# More on Sibilant Devoicing in Spanish Diachrony: An Initial Phonetic Approach
## 3 The Perception Experiment
### Results
The statistical model (answer \(\times\) sibilant type \(\times\) dialect \(\times\) stress) was significant (F(22, 5749) = 7.446, \(p<0.0001\)), though only one main effect, sibilant type, was relevant (F(7, 5749) = 14.732, \(p<0.0001\)). As commented, stimuli corresponding to voiceless categories are identified significantly less often as voiced than stimuli corresponding to voiced categories, pointing to a correct identification of the items. The aforementioned exceptions are relevant: [f] displays significantly more voiced labellings than expected (sd = 0.091, t(5749) = 3.098, \(p<0.002\)), and [d\(\overline{3}\)] displays significantly fewer voiced identifications than expected (sd = 0.094, t(5749) = \(-4.574\), \(p<0.0001\)). In these two cases, the inclination to identify sounds corresponding to voiceless or voiced categories as such becomes somewhat blurred. For [f], most of the examples (66.9%) were classified as voiced, thus reversing the expected behaviour; for [d\(\overline{3}\)] there is also an inversion, but to a lesser extent (53.3% of the stimuli were labelled as voiceless). It is important to note that both speaker and stimulus influence the results. There is a significant interaction between phonological category and dialect (F(7, 5749) = 2.766, \(p<0.007\)). Participants from Majorca tend to classify [3] instances as voiced to a significantly lesser degree than participants from Girona (F(1, 5749) = 4.169, \(p<0.041\)). There is no statistically relevant interaction between phonological category and stress (F(6, 5749) = 1.503, \(p<0.173\)), but some interesting tendencies deserve attention. Overall, significant results show that voiced and voiceless segments are being correctly parsed with their expected voicing feature, but if we break down the effects, we observe that cases of [d\(\overline{3}\)] are always identified as voiceless (100% of the stimuli) in unstressed syllable (sd = 0.024, t(5749) = \(-15.936\), \(p<0.0001\)). This is relevant information since the misparsing rates for [d\(\overline{3}\)] in stressed syllables are much lower (only 6.7%). To sum up, despite a global tendency to correctly identify the stimulus with the appropriate phonological category (i.e., with the expected voice feature), there are two afficate categories which display unexpected levels of confusion, [f] and [d\(\overline{3}\)]. The former tends to be interpreted as voiced while the latter is perceived as voiceless when in an unstressed context. It was also interesting to examine whether fraction of unvoiced frames and duration, the most robust indicators of voicing in the acoustic experiment, had an effect in the domain of perception. As can be seen in Table 9 and in Figure 4, stimuli identified as voiceless are in general longer and display a higher portion of unvoiced frames than those identified as voiced in every category, the only exception being [d\(\overline{3}\)]. This general observation is confirmed by the statistical analysis. The mixed-effect binomial logistic regression (answer \(\times\) fraction of unvoiced frames \(\times\) duration) demonstrates that neither fraction of unvoiced frames nor duration condition the participant's response as main effects; however, two- and three-way interactions (sibilant type \(\times\) fraction of unvoiced frames, sibilant type \(\times\) duration, sibilant type \(\times\) fraction of unvoiced frames \(\times\) duration) are significant. Fraction of unvoiced frames influences participants' answers depending on the sibilant (F(7, 5740) = 3.747, \(p<0.0001\)). If the portion of unvoiced frames increases (see data in Table 8), there are significantly fewer stimuli identified as voiced among the instances of [s], [z], [l], [f], [f] and [d\(\overline{3}\)].15 [s] also follows this tendency, but its results are not statistically relevant. [d\(\overline{3}\)], however, tends to have a slightly lower portion of unvoiced frames when labelled as voiceless.