28.2 Memory For Auditory Presentations

28.2.1 Memory Theory

A short description of current thinking may be helpful in order to put auditory memory in perspective (see also 3.2, 3-3)_ Potter (1990) distinguishes between three kinds of short-term memory: iconic, very short-term conceptual, and short-term verbal memory. Potter notes that these three types Of memory are subject to differing types of interference and differing rates of forgetting. Iconic memory serves as a short-term visual buffer. It recognizes objects in 200 to 300 milliseconds and then holds that information for about 200 milliseconds. Very short-term conceptual memory receives scenes from iconic memory and stores diem temporarily in conceptual form. These memories are not interfered with by iconic memory, but may be by other conceptual tasks. Very short-term conceptual memory decays in about I second. If these concepts are not embedded into a train of thought, they are lost. Finally, we have short-term verbal memory. This memory consists of an auditory buffer, which is severely limited in its capacity but may be maintained by continuous rehearsal. Its capacity is about 1.3 to 1.7 seconds, and its decay rate is nearly the same, allowing us to "replay" words or sounds heard a short time before. Meaningful background noise can interfere with verbal memory, and because this buffer is used for understanding written text, interference between the two channels may be experienced. This relates to the multichannel theories of learning that will be discussed later.

Potter (1990) stated that long-term memory may have three forms corresponding to the three forms of short-term memory. The dominant form of long-term encoding is conceptual, but visual and auditory long-term memories are also available. One implication of this conception of memory is that the extremely limited capacity of short-term memory implies that we should limit the number of chunks to be associated at any one time to three or four and that these not be redundant, because the short-term conceptual and verbal buffers are so vulnerable to interference. There is no reason to believe that information stored in any of one of the three short-term memories is more likely to be remembered because it was in that memory.

28.2.2 Early Comparison Studies

There have been many attempts to compare the relative instructional effectiveness of material presented through an audio or through a textual or visual medium. Erickson and King (1917) performed one of the earliest studies of the effectiveness of the auditory medium. Four groups of students from thud to ninth grade were chosen, and each group was divided in half One-half received the lesson from silent reading, whereas the other half was given similar material orally by the teacher. The following day, the order was reversed as to which half would read or listen. This procedure was followed two more times, for a total of four lessons. At the third- and fourth-grade level, the median score of the oral group was much higher than the medians of the group that read. At the fifth- and sixth-grade levels, the results were inconclusive. At seventh-, eighth-, and ninth-grade levels, the medians of the oral groups were much higher than in the groups that read the lesson. Needless to say, in these early studies experimental design was not what might be desired. Specific variables such as teachers' skill and interest were not taken into account nor was the subject matter. Also, the only datum that was examined was the median score of the group.

Worchester (1925) tested 13 students to see whether oral or reading presentation of connected material was remembered better after I day, 2 days, and 7 days. In spite of methodological shortcomings, die author concluded that neither medium has a marked degree of superiority in the rate of learning of meaningful connected material.

The relative effectiveness of visual and auditory presentations of advertising material was studied by DeWick (1935). A group of 73 college students was divided into two groups. Three presentations of audio and visual advertisements were based on real advertising found in current magazines and on radio. One group heard the advertisement; the other looked at it in the booklet form. The auditory and visual advertisements were different. Time was held constant. After the experiment, the students were asked to write the names of products in order of presentation and then to describe the content. Next, the groups were switched and the same procedure followed. Five months later, all students were given the opportunity to recall the advertisements presented in both media. DeWick reported that: (a) The auditory presentation was superior in the recall of trade names after a delay of from 5 days to 5 months; (b) in immediate recall, both were similar; (c) recall was progressively weaker with visual presentations; (d) recall of ideas expressed in the advertisements was greater with the auditory method than with the visual.

Stanton (1934) conducted a follow-up study of DeWick, whose work was unpublished at the time. The auditory presentation was given without embellishments, such as music, and the visual material was presented without illustrations or other attention-getting devices. The same procedure was followed as in DeWick's study. Recall and recognition tests were given at three time intervals: I day, 7 days, and 21 days. The auditory method of presentation was superior. Recall was highest for auditory presentations at 7 days, and recognition was highest at 21 days.

The above studies addressed memory, but they did not investigate comprehension. Young (1936) tested comprehension with 2,000 intermediate students from Iowa and Texas. Four modes were used to present the material: (a) The teacher read aloud to students; (b) teacher read aloud and students read the selection silently; (c) students read selection once; and (d) students read for the time allotted the teacher to read orally. At the end of each presentation, a comprehension test was given; a delayed test was given I month later. Young reported that the students got very little information from an oral presentation and remembered even less after a month. However, the oral presentation was more effective than either of the silent reading, both immediately and after a month. He also found that the children who do poorly in comprehending through reading also do poorly in comprehending through hearing.

Larsen and Feder (1940) asked whether psychological abilities differentiate between the processes involved in reading and listening comprehension. After hearing and reading selected materials that varied in difficulty, 151 students were given both reading and listening comprehension tests. On these tests, there was a superiority of performance on reading comprehension over listening comprehension. However, this superiority depended on the aptitude of the student. Students with lower aptitudes tended to show equal results in listening and reading. The higher-ability groups showed a superiority in the reading comprehension tests. The authors concluded that comprehension is a central function operating independently of the mode of presentation. This study foreshadows modern results that emphasize the relative effectiveness of auditory presentations for students, who, for age or other reasons, do not read well.

In general, these studies, whatever their shortcomings, indicate that auditory presentations can be at least as effective as live or print presentations and are practical alternatives to conventional instruction. Under certain circumstances, especially when the materials are well prepared, auditory presentations may be superior.