Mean section time

This variable is concerned with the time subjects on average spent learning an instructional section. Factors affecting this variable were the presentation conditions, the number of propositions, the number of objects, and the number of visits to that section. Both between-conditions and within-condition analyses were carried out.

Between-conditions analyses made it possible to relate any differences between presentation conditions to specific structural details concerning the multimedia information, whereas within-condition analyses were suited to revealing specific details regarding the course of information processing.

7.5.3.1 Between conditions analyses

First, the mean section time for the four experimental text-picture conditions was compared. Figure 10 shows the mean section time as a function of experimental condition:

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writt-stat writt-mov spok-stat spok-mov Condition

Mean section time (seconds)

Figure 10: Mean section time by condition

Both text mode (F(1; 1328) = 5.297; p < 0.05) and picture mode (F(1; 1328)

= 73.110; p < 0.001) as well as the interaction between them (F(1; 1328) = 40.826; p

< 0.001) had a significant effect on the mean section time. When written texts or moving pictures were presented, the mean section time was longer. Post-hoc comparison using Bonferroni tests showed that the mean section time of Condition (written/moving) was significantly longer than that of the other conditions, whereas the mean section time of Condition (written/static) was the shortest among the four experimental conditions.

Figure 11 depicts the mean section time as a function of section. By comparing the mean section time between the four conditions separately for each section, significant differences could be found in sections S0, S1, S2, S3, S7, S8 and S9. This means that the presentation mode mostly took effect in the first and the last sections of the learning material.

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s 0

s 1

s 2

s 3

s 4

s 5

s 6

s 7

s 8

s 9 Section

Mean section time (sec)

written/static written/moving spoken/static spoken/moving

Figure 11: Mean section time as a function of experimental condition, by section

7.5.3.2 Within-condition analyses

The analysis of the mean section time within each condition indicated that there were some significant differences in the mean section time between sections for Condition (written/static) (F(9; 440) = 2.201; p < 0.05), Condition (spoken/static) (F(9; 335) = 3.968; p < 0.001), and Condition (spoken/moving) (F(9; 250) = 3.203; p < 0.005).

The Bonferroni tests revealed that the differences for Condition (spoken/static) were between S0 and S1, S0 and S7, and S5 and S7, whereas those for Condition (spoken/moving) were between S5 and S7, and S7 and S9.

7.5.3.3 Effect of the number of propositions

The criteria used for counting the number of propositions were developed by Kintch (1974), which can be regarded as a valid measure of the semantic content of a text.

Word categories regarded as constituting a proposition were verbs, adjectives,

adverbs, conjunctions, prepositions, and quantifiers. Table 1 shows the number of propositions in each section.

S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 11 5 15 14 15 14 16 12 11 11

Table 1: Number of propositions of the ten instructional sections

Figure 12 shows the mean section time as a function of the number of propositions. The number of propositions had a significant effect on the mean section time (F(5; 1326) = 7.233; p < 0.001). Due to the large variance between the values, it seemed appropriate to divide them into two conditions (few propositions (5, 11, or 12) vs. many propositions (14, 15, or 16)) to find out the general characteristics of the relationship that holds between the number of propositions and the mean section time.

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5 11 12 14 15 16

Number of propositions

Mean section time (seconds)

Figure 12: Mean section time as a function of the number of propositions

A t-test showed that subjects took significantly less time to learn the sections that contained few propositions (mean = 18.827 sec) than those containing many propositions (mean = 21.962 sec) (t(1330) = -3.526; p < 0.001). Altogether, the data indicated that, the higher the number of propositions, the higher the mean section time. Pairwise comparisons by means of Bonferroni tests revealed that significant differences in the mean section time existed between propositions 5 and 14, 5 and 15, 11 and 12, 12 and 14, 12 and 15, 12 and 16.

7.5.3.4 The effect of the number of objects

The number of objects shown in the pictures can be considered to be an indicator of the complexity of the pictorial information. The method used for counting the objects in the diverse sections was as follows. Each part of the puzzle was counted as an object. If a part of the puzzle was fitted into another part or other parts, then the aggregated parts were regarded as one object. The number of objects was obtained by counting the objects that were to be seen in the pictures or video clips. The procedure for counting objects in the static pictures, however, differed slightly from that in relation to the video clips. In the static-picture version, there were two pictures in each section. The number of objects in a section was calculated by adding the number of objects in those two pictures. In the moving-picture version, the subjects saw how the parts of the puzzle were assembled in action. In this case, the number of objects in a section was obtained by counting the objects initially shown in the video clip. Tables 2 and 3, respectively, show the number of objects in the static and the moving pictures of each section:

S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 13 6 6 5 3 3 3 3 5 3

Table 2: The number of objects in each section of the static-picture version

S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 12 4 4 3 2 2 2 2 3 2

Table 3: The number of objects in each section of the moving-picture version

Figure 13 gives the mean section time as a function of the number of objects.

The effect of the number of objects on the mean section time was significant (F(6;

1325) = 15.337; p < 0.001). It needs to be borne in mind that the number of objects was dependent on picture mode: objects 5, 6, and 13 occurred only in the static pictures, whereas objects 2, 4, and 12 occurred only in the moving pictures.

Therefore, the effect of the number of objects should be analyzed separately for static and for moving pictures.

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2 3 4 5 6 12 13

Number of objects

Mean section time (seconds)

Figure 13: Mean section time as a function of the number of objects

By taking picture mode into account, the data showed that, for static pictures, there was a strong tendency (F(3; 791) = 2.397; p = 0.067) towards a positive relationship between the number of objects and the mean section time. For moving pictures, the number of objects had a significant effect on the mean section time (F(3;

533) = 3.121; p < 0.05). The mean section time increased as the number of objects increased. Pairwise comparisons by means of Bonferroni tests indicated that significant differences existed between objects 2 and 3, 2 and 5, 2 and 6, 3 and 4, 3 and 12, 4 and 5, 4 and 6, 5 and 12, 6 and 12.

7.5.3.5 The effect of the number of visits to the same section

Finally, the number of visits to the same section, i.e. the frequency with which a subject viewed the same section, had a significant effect on the mean section time (F(11; 1320) = 74.827; p < 0.001). The data are given in Figure 14. The mean section time decreased as the number of visits increased. It appears that subjects spent more time processing information during their first encounter with the learning materials.

In their successive visits to the same section, subjects possibly concentrated only on the information they wanted to rehearse in order to memorize the materials.

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1 2 3 4 5 6 7 8 9 10 11 12

Number of visits to the same section

Mean section time (seconds)

Figure 14: Mean section time as a function of the number of visits to the same section