Split attention, however, will result whenever a learner needs to simultaneously attend to two or more sources of instruction or activities.
Multiple sources of purely text based instructional materials will induce a split attention effect if two or more sources must be considered simultaneously. For example, this is likely to occur when cross referencing documents, or even cross referencing within a single document.
Chandler and Sweller (1992) provided evidence that a split attention effect occurs when reading conventional experimental papers because the results section and the discussion section are reported separately, yet need to be considered simultaneously to understand the complex of results and their implications. Here the split attention effect may be eliminated and intelligibility increased, by restructuring experimental papers to integrate the results and discussion sections.
A split attention effect may also result from mixing activities. For example, when learning to use a software package it is common practice for the learner to simultaneously refer to a hard copy tutorial (or manual) and the computer. The tutorial provides step-by-step instructions for performing each task and the learner attempts to carry out each step on the computer. While this may seem to be an obvious way of learning a software package, experimental investigations have shown that far more effective learning strategies are available.
The simplest modification is to eliminate the use of the computer in the learning phase and replace it by appropriate pictures and diagrams. Provided the manual contains all of the relevant information, then students who study the manual alone outperform students who perform each step in sequence on the computer based upon the manual instructions. The irony here is that the manual-only-group complete their "training" without ever having used the software package, yet in testing, on a computer with the real software, they perform better than the group who has already spent time using the software package. See Chandler and Sweller (1996) for details.
Another alternative is to develop a computer based training package which integrates text based instructions into a computer simulation of the target computer package. When this is done the manual may be eliminated from the training process, leaving students to focus their attention wholly on the computer screen. This eliminates split attention and facilitates learning. See Cerpa, Chandler & Sweller (1996).