Subcategoría 2: Experimentación del docente como un líder orientador:

A three-way RM-ANOVA was completed to examine the effects of polarity, h1 and vowel on EFR amplitude in the F1 band. Twenty-eight of the 31 adults who participated in the study were included in the analysis, as three subjects were removed due to

excessive noise. Prior to the comparison of within-subject effects, a Mauchly’s test for sphericity was computed for each within-subject factor to determine if the variances of the differences between all possible pairs of groups were significantly different. The test indicated that the assumption of sphericity had not been violated for the three-way interaction of polarity, h1 and vowel, χ2_{(2) = 0.799, p = 0.671; therefore, it was}

unnecessary to correct the degrees of freedom. The RM-ANOVA revealed a significant three-way interaction between the effects of polarity, h1 and vowel on EFR amplitude,

F(2, 54) = 3.184, p = 0.049, η2partial = 0.105. Post-hoc tests using the Sidak correction for

multiple comparisons were completed to further investigate this interaction. For the vowel /u/ with h1, polarity A amplitude (140.11 ± 11.56 nV) was significantly greater than polarity B amplitude (117.59 ± 8.81 nV) by a mean of 22.52 nV, p = 0.011, 95% CI [5.49, 39.55]. For the vowel /u/ without h1 the trend was reversed: polarity A amplitude (108.72 ± 9.13 nV) was significantly lower than that of polarity B (138.26 ± 11.01 nV) by a mean of 29.54 nV, p < 0.001, 95% CI [14.54, 44.54]. The amplitude of polarity A was also significantly greater than that of polarity B for the vowel /a/ with h1 (128.18 ± 11.11 nV and 103.49 ± 9.27 nV, respectively) by a mean of 24.69 nV, p = 0.002, 95% CI [10.10, 39.28]. The mean amplitude difference between polarity A and B approached significance for the vowel /i/ without h1, p = 0.072. There were no significant differences between polarity conditions for /a/ without h1 and /i/ with h1. EFR amplitude differences across conditions, as well as the average electrophysiological noise estimate for each are illustrated in Figure 8.

A two-way RM-ANOVA was conducted to examine the effects of polarity and vowel on EFR amplitude in the F2+ carrier band. EFR data from the same 28 adults as in the F1

Figure 8: Mean EFR amplitudes across vowel stimuli for the F1 band.

Error bars represent ±1 SD (N = 28). * indicates a significant difference at p < 0.05. Grey bars represent the mean noise estimate in each condition.

analysis were included. Since h1 would have no bearing on EFR amplitudes in the F2+ band, EFRs with and without h1 were combined under each vowel category, thereby doubling the sample size (N = 56). Mauchly’s tests computed for each within-subject variable indicated that sphericity had not been violated for the main effect of vowel or for the interaction of polarity and vowel, χ2_{(2) = 1.038, p = 0.595 and χ}2_{(2) = 1.069, p =}

0.586, respectively. Only vowel was found to have a significant main effect on EFR amplitude, F(2, 110) = 30.04, p < 0.001, η2

partial = 0.35. Pairwise comparisons with Sidak

correction completed post-hoc revealed that the amplitude of /a/ (113.73 ± 4.37 nV) was significantly greater than that of /u/ (83.71 ± 5.16 nV) by a mean difference of 30.02 nV,

p < 0.001, 95% CI [18.40, 41.65]. The amplitude of /a/ was also significantly greater than that of /i/ (83.38 ± 4.91 nV) by a mean difference of 30.36 nV, p < 0.001, 95% CI [19.12, 41.59]. The amplitudes of /u/ and /i/ were not significantly different from each other. A main effect of polarity on EFR amplitude approached significance, F(1, 55) = 30.04, p = 0.069, η2partial = 0.059. EFR amplitude differences across conditions in the F2+ carrier are

illustrated in Figure 9.

In agreement with the findings of Easwar et al. (2015), the degree of polarity sensitivity of EFR amplitude varied considerably across individuals. Histograms were constructed to compare individual amplitude differences between polarities across vowel, h1 and carrier conditions. Figures 10 through 13 illustrate the directionality of amplitude changes by plotting the differences of polarity A amplitude minus polarity B amplitude. Positive differences indicate a greater amplitude in the polarity A condition than the polarity B condition, whereas negative differences indicate the reverse. Though the majority of subjects exhibited small amplitude differences less than 30 nV, seven individuals exhibited differences greater than 100 nV in at least one condition.

Furthermore, it would appear that, in general, those who exhibit large differences in one vowel condition tend to have similarly large differences in the other two vowel

conditions as well. Amplitude difference data was grouped into the three vowel categories for each F1 and F2+ band and correlated using Pearson’s correlation

Figure 9: Mean EFR amplitudes across vowel stimuli for the F2+ band. Error bars represent ±1 SD (N = 56). Grey bars represent the mean noise estimate in each condition.

Figure 10: Comparison of EFR amplitude differences between polarities for /u/

with and without h1 in the F1 band.

The vertical dashed line marks the bin containing zero difference in response amplitude between the two polarities.

Figure 11: Comparison of EFR amplitude differences between polarities for /a/

with and without h1 in the F1 band.

The vertical dashed line marks the bin containing zero difference in response amplitude between the two polarities.

Figure 12: Comparison of EFR amplitude differences between polarities for /i/

with and without h1 in the F1 band.

The vertical dashed line marks the bin containing zero difference in response amplitude between the two polarities.

Figure 13: Histogram of EFR amplitude differences between polarities across vowels in the F2+ band.

The vertical dashed line marks the bin containing zero difference in response amplitude between the two polarities.

coefficient. A positive, moderate-strength correlation was found between /u/ and /i/ in the F1 band, indicating that as the degree of polarity sensitivity increased in one vowel it also increased in the other, r = 0.462, N = 56, p < 0.001, critical p value = 0.008 (see Figure 14). There were also positive correlations between /u/ and /a/ (r = 0.272, N = 56, p = 0.042, critical p value = 0.033) and /a/ and /i/ (r = 0.283, N = 56, p = 0.035, critical p

value = 0.025) in the F1 band, though these relationships were not as strong and failed to reach significance (see Figures 15 and 16). In the F2+ band, a moderate-strength, inverse correlation between /u/ and /i/ approached significance, r = -0.307, N = 56, p = 0.021, critical p value = 0.017 (see Figure 17).

It is possible that fluctuations in noise between polarity A and polarity B conditions could be contributing to EFR amplitude differences. To account for this potential confound, correlation analyses were completed comparing the absolute differences in noise

estimates to those in EFR amplitude between the polarity conditions. Spearman’s rho was used to analyse the correlations due to the highly right-skewed nature of the absolute difference distributions. The correlations indicated no significant relationships between the variables in the F1 (r = 0.104, N = 168, p = 0.179) and F2+ bands (r = 0.026, N = 168,

p = 0.738). Therefore, as Easwar et al. (2015) also concluded, it is unlikely that variations in noise are significantly contributing to the EFR amplitude differences observed between polarity conditions.