British Journal of Educational Technology. VO121 NO 3 1990. 215-225. Using extended captions to irnprove learning from instructional illustrations. Robert M ...
British Journal of Educational Technology
VO121 NO 3 1990
215-225
Using extended captions to irnprove learning from instructional illustrations Robert M Bernard Dr Bernard is an Associate Professor in the Department of Education (Educational Technology) at Concordia University, 1455 de Maisonneuve Boulevard West. Montreal. PQ. Canada, H3G 1 M 8 .
Abstract This article examines two strategies for improving the effectiveness of illustrations in text. Descriptive captions repeated the contents of illustrations verbally, whereas instructive captions focused learners' attention on salient features of illustrations without descriptive text. Contrary to much of the literature on pictures and prose, these illustrations provided information that did not overlap the main body of text. 'Two measures of learning outcomes were used: one which assessed learning from the illustrations alone and one that assessed learning from the verbal text alone. Results favoured the caption conditions over the illustration-only condition. However, no additive effects of the captions were observed. In addition, the illustration plus descriptive caption condition outperformed the descriptive caption condition alone and the memory for accompanying text did not suffer from the presence of the illustrations or captions.
Introduction Illustrations and pictures in text are so ubiquitous and appealing that at first glance it may seem odd that so much research effort has been directed towards establishing their validity as accompaniments to instructional text. Enough studies have been conducted and reviewed (Levin and Lesgold, 1978; Levin, Anglin and Carney, 1987; Levie and Lentz, 1982)to conclude that ihstrations and pictures facilitate the learning of textual content when the content of text and illustrations overlap. In a majority of these studies it was the contribution of illustrations to text that was under scrutiny-that is, their supportive role (Duchastel, 1978) as captions to print-based instruction. In only a few cases has the intrinsic value of illustrations been the point of inquiry, and findings in these few studies have sometimes yielded disappointing results (eg Jahoda et al, 1976). Weidenmann (1989)suggests that the supportive role, upon which most past research illustrations is based, should be viewed from the reverse perspective. What contribution can the text make to learning from pictures? On a n intuitive level, this question is
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answerable by considering the need, in a vast majority of cases, for captions to support illustrations. Captions provide context, and to some extent can explain pictorial relationships, but most that are used in actual textbook materials are not developed sufficiently to offer learning support or to help students unravel complex visual relationships (Brody, 1982). Reference to illustrations in text (eg see Figure X) is one mechanism commonly used to cue readers to their presence and importance, but it is hard to see how these sparse references can contribute to pictorial learning. Studies of more elaborate global instructions to examine illustrations (eg ‘the information contained in the illustrations is as important as information contained in text’) have failed to produce better pictorial learning than conditions without such instructions (Hayes and Readance, 198 3 ; Moore and Skinner, 1985: Gram, 1987). Clearly there is a need to investigate technique that will increase attention and produce better memory and understanding of illustrations, when they are designed to be independent of text. Two studies employed different types of captions to achieve this purpose. Holliday ( 19 76) found that students learned more from a complex illustration with ‘instructive questions’ appended, than from the illustration alone, from text alone or from combined text and illustration. Holliday suggested that the illustrations were too complex for a verbal description to be useful. In the second, Weidenmann (1989) compared three conditions of image processing instructions: ( a )imagination instructions (eg ‘Imagine you had to play the leader in that study etc.’);(b) picture-oriented instructions (eg ‘Noticehow different the leader behaves in the two pictures etc.’ and (c)no instructions. Results favored the condition ieceiving picture-oriented instructions on both an overall recall measure and a picture-only subscale. Together, these two studies suggest that more elaborate instructions than those typically designed to accompany illustrations are necessary to cue the reader to significant aspects of illustrations. This study examined two kinds of extended captions, each designed to increase picture learning. but in different ways. Instructive captions did not contain picture content, but were designed to encourage closer examination of the illustrations. Descriptive captions reiterated the important aspects of the content of illustrations, without telling the learner how to ‘read’ the illustration. Both instructive and descriptive captions were expected to produce greater recall and understanding than the illustration alone. Two additional questions were formulated to attempt to validate the findings of previous research. The first was whether memory for textual content not covered in the illustration would be affected by the presence of illustrations and captions. Previous studies where separate measures of text-relevant and picture-relevant recall were used have indicated that the presence of pictures does not detract from learning non-pictured text (Peeck, 1980: Sewell and Moore, 1980). The second question, that has appeared repeatedly in the literature, is whether the presence of text-relevant illustrations enhances recall of subject matter.
Extended captions to improve illustrations
2 17
Method Sarnple The sample consisted of 143 nursing students enrolled in a junior college in western Ontario. They ranged in age from 18 to 2 1 years and were tested in their regular classroom setting. Subjects were randomly assigned to six treatment conditions.
Design The primary design was a 2 x 2 factorial (see Figure 1).The two independent variables were the presence or absence of instructive and descriptive captions to the illustrations in text. Descriptive captions were operationally defined as short paragraphs explaining the most salient features in the illustrations. They repeated the contents of the illustrations as much as possible. Instructive captions were defined as a short set of directions on how best to approach learning from the illustration. These captions contained no content information, and were intended to activate a process of examining the illustrations in detail. One group received both descriptive and instructive captions, two other groups received one or other caption alone, while a fourth condition received neither. This level served as a control group to the design, to determine the relative potency of the caption conditions compared with the illustrations by themselves. Two additional control conditions that lay outside of the main design served as aids to interpretation. These groups are shown on the right side of Figure 1.One control group received the descriptive treatment only without the illustrations, to help determine the
factorial design instructive caption present
control conditions (non-illustrated)
instructive caption absent
descriptive caption present
descriptive caption present
descriptive caption absent
descriptive caption absent
Figure 1: Design of the study
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contribution of the illustration to the caption passage. This condition, when compared with the illustrated, descriptive caption condition, provided a contrast similar to those appearing in the standard picture-prose literature. Another, a baseline condition, received neither captions nor illustrations. Although technically these control groups could have been included in the main design, their presence would have biased the primary analysis by almost guaranteeing, because of their nature, the presence of a two-way interaction. As a result, they were assessed independently through separate analytical comparisons with the illustrated conditions (Keppel, 1983).
Materials Instructional text: A specially developed unit of instruction, entitled ‘The Nature of Pain’ was written and pilot tested. The content for the unit was derived from texts and articles on pain and pain management (Melzack, 1966) and was checked for accuracy by a physician who is a n expert in this area. The main text was about 18 5 0 words in length, exclusive of the captions. Four illustrations were developed to accompany the text and were placed at roughly equal intervals in the unit. The first was an ‘analogical’ illustration (Knowlton, 1 9 6 6 ) depicting the ’felt-self’.and showed in pictorial form the relative proportions of nerve endings in various parts of the body that cause a toothache, for instance, to hurt more than a leg cramp. The second illustration was a literal picture of ’the pathway of pain’, that showed, through cross-sectional drawings and blowups, the various components in the skin, the spinal cord and brain that are involved in sensing, transmitting and interpreting pain. The third illustration was a flow diagram that depicted ‘the ulcer cycle’ and its physiological components. This illustration used standard boxes and arrows to show the components of the cycle and the direction of their emergence. The final illustration was a diagram depicting the characteristics of organic, psychosomatic and psychogenic pain. Darkened, half-darkened or shaded squares were used to indicate whether the characteristics of pain (eg a clear-cut onset) were absent, present or sometimes present in each pain category. Different types of illustrations were used to improve the ecological validity of the instructional unit, and to match the instructional function of the text to the most appropriate form of representation. Descriptive and instructive captions: Descriptive and instructive captions (see Figure 2 ) were developed for each illustration. The descriptive captions contained information and description that overlapped the illustration as exactly as possible. In conditions containing this caption, the illustration performed the function of reiteration (Duchastel, 1978). The descriptive captions were positioned just after the relevant illustration. The instructive captions were designed to aid in processing the illustration, by suggesting possible ‘pathways’ through the illustrations. They did not contain any
Extended captions to iniprove illustrations
Legend:
,Instructive
m
Caption
11
Descriptive Caption
S t u d y t h e d i a g r a m c a r e f u l l y . L o c a t e t h e name and main p a r t s o f t h e n e r v o u s s y s t e m i n c l u d e d i n t h e i l l u s t r a t i o n . Next, t r a c e t h e painprocess representedstep-by-stepinthedirectionofthe a r r o w s . W h i l e y o u t r a c e t h e r o u t e , d e s c r i b e it i n yourownwords t o h e l p you r e m e m b e r i t .
2 19
...
Cerebral cortex (registers pain)
Limbic system motion and m e w )
(moremen! cenier)
Spinalmrd
The neuron c o n s i s t s o f a c e l l body, a n u c l e u s , axons and d e n d r i t e s . Dendrites r e g i s t e r t h e impulses - t h e y a r e t h e ' r e c e i v e r s ' , i f you l i k e . T h e w o n s c o n d u c t t h e i m p u l s e s a c r o s s t h e s y n a p s e (thegapbetweentheneurons)t o o t h e r p a r t s o f t h e nervous s y s t e m - t h e ' s e n d e r s ' . T h e s h e a t h w h i c h s u r r o u n d s t h e axon c o n t a i n s a s u b s t a n c e , m y e l i n , w h i c h a f f e c t s t h e s p e e d a t which t h e e l e c t r i c a l i m p u l s e s can b e c o n d u c t e d . First-order neuronawithathickrnyelin sheath, c a r r y i n f o n n a t i o n a b o u t s h a r p pain, while second-ordernouronswithathinmyelin s h e a t h a c t a s a slow pathway f o r d u l l p a i n . Both pathways t r a v e l up t h e spinalcordandterminateinthethalamuawherethe s i g n a l 9 a r e distributedtothecerebralcortex (where p a i n i s r e g i s t e r e d ) , t o t h e l i m b i c s y s t e m (whereemotions andmemoryis a r o u s e d ) and t o t h e basal ganglia (where movement o r i g i n a t e s ) .
Figure 2: Sample illustration showing the instructive and descriptive captions
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content information. Because these captions could not stand on their own without the illustration. they were not tested alone, as were the descriptive captions.
Instruments:Two measures were developed to assess learning achievement. One was a thirty-item multiple choice test of factual content eg ‘A patient describes his/her pain with a clenched fist. This is a n example of: ( a )the pathway of pain; (b)the ‘felt-self’;(c) the pantomime of complaint: (d) the learned nature of pain: (e) the cycle of pain. The other was a 10-item cued recall test (eg What is the relationship between the physical self and the ‘felt-self’!). These instruments were pilot tested on a sample of 1 1 5 students and modified on the basis of their responses. The two instruments were collapsed into a single measure for the purpose of analysis. Twenty-thrce of the 40 items (henceforth called picture items) were specific to information contained in the illustrations and their captions. Five of these questions were in a picture format (Szabo, Dwyer and DeMelo, 1981).The remaining 1 7 items were specific to the verbal portion of the unit which surrounded the illustrations (henceforth called verbal items). Since no experimental manipulations were involved which would affect these items differentially, their means were not expected to differ from group to group. These items, in fact, formed a natural means for checking selection bias within the design. The comprehension portion of the Nelson-Denny Reading Test was used to control for variation due to inter-subject differences in reading ability. This test requires 20 minutes to administer and is considered a valid measure of reading ability for young adults. Scores on this reading measure were used as a covariate in the design, to reduce unexplained variation in the design. Pror.edure The experimental materials were administered to nine intact groups in their regular English or Social Sciences classes. Since the experimental task was individualised, materials were randomly assigned to subjects within these classes. All sections of the experimental procedure were monitored and timed by two research assistants. After the Nelson-Denny Reading Test was administered, subjects were instructed to read and study the experimental text for 20 minutes. An interpolated task-a mathematics quiz-was administered for two minutes, to reduce the effects of residual short-term memory for textual content. Subjects were then administered the cued recall and multiple-choice tests, respectively. Subjects were allowed to leave the testing area upon completion. Results Comparisons among illustrated conditions Table 1 shows the means and standard deviations on verbal items and picture items for each group in the design. It should be noted that the term ’picture items’ is literally correct only for illustrated conditions, since two conditions received instructional units
Extended captions to improve illustrations
22 1
Table 1: Means and standard deviations of verbal and picture items Instructive caption (illustrated) Descriptive caption
Present
Absent
Nonillustrated
V d a l items Present M SD n Absent M SD n
7.4 2.5 25
8.3 3.3 24
7.7 3.1 25
7.6
9.0 2.8 24
7.7 3.1 24
2.5 21
Picture itenis
Present M
12.9 4.7
14.0
SD
6.0
11.5 4.2
Absent M SD
12.9 6.0
9.8 4.6
5.9 2.3
without illustrations. Variation within measures is fairly consistent among groups, with the exception of the non-illustrated, no caption control condition (picture items), where the standard deviation is low. This resulted because subjects in this group performed only slightly above the level expected by guessing. Verbal items: The primary design was tested on the verbal items using two-way analysis of covariance. As expected, no significant differences were found, neither for main effects nor for the interaction. In fact, the consistency in this measure across the design suggests that: (a) the verbal and illustrative components of the instructional text were completely independent in regard to content and treatment effects; and (b) subjects were properly assigned at random to experimental groups. Picture items: Table 2 shows the results of the ANCOVA on picture items. Not shown in this table are the results of the non-significant test of homogeneity of regression, an assumption in ANCOVA that individual treatment regression coefficients are not different within chance.
Two effects were significant, the descriptive caption by instructive caption interaction, and the main effect for descriptive caption. The interaction, depicted in Figure 3 , reveals a lower mean for the condition where neither caption is present (ie illustrations only). Analytical comparisons in the design revealed that this group differed from all other
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Table 2: ANCOVA Analysis of Primary Design
ss
Source
df
Regression Descriptive ( A ) Directive (B) AxB Error (adj)
416.6 134.0 28.3 94.6 2122.0
1 1 89
Total
2795.49
93
12.0
1 1
MS
F
P
416.6 134.0 28.3 94.6 23.8
17.5 5.6 1.2 4.0
