The modality effect is a term used in experimental psychology, most often in the fields dealing with memory and learning, to refer to how learner performance depends on the presentation mode of studied items.
For example, Gibbons demonstrated modality effects in an experiment by making participants count either beeping sounds or visually presented dots.
[7] Bennet Murdock used a basic free recall paradigm, with different types of lists, mixing auditorally and visually presented words.
By using techniques similar to Murdock's free recall paradigm, plus the addition of varied amounts of distraction time (filled with counting backwards), Glenberg showed that the modality effect is not affected by a disruptive task and therefore is theoretically not restricted to short term memory.
In contrast, the narration is dealt with by the 'Phonological Loop' while the 'Visuospatial Sketchpad' deals separately with the original image and hence both pieces of information can be processed simultaneously.
Teachers can hence seek to avoid overloading students' working memories by not using slides containing many images and text at the same time.