Media, mental imagery, and memory

Media, Mental Imagery, and Memory

Robert L. Clark

Robert L. Clark is assistant professor of mass com- munications in the Department of Mass Commumca- tion, Central Missouri State Umversity, War- rensburg MO 64093.

Recent research indicates that the human information-processing system can gather and store a limited amount of information at any one time. An individual receives stimuli in many forms: auditory, verbal, visual and others, and combinations of these. Stimuli can be presented by single and multiple-channel media; in multichannel presentations interference affects processing and retention. Thirty-two students at the University of Oregon were tested to determine the effects of media on mental imagery and memory. The model incorpo- rates a dual-coding hypothesis, and five single and multiple-channel treatments were used.

ECTJ, VOL. 26, NO. 4, PAGES 355-363 ISSN 0148-5806

One new area of educational research con- cerns the effects of media on mental imagery. The effects of mental imagery on retention are well known; mental imagery is the chief mnemonic device used by those who perform astonishing memory feats. The purpose of this study is to formulate a model of memory that examines the effects of visualization. Such a model could be used to predict the effect of media presentation on mental imagery and learning.

Media research during the past decade indicates that the effectiveness of a presentation depends on the material and the learn ing object ives . No longer is one medium considered intrinsically superior to all others. Educators now have a variety of media available to them; they need only select the best medium for the job. Choos- ing the right one is not always easy because the medium most effective with specific material is not always obvious. Many educators still feel that multichannel media are more effective than s ingle-channel media because of the greater involvement of the individual student. This view fails to consider the way students process mental images. Such a view also seems to conflict with studies indicating that the individual may not be able to process all the stimuli made available t h r o u g h mul t i channe l media.

A closer look at the s t u d e n t ' s information-processing mechanism pro- vides guidelines for selecting the medium best suited to the learning objectives. Re- cent research suggests a model of the human information-processing mechanism

356 EDUCATIONAL COMMUNICATION & TECHNOLOGY [] WINTER 1978

which may be useful to the media specialist in determining which channel or channels to use and what their content should be.

During the last 20 years there has been enough research to indicate that the capacity of human information processing is limited. Broadbent 's model (1958) of the information-processing system used a fil- tering mechanism to keep incoming stimuli from exceeding the capacity of the system. According to Broadbent's model, the filter selects from the stimuli available those which are most expedient and passes them on for processing while it rejects all other stimuli. Broadbent (1971) modified some of his earlier conclusions but still accepted the idea of a filter which protects a processing system of limited capacity.

Treisman (1969) proposed a system using an attenuator rather than a filter. Her model proposes that rejected stimuli are not blocked from the processing system but are processed at a lower level. For example, subjects listening to a message presented to one ear can pick up the same message when it is shifted to the other ear. They can process the entire message, with- out missing any words, even while random sounds are presented in the opposite ear. Treisman's model attempts to explain how such information processing occurs.

Travers (1966) designed and tested a model using different media; he theorized that the system jams when overloaded with incoming stimuli and information is lost. In a later work Travers (1970) pointed out two limits on the system's capacities: (a) a limit of how much information the system can process at one time, and (b) a limit of how much the short-term store (one component of the system) can hold.

The work of Broadbent, Treisman, Trav- ers and others consistently indicates that the human information-processing system has limited capacities for assimilating incoming stimuli. But, how the media spe- cialists can translate findings produced under experimental conditions to real-life instructional situations is not clear. The consistency of these studies makes one wonder if involving all the senses in in- struction produces greater learning.

Recent studies also indicate that subjects use the same mechanisms in mental im-

agery as they use in processing incoming stimuli. Brooks (1967) found that reading descriptions interfered with imagining the spatial relationships being described. He found that subjects performed better when listening to descriptions than when reading descriptions themselves. Atwood (1971) found that a visual-interfering task hindered visualization more than an auditory-interfering task. Atwood also found that the auditory-interfering task caused more interference with learning abstract (nonvisual) material than did the visual-interfering task. Bower (1970) found that a visual-tracking task interfered more with visualization than did a tactile- tracking task.

The work of Brooks, Atwood, Bower and others supports the idea of separate sensory systems with shared imagery compo- nents. Paivio (1971) explains the mnemonic effect of mental imagery in a dual-coding theory: verbal and spatial (visual) codes can be stored in the long-term memory and an item that is stored in both forms is more accessible to retrieval.

Four basic points have been gathered from the literature for inclusion in a model of memory and mental imagery:

1. The human learning mechanism has definite limits as to the amount of information that it can process at one time.

2. The human learning mechanism also has limited storage capacity in what is called the short-term store.

3. Visual tasks interfere with the formation of visual images.

4. The dual-coding theory explains the mnemonic effects of mental imagery on learning.

DEVELOPING A MODEL

In the typical information-processing model raw sensory stimuli enter a sensory register where they exist only for a few seconds. After encoding, this information is kept in the short-term store, where it is subject to rapid decay if not maintained by repetition. Through repetition or other processes, information may be kept in the long-term store and not subjected to rapid decay, since the long-term store has no known capacity limits. It is generally con-

MEDIA, MENTAL IMAGERY, AND MEMORY 357

sidered that for material to be called back from the long-term store it must pass through the short-term store to be remem- bered or compared with incoming stimuli.

The model in Figure 1 is concerned only with auditory and visual input and was designed to be consistent with findings of the experiments previously summarized. Both visual perception and visual imagery use the same channel but a separate channel is indicated for processing auditory and verbal stimuli. The separation of these func- tions is consis tent with work among b ra in -damaged individuals and other studies done by Klatzky and Atkinson (1971) which indicate specialization of the right and left halves of the brain in processing visual-spatial and auditory-verbal information. The model also uses the same channels for forming imaginal representations of sensory inputs.

The dual-coding theory is also repre- sented in this model. The model shows separate paths for coding and storing ver-

bal and spatial representations in memory. Both codes may be kept in the long-term store, thus effectively increasing the amount of information available at the time of retrieval.

Stimuli entering the system from the auditory and the visual senses are coded in the sensory registers for entrance into the system. After coding, the stimuli are transferred to the short-term store for processing. In the model, the auditory-verbal stimuli enter the top half of the short-term store where they are interpreted by com- parison with internal representations in the long-term store. The system determines whether the verbal stimuli are concrete (representations of visual-spatial stimuli) or abstract. If the stimuli evoke concrete images, the corresponding spatial representations may be brought from the long- term store into the visual-spatial portion of the short-term store. This process is re- ferred to as visualization.

In the model, visual stimuli entering the

FIGURE 1 A Model of the Aud#ory and V~sual Memory System Based On Dual-Coding Theory

RESPONSE OUTPUT

STIMULUSI~ INPUT/ l

AUDITORY SENSORY REGISTER

STIM U LUSiSiS~ VISUAL �9

AUDITORY VERBAL RESPONSE GENERATOR

SHORT-TERMtSTORE

, I AUDITORY-VERBAL sYsw I"

_ I(ALSO AUDITORY-IMAGERY) I .

'I ~ I" r" VISUAL-SPATIAL

SYSTEM

I RESPONSE OUTPUT ~ [

(ALSO VISUAL IMAGERY)

VISUAL-SPATIAL RESPONSE GENERATOR

LONG-

TERM

P

t" STORE


system are encoded in the visual sensory register and transferred to the lower half of the short-term store for processing. Here the determination must be made whether the stimuli are verbal or nonverbal (spatial). Nonverbal stimuli may be processed directly for storage. Verbal stimuli must be transferred to the auditory-verbal portion of the short-term store for further interpre- tation. Once transferred (by calling up the proper representations from the long-term store), these stimuli are processed in exactly the same way as auditory-verbal stimuli. Thus, as more steps are added in processing the print, visual channel space in the short-term memory is used up, effectively reducing the amount of space available for visualization.

THE HYPOTHESES

Five hypotheses were designed specifically to test the effects of media presentations of concrete-verbal and visual information:

1. Images presented in other than direct form will be more difficult to recall than images presented directly. Verbal descriptions will be less effective than seeing the object.

2. Nonredundant visual information re- duces short-term memory capacity, result- ing in a reduction of memory for visual forms presented by auditory-verbal descriptions.

3. Multiple-channel presentations of redundant information are superior to (a) single-channel presentations and to (b) nonredundant multiple-channel presentations.

4. The processing of visual stimuli, other than direct stimuli, will reduce the channel space for creating mental images. Auditory presentation alone will be more effective than either print or auditory presentation with a nonredundant visual stimulus.

5. Visual-verbal stimuli will use more of the channel space than nonredundant visual stimuli, thus reducing the space available for creation of mental images. Print will be the least effective means of presentation for spatial information.

To test these hypotheses, students received a set of geometric designs, presented verbally or by spatial representation

(drawings of the designs). (Because of the spatial nature of the designs, it was predicted that spatial representation would be more effective.) Two presentations (treatments) were made using the drawings of the designs. In one, each drawing was presented by itself; in the other, a drawing was presented simultaneously with an auditory-verbal presentation. Effectiveness of presentation was judged by comparing the subject's reproductions of the designs with the originals.

According to the dual -coding hypothesis, the combination multichannel presentation would be the most effective. However, advocates of the interference hypotheses predict that the single-channel, auditory treatment would be the most effective of the verbal presentations because the visual channel in these presentations (being nonredundant) would interfere with visualization of the designs. The amount of interference would depend on the channel space used for the visual. Since the nonredundant visual used with the auditory presentation is really unnecessary, it can be filtered out and would not produce as much interference as the processing of prints with the printed-verbal presentation.

Therefore, subjects should respond to the presentations in the following order (from most effective to least):

1. Multiple-channel redundant presentation.

2. Visual-only presentation (spatial representation).

3. Audio-only presentation of verbal descriptions.

4. Presentation of auditory-verbal descriptions with a nonredundant visual (i.e., the instructor).

5. Printed word descriptions of spatial relationships.

PROCEDURE

Sixty students were selected randomly from two basic broadcasting courses at the University of Oregon. This number repre- sented one-third of the students in the courses. Of the 60 students, 41 volunteered for the experiment and 32 were ultimately


tested in hour- long individual sessions. Most students were sophomores.

Instructions for drawing geometric designs were given in five different treatments representing single and multiple- ch.annel media: (a) visual-only presen- t a t i o n s - s h o w i n g the design; (b) printed instructions for drawing the designs; (c) auditory descriptions; (d) auditory descriptions with simultaneous visual presentation of the design; and (e) auditory instructions while showing the person giving the instructions.

The Lieb Geometric Design Test (1960) was used in this experiment. Fifteen Lieb designs were randomly selected: five from her moderately difficult category and ten from her most difficult category. Verbal descriptions written for each design were tested on the subjects for accuracy of com- munications. Subject feedback was used to refine the descriptions so that the instructions could be easily understood. Figure 2 shows descriptions and drawings of the designs.

Videotape and audiotape were used for storage and dissemination of the messages except for the printed descriptions which were recorded in booklets. To make it easier to compare the results later and to make the subjects rely on memory, the booklets were arranged with one sentence per page and subjects were not allowed to turn back once they had turned a page. The same words were used in all verbal presentations and the same audio track was used for all aud i to ry-channe l presentat ions . Subjects were given a short practice ses- sion before the experiment so they would know what to expect and would under- stand the terms used.

The 32 subjects were presented the designs and tested individually. Each subject received 15 designs, three by each treatment. After the presentation of each design the subject was given a sheet of paper on which to draw the design. After complet- ing all the designs subjects were asked about the experiment. In response to one question, "How did you remember the designs that you did not see?," all subjects but one said they visualized the design as it was described.

After the question period the subjects

were tested for recognition of the designs. Thirty cards were shown, 15 with the designs and 15 with distractors randomly selected from Lieb designs not used in the experiment. The subjects were asked to identify which designs they had seen previously.

The designs were r a n d o m l y rota ted through the treatment for each subject. This control eliminated differences that might be caused by variation in the diffi- culty of the designs. All subjects received all treatments in a repeated-measures experimental design which effectively con- trolled inter-subject differences in ability to work with the designs.

A stopwatch was used to record the time spent reading descriptions and viewing the visual-only presentations (subjects were not required to view the design for the full time it was on the screen in this presentation). Time spent on all other presentations was the same for all subjects.

THE RESULTS

The subjects' reproductions were scored by three judges following these instructions:

Comparisons must be made on the following basis. One point should be given for each error when the reproductions differ from the originals in any of the following respects. 1. If a part is missing, added, or changed for a

different part; 2. If two parts are not in the right relahonship to

each other (not touching, above when it should be below, etc.), one point for each part should be given;

3. If parts are reversed (wrong area shaded in), one point should be given for the reversal, not for each part reversed.

Some of the errors may fall into two or more of the foregoing error categories. However, it does not matter which category you put the error into. One point only is scored for each error.

The analysis of variance on the immediate recall test for treatments was significant at the .001 level. A Newman-Keuls Sequential Range Test was performed to find which t reatments differed significantly. The results are presented in Table 1. Recognition test results followed the same pattern as the immediate recall test.

350 EDUCATIONAL COMMUNICATION & TECHNOLOGY [] WINTER ]978

TABLE 1

Newman-Keu ls Sequent ia l Range Test on Recall S c o r e s

Mean differences

G ro up" Mean D V A I

P 22.47 18.55** 8.53* 1.25 I 22.19 18.25"* 8.25* .97 A 22.22 17.28** 7.28* V 13.94 10.00"* D 3.94

.28

ap = print, I = audio-visual instructor, A = audio-only, V = visual-only, D = audio-visual design. Lowest mean indicates best performance.

*Significant at .05 level. **Significant at .005 level.

The auditory-visual presentation showing the design was significantly higher than all other treatments as predicted by the dual-coding hypothesis. The visual- only presentation was second, as was ex- pected; it was significantly better than the print and the audiovisual showing the instructor and the audio-only. No other differences were significant.

Though the difference between audio- only presentation and print was not significant, data collected show that subjects spent on the average nearly 30 percent more time reading descriptions than listening to them. The difference in the analysis of variance favoring audio-only presentation along with the time data definitely supports the hypothesis of interference of print with visualization.

The model's prediction of the compara- tive effectiveness of the treatments proved correct in this experiment. The dual-coding hypothesis is one of two possible explana- tions for the difference between visual- only and audiovisual design presentation. The other factor which could account for the difference is the variation in time spent viewing the designs in these treatments. For the visual-only treatment, subjects on the average spent only one-fifth the time viewing the design as they did in the mul-- tichannel presentation. Further research is needed in this area to determine which ex- planation is correct.

RECOMMENDATIONS

All of the hypotheses received some sup-

port from the data collected. However, the model needs further testing with a few ad- ditional controls. The Lieb Geometric De- sign Test seems to be a useful instrument for testing media effects on mental imagery.

If this model could be further substan- tiated through more extensive experi- mentation, it could prove very useful to the media specialist in determining which medium to use and how to use it to produce the greatest learning.

REFERENCES

Atwood, G. An experimental study of visual imagination and memory. Cognitive Psychol- ogy, 1971, 2, 290-299.

Bower, G. H. Analysis of a mnemonic device. American Scientist, September-October 1970, 58, 496-510.

Broadbent, D. E. Decision and stress. London: Academic Press, 1971.

Broadbent, D. E. Perception and communication. Oxford: Pergamon, 1958.

Brooks, L. R. The suppression of visualization by reading. The Quarterly Journal of Experi- mental Psychology, 1967, 19, 289-299.

Klatzky, R. L., & Atkinson, R. D. Specialization of the cerebral hemispheres in scanning for information in short-term memory. Perception Psychophysics, 1971, 10, 335-338.

Lieb, B. The relationship between some aspects of communicative speaking and communicative listening in freshmen men and women. Unpublished master's thesis, Pennsylvania State University Graduate School, 1960.

Paivio, A. Imagery and verbal processes. New York: Holt, Rinehart and Winston, 1971.

Travers, R. M. Man's information system. Scran-


ton: Chandler Publishing, 1970. Travers, R. M. Studies related to the design of audio

vzsual teaching materials: final report. Washington, D.C.: U.S. Department of

FIGURE 2 Designs and Written Descriptions

Health, Education and Welfare, 1966. Treisman, A. M. Strategies and models of selec-

tive attention. Psychological Review, 1969, 76, 282-299.

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FIGURE 2 (continued) Designs and Written Descriptions

Number one. (Pause 4 sec.)

Draw a triangle with three equal sides. Now draw two l ines--one from the center of the left side of the triangle straight down to the base and one from the center of the right side of the triangle straight down to the base. Now connect the tops of these two lines with another line, so that you will have a square inside the triangle. Shade in the area to the right of the square inside the triangle. Now, draw two lines that cross in the center of the square from corner to corner.

Number two. (Pause 4 sec.)

Draw an equal-sided triangle. Shade in the triangle. Using the right side of the triangle draw a parallelogram sitting to the right of the triangle which is twice as long as it is high. The base of the parallelogram and the base of the equal-sided triangle make one long line. Find the center of this line and draw a line straight down about two-thirds of the height of the parallelogram. Now, draw two straight lines from the ends of this line to the bottom corners of the parallelogram. This will make two right t r iangles--one on each side of the line. Now, from the center of the line between the two triangles draw a line across each triangle at 45 degrees from the center line and down to the opposite side of each triangle. Using the top of the parallelogram as a base draw a right triangle above the parallelogram the same height as the parallelogram with the right angle on the right side.

Number three. (Pause 4 sec.)

Draw a square so that it is sitting on one corner like a diamond. Inside the square draw a rectangle that is twice as wide as it is tall. The corners of the rectangle should touch the edges of the square. Shade in the area inside the rectangle. At the ends of the rectangle there are two triangles formed by the corners of the square. Divide each of these triangles in half by drawing a line from the corner of the square to the line forming the end of the rectangle.

Number four. (Pause 4 sec.)

First, draw a circle. Shade in the area within the circle. Next, around the circle, on three s ides-- left, right and on top - -d raw three connechng straight hnes, close to but not touching the circle, so that if the bottom line were added it would make a square. Using the line to the left of the circle make a square sitting to the left of the circle. Make a square sitting to the right of the circle using the line at the right of the circle. Make a square sitting above the circle using the line above the circle. Next, divide each square in half with a line from corner to corner. The left and right squares are divided in half with lines running from the bottom corners next to the circle to the top corners away from the circle. The top square is divided with a line from the bottom left-hand corner to the top right-hand corner.

Number five. (Pause 4 sec.)

Draw three circles the same size sitting side by side and touching. Shade in the area within the circle on the right. Then, draw a rectangle around the three circles touching their edges. Divide the rectangle into a top and bottom half by drawing a line through the middle from side to side. Now, draw two more lines through the rectangle from corner to corner.

Number six. (Pause 4 sec.)

Draw a square. Divide the square into four equal parts with a line running from the top to the bottom and another running from side to side. Make another square inside the large square by connecting the ends of the crossing lines. Shade in the area above and to the right of the new square within the larger square.

Number seven. (Pause 4 sec.)

Draw two circles the same size. They should be placed beside each other so that there is room for three more circles the same size between them. In each circle draw a line across the diameter from side to side. In the circle on the left draw a line from the center to the bottom. Draw a.straight line from the top of one circle to the top of the other circle. Draw two perpendicular l ines--one at each end of the line on top of the circles. The perpendicular lines should be slightly longer than the diameter of the circles. Now, draw two straight lines sloping down from the tops of the perpendicular lines to meet at the center of the line on top of the circles.

MED~A, MENTAL IMAGERY, AND MEMORY 363

Number 8. (Pause 4 sec.)

Draw two equal size c i rc les--one above the other and touching. Inside each make a square that has its corners touching the circle. Shade in the area above the square in the top circle. Divide the square in the top circle in half with a line from its upper left-hand corner to its lower right-hand corner. Shade in the area to the right of the square in the bottom circle. Draw a triangle in the square in the bottom circle by drawing two lines from the left-hand corners to the center of the square.

Number 9. (Pause 4 sec.)

Draw a circle. Inside the circle draw an equal-sided triangle with its points touching the circle. The upper left-hand corner of the square draw a line to the c i rc le--d iv id ing that area in half. Inside the circle draw another circle, centered so as to form a letter "O". Now, inside the smaller circle draw another circle making a smaller letter "O". Shade in the area between the smallest circle and the next larger circle. Inside the smallest circle make a cross, with one line from top to bottom and one line from side to side.

Number ten. (Pause 4 sec.)

Draw a circle. Inside the circle draw an equal-sided triangle with its points touching the circle. The triangle should be pointed up. Shade in the area inside the circle to the right of the triangle. Now, draw two lines from the bottom two corners of the triangle to the center of the sides opposite the corners.

Number eleven. (Pause 4 sec.)

Draw two circles the same stze--placed beside each other so that there would be room for three more circles the same size between them. Divide each of the circles in half with a line running from its top to its bottom. Shade in the right half of the circle on the right. Connect the tops of the ctrcles with a straight line. Connect the bottoms of the circles with another straight line. These two lines together with the lines dividing the circles in half form one long rectangle. Using the line resting on the tops of the circles as a bottom make a parallelogram the height of the circles' diameters sloping slightly to the right. Divide the parallelogram in half with a sloping line in the center forming two smaller parallelograms. Divide each half in half again with two more sloping lines.

Number twelve. (Pause 4 sec.)

Draw two ctrcles the same size one above-the other and touching. Shade in the bottom circle. Divide the top circle in half with a line from top to bottom. Shade in the right half of the top circle. Draw a square the same size as the top circle sitting to its right and touching it. Divide the square in half with a line from the lower left-hand corner to the upper right-hand corner. On the left of and touching the bottom circle draw an equal-stded triangle pointing away from the circle. The triangle's sides are the same size as the circle's diameter. Divide the triangle in half by drawing a line from its point to the side touching the circle.

Number thirteen. (Pause 4 sec.)

Draw a rectangle that is about four times as long as it is high. In the center of the rectangle draw a circle that touches top and bottom of the rectangle. Make a cross inside the c i rc le - -by drawing one line from top to bottom and another from side to side. Draw a second rectangle below the first one. The first one should rest on top of the second one so as to form a "T". The second rectangle is about one-half as wide as the first one is long and about twice as high as it is wide. In the center of the second rectangle draw a circle. The circle should touch both sides of the rectangle. Divide the circle in half with a line from top to bottom. Shade in the left half of the circle.

Number fourteen. (Pause 4 sec.)

Draw a square. Shade in the area inside the square. Using the square's bottom line draw a rectangle one-half as high as it is wide below the square. Divide the rectangle into four parts with two lines from corner to corner crossing in the center of the rectangle.

Number fifteen. (Pause 4 sec.)

Draw a rectangle three times as wide as it is high. The rectangle should be standing on tts lower right-hand corner, so that it slopes 45 degrees to the left. Inside the rectangle draw three circles that completely fill the rectangle-- touching on all sides. Divide the left and right circles in half with lines from top to bottom. Shade in the right half of the left circle. Divide the center circle in half with a line from side to side.

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Media, mental imagery, and memory