Normalised F1 values

The statistical analysis yielded no main effect of gender and age either for the normalised F1 values for /e/-/ε/, or for the normalised F1 values for /o/-ↄ/. These effects are congruent with the raw F1 statistical analysis results. Figure 3.10 depicts that the mean differences for /e/-/ε/ and /o/-/ↄ/ for females is quite close to the corresponding differences for males. Figure 3.11 also highlights strong similarities of F1 difference for /e/-/ε/ across age groups. Particularly, the F1 mean differences among youngsters and young people, middle-aged adults and older adults show some degree of overlap specifically between the groups of youngsters and young people and older adults. In terms of the F1 differences for /o/-/ↄ/, they are identical for middle-aged adults and older adults, but slightly lower for youngsters and young people. Overall, the normalised F1 difference is consistent

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with the raw F1 difference, as both corroborate that the acoustic distance is steadily higher for /e/-/ε/ than for /o/-/ↄ/ across different gender/age groups.

Figure 3.10 Mean of the normalised F1 differences for the vowel pairs /e/-/ε/ and /o/-/ↄ/ conditioned by gender

Figure 3.11Mean of the normalised F1 differences for the vowel pairs /e/-/ε/ and /o/-/ↄ/ conditioned by age

The statistical results supported the finding of a main effect of language dominance for /e/-/ε/

[F(1,67) = 12.59, p = .0007], but not for /o/-/ↄ/. Nevertheless, in the case of the raw F1 values (see section 3.2.1.1) the difference between the vowels of the mid-front and mid-back pairs achieved significance. Figure 3.12 highlights the main effect of language dominance. It particularly reports

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a larger gap between the mean of the F1 /e/-/ε/ difference conditioned by Catalan-dominants, in comparison to that of the F1 /e/-/ε/ mean difference, conditioned by Spanish-dominants.

Nevertheless, the gap is narrower between the F1 /o/-/ↄ/ mean difference of the Catalan-dominant group and the F1 /o/-/ↄ/ mean difference of the Spanish-dominant group. In general terms, both the normalised and raw F1 differences, show a clear trend for a greater acoustic distance between the vowels of the /e/-/ε/ pair than for the vowels of the /o/-/ↄ/ pair across language dominance conditions.

Figure 3.12Mean of the normalised F1 differences for the vowel pairs /e/-/ε/ and /o/-/ↄ/ conditioned by language dominance

3.2.2.2

a) No significant interaction was obtained between gender and age either for /e/-/ε/ or for /o/-/ↄ/, as illustrated in Figures 3.13 and 3.14.

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Figure 3.13Mean of the normalised F1 differences for the vowel pair /e/-/ε/ conditioned by gender x age

Figure 3.14 Mean of the normalised F1 differences for the vowel pair /o/-/ↄ/ conditioned by gender x age

Besides the absence of a ‘gender x age’ significant interaction, the means of the dataset plotted in Figures 3.13 and 3.14 indicates similar trends as the ones appeared earlier in section 3.2.1.2 (Figures 3.4 and 3.5) concerning the mean values difference of the raw F1 /e/-/ε/ and /o/-/ↄ/. In Figures 3.13 and 3.14, slightly divergent bars highlight small differences between females and males across age. In a similar vein, differences for each of the three age groups across gender can be noted. As shown earlier in section 3.2.1.2 (see Figures 3.4 and 3.5), Figure 3.13 also reveals that within the male group, the F1 difference for /e/-/ε/ increases progressively across age groups.

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Similarly, within the female group, the F1 difference for /o/-/ↄ/ develops gradually across age groups, despite a less symmetrical incline observed between females of 35-54 and 55-75 years (see Figure 3.14).

b) The ‘gender x language dominance’ interaction, on the other hand, achieved significance regarding the /o/-/ↄ/ pair, [F(1,64) = 10.47, p = .0019], but not for /e/-/ε/ (see Figures 3.15 and 3.16).

According to the pairwise comparison tests, the significant effect for the /o/-/ↄ/ pair was associated with a larger difference for Catalan-dominant females than for Spanish-dominant females [F(1,64)

= 16.75, p = .0001], unlike between Catalan-dominant and Spanish-dominant males no significant effect came out from their difference (see Figure 3.16). The same significant effect for the /o/-/ↄ/

pair of the raw F1 difference can be noticed in section 3.2.1.2 (see Figure 3.7). Moreover, as the same figure reveals in parallel with the results of the raw F1 dataset, pairwise comparisons also yielded a significant difference between Catalan-dominant speakers of different gender [F(1,64) = 7.54, p = .0078] in the sense that females performed better than males. The differences among Catalan-dominant males and both dominant males and females, and between Spanish-dominant females and males, did not achieve any significance.

Figure 3.15Mean of the normalised F1 differences for the vowel pair /e/-/ε/ conditioned by gender x language dominance

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Figure 3.16 Mean of the normalised F1 differences for the vowel pair /o/-/ↄ/ conditioned by gender x language dominance

c) The interaction of ‘age x language dominance’ for the /e/-/ε/ and /o/-/ↄ/ vowel pairs was non-significant.

A number of trends were discussed earlier in section 3.2.1.2 (see Figures 3.8 and 3.9) about the raw F1 difference of the /e/-/ε/ and /o/-/ↄ/ vowel pairs, which fully correspond to the present trends about the normalised F1 difference of the mid-vowel pairs highlighted in Figures 3.17 and 3.18.

In this regard, a clear trend is shown by the Catalan-dominant bilinguals for displaying a greater acoustic distance between the vowels of the /e/-/ε/ and /o/-/ↄ/ pairs than the Spanish-dominant bilinguals across all age groups. Finally, regarding the Catalan-dominant group, the acoustic distance for the /o/-/ↄ/ vowel pair develops gradually across age groups; the older the speakers are, the better they perform.

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3.17Mean of the normalised F1 differences for the vowel pair /e/-/ε/ conditioned by age x language dominance

Figure 3.18Mean of the normalised F1 differences for the vowel pair /o/-/ↄ/ conditioned by age x language dominance