1.1 /s/-aspiration in Spanish

The weakening of syllable-final fricatives is a process that is common to many languages (see Solé, 2010, for an overview with a focus on the Romance languages). In Spanish, the weakening of syllable-final /s/—usually referred to as /s/-aspiration—occurs in many varieties and has been the object of numerous studies within the field of Hispanic linguistics. From a dialectological point of view, /s/-aspiration has been of interest since it allows an areal division of Spanish varieties (for European Spanish, see Samper Padilla, 2011; for American Spanish, see Canfield, 1981, or Lipski, 1994). The realization of syllable-final /s/ has also attracted a long-standing interest from the variationist community and has been shown to vary with speech style and with the social variables of the speaker (e.g., Fontanella de Weinberg, 1973, for Buenos Aires; Cedergren, 1978, for Panama City; López Morales, 1983, for San Juan de Puerto Rico; Samper Padilla, 1990, for Las Palmas de Gran Canaria; and Momcilovic, 2009, for Madrid). Syllable-final /s/ in Spanish has been studied within the theoretical framework of the functionalist hypothesis (e.g., Hernández-Campoy & Trudgill, 2002; Ma & Herasimchuk, 1971; Poplack, 1981; Terrell, 1979) since it functions as a plural marker for nouns, and in the context of resyllabification (e.g., Harris, 1983; Hualde, 1991) as a loss of syllable-final /s/ goes along with a change in syllable structure from CVC to CV.

In Spanish, the above-mentioned process of lenition is not limited to /s/ in syllable-final position, but also affects syllable-final /θ/ (e.g., capaz [kaˈpah]), and it may additionally affect syllable-initial /s/ as well as /θ/ in word-medial and word-initial position (Brown & Torres Cacoullos, 2002; Jiménez Sabater, 1975). In the latter position, however, it occurs less frequently and is often sociolinguistically stigmatized (Narbona et al., 2003, p. 205). Several factors have been shown to favour a weakening of syllable-final /s/ in Spanish, such as its occurrence in unstressed syllables (e.g., Alba, 1990; File-Muriel & Brown, 2011), a fast speech rate (File-Muriel & Brown, 2011), high lexical frequency (e.g., Brown, 2009), and word-medial position preceding consonants (e.g., Alba, 1990; Momcilovic, 2009; Samper Padilla, 2011).

As the term indicates, /s/-aspiration in Spanish generally results in aspiration,¹ i.e., a glottal fricative (e.g., pasta [ˈpahta]). However, early dialectological work (Alther, 1935; Alvar, 1955) reports on the high variability of syllable-final /s/ when it comes to its phonetic realization: many different phonetic variants are possible and effects often spread to adjacent segments. /s/-lenition may, for instance, be associated with the lengthening and/or lowering of the preceding vowel (Martínez Melgar, 1994, for Eastern Andalusian Spanish; Narbona et al., 2003) and/or with lengthening of the subsequent consonant (see Alvar, 1955, for Andalusian, and Ruiz Hernández & Miyares Bermúdez, 1984, for Cuban Spanish). This variability is reflected in the various transcriptions in dialectological and some variationist studies as, for instance, [∅], [^s], [h], [^hs].

/s/-aspiration in Spanish is usually considered a linguistic change that is stable (Gimeno, 2008; Labov, 1994). Labov (1994, pp. 583–585) describes the variable realization of syllable-final /s/ in varieties of Spanish as the result of a historical sound change, namely the “massive weakening and deletion of final /s/”. A closer look into the synchronic variation and the differences in the production of syllable-final /s/ among several Spanish dialects therefore could enhance our understanding of the historical process of /s/-weakening itself. In order to be stable across time, the variable rule (i.e., the probability of /s/ being realized as [h] or [∅]) must be acquired by children and be transmitted from one generation to the following (Labov, 1994, pp. 583–584).

Despite its variability, the phenomenon of /s/-lenition has usually been analyzed auditorily and categorized as either full [s], lenited /s/ [h], or elision [∅] to trace the process of lenition from an alveolar fricative to its loss, [s] → [h] → [∅]. Although this method gives an idea of the distribution of variants according to the independent variables (e.g., age, gender, register, or phonological context), it gives the impression that /s/ varies categorically, and it does not account for compensatory processes of /s/-lenition such as a lengthening of the preceding vowel or the following consonant. The method routinely used in variationist studies might have contributed to the view of /s/-weakening as a case of stable variation since it does not account for more fine-grained phonetic variation and change such as the above-mentioned lengthening of adjacent segments. Only a few studies have quantified /s/-lenition in Spanish with gradual, acoustic parameters such as duration, centre of gravity, or voicing. File-Muriel and Brown (2011) showed for Caleño Spanish (Colombia) how phonological context, speaking rate, and lexical stress variably affected the gradual acoustic parameters of /s/, namely its durational, spectral, and voicing properties, suggesting that /s/-lenition should more appropriately be described as a gradient than a categorical phenomenon (see also Erker, 2010, and Torreira & Ernestus, 2012, for similar approaches).

The current study represents a counter-example to the commonly assumed stable variation of /s/-aspiration in Spanish. It will show how syllable-final /s/ preceding voiceless stops is in Andalusian Spanish variably realized as aspiration preceding the stop closure (e.g., pasta [ˈpahta]), following the stop closure (pasta [ˈpat^ha]), or both ([ˈpaht^ha]), and how its realisation changes in apparent-time, giving rise to a new sound in this variety, a post-aspirated stop. Consistent with previous studies (O’Neill, 2010; Parrell, 2012; Ruch & Harrington, 2014; Torreira, 2007a, 2007b), the study will refer to aspiration that occurs preceding the oral stop closure as pre-aspiration, and aspiration occurring after the stop closure as post-aspiration. In this paper, pre- and post-aspiration will be used as phonetic, not phonological, terms. It should be noted that from a phonological point of view the type of pre- and post-aspiration in Andalusian Spanish is different from that which appears in languages such as Icelandic or Scottish Gaelic that have it segmentally: in Andalusian Spanish, pre- and post-aspiration result from the debuccalisation of /s/ preceding voiceless stops, and (pre-)aspiration is not limited to this position but can occur in all contexts where syllable-final /s/ is debuccalized (e.g., isla ‘island’ [‘ihla], mismo ‘the same’ [‘mihmo], etc.).

1.2 /s/ + voiceless stop sequences in Andalusian Spanish

In Andalusian Spanish — spoken in the southern part of Spain — syllable-final /s/ is generally weakened even in formal speech situations (Carbonero Cano, 1982; Villena Ponsoda, 2008). /s/-lenition can therefore be considered as a completed sound change in this variety. However, the realisation of lenited /s/ is itself highly variable synchronically. The phonological sequences /sp, st, sk/ are of particular interest since they have recently been found to be produced with aspiration preceding the stop closure (henceforth pre-aspiration; Gerfen, 2002; O’Neill, 2010), with aspiration subsequent to the stop closure (henceforth post-aspiration; Parrell, 2012; Torreira, 2007a, 2012), and with a long stop closure (O’Neill, 2010; Torreira, 2007a, 2012).

Gerfen (2002) analyzed minimal pairs of bisyllabic words with V(s)CV, where C was a voiceless stop (e.g., casta /ˈkasta/, realized as [ˈkahta] vs. cata /ˈkata/) produced by 10 younger speakers of Eastern Andalusian Spanish (EAS). He found that /sC/- and /C/-sequences differed not only in the presence of aspiration preceding the stop closure, but also in terms of the relationship between stop closure duration and vowel duration, the latter being significantly greater in /sC/- sequences than in intervocalic stops. Torreira (2007a) investigated /s/ + voiceless stop sequences in younger speakers of Western Andalusian Spanish (WAS) and discovered that in this variety, words such as lista were produced with aspiration following a long stop closure (i.e., [ˈlitː^ha]). He further observed that the stop closure was longer in /s/ + voiceless stop sequences than in intervocalic stops, and longer than in /s/ + voiceless stop sequences in two other Spanish varieties with /s/-weakening, namely Buenos Aires and Puerto Rican Spanish (Torreira, 2007a). A precise comparison of the production of /s/ + voiceless stop sequences among four Andalusian varieties was carried out by O’Neill (2010). Systematic differences between the two Western (Cádiz, Seville) and the two Eastern varieties (Almería, Granada) are reported for the duration of the stop closure and the aspiration following the stop closure. Speakers from Cádiz and Seville were found to produce a shorter stop closure than speakers from Almería and Granada, and a longer voice onset time (VOT). This regional variation is interpreted as the result of a sound change in progress with the possible result that post-aspirated stops [p^h, t^h, k^h] are already phonologized in Western Andalusian varieties (O’Neill, 2010, p. 39).

The hypothesis of a sound change in progress was explicitly addressed in Ruch and Harrington (2014). In an apparent-time study with 24 speakers of an Eastern (Granada) and 24 speakers of a Western (Seville) variety, they provided evidence for a sound change in progress from pre- to post-aspiration not only in Western, but also in Eastern Andalusian /st/-sequences: younger speakers produced words with medial /st/ (e.g., estanco ‘kiosk’ /esˈtanko/) with a long post-aspiration and a short or even absent pre-aspiration ([eˈt^haŋko]), while older speakers showed a short post-aspiration and a longer pre-aspiration ([eˈht^haŋko]), these age-dependent differences being more marked among Seville than among Granada speakers. For younger Sevillian speakers, the long post-aspiration was additionally associated with a shorter closure duration, although the latter was still longer in /st/-sequences than in intervocalic stops (e.g., etapa ‘stage’ /eˈtapa/). A first aim of this paper is to test if the sound change from pre- to post-aspiration also affects /sp/- and /sk/-sequences.

Different scenarios have been proposed to explain the change from pre- to post-aspiration. For example, Parrell (2012) formulated an articulatory model based on acoustic data elicited in an experiment with manipulation of speech rate. The hypothesis to be tested was that a faster speech rate would be associated with a longer VOT as the result of a reorganization of the articulatory gestures from anti-phase (in pastándola, ‘grazing it’, [pahˈtandola]) to in-phase ([paˈt^handola]). Acoustic data from 20 younger Seville speakers confirmed the hypothesis of longer pre-aspiration in slow speech and longer post-aspiration in fast speech. At the same time, the results demonstrated that the phenomenon of pre- and post-aspiration in Andalusian Spanish might be of a more complex nature, since some speakers produced long post-aspiration across all speech tempi, and the oral stop closure was more variable than predicted by Parrell’s (2012) model.

Another model is proposed by Torreira (2012). Here, the influence of lexical stress and speech rate on the production of /sp, st, sk/ in Western Andalusian Spanish was investigated. He tested the idea made explicit in Kessinger and Blumstein (1997) that, if post-aspiration is an acoustic cue to /sp, st, sk/ in Western Andalusian Spanish, it should be longer in stressed than in unstressed syllables, and longer in slow than in fast speech (i.e., in hyper-articulated words). Since no systematic effects were found in the data of three speakers from Cádiz, the author concluded that post-aspiration in this variety was the result of articulatory overlap rather than intended by the speaker, and that post-aspiration is not a robust cue to /sp, st, sk/ sequences in Western Andalusian Spanish. Torreira (2012) points to the long oral closure that was consistently produced by WAS speakers, which he suggests is a compensatory lengthening for the realignment of the oral closing gesture with respect to the glottal opening (Torreira, 2012, p. 61). He points to other reports of long consonants after a lenited /s/ in Western Andalusian Spanish (e.g., isla [ˈihlːa]), and suggests that overlap between a long oral gesture and the glottal gesture may be the more general production pattern for /s/ + consonants in this variety.

Yet another model that is based on acoustic and perceptual data is proposed by Ruch and Harrington (2014). Their apparent-time data of an Eastern and a Western Andalusian variety indicated that (1) pre-aspiration fades gradually over time, (2) post-aspiration increases gradually, and (3) intervocalic /t/ and /st/ sequences are distinguished systematically by closure duration and voice termination time (VTT), and also by voice onset time (VOT) for all but older Eastern Andalusian speakers. Correlation analyses within /st/-tokens indicated that, within a speaker, pre-aspiration shortening and post-aspiration lengthening are not necessarily interrelated with each other, but instead, younger WAS speakers showed a trading relationship between closure duration and VOT. Based on these findings, the authors hypothesized that closure lengthening might have arisen prior to the emergence of post-aspiration, and that, “if the sound change of post-aspiration were to lengthen further (…), post-aspiration on its own may eventually become the primary cue for distinguishing intervocalic /st/ from intervocalic /t/ in Andalusian Spanish” (Ruch & Harrington, 2014, p. 24). This interpretation contrasts with Torreira’s (2012) view of post-aspiration not as an intended cue to /sp, st, sk/ by the speaker, but as a result of articulatory overlap. A perception experiment in Argentinian Spanish (a variety of Spanish in which syllable-final /s/ is also weakened; see Aleza Izquierdo & Enguita Utrilla, 2002) showed that, even in a non-post-aspirating variety, post-aspiration is parsed with the underlying phonological /st/-sequence and serves as a perceptual cue. Based on these findings, the authors argue that an articulatory model may not entirely explain the change from pre- to post-aspiration, but instead perceptual factors may also be involved in the sound change.

The studies by Parrell (2012) and Ruch and Harrington (2014) are based on isolated words containing /st/-sequences. Torreira (2007b, 2012) and O’Neill (2010) also considered words containing /sp/- and /sk/-sequences, but did not specifically analyze the effect of place of articulation. From previous work on the realization of syllable-final /s/ in Spanish varieties, it is evident that the aspiration resulting from /s/-lenition varies according to the phonological context. In an acoustic study on Canarian Spanish, Marrero (1990) found weakened /s/ to be realized as breathy voice preceding labial and dental stops, and as voiceless aspiration preceding velar stops. Sánchez-Muñoz (2004) found /sk/-sequences in a Castilian variety to be realized more often with aspiration than /sp/- or /st/-sequences, the latter being produced more frequently without aspiration. Similar observations are reported in Alther (1935, p. 121) who describes that /s/ preceding /p/ is reduced in the vast majority of cases, while /s/ preceding /t/ can be realized as [h], as a velar fricative, or may be assimilated to the subsequent stop.

Although the phonemic status of aspiration in Spanish is different from pre-aspiration in languages that have phonemic pre-aspirated stops (see Section 1.1), a view on the phonetics of pre-aspiration in such languages could also be enlightening in the case of Andalusian Spanish, especially when it comes to phonetic and auditory principles. Helgason (2002, p. 41) argues that “two phonetically similar sound sequences that differ only in terms of phonological interpretation should not respond in different ways to the same auditory constraint”. In the next section the paper will offer a brief review of the literature on the phonetics of pre-aspiration in languages that have it phonologically such as Scottish Gaelic and Icelandic, or as phonetic variants of, for instance, geminates, such as Italian or Swedish.

1.3 Place of articulation and pre-aspiration in other languages

Clayton (2010, p. 165) reports pre-aspiration in Scottish Gaelic and Icelandic to be longest preceding velar stops and shortest preceding bilabial stops, confirming Ní Chasaide’s (1985) findings for pre-aspiration in Irish, Scottish Gaelic, and Icelandic. Clayton (2010, p. 192) assumes this variation to be conditioned by physiological or articulatory factors rather than being language-specific. His comparison between different phoneme inventories of various Scottish Gaelic varieties (Clayton, 2010, pp. 129–130) further shows de-aspiration to occur first among bilabial stops, and only later among alveolar stops. Buccalization of pre-aspiration, on the other hand, is more frequent in the velar than in the alveolar and bilabial context.

Turning now to dialects that have pre-aspiration as a phonetic variant, similar patterns have been observed: a phonetic study on emerging pre-aspiration in Standard Swedish (Helgason & Ringen, 2008) reports pre-aspiration to be longer in the velar and dental than in the bilabial context. Stevens and Hajek (2004) found emerging pre-aspiration in Italian dialects more often preceding velar than dental geminates. This pattern may be related to articulatory constraints, as suggested by Ní Chasaide and Ó Dochartaigh (1984, p. 153) and Helgason and Ringen (2008). Helgason and Ringen (2008, pp. 623–624) argue, based on Hardcastle (1973), that the lower velocity of the tongue body movement for velars compared to coronals and bilabials might lead to a longer transition phase (i.e., pre-aspiration) between the preceding vowel and the silence due to the oral closure.

A second aim of this study is to systematically analyze the influence of place of articulation on the production of /s/ + voiceless stop sequences among older and younger speakers in two different varieties. The idea is to compare synchronic variation in the production of /sp, st, sk/ — as inferred from variation within the group of older EAS speakers — with diachronic change, which will be analyzed in terms of apparent-time comparisons between older and younger speakers in both varieties. By doing so, the paper hopes to shed light on the role of articulatory and perceptual factors in sound change actuation. The so-called actuation problem (Weinreich et al., 1968) addresses the questions of why a change takes place in a particular language at a given time, and of what factors contribute to this change (Weinreich et al., 1968, p. 102).

1.4 Sound change actuation

When relating specifically to sound change, the actuation problem has been re-defined in different ways (see Stevens & Harrington, 2014, for an overview). While some authors distinguish between sound change initiation and spread, others draw the line between variation and selection of variants on the one hand and spread of change on the other (Stevens & Harrington, 2014, p. 4). In the present paper, the term sound change actuation is used when referring to the critical moment where the listener becomes speaker, or, in other words, sound change actuation is defined as the transition from initiation to spread: Why would a listener adopt a particular new pronunciation form and use it in his own speech?

Directly related to this issue is the role of articulatory as opposed to perceptual factors in sound change: Is sound change mainly speaker-driven, or is it primarily listener-driven? Ohala’s (1993) model proposes that sound change arises from the misperception of the acoustic signal by the listener, that is, when the listener erroneously interprets the acoustic effects of coarticulation as a new sound instead of attributing it to its articulatory source. Other models, such as Articulatory Phonology (Browman & Goldstein, 1991, 1992), suggest that several types of sound change result from the variability that normally occurs in speech, namely reductions in the magnitude of articulatory gestures as well as increase in gestural overlap. When the listener fails to “correctly identify which of two overlapping gestures is the source of some aspect of the acoustic signal” Browman & Goldstein, 1991, p. 313, then sound change can arise: the listener when becoming the speaker will use a different gestural configuration for the same sound. Common to these and other views is the idea that sound change arises from synchronic variation in spoken language. While Ohala’s (1993) model focuses more on the perceptual consequences of variation in articulation, Browman and Goldstein’s (1991, 1992) main focus lies on the articulatory sources of variation.

How strong must the coarticulatory effects be in order to be perceivable and to be misinterpreted by the listener, and how strong may they be in order to be taken up by the listener? Why should a listener take up a pronunciation form that deviates from what he usually hears? Baker et al. (2011) suggest that sound change arises from the individual differences in coarticulation among speakers, arguing that “if every speaker produces essentially the same amount of coarticulation, then there is nothing to imitate in the first place” (Baker et al., 2011, p. 350). Only if the phonetic effect of coarticulation is large enough and perceptible can the listener interpret it as a different production target, and only then can it be imitated. In contrast, from an exemplar-theory (Pierrehumbert, 2001) point of view, we would expect phonetically similar productions to be imitated, and phonetically deviant productions not to be stored in the set of exemplars used for speech production (Garrett & Johnson, 2013, pp. 86–87). Slightly different, but still similar variants, on the other hand, are stored in memory and can gradually shift a cloud of exemplars in one direction and would therefore predict sound change to be accumulative.

In what concerns the emergence of post-aspirated stops in Andalusian Spanish, the role of both articulatory (Parrell, 2012; Torreira 2012) and perceptual factors (Ruch & Harrington, 2014) has been discussed and tested, with different and, to some extent, conflicting results (see Section 1.2). In the present study this issue is readdressed by systematically investigating the influence of the place of articulation in two varieties and two apparent-time stages of the sound change. By doing so, a comparison can be made of phonetic variation in the production of /sp, st, sk/ in groups of speakers that have to a different degree undergone the sound change from pre-to post-aspiration. The paper will acoustically compare /sp, st, sk/-sequences produced by older EAS speakers — who have not yet undergone the sound change — with those of younger WAS speakers, who appear to be the most advanced in the sound change, and two intermediate groups, older WAS and younger EAS speakers (Ruch & Harrington, 2014). The influence of stop type on the duration of pre- and post-aspiration will also be analyzed. If for VOT the typical pattern as predicted by articulatory and aerodynamic factors among all four speaker groups is found, that is, the greatest VOT for the velar, the shortest for the bilabial context (Cho & Ladefoged, 1999), then the effect of stop type on VOT will be ascribed to universal phonetic principles (Maddieson, 1997). If a VOT-pattern is found that differs from the predicted one, or diverging patterns between younger and older speakers, perceptual factors are more likely to be involved in the emergence of post-aspiration. This analysis will further shed light on the relationship between fading of pre-aspiration and emergence of post-aspiration, the contexts where the sound change might have started, and how it is generalized within the phonological system of one speaker.

Based on the literature on Andalusian Spanish and on findings for languages with phonological pre-aspiration, it is expected that pre-aspiration in Andalusian Spanish /s/ + voiceless stop sequences will be longer in velar than in dental stops, and shortest preceding bilabial stops, and VOT is expected to be longest in /sk/, and to be shortest in /sp/. At the same time, it is expected that pre-aspiration will fade faster in the bilabial than in the velar context, a hypothesis that will be tested by combining the factors age and stop type. Younger and older speakers are hypothesized to differ in pre-aspiration more clearly among bilabial than among velar stops. Concerning words with intervocalic stops, the typical VOT pattern (Cho & Ladefoged, 1999) is expected to occur, with velars showing the longest and bilabials showing the shortest VOT, and no difference among the age groups or varieties.

A third issue to be addressed in this paper is the perception of post-aspirated stops. Conflicting claims have been made about the possible phonologization of post-aspirated stops in Andalusian Spanish based on acoustic data. As discussed in Section 1.2, Torreira (2012) concluded that post-aspirated stops in Western Andalusian Spanish are the result of articulatory overlap, and that no series of phonologized post-aspirated stops exists in this variety. Parrell (2012) observed that some speakers produced a long VOT across all speech rates, suggesting that this came about because post-aspirated stops might be phonologized to a certain degree in Western Andalusian Spanish.

If listeners of Andalusian Spanish are able to distinguish a minimal pair /pasta/-/pata/ based only on the presence or absence of post-aspiration, it can be concluded that post-aspiration is interpreted as a cue to /sp, st, sk/ on its own, and that the originally phonetic effect of a long post-aspiration is interpreted as a distinct phonetic target. Following Hyman (1976, 2013) phonologization is defined as the exaggeration of a phonetic effect “beyond what can be considered universal” (Hyman, 2013, p. 6). The use of such an exaggerated phonetic effect in the perception of a phonological contrast—in the absence of pre-aspiration or [s]—would then indicate that post-aspiration in Andalusian Spanish is to a certain degree phonologized (see Baker et al., 2011; Beddor, 2009; Harrington & Stevens, 2014; Kirby, 2014, for similar accounts of phonologization).

In order to test if and to what degree listeners of Andalusian Spanish make use of post-aspiration to distinguish between /t/ and /st/, a forced-choice perception experiment was conducted with a minimal pair pata-pasta that differed only in VOT. The perception experiment was accomplished using younger and older listeners of Eastern and Western Andalusian Spanish. The idea was to assess whether listeners of EAS and WAS differed in the perception of the phonological contrast, and to learn if the sound change in apparent-time found for production of /st/ (Ruch & Harrington, 2014) also takes hold in perception. The hypothesis tested is that younger and WAS listeners will distinguish pata and pasta more categorically than older and EAS listeners. The results of this perception test were further correlated with the production data of the same speakers. The findings of several studies suggest a relationship between the perception and the production of a phonological contrast in a sound change in progress (e.g., Fridland & Kendall, 2012; Harrington et al., 2008; Kleber et al., 2012). In the case of Andalusian Spanish, the question is whether a speaker who realizes the contrast between /t/ and /st/ in production based on post-aspiration is also more sensitive to post-aspiration as a cue to the /t/-/st/ distinction in perception. However, empirical work on vowel mergers illustrates how perception and production can be misaligned, that is, how a perceived phonological contrast is by the same speaker merged in production (Babel et al., 2013; Labov et al., 1991). Further evidence against a direct production-perception link comes from studies on compensation for coarticulation (Grosvald & Corina, 2012; Kataoka, 2011) in which the degree between perceptual compensation for coarticulation and the production of coarticulation was not correlated within speakers. An analysis of the relationship between production and perception may provide further insights into the role of perceptual or articulatory factors that contribute to the sound change.

In summary, there are three aims to this study. First, to assess whether the sound change from pre- to post-aspiration for /st/ found by an apparent-time study (Ruch & Harrington, 2014) takes hold also for /sk/- and /sp/-sequences. Second, to systematically compare velar, dental, and bilabial stops in order to understand in which contexts the sound change might have started and which articulatory factors might have brought it about. And third, to tackle the hypothetical process of phonologization of post-aspirated stops in this variety of Spanish by testing if Andalusian listeners use post-aspiration as a perceptual cue to /st/-sequences.

2.2 Results

2.2.1 The production of pre- and post-aspiration in Andalusian Spanish

2.2.1.1 Voice termination time

Figure 2 shows the mean values for voice termination time (VTT) as a function of age, variety, and place of articulation, separately for hC-words (e.g., estado, escapa, espada) and C-words (e.g., etapa, secaba, separa). As is apparent from Figure 2, VTT mean values per speaker for hC-words are mostly positive which means that voicing ends prior to the oral closure, i.e., they are pre-aspirated. VTT values for C-words, on the other hand, are mostly negative, i.e., voicing extends into the oral closure (see Torreira & Ernestus, 2011, for similar results on conversational Madrid Spanish). A mixed model with VTT as the dependent variable, Sequence (hC-words vs. C-words), Age (older vs. younger speakers), and Variety (EAS vs. WAS speakers) as fixed factors, and Speaker and Word as random factors showed a significant three-way interaction (χ²[1] = 23.2, p < 0.001). Post-hoc Tukey tests showed that younger and older speakers did not differ significantly in C-words, while younger and older speakers did differ significantly in hC-words in WAS (p < 0.001), but not in EAS (although the same trend is observable from Figure 2 also for this variety). This means that younger speakers of Western Andalusian Spanish produced a shorter pre-aspiration than older speakers in hC-words. The difference between hC- and C-words was significant in all four speaker groups (p < 0.001).

Figure 2

Voice termination time (VTT) in hC-words (green) and C-words (yellow), separately for variety (EAS vs. WAS), age group (older vs. younger), and place of articulation (/p/ vs. /t/ vs. /k/). Each boxplot contains one mean value per speaker.

Furthermore, Figure 2 shows that VTT varies with age and place of articulation: VTT is longest before velar stops, and longer for older than for younger speakers. Because of the three-way interaction mentioned above between Age, Variety, and Sequence, further statistical tests were conducted separately for hC- and C-words.

A mixed model on the hC-data with VTT as the dependent variable, with Age, Variety, and Stop Type as fixed factors, and Speaker and Word as random factors showed a significant effect of Age (χ²[4] = 13.1, p < 0.05) and Stop Type (χ²[6] = 39.4, p < 0.001) on VTT. There was no significant difference in VTT between Eastern and Western Andalusian speakers. The results of post-hoc Tukey tests showed that among hC-words, velar and bilabial stops (EAS: p < 0.001; WAS: p < 0.001) as well as velar and dental stops (EAS: p < 0.001; WAS: p < 0.001) differed significantly between younger and older speakers of both varieties. The difference between dental and bilabial stops was not significant.

2.2.1.2 Voice onset time

It has been shown for numerous languages that voice onset time varies with place of articulation (Cho & Ladefoged, 1999). If we find the same VOT pattern in hC- and in C-words, it could very likely be attributed to articulatory or aerodynamic principles. A different VOT pattern in hC- compared to C-words on the other hand will improve understanding of which factors favour the emergence of post-aspiration, and how it spreads from one place of articulation to the other. As is apparent from Figure 3, we find the typical VOT pattern in C-words and in hC-words: bilabial stops show the shortest voice onset time, velar stops the longest. Among younger WAS speakers, however, VOT in dental stops exceeds that of velar stops in hC-words. At the same time, VOT is generally longer in hC-words than in C-words, with younger and WAS speakers showing the longest VOT.

Figure 3

Voice onset time (VOT) in hC-words (green) and C-words (yellow), separately for variety, age group, and place of articulation. Each boxplot contains one mean value per speaker.

A mixed model with VOT as the dependent variable, Sequence, Age, and Variety as fixed factors, and Speaker and Word as random factors showed a significant three-way interaction (χ²[1] = 30.4, p < 0.001). Post-hoc Tukey tests confirmed that hC- and C-words differed in terms of VOT among younger (WAS: p < 0.001; EAS: p < 0.05), but not among older speakers. This means that younger speakers of both varieties produced hC-words with a longer post-aspiration than C-words, while older speakers of both varieties did not differ in their VOT.

In order to test the influence of Age, Variety, and Place of Articulation, a second mixed model was applied to hC-words. Among hC-words there was a significant three-way interaction (χ²[2] = 10.2, p < 0.01) among Place of Articulation, Age, and Variety, so that post-hoc Tukey tests were conducted. Age turned out to be significant among all three stop types in WAS (hp: p < 0.001; ht: p < 0.001; hk: p < 0.001) and in EAS among ht (p < 0.001), but not among hp- and hk-words. Thus, in EAS, younger speakers produced a longer VOT duration than older speakers only in one particular stop type (ht-sequences). The above-mentioned observation that VOT is longer in velar than in alveolar stops was confirmed statistically: there was a significant difference in VOT between velar and bilabial (p < 0.001), alveolar and bilabial (young WAS: p < 0.001; old WAS: p < 0.001; young EAS: p < 0.001; old EAS: p < 0.05), and between velar and alveolar stops in all speaker groups (old WAS: p < 0.001; young EAS: p < 0.05; old EAS: p < 0.001) except in young WAS speakers. This is in line with what is evident from Figure 3 that the VOT of velar and alveolar hC-sequences does not differ in young WAS speakers.

Although the number of words presented per second was controlled in the experimental setting, variation in speech rate cannot be excluded. To ascertain that the observed differences in VTT and VOT are not a result of a variation in speech rate between the varieties and age groups, an analysis of total word duration was carried out. The average word durations per speaker and stop sequences are displayed in Figure 4. Younger WAS speakers exhibit slightly shorter word durations (i.e., a faster speech rate) than the other three speaker groups. However, a mixed model with Word Duration as the dependent variable, Age and Variety as fixed factors, and Word and Speaker as random factors revealed no significant effects. If the age- and variety-dependent differences in VTT and VOT are due to differences in speech rate, then similar patterns should be found for word duration, VTT, and VOT. This was not the case: older and younger speakers displayed different VTT in both EAS and WAS, although in EAS there was no difference in word duration. Young WAS speakers showed a longer VOT, but shorter word duration.

Figure 4

Word duration in hC- and C-words according to variety and age group (one mean value per speaker).

To exclude the possibility that the effect of stop type on VOT and VTT was due to differences in lexical frequency of the target words, an additional test was conducted. If the sound change is favoured by lexical frequency, more frequent target words should show a longer VOT and a shorter VTT than less frequent words.

The lexical frequency of target words was classified as “high” and “low” according to the frequency table based on the movie subtitles corpus for Spanish (Cuetos et al., 2011). A token frequency count of higher than 25 within a million words was categorized as “high”, a count less than 25 as “low”. There was no effect of lexical frequency on VOT or VTT for any of the varieties and age groups.

2.2.1.3 Discussion

hC-sequences and intervocalic stops clearly differed in terms of voice termination time, the former displaying mostly positive, the latter mostly negative values. Overall, younger speakers produced hC-sequences with a shorter VTT than older speakers, but this difference was significant only in WAS, not in EAS, suggesting that in WAS pre-aspiration is fading in apparent-time. Within hC-sequences, VTT was significantly longer in the velar than in the bilabial and the dental context. There was no interaction among place of articulation, age, and variety indicating that pre-aspiration is shortening to an equal degree across stop types. The finding of a longer VTT preceding velar than preceding bilabial/dental stops is consistent with dialectological studies on Andalusian Spanish as well as with phonetic studies of pre-aspiration in languages that have it segmentally such as Icelandic or Scottish Gaelic (see Section 1.3).

Voice onset time was much more variable across phonological sequences, varieties, and age groups. VOT in hC-sequences was longest for young WAS speakers, and generally longer for WAS and younger than for EAS and older speakers. These results indicate that in Andalusian /s/ + voiceless stop sequences VOT is lengthening in apparent-time and therefore confirm the findings of a previous study (Ruch & Harrington, 2014) for a larger data set. A subsequent analysis of place of articulation, age, and variety indicated that younger and older speakers differed in terms of VOT for all three stop types /sp, st, sk/ in WAS, and only for /st/ in EAS. This pattern suggests that the sound change is more advanced in WAS than in EAS, and is in line with previous studies that found long post-aspiration in Western Andalusian varieties (e.g., Parrell, 2012; Torreira, 2012), and differences between WAS and EAS varieties in terms of VOT (O’Neill, 2010). Furthermore, the observed pattern suggests that, at least in EAS, the sound change first affects /st/-sequences, and only later might generalize to /sp, sk/-sequences. As expected by phonetic principles and VOT data from many different languages (Cho & Ladefoged, 1999), velar stops displayed the longest, and bilabial stops the shortest VOT in C- as well as in hC-sequences on average. Interestingly, this pattern did not hold for hC-sequences in young WAS speakers, where /st/ displayed a post-aspiration duration as long as /sk/. It seems, though very unlikely, that long post-aspiration in /st/ is the result of universal principles or coarticulatory overlap in the speech of younger WAS speakers. The found pattern instead suggests that a long post-aspiration is intended by the speakers as an articulatory target for /st/-sequences. Although not significantly so, the measured VOT in hC-sequences in older speakers of both varieties slightly exceeded the VOT in singleton stops. It is possible that this extended VOT arises as a result of coarticulation or a looser coupling between the glottal adduction and the oral release of the stop. This idea will be discussed in further detail in Section 5.

In the next paragraph three more durational parameters of C- and hC-sequences will be investigated in our production data: the total duration of the voiceless interval, the duration of the preceding vowel, and the oral stop closure.

2.2.2 Temporal coordination of glottal and oral gestures

The aim of these subsequent analyses is to understand how glottal and oral events are coordinated temporally, and what coordination mechanism might have given rise to the diachronic change from pre-aspiration to post-aspiration. Is the diachronic change mainly due to a change in the duration and timing of the oral closure gesture, or is the timing of the glottal opening gesture itself changing over time?

In order to shed light on these questions, three additional analyses are carried out. First, the total duration of the voiceless interval in hC-sequences will be compared across age groups and varieties to see if the duration of the glottal opening changes with the sound change. Second, the timing of the onset of pre-aspiration will be analyzed relative to an anchor point, in this case, the onset of voicing in the preceding vowel. This will be done to further understand if the fading of pre-aspiration and the emergence of post-aspiration came about due to a rightwards shift of the glottal opening, and whether the sound change is associated with a change in the duration of the preceding vowel. Third, oral stop closure duration will be looked at within (h)C-sequences in both varieties and age groups and at the different places of articulation. The aim here is to understand if the fading of pre-aspiration and the lengthening of post-aspiration are associated with a change in the oral closure duration.

The total duration of the voiceless interval in hC-sequences will be quantified by summarizing voice termination time, duration of the oral stop closure, and voice onset time. This procedure is based on the idea that one underlying glottal gesture is present for each aspirated /s/ + stop sequence. Although no physiological data for Andalusian Spanish is so far available, the idea of a single glottal opening gesture is supported by acoustic data provided by Torreira (2012), who found a consistent co-variation between the sum of pre-aspiration and closure duration and VOT, as well as by Parrell (2012), where pre-aspiration duration co-varied with post-aspiration duration.

Figure 5 displays the total duration of the voiceless interval in hC- and C-sequences. The values appear to be very stable not only across variety and age group, but also across place of articulation. It is further apparent that the total duration of the voiceless interval is greater in hC-sequences than in C-sequences in all four speaker groups and among all three places of articulation. A mixed model with the total duration of the voiceless interval as the dependent variable, with Age, Variety, and Sequence as fixed factors, and with Word and Speaker as random factors showed a significant three-way interaction (χ²[1] = 4.0, p < 0.05). The interaction might have come about because of younger WAS speakers displaying a slightly shorter total duration for the intervocalic stop /t/, while the other three speaker groups showed slightly longer total durations in this context. Post-hoc Tukey tests confirmed what is evident from Figure 5 that C- and hC-sequences clearly differed in all four speaker groups (p < 0.001), and that there was no influence of Age or Variety on this measure. These results show that speakers of Eastern and Western Andalusian Spanish distinguish C- from hC-sequences in production, the latter being produced with a very long voiceless interval (mean = 155.8 ms) which is almost twice as long as in intervocalic stops (mean = 82.4 ms).

Figure 5

Total duration of the voiceless interval in intervocalic stops (yellow) and in hC-sequences (green) according to place of articulation, variety, and age group.

The next step is to analyze the duration of the preceding vowel in hC-sequences. If the gradual shift from pre- to post-aspiration came about because of a rightwards shift of the glottal opening, i.e., because the glottal opening takes place later in time, we would expect younger speakers to produce a longer preceding vowel than older speakers. Indeed, some studies (Carlson, 2012; Figueroa, 2000; Resnick & Hammond, 1975) suggest that lengthening of the preceding vowel compensates for /s/-weakening (in their case, /s/-deletion) in some varieties of Spanish. The question in the present study is if the fading of pre-aspiration (not the debuccalisation of /s/) is compensated for by vowel lengthening. The preceding vowel duration will be quantified by measuring the interval between the onset of the preceding vowel (V1.Onset) and the offset of voicing (V1.Offset). C-sequences are taken into account by way of comparison.

In 120 hC-tokens (9.6%) and in 189 C-tokens (24.6%), VTT was negative, meaning that voicing extended into the oral closure. In these cases, the interval between V1.Onset and Cl.Onset was used instead to assess vowel duration. The duration of the preceding vowel is shown in Figure 6. Vowels preceding C-sequences are slightly longer than those preceding hC-sequences. This difference is, however, not very consistent: vowel duration preceding hC-sequences appears to be longer in Eastern than in Western Andalusian Spanish, and in Western Andalusian Spanish slightly longer for older than for younger speakers. Taken together, vowels preceding C- or hC-sequences seem to be shorter when produced by young WAS speakers than when produced by older WAS speakers, which may be attributed to the observed differences in speech rate (see Figure 4).

Figure 6

Duration of the vowel preceding singleton stops (yellow) and hC-sequences (green). Each boxplot contains one mean value per speaker.

In a first step the influence of phonological sequence (hC vs. C), age, and variety on vowel duration was tested using a mixed model in which Speaker and Word were included as random factors. This model showed a significant effect of Sequence (χ²[3] = 27.0, p < 0.001) and Age (χ²[3] = 22.1, p < 0.001) on Vowel Duration. Since there was a two-way interaction between Age and Sequence (χ²[1] = 19.6, p < 0.001), post-hoc Tukey tests were conducted and indicated that Vowel Duration preceding /C/ and /sC/ differed only in older (p < 0.001), but not in younger speakers. There was no significant difference in Vowel Duration between older and younger speakers in any of the phonological sequences.

In a second step the influence of age and variety on vowel duration was tested for hC-tokens with a positive VTT only. A mixed model with Vowel Duration as the dependent variable, Age and Variety as fixed factors, and Word and Speaker as random factors revealed no significant effects. This suggests that younger and WAS speakers do not realize the glottal abduction (devoicing gesture) later in time than older and EAS speakers; in other words, there is no rightwards shift of the devoicing gesture in apparent-time.

As a last step, closure duration in C- and hC-words will be looked at. Figure 7 suggests that closure duration is longer in hC- than in C-sequences, a tendency that seems to be more marked in EAS than in WAS. A mixed model with Closure Duration as the dependent variable, Age, Variety, and Sequence (hC- vs. C-words) as fixed factors, and Speaker and Word as random factors confirmed that Closure Duration was significantly longer in hC-sequences than in singleton stops (χ²[3] = 55.5, p < 0.001) in both varieties. Furthermore, there was a significant interaction between Sequence and Age (χ²[1] = 7.7, p < 0.01) as well as between Sequence and Variety (χ²[1] = 30.5, p < 0.001). The results of post-hoc Tukey tests displayed highly significant differences between C- and hC-sequences for all four speaker groups (p < 0.001), and a significant difference in Closure Duration of hC-sequences between young WAS speakers and the two EAS speaker groups (p < 0.05). This means that younger WAS speakers produced shorter closure durations. There was no significant effect of Age or Variety on the closure duration in C-words.

Figure 7

Duration of the oral closure in intervocalic stops (yellow) and hC-sequences (green). Each boxplot contains one mean value per speaker.

The results for closure duration have to be interpreted with caution because of the slightly faster speech rate of young WAS speakers (see Section 2.2.1). It might be the case that the reduction processes due to a faster speech rate affect the long closure duration in hC-sequences to a greater extent than in singleton stops. If this is the case, then the smaller difference between C- and hC-sequences in young WAS speakers cannot be traced back to the sound change, but to speech reduction processes that affect long segments to a greater degree than short segments.

2.3 Discussion

In this section further durational parameters have been analyzed that might be related to the change from pre- to post-aspiration in Andalusian Spanish: the total duration of the voiceless interval in (h)C-sequences, the duration of the preceding vowel, and the duration of the stop closure. The aim of these analyses was to shed light on the stability and variation of these durational parameters, and to investigate whether the sound change is associated with a change in one of these parameters.

The total duration of the voiceless interval was significantly longer in hC-sequences than in intervocalic stops for both varieties and age groups. The analysis further demonstrated that the total duration of hC-sequences—as inferred from the total duration of the voiceless interval—is very stable across varieties, place of articulation, and age groups, and is not affected by the sound change.

There was no effect of age or variety on the duration of the preceding vowel, suggesting on the one hand that, relative to the onset of the preceding vowel, the glottal opening gesture does not take place later in time in younger than in older speakers. At the same time, this finding does not support compensatory vowel lengthening that has been suggested as taking place in Eastern Andalusian (Carlson, 2012), in Cuban (Resnick & Hammond, 1975), and in Puerto Rican Spanish (Figueroa, 2000). By contrast, vowels were slightly shorter when followed by a phonological /s/ + voiceless stop than when preceding intervocalic stops. This finding, again, does not support the assumption of vowel lengthening as a compensation for /s/-lenition. An inter-dialectal comparison at this point, however, is difficult because of the different methods used to measure pre-aspiration and vowel duration. In an auditory or manual segmentation procedure, for instance, the breathy part of the vowel (voiced aspiration) can be treated either as part of the vowel or as pre-aspiration (see Gerfen, 2002, for a discussion of this issue).

Closure duration appeared to be an important parameter for distinguishing C- and hC-sequences in production, displaying significantly longer durations in hC- than C-sequences in all four speaker groups. This effect, however, appeared to be less marked in younger Western Andalusian speakers, who also pronounced the longest post-aspiration (see Section 2.2.1). The long stop closures that were found not only for younger, but also for older speakers in both varieties suggest that long stop closures did not arise to compensate for the shortening of pre-aspiration, but might have arisen previous to the sound change to compensate for /s/-weakening (see Gerfen, 2002; Ruch & Harrington, 2014).

Taken together, the results of the closure duration, the duration of the voiceless interval, and the previous vowel suggest that the shortening of pre-aspiration came about because the oral closure is formed earlier in time, while the timing of the glottal abduction relative to the preceding vowel remains relatively constant across age, variety, and place of articulation.

3.2 Results

For data analysis the remaining 74 subjects were, again, divided in an older (> 50 years; 36 subjects, mean age 67.2 years) and a younger (< 50 years; 38 subjects, mean age 26.8 years) group. Men and women were approximately equally distributed among the two dialect and age groups (see Table 4).

A generalized linear mixed model in R was used to calculate the slope and the intercept individually for each listener. The Listeners’ Judgement was set as the dependent variable (two levels: pata/pasta), the VOT Step as fixed factor (9 levels), and the Listener (74 levels) and the Continuum (two levels: pasta-/pata-continuum) as random factors.³ The speaker-specific slope m and intercept k were then used to calculate a psychometric curve for each listener.⁴ It turned out that for five listeners the cross-over point (i.e., the 50% decision boundary) was situated outside the stimuli range, meaning that their answers were not consistently influenced by VOT. They were all over 50 years of age, one was from Granada and four from Seville of which one reported having hearing problems. The data of these five listeners were excluded from further analysis.

Figure 8 displays the decision boundaries for all four listener groups. As expected, older listeners needed a longer VOT to perceive pasta than younger subjects, that is, they show a higher value for the cross-over point. No difference can be seen between EAS and WAS listeners in what refers to the cross-over point. An ANOVA with the Cross-over Point as the dependent variable and Age and Variety as between-subject factors showed a highly significant effect of Age (F[1,65] = 37.6, p < 0.001) on the dependent variable; the effect of Variety was not significant and there was no interaction between the factors.

Figure 8

Cross-over point (50% decision boundary) in the perception experiment (one value per listener), separately for old (dark grey) and young (white) speakers of EAS (left two boxplots) and WAS (right two boxplots).

Figure 9 shows the psychometric curves separately for age and variety. The endpoints of the VOT-continua were identified consistently as /pata/ or /pasta/ by all four listener groups. The mean psychometric curves of the younger listeners appear to be steeper than those of the older listeners. At the same time, Eastern Andalusian subjects show a flatter psychometric curve than Western Andalusian subjects, this difference being more marked for younger than for older subjects. An ANOVA with the speaker-specific Slope as the dependent variable and Age and Variety as between-subject factors showed a significant effect of Age (F[1,65] = 33.4, p < 0.001) and Variety (F[1,65] = 19.6, p < 0.001) and an interaction between them (F[1,65] = 6.3, p < 0.05). In a post-hoc Tukey test, Age turned out to be significant only among WAS (p_adj < 0.001), but not among EAS listeners, and there was no significant effect of Variety among the older listeners.

Figure 9

The mean psychometric curves in the perception experiment. Dashed lines refer to young speakers, solid lines to old speakers; black lines refer to WAS and grey lines to EAS speakers.

As explained in Section 3.1, the stimuli for this perception experiment were generated based on two different productions: /pata/ [ˈpata] and /pasta/ [ˈpat^ha]. As displayed in Table 3, the first of the two naturally produced baseline tokens contains additional cues to /pata/, the latter additional cues to /pasta/. Although the main aim of the perception experiment lays on the role of VOT, a comparison between the two continua—the pata- and the pasta-continuum—may give some indication of whether other acoustic cues besides post-aspiration potentially play a role in the perceptual distinction between pata and pasta. The psychometric curves were again calculated for all 74 listeners, but this time separately for each of the two continua. The data of 8 listeners had to be removed because they did not converge in one or in both continua. Figure 10 shows the psychometric curves separately for EAS and WAS listeners, and separately for the two continua. In both varieties, the curves of the pasta-continuum are slightly left-shifted, meaning that the participants gave fewer pata answers than when the continuum was generated based on [ˈpata]. This trend seems to be more pronounced for older than for younger listeners. A repeated-measures ANOVA with Cross-over Point as the dependent variable, Continuum as within-subject factor, and Age and Variety as between-subject factors showed a highly significant effect of Continuum (F[1,62] = 115.3, p < 0.001) and a significant interaction between Age and Continuum (F[1,62] = 32.3, p < 0.001). In post-hoc t-tests with Bonferroni correction, Continuum appeared significant in both older (p_adj < 0.001) and younger listeners (p_adj < 0.001). Age turned out to be significant only in the pata- (p_adj < 0.001), but not in the pasta-continuum. There was no influence of Continuum on the slope of the psychometric curve, and no significant interaction.

Figure 10

Psychometric curves showing the perception of VOT according to continuum, variety, and age group.

3.3 Discussion

The results showed that younger and older listeners of Eastern and Western Andalusian Spanish were able to distinguish the minimal pair pata-pasta that differed only in VOT of /(s)t/. The age-dependent differences in the cross-over point suggest that younger listeners are more sensitive to post-aspiration as a cue for /st/ than older listeners. The differences between EAS and WAS listeners in the slope of the psychometric curves, on the other hand, indicate that the latter have a more categorical perception of post-aspiration in this minimal pair, i.e., they distinguish more consistently between stimuli containing either a short or a long VOT.

Stimuli that had been resynthesized based on an original pasta token were more likely to be perceived as pasta. When the cross-over point was calculated separately for each continuum, age appeared to be significant only in the pata-continuum. This finding underlines the importance of additional cues to /st/. It is possible that older listeners based their judgements primarily on the C:V1-ratio, and not on VOT. The measurements in Table 3 demonstrate that the C:V1-ratio was greater in the stimuli of the pasta- than in those of the pata-continuum (1.05 for VOT-step 1 in the pata-continuum, 1.35 for VOT-step 1 in the pasta-continuum).

As hearing is known to decline with age (Boenninghaus & Lenarz, 2005, p. 109), the question arises whether the reported age-dependent differences in the perception of post-aspiration are due to hearing loss in the elderly subjects. Additional analyses were conducted in order to address this question. The 9 subjects with self-reported hearing problems (all of them older than 50 years) and all other 16 subjects older than 65 years⁵ were excluded for these tests. The same statistical tests as described above were performed on the data of the remaining 48 listeners. For this reduced dataset the same significant effects of Age on the Cross-over Point (F[1,44] = 14.9, p < 0.001) and on the Slope of the psychometric curve (F[1,44] = 7.7, p < 0.01) were found.

The fact that continuum had a significant effect also among older listeners suggests that older listeners did perceive the phonetic details that distinguished the two continua, and thus supports the interpretation that the differences between older and younger listeners in crossover-point and slope of the psychometric curve do not have to be attributed to hearing-loss, but can be interpreted as a sound change in progress. In order to fully exclude hearing degradation as an artefact to listener age, future perception experiments with Age as an independent variable should include a control continuum (e.g. /x/-/f/) or a same-different test on the stimuli.

With the caveat that the effect of hearing loss may not be entirely excluded, the results of the forced-choice perception experiment suggest that the sound change in progress from pre- to post-aspiration also affects perception.

Except for 5 out of 74 listeners, the endpoint of the continua with a VOT of 55 ms was identified very consistently as /pasta/ even by the older EAS subjects. This result is surprising when it is considered that older EAS subjects in the production task did not use post-aspiration for distinguishing hC- and intervocalic C-sequences.

Still, on a whole, there seems to be a relationship between production and perception of post-aspiration such that the group of younger Western Andalusians displaying the longest VOT in production showed also a more categorical perception of post-aspiration in the forced-choice perception experiment, and older Eastern Andalusians producing the shortest VOT were also the least sensitive to post-aspiration in the perception experiment. The more abrupt psychometric curves of the younger WAS listeners suggest that the post-aspirated stop [t^h] is for this group, to a certain degree, phonologized. The next section tests whether this group relationship also holds true at an individual speaker-listener level.