0 1 2 3 4
fast medium slow
pacing of instruction ra ti n g s co res ( m ax . 6) spoken text written text
Figure 9. Mean ratings of cognitive load caused by the format of presentation.
After completion of the performance tasks, participants were asked to give more detailed descriptions of their cognitive load by judging statements about several aspects of the presentation. Mean scores for each experimental group are shown in Table 8. A multivariate analysis of variance (MANOVA) with the between-subjects factors text presentation (spoken vs. written) and pacing (fast, medium, slow) and with the nine judgments as dependent measures revealed a main effect of text presentation format (F(9,76)=9.358, Wilks-Lambda=0.47, p<.001, η2=.53), a main effect for pacing (F(18,152)=2.84, Wilks-
Lambda=0.56, p<.001, η2=.25), but no interaction (F(18,152)=1.37, Wilks-Lambda=0.74, p>.10). Participants, although unaware of the experimental manipulation, significantly differed in their perceptions of the presentation depending on both, text presentation format and presentation duration. Post-hoc
ANOVAs revealed that the main effects were caused by different judgments in the following statements. Participants in the written text conditions were less likely to agree that they missed part of the textual information (F(1,84)=30.63, MSE=49.88, p<.001, η2=.27) but showed higher agreement when asked if they felt distracted from illustrations by textual information (F(1,84)=21.03, MSE=25.6, p<.001, η2=.20). Furthermore, they estimated the pacing to be faster than participants in the spoken text conditions (F(1,84)=7.21, MSE=4.9, p<.01, η2=.08). The main effect of pacing in the MANOVA was caused by the same three items but in a different order of effect sizes plus one additional item. As expected, participants estimated the presentation duration in accordance with the actual experimental variation, i.e. fast pace groups perceived the pacing as “rather fast”, medium pace groups between “rather fast” and “medium”, and slow pace groups between “medium” and “rather slow” (F(2,84)=20.43, MSE=13.88, p<.001, η2=.33). Participants felt more distracted by textual information in the fast pace conditions (F(2,84)=4.94,
MSE=6.01, p<.01, η2=.11). Furthermore, the faster the actual pace the more participants would have liked to stop the presentation at certain points (F(2.84)=4.892, MSE=10.544, p<.05, η2=.10). Finally, participants were more likely to agree that they missed part of the textual information when pacing was fast (F(2,84)=3.28, MSE=5.34, p<.05, η2=.07).
Performance Measures
Scores for performance measures were obtained in the same way as in Experiment 1. No participants had to be excluded from analyses of performance measures. For retention and visual memory tests a second rater scored a subset of 20 participants’ data independently. Inter-rater-reliability for these subsets were r=.93 for retention and r=.89 for visual memory. Thus, the following analyses were conducted with the scores obtained by the first rater for n=90 data sets. shows mean values and standard deviations of performance scores for retention, transfer and visual memory tests.
Table 9
Table 9
Mean values and standard deviations of performance scores for retention, transfer, and visual memory tests.
Pacing
fast (140 s) medium (187 s) slow (249 s)
M (SD) M (SD) M (SD) Spoken text 10.0 (1.9) 11.7 (3.2) 11.3 (3.3) Retention Written text 9.1 (5.5) 10.9 (3.6) 11.9 (3.5) Spoken text 3.2 (1.2) 3.7 (0.6) 3.7 (0.5) Transfer Written text 3.3 (0.8) 3.3 (0.8) 3.3 (0.8) Spoken text 5.9 (1.5) 6.8 (1.7) 6.6 (1.8) Visual Memory Written text 4.8 (2.6) 5.5 (2.2) 6.5 (2.0)
Analyses of variance (ANOVA) with the between-subjects factors text presentation (spoken vs. written) and pacing (fast, medium, slow) provide the following results. For retention ANOVA revealed a marginally significant main effect for pacing (F(2,84)=2.78, MSE=36.78, .10>p>.05, η2=.06). Participants in the medium and slow pace conditions tended to remember more main ideas than in the fast presentation condition. No significant main effect for text presentation format and no interaction were obtained (Fs<1). ANOVA on problem solving transfer revealed no main effect for text presentation format (F(1,84)=1.60, MSE=1.11, p>.10), no main effect for pacing (F<1), and no interaction (F(2,84)=1.07,
MSE=0.74, p>.10). ANOVA on scores of the visual memory test revealed a significant main effect for text
presentation format (F(1,84)=4.22, MSE=16.9, p<.05, η2=.05), a marginally significant main effect for pacing (F(2,84)=2.58, MSE=10.35, .10>p>.05, η2=.06), but no interaction (F<1). Participants in spoken text conditions performed better on visual memory than participants in written text conditions. Furthermore participants tended to perform better the more time they had for inspecting the instruction.
Viewing behavior
Calibration failed in 5 cases. The remaining 85 cases were further processed in the same way as in Experiment 1. Viewing positions were transformed into single fixations and saccades. Fixations and saccades were further cumulated into viewing durations and numbers of fixations on areas of interest (AOI, see ). Four participants whose viewing times on AOIs summed up to less than 75% of total presentation time were excluded from further analyses. Thus, the following analyses were conducted with a set of 81 data cases.
Figure 8
Overall, participants spent 92% of their time viewing AOIs. Means and standard deviations of viewing time on illustration and text as well as summed viewing time on AOIs for each group are shown in
.
Table 10
Table 10
Mean viewing durations on areas of interest (AOI) for illustrations, on-screen text (if present) and sum of text and illustration areas (Total AOI) for each of the six experimental groups.
Pacing
Fast (140s) Medium (187s) Slow (249s)
Spoken text Written text Spoken text Written text Spoken text Written text
Viewing times (sec.) M (SD) M (SD) M (SD) M (SD) M (SD) M (SD)
Illustration 124.4 (6.7) 39.3 (15.3) 171.9 (2.8) 58.8 (27.9) 228.4 (10.7) 97.0 (21.3)
Text - - 91.5 (16.4) - - 116.7 (27.6) - - 139.4 (21.5)
An analysis of covariance (ANCOVA) with the between-subjects factors text presentation (spoken vs. written) and pacing (fast, medium, slow) and with presentation duration as covariate on summed fixation times on illustration as dependent measure revealed a main effect for text presentation format,
F(1,75)=926.16, MSE=241,236, p<.01, η2=.93. Participants in the spoken text groups spent more time inspecting illustrations than participants in the written text groups. Pacing had no main effect on fixation times irrespective of presentation duration (F<1). The interaction between text presentation and pacing was significant, F(1,75)=15.09, MSE=3,931, p<.01, η2=.29. Relative to the pacing of instruction more time was spent inspecting illustration the longer the presentation lasted. This interaction can be explained by the viewing behavior of participants in written text conditions. An ANOVA on the ratio of time spent viewing text to time spent inspecting illustrations as dependent measure and with pacing (fast, medium, slow) as between-subject factor revealed a significant difference (F(2,37)=3.93; MSE=5.98; p<.05; η2=.18). As shown in , this ratio dropped from 2.8 for fast pace to 2.1 for medium and 1.5 for slow pace of presentation, respectively. Post-hoc Tukey-tests revealed a significant difference between fast and slow pace conditions. Participants spent relatively more time inspecting illustrations compared to reading text the longer the presentation lasted. The value of 1 was not included in the 95% confidence intervals for each of the ratios. Thus, in all pacing conditions still relatively more time was spent reading than inspecting illustrations.