4.1.1.1 Mean Fixation Duration
Table 6 lists the mean fixation duration of the subject groups as they read one page of notes, regardless of their fixations falling within or outside of the ROIs. LMM analysis (Table 7) showed that there is no main effect of Expertise, Layout, or Language, indicating that all the subjects’ fixation durations are similar in length in all four note conditions; yet a Layout × Language interaction was found (b=0.054, t=2.08, p=0.038). Such interaction can be explained by Figure 4: when notes are arranged in a vertical layout, reading SL or TL does not exert significant difference on mean fixation duration; on the contrary, if notes are arranged horizontally, reading TL significantly reduces the mean fixation duration than reading SL.
Table 6. Mean fixation duration (ms) in global analysis, with standard deviations in parentheses Trainee 261.45(7.08) 265.32(7.79) 257.61(5.79) 247.74(6.16) Professional 270.16(7.64) 269.23(6.71) 271.07(5.79) 260.67(5.79)
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Table 7. LMM statistics for log(Mean Fixation Duration) in global analysis
Variable Estimate t value Pr(>|t|)
(Intercept) 5.530 139.470 0.000
Expertise(T-P) -0.044 -0.560 0.578
Layout(H-V) -0.011 -0.820 0.410
Language(SL-TL) 0.014 1.090 0.278
Expertise(T-P):Layout(H-V) -0.023 -1.030 0.302
Expertise(T-P):Language(SL-TL) -0.011 -0.510 0.610
Layout(H-V):Language(SL-TL) 0.054 2.080 0.038
Expertise(T-P):Layout(H-V):Language(SL-TL) 0.021 0.470 0.636 Note: T = Trainee; P = Professional; H = Horizontal; V = Vertical; SL = Source; TL = Target
Trainee Professional
Figure 4. Mean Fixation Duration (ms) in global analysis
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4.1.1.2 Number of Fixations
The number of fixations used by the subjects for reading one page of notes is shown in Table 8. LMM analysis (Table 9) yielded a main effect of Expertise (T>P, b=18.697, t=3.336, p=0.001). Additionally the interaction of Expertise × Layout × Language (b=-9.779, t=-1.945, p=0.052) reached marginal statistical significance. This data suggest that in all four note conditions, the professionals used significantly fewer fixations to read one page of notes than the trainees, but the two subject groups were differentially affected by Layout and Language. In the Vertical Layout condition, both groups read the notes in TL with fewer fixations than in SL. In the Horizontal Layout condition, reading the notes either in SL or TL does not make much difference, as revealed by similar number of fixations for both groups. Such pattern can be seen in Figure 5.
Table 8. Number of fixations (counts) in global analysis, with standard deviations in parentheses Trainee 101.94(3.93) 91.96(3.27) 97.69(3.41) 102.18(3.28) Professional 82.48(2.26) 76.33(2.23) 80.63(2.56) 79.00(2.03)
Table 9. LMM statistics for log(Number of Fixations) in global analysis
Variable Estimate t value Pr(>|t|)
(Intercept) 88.855 25.607 0.000
Expertise(T-P) 18.697 3.336 0.001
Layout(H-V) 1.589 0.372 0.710
Language(SL-TL) 2.010 0.468 0.640
Expertise(T-P):Layout(H-V) 2.824 1.123 0.262
Expertise(T-P):Language(SL-TL) -2.956 -1.167 0.244
Layout(H-V):Language(SL-TL) -5.436 -0.636 0.525
Expertise(T-P):Layout(H-V):Language(SL-TL) -9.779 -1.945 0.052 Note: T = Trainee; P = Professional; H = Horizontal; V = Vertical; SL = Source; TL = Target
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4.1.1.3 Mean Saccade Length
Table 10 illustrates the average length of the subjects’ saccadic movements, regardless of their directions, while reading one page of notes. LMM analysis (Table 11) performed on the data indicated a main effect of Layout (H>V, b=0.120, t=6.090, p=0.000). Several interactions among the three factors were found: Expertise × Layout (b=-0.046, t=-2.170, p=0.030); Expertise × Language (b=0.043, t=2.030, p=0.043); and Expertise × Layout × Language (b=0.098, t=2.310, p=0.021). Figure 6 depicts the differential effect of Layout and Language on the two subject groups.
Overall speaking, all the subjects moved their eyes through longer distance while reading the horizontal notes than the vertical notes. However, in the Vertical Layout condition, reading the notes in SL or TL did not affect the saccade length of both subject groups, and the trainees demonstrated significantly longer saccades than the professionals regardless of language. In the Horizontal Layout condition, SL and TL still did not exert any effect on the professionals’ saccade length whereas reading TL significantly made the trainees’ saccades shorter, to the same level as the professionals’.
Figure 5. Number of fixations (counts) in global analysis
Trainee Professional
Number of Fixations
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Table 10. Mean saccade length (pixels) in global analysis, with standard deviations in parentheses
Vertical Layout Horizontal Layout Source
Language
Target Language
Source Language
Target Language Trainee 74.52(2.38) 75.33(1.97) 84.88(1.79) 79.78(1.73) Professional 69.20(1.52) 66.52(1.09) 77.31(1.06) 79.06(1.33)
Table 11. LMM statistics for log(Mean Saccade Length) in global analysis
Variable Estimate t value Pr(>|t|)
(Intercept) 4.298 167.300 0.000
Expertise(T-P) 0.060 1.240 0.215
Layout(H-V) 0.120 6.090 0.000
Language(SL-TL) 0.028 1.430 0.154
Expertise(T-P):Layout(H-V) -0.046 -2.170 0.030
Expertise(T-P):Language(SL-TL) 0.043 2.030 0.043
Layout(H-V):Language(SL-TL) 0.018 0.450 0.655
Expertise(T-P):Layout(H-V):Language(SL-TL) 0.098 2.310 0.021 Note: T = Trainee; P = Professional; H = Horizontal; V = Vertical; SL = Source; TL = Target
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4.1.1.4 Mean Regression Rate
The mean regression rates of the subjects in four note conditions are listed in Table 12. LMM analysis (Table 13) found two main effects: Expertise (T>P, b=0.020, t=2.760, p=0.006) and Layout (H>V, b=0.020, t=6.360, p=0.000). The factor Language showed no main effect and there was no interaction among the three factors. This result can be interpreted to indicate the two following points. First, reading the horizontal notes required the subjects to make more regressive saccades than reading the vertical notes. Second, the trainees’ eyes regressed more than the professionals’, regardless of note condition. Obviously language does not affect whether the subjects’ eyes move forward/downward or backward/upward. Such reading patterns can be seen in Figure 7.
Table 12. Mean Regression Rate (%) in global analysis, with standard deviations in parentheses
Vertical Layout Horizontal Layout Source
Language
Target Language
Source Language
Target Language Trainee 45.21(0.36) 45.16(0.42) 46.92(0.38) 47.52(0.34) Professional 42.92(0.47) 43.59(0.45) 45.35(0.43) 44.97(0.42)
Trainee Professional
Saccade Length (pixels)
Figure 6. Mean Saccade Length (pixels) in global analysis
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Table 13. LMM statistics for log(Mean Regression Rate) in global analysis
Variable Estimate t value Pr(>|t|)
(Intercept) 0.452 121.350 0.000
Expertise(T-P) 0.020 2.760 0.006
Layout(H-V) 0.020 6.360 0.000
Language(SL-TL) -0.002 -0.760 0.448
Expertise(T-P):Layout(H-V) 0.001 0.280 0.780
Expertise(T-P):Language(SL-TL) 0.000 -0.040 0.968
Layout(H-V):Language(SL-TL) 0.002 0.340 0.734
Expertise(T-P):Layout(H-V):Language(SL-TL) -0.015 -1.470 0.143 Note: T = Trainee; P = Professional; H = Horizontal; V = Vertical; SL = Source; TL = Target
Trainee Professional
Figure 7. Mean Regression Rate in global analysis
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4.1.1.5 Total Reading Time
Total reading time was computed by adding up all fixation and saccade durations each subject used while reading and simultaneously interpreting one page of notes.
The means and standard deviations of the two subject groups are displayed in Table 14. LMM analysis (Table 15) revealed a main effect of Expertise (T>P, b=0.148, t=2.170, p=0.030), and an interaction between Expertise and Language (b=-0.052, t=-2.530, p=0.012). This result indicates that regardless of note layout, the trainees spent significantly longer time reading and interpreting one page of notes than the professionals. In addition, TL is apparently more helpful than SL for the professionals during interpreting because TL reduces their total reading time. On the contrary, TL does not seem to be of that much help for the trainees as reading SL and TL lead to similar length of total reading time (Figure 7).
Table 14. Total reading time (s) in global analysis, with standard deviations in parentheses
Vertical Layout Horizontal Layout Source
Language
Target Language
Source Language
Target Language Trainee 33.27(1.22) 31.02(1.26) 32.09(1.21) 32.05(1.11) Professional 28.00(0.71) 25.72(0.72) 27.21(0.78) 26.08(0.65)
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Table 15. LMM statistics for log(Total Reading Time) in global analysis
Variable Estimate t value Pr(>|t|)
(Intercept) 10.219 240.300 0.000
Expertise(T-P) 0.148 2.170 0.030
Layout(H-V) 0.003 0.070 0.946
Language(SL-TL) 0.030 0.570 0.569
Expertise(T-P):Layout(H-V) 0.021 1.020 0.309
Expertise(T-P):Language(SL-TL) -0.052 -2.530 0.012
Layout(H-V):Language(SL-TL) -0.025 -0.240 0.811
Expertise(T-P):Layout(H-V):Language(SL-TL) -0.011 -0.260 0.793 Note: T = Trainee; P = Professional; H = Horizontal; V = Vertical; SL = Source;
TL = Target
Figure 8. Total Reading Time (ms) in global analysis
Trainee Professional
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4.1.2 Local (ROIs) Analysis
4.1.2.1 First Fixation Duration, Single Fixation Duration, and Gaze Duration
First fixation duration, single fixation, and gaze duration are duration measures on a ROI in the first pass, given that it was not skipped. They all imply “early”
information processing, hence are presented together in Table 16. First fixation duration on a ROI refers to the time spent fixating on it for the first time in the first pass. LMM analysis (Table 17) yielded no main effect of any factor and no interaction was found. Single fixation duration is the duration of “the only” fixation on a ROI in the first pass. From Table 17, a main effect of Language (SL>TL, b=0.037, t=2.210, p=0.028) can be found, indicating that for both the professionals and the trainees, while fixating on a ROI for only once in the first pass, reading its information in SL takes longer time than reading that in TL, regardless of note layout, as shown in Figure 9. Gaze duration refers to the sum of all fixation durations on a ROI in the first pass. LMM statistical result (Table 17) shows that Layout (H<V, b=-0.051, t=-1.950, p=0.051) reached marginal significance, suggesting that all the subjects spent shorter time reading the information in the ROIs in the first pass while reading the horizontal notes than the vertical notes, regardless of note language (Figure 10).
Table 16. First fixation duration, single fixation duration, and gaze duration (ms) in local (ROIs) analysis, with standard deviations in parentheses
Vertical Layout Horizontal Layout
Table 17. LMM statistics for log(First Fixation Duration), log(Single Fixation Duration), and log(Gaze Duration) in local (ROIs) analysis log(First Fixation Duration) log(Single Fixation Duration) log(Gaze Duration) Variable Estimate t value Pr(>|t|) Estimate t value Pr(>|t|) Estimate t value Pr(>|t|)
(Intercept) 5.364 165.000 0.000 5.374 161.590 0.000 5.656 171.960 0.000
Expertise(T-P) -0.080 -1.250 0.211 -0.060 -0.910 0.363 -0.048 -0.770 0.439
Layout(H-V) -0.016 -0.920 0.360 -0.018 -1.050 0.293 -0.051 -1.950 0.051
Language(SL-TL) 0.022 1.270 0.203 0.037 2.210 0.028 0.014 0.520 0.601
Expertise(T-P):Layout(H-V) -0.010 -0.380 0.705 -0.003 -0.090 0.924 0.020 0.620 0.538 Expertise(T-P):Language(SL-TL) -0.011 -0.420 0.678 0.020 0.670 0.505 -0.019 -0.600 0.546 Layout(H-V):Language(SL-TL) 0.047 1.350 0.178 0.027 0.790 0.431 0.003 0.050 0.959 Expertise(T-P):Layout(H-V):Language(SL-TL) 0.060 1.150 0.250 0.054 0.910 0.361 0.022 0.350 0.729 Note: T = Trainee; P = Professional; H = Horizontal; V = Vertical; SL = Source; TL = Target
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Trainee Professional
Figure 9. Single Fixation Duration (ms) in local (ROIs) analysis