as active processors conflicts with a common view of humans as passive processors who seek to add as much information as possible to memory – that is, as tape recorders who file copies of their experiences in memory to be retrieved later. Active learning occurs when a learner applies cognitive processes to incoming material – processes that are intended to help the learner make sense of the material. The outcome of active cognitive processing is the construction of a coherent mental representation, so active learning can be viewed as a process of model building.
This assumption suggests two important implications for multimedia design: (1) the presented material should have a coherent structure and (2) the message should provide guidance to the learner for how to build the structure. Three processes that are essential for active learning are selecting relevant material, organizing selected material, and integrating selected material with existing knowledge (Mayer, 1996, 1999a, 1999b, 1999c; Wittrock, 1989).
The Principles of Multimedia Design
Based on the cognitive theory of multimedia learning, I can suggest several design principles that my colleagues and I have tested.
1. Multimedia Principle: Students learn better from words and pictures than from words alone.
Theoretical Rationale: When words and pictures are both presented, students have an opportunity to construct verbal and pictorial mental models and to build connections between them. When words alone are presented, students have an opportunity to build a verbal mental model but are less likely to build a pictorial mental model and make connections between the verbal and pictorial mental models.
2. Spatial Contiguity Principle: Students learn better when corresponding words and pictures are presented near rather than far from each other on the page or screen.
Theoretical Rationale: When corresponding words and pictures are near each other on the page or screen, learners do not have to use cognitive resources to visually search the page or screen and learners are more likely to be able to hold them both in working memory at the same time. When corresponding words and pictures are far from each other on the page or screen, learners have to use cognitive resources to visually search the page or screen for corresponding words and pictures. Thus, learners are less likely to be able to hold them both in working memory at the same time.
3. Temporal Contiguity Principle: Students learn better when corresponding words and pictures are presented simultaneously rather than successively.
Theoretical Rationale: When corresponding portions of narration and animation are presented at the same time, the learner is more likely to be able to hold mental representations of both in working memory at the same time, and thus the learner is more likely to be able to build mental connections between verbal and visual representations. When corresponding portions of narration and animation are separated in time, the learner is less likely to be able to hold mental representations of both in working memory at the same time and thus less likely to be able to build mental connections between verbal and visual representations. If the time between hearing a sentence and seeing the corresponding portion of animation is short, then the learner may still be able to build connections between words and pictures. However, if the learner hears a long passage and views an entire animation at separate times, then the learner is less likely to build connections between words and pictures.
4. Coherence Principle: Students learn better when extraneous material is excluded rather than included. The coherence principle can be broken into three complementary versions: (1) student learning is hurt when interesting but irrelevant words and pictures are added to a multimedia presentation; (2) student learning is hurt when interesting but irrelevant sounds and music are added to a multimedia presentation; and (3) student learning is improved when unneeded words are eliminated from a multimedia presentation.
Theoretical Rationale: Extraneous material competes for cognitive resources in working memory and can divert attention from the important material, can disrupt the process of organizing the material, and can prime the learner to organize the material around an inappropriate theme.
5. Modality Principle: Students learn better from animation and narration than from animation and on-screen text; that is, students learn better when words in a multimedia message are presented as spoken text rather than printed text.
Theoretical Rationale: When pictures and words are both presented visually (i.e., as animation and text), the visual/pictorial channel can become overloaded but the auditory/verbal channel is unused. When words are presented auditorialy, they can be processed in the auditory/verbal channel, thereby leaving the visual/pictorial channel to process only the pictures.
6. Redundancy principle: Students learn better from animation and narration than from animation, narration, and text.
Theoretical Rationale: When pictures and words are both presented visually (i.e., as animation and text), the visual channel can become overloaded.
7. Individual Differences Principle: Design effects are stronger for low-knowledge learners than for high-knowledge learners, and for high-spatial learners rather than for low-spatial learners.
Theoretical Rationale: High-knowledge learners are able to use their prior knowledge to compensate for lack of guidance in the presentation – such as by forming appropriate mental images from words – whereas low-knowledge learners are less able to engage in useful cognitive processing when the presentation lacks guidance. High-spatial learners posses the the cognitive capacity to mentally integrate visual and verbal representations from effective multimedia presentations; in contrast, low-spatial learners must devote so much cognitive capacity to holding the presented images in memory that they are less likely to have sufficient capacity left over to mentally integrate visual and verbal representations.
Empirical Evidence: These seven principles were tested individually by comparing the retention and transfer performance of students receiving an instructional message based on the specific design principles with the performance of a control group. The retention tests involved the recall of information from the lesson within a specific time limit. The transfer tests involved answering problem solving questions within a time limit for each question. The focus of our research is on problem solving transfer, because transfer performance is a reflection of how well students understand an instructional message.
The empirical evidence confirms that all seven of the design principles impact positively on student learning. Almost all tests conducted demonstrated an increase in student retention, performance and 100% of the tests relating to transfer demonstrated an increase in student performance.
Another condition that is beginning to receive some preliminary research support in our laboratory is the personalization effect: Multimedia messages result in better transfer performance (but not retention) when the verbal material is presented in a conversational style – using first and second person – than when the identical verbal material is presented in a nonconversational style – using third person. In two studies conducted by Roxana Moreno and me, students who received personalized voice or text performed better on transfer than did students who received nonpersonalized voice or text (Moreno & Mayer, in press). One interpretation consistent with the cognitive theory of multimedia learning and with other research on personalization (Reeves & Nass, 1996) is that students work harder to make sense of the material when they feel they are engaged in social interaction.
Finally, we are also beginning to find some preliminary research support for an interactivity effect: Multimedia messages result in better transfer performance (but not retention) when learners are able to control the pace of presentation. In a study conducted by Paul Chandler and me, we created an interactivity treatment in which the presentation was broken down into sixteen short segments, each containing a sentence or two as well as ten to fifteen seconds of corresponding animation. Students could go on to the next segment by clicking on a button labeled “Click here to continue.” Results from our first study show that students who were able to control the presentation pace – by clicking on a button to receive each of sixteen segments – performed better on transfer tests than did students who received the entire presentation as a continuous unit. One interpretation consistent with cognitive theory of multimedia learning and with other research on interactivity (Rieber, 1994) is that students can avoid overloading their working memory when they control the presentation rate.
Conclusion
Our work allows us to suggest the characteristics of an effective computer-based multimedia presentation. First, the presentation should consist of both words and pictures – that is, narration and animation rather than narration alone. In short, the presentation should be multimedia. Second, corresponding portions of the animation and narration should be presented simultaneously in time. In short, the presentation should be integrated. Third, only the core cause-and-effect explanation should be presented, without extraneous words, sounds, and pictures. In short, the presentation should be concise. Fourth, the words should be presented as speech (i.e., narration) rather than as text (i.e., on screen text) or as speech and text. In short, the presentation should be channeled, with words directed toward the auditory channel and pictures directed toward the visual channel. Finally, the material itself should have a potentially meaningful structure, such as a cause-and–effect chain.
In summary, multimedia learning offers a potentially powerful way for people to understand things that would be very difficult to grasp from words alone. This article demonstrates the potential benefits of learning that involves the structured integration of words and pictures. It offers a glimpse of how we can improve on verbal messages, which have become the basis for most instruction. And, it offers a vision of the potential of multimedia instructional messages to improve human understanding.