Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
How do persons with apraxia of speech deal with morphological stress in Spanish? A

preliminary study

Lorraine BAQUÉ

Laboratori fLexSem, Universitat Autònoma de Barcelona, Dept. Filologia Francesa i

Romànica, Bellaterra (Cerdanyola del Vallès, Barcelona), Spain



ABSTRACT

Equal stress across adjacent syllables and extended syllable durations are amongst the most

salient features of acquired Apraxia of Speech (AOS). Most studies conclude that there is a

deficit in durational cue processing, whereas the other acoustic stress correlates remain

relatively unimpaired. Spanish is a free-stress language in which stress patterns are

contrastive, especially in verbal forms (e.g. lavo /ˈlabo/ ‘[I] wash’ vs lavó /laˈbo/ ‘[He/she]

washed’). The aim of this preliminary study is to determine whether persons with AOS are

able to make the intended stress pattern identifiable and, if so, to determine which acoustic

cues they use to avoid the ‘equal stress’ phenomenon. The results show that, for each

parameter considered (duration, intensity, fundamental frequency), apraxic participants’

productions differed from those of controls to varying degrees depending on the task.

However, 91.7% of the apraxic participants’ realisations were perceived as corresponding to

the intended tense and person. These results are interpreted as deriving from a motoric deficit

affecting morphological stress processing by subjects with AOS combined with an

idiosyncratic compensatory use of the stress cues in order to avoid ‘equal stress’.



KEYWORDS: Apraxia of speech, Morphological stress, Spanish, Equal stress, Acoustics,

Compensation
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
INTRODUCTION

Although the number of levels of speech processing vary across psycholinguistic models, the

last stage of speech production is assumed to be the phonological representation that feeds

into the motor control system (see Browman & Goldstein, 1992; Plaut & Kello, 1999. for a

different viewpoint). Most accounts of phonological encoding (Caramazza, 1997; Dell, 1986;

Garrett, 1980; Levelt, 1989; Levelt, Roelofs, & Meyer, 1999) postulate separate and parallel

retrieval of the metrical and segmental representations of word forms (Butterworth, 1992;

Levelt, 1989, 1992; Levelt et al., 1999) and some sort of mechanism for (re)syllabification of

the words in context. It is usually assumed that during phonological word-form retrieval

segmental information is accessed separately from information concerning stress pattern and

number of syllables. These two representations are then assembled incrementally by a

segment-to-frame mechanism (Keating & Shattuck-Hufnagel, 2002; Levelt, 1989; Levelt et

al., 1999; Schiller, 2003; Schiller, Jansma, Peters, & Levelt, 2006; Shattuck-Hufnagel, 1983)

in phonological words containing one or more lexical items (Hall & Kleinhenz, 1999; Hayes,

1989; Nespor & Vogel, 2007; Peperkamp & Wiltshire, 1999; Selkirk, 1995) before the

articulation is planned and executed.

However, the exact content of retrieved metrical representations differs across models with

regard to at least two issues, namely, whether or not the representations include a) the

syllable-internal structures (Dell, 1988; Levelt, 1992; Levelt & Wheeldon, 1994; Roelofs,

1997; Roelofs & Meyer, 1998; Sevald, Dell, & Cole, 1995; Stemberger, 1984, 1990) and b)

the lexical stress pattern. Concerning the latter, lexical stress assignment is seen as resulting

from either a) the retrieval of a stored stress pattern representation for each lexical item

(Butterworth, 1992; Laganaro, Vacheresse, & Frauenfelder, 2002), b) the retrieval of stored

stress patterns for irregular items and the computation of regular ones (Colombo, 1992; Levelt

et al., 1999; Roelofs & Meyer, 1998), c) analogical mechanisms that compute stress pattern
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
on the basis of the stress pattern of similar words, or d) the combination of two different

processes: stress pattern retrieval on the one hand and phonological and/or morphological

rule-based or statistically-based computation on the other (Butterworth, 1992; Laganaro et al.,

2002).

Spanish is a free-stress language in which stress pattern plays a distinctive role at the

semantic-lexical level for a few items (plato ‘plate’ /ˈplato/ vs plató ‘[television] studio’

/plaˈto/) and very systematically at a morphological level (cálculo ‘calculation’ /ˈkalkulo/,

calculo ‘[I] calculate’ /kalˈkulo/, calculó ‘[He/she] calculated’ /kalkuˈlo/; tapo ‘[I] cover’

/ˈtapo/, tapó [He/she] covered’ /taˈpo/, etc.). Although stress may occur on each one of the

three (or four if we take into account some wordforms made up of a verb and two or more

pronoun) last syllables of a word, 95%-97% of nouns are either oxytones ending in a

consonant or paroxytones ending in a vowel (Hualde, 2005; Alcoba Rueda, 2013). In addition,

the stress pattern is constrained by some specific phonological rules (e.g. words ending in a

glide are always oxytone). It is worth noting that in the standard dialect used in Spain the

vowel system exhibits little variation based on lexical stress (Delattre, 1969; Quilis &

Esgueva, 1983) as compared to languages such as English, and no vocalic neutralisation. Thus

stress contrasts in Spanish are mainly realised by means of prosodic cues such as fundamental

frequency (F0) and duration (Quilis, 1981; Llisterri, Machuca, Ríos, & Schwab, 2014) or F0

and intensity (Llisterri, Machuca, de la Mota, Riera, & Ríos, 2005).

Apraxia of speech (AOS) is an acquired neurological disorder assumed to impair retrieval

and/or implementation of articulatory plans, despite the absence of muscle weakness or

paralysis. Among the main features of apraxic speech are effortful speech production with

groping (Johns & Darley, 1970), articulatory imprecision (Haley, Ohde, & Wertz, 2001),

difficulty initiating speech (Johns & LaPointe, 1976), and dysprosodia, characterised by

slowed speech rate, syllable segregation, rhythm and intonation abnormalities, and stress
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
contrastiveness reduction—also known as ‘equal stress’—not attributable to stress assignment

deficits (Duffy, 2013; Gandour & Dardarananda, 1984; Kent & Rosenbek, 1983; Malcolm R.

McNeil et al., 2009; Ogar, Slama, Dronkers, Amici, & Gorno-Tempini, 2005; Ouellette &

Baum, 1994; Vergis et al., 2014; Walker, Joseph, & Goodman, 2009).

Concerning ‘equal stress’, it has been argued that it could result from a basic timing deficit

(Danly & Shapiro, 1982) that affects durational cue processing (Emmorey, 1987; Gandour,

Petty, & Dardarananda, 1989; Marquardt, Duffy, & Cannito, 1995; Ouellette & Baum, 1994;

Vergis et al., 2014; but see Ross, Shayya, & Rousseau, 2013; Walker et al., 2009, for different

results), while the other acoustic stress correlates remain unimpaired. From this point of view,

target weak syllables, usually shorter and showing greater coarticulation than strong ones,

could be more difficult for patients with AOS. However, syllable segregation may lead to the

production of units with similar not only duration but also intensity and F0, and thus enhance

the perception of weak syllables being stressed to a similar degree as strong ones (Odell &

Shriberg, 2001). In addition, it has been found that in AOS both task complexity and length of

items have an effect on speech production, and particularly on weak syllable lengthening,

which is responsible for a difficulty in stress contrast marking that is greater in sentences than

in isolated words (Strand & McNeil, 1996; Vergis et al., 2014).

Notwithstanding the foregoing, most studies report no or very few perceived stress pattern

errors affecting lexical recognition in AOS (Malcolm R. McNeil et al., 2009; Nickels &

Howard, 1999; Odell, McNeil, Rosenbek, & Hunter, 1991; Odell & Shriberg, 2001; Vergis et

al., 2014). It might be conjectured that speakers with AOS somehow develop compensatory

strategies (Edmonds & Marquardt, 2004; Goldstein, 1939; Kolk & Heeschen, 1990; Lashley,

1929; Luria, 1970; Simmons-Mackie & Damico, 1997) to overcome their difficulties and

allow them make the intended stress pattern identifiable by their interlocutor. A compensatory

strategy can be defined as the often spontaneously acquired use of atypical (values of)
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
parameters in order to compensate for the impairment of another parameter with the aim of

making the intended phonological category successfully cued (Khasanova, Cole, &

Hasegawa-Johnson, 2014). Actually, some of the main features of AOS such as slowed

speech, syllable segregation, and syllable or phoneme simplifications have been regarded as

resulting at least partly from compensatory strategies (Edmonds & Marquardt, 2004; Johns &

Darley, 1970; Kent & Rosenbek, 1982). However, though compensation has been mentioned

in relation with atypical stress cues (e.g. Odell, McNeil, Rosenbek, & Hunter, 1991)—and in

fact we ourselves have argued in a previous preliminary study (Baqué, 2017) that such

compensatory strategies may account for some of the characteristics of stress patterns in

several patients suffering from non-fluent aphasia and concomitant AOS—to our best

knowledge no specific studies have focused on compensation for stress contrast marking

difficulties in AOS.

STUDY AIMS

The aim of this exploratory study was to investigate whether persons with AOS are able to

make the intended stress pattern identifiable when it conveys a morphological value

(paroxytone 1st person of the present tense vs oxytone 3rd person of the preterite tense). To

this end, we analysed separately the three acoustic parameters involved in stress contrast

marking in Spanish, namely duration, F0 and intensity, in order to determine whether they

were equally impaired and, if that was the case, to determine which acoustic cues the patients

used in order to avoid the ‘equal stress’ phenomenon. Since there is in Spanish a very clear

tendency towards F0 displacement, especially in paroxytone words in non prepausal position

(Llisterri, Marín, de la Mota, & Ríos, 1995), we decided to analyse syllable mean F0 instead

of maximum F0 value. Concerning intensity, several acoustic measures have been used to

account for lexical stress contrasts (Gordon & Roettger, 2017), including, among other things,

mean vowel or syllable intensity, peak syllable intensity, overall intensity or intensity integral,
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
which is related to the increased perception of loudness in a longer stimulus relative to a

shorter one. In order to disentangle the processing of duration and intensity cues, we decided

to discard composite measures such as intensity integral and focused instead on syllable

maximum intensity values, reported by several authors since Fry (1955) as contributing to

stress contrasts perception in different languages (for Spanish, see Torreira, Simonet, &

Hualde, 2014).




METHOD


Participants


Two small groups of right-handed native speakers of Spanish took part in this experiment,

comprising three participants with apraxia of speech (AX) and three non-aphasic controls

(N0). Inclusion criteria for all participants were that they had to a) be native speakers of

Spanish from the Spanish-Catalan speaking region of Spain, b) be aged between 25 and 50, c)

have undergone higher education and d) have given their informed consent. For the AX group

the specific inclusion criteria were that they a) had acquired apraxia of speech following a

cerebral vascular accident (CVA) or tumour surgery, b) were diagnosed by their speech

pathologist with apraxia of speech but no or very minimal aphasia and c) obtained language

examination scores according to the MTBA (Labos, Del Río, Zabala, & Nespoulous, 2005),

COGNIFON (Baqué et al., 2006) and/or TBR (Peña-Casanova, 2005) examination protocols

compatible with apraxia of speech with no or very minimal aphasia as reported by two other

speech pathologists. As can be inferred from the obtained examination scores (see Appendix

A, Table 3), frequent phonetic deviations but no evidence of agrammatism, oral

comprehension deficits, asyntactic comprehension or impairment in phoneme or stress

discrimination tasks were found for each of the three participants in the AX group. Controls
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
were subjects with no reported deafness or linguistic, neurological, cognitive or psychiatric

disorders. The two groups were matched for age (mean: AX = 39.7 SD 6.4; N0 = 36.0 SD

7.2), sex (two females and one male in each group) and educational level (higher education)

(see Appendix A for more detailed information).



Material and procedure

In this study we selected 12 disyllabic CV.CV1 verbal forms from the Spanish COGNIPROS

morphological corpus (Baqué, Estrada, & Daoussi, 2016) on the basis of three factors: 1) the

fact that their morphological value (1st person of the present tense vs 3rd person of the preterite

tense) is conveyed exclusively by the stress pattern (paroxytone vs oxytone, respectively, as in

lavo /ˈlabo/ ‘[I] wash’ vs lavó /laˈbo/ ‘[He/she] washed’), 2) lexical frequency (mean

logfreqN = 1.23 SD 0.47 in EsPAL, see Duchon, Perea, Sebastián-Gallés, Martí, & Carreiras,

2013) and age of acquisition (mean = 4.94 SD 0.88, following Alonso, Díez, & Fernandez

(2016)), and 3) ‘imageability’ (mean = 4.96 SD 0.90 as measured on a 7-point Likert scale,

(Duchon et al., 2013)). Each item could appear either isolated or in a short sentence (e.g. Lavo

/ Lavo la taza ‘[I] wash / [I] washed the cup’).

All participants were asked to perform three tasks, namely 1) a sentence-cued sentence

elicitation task using a picture prompt, or what is known as 'sentence naming', 2) reading

isolated words and 3) reading short sentences. Since all the verbs selected were transitive and

a direct object was therefore obligatory in most cases, the picture naming task was only cued

by means of a sentence because we predicted that otherwise participants would probably have

responded by naming the action of the verb in infinitive form rather than using the target

inflected form. In the three tasks, while viewing the prompt, participants heard a context

sentence in which the target morphological value was made explicit such as Yo, cada día,

1
    C = consonant; V = vowel.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
hago lo mismo de siempre ‘Every day, I do the same as always’ to target 1st person present

tense or Sara, ese día, hizo lo mismo de siempre ‘That day, Sara did the same as always’ to

target 3rd person preterite tense.

Participants’ speech was recorded with a sampling frequency of 44.1 kHz and 24-bit

resolution and stored in WAV PCM format using Adobe Audition CS5.5 software on a PC.

The recording equipment consisted of an Audio Technica Condenser Microphone AT2050, a

Roland Cakewalk UA-25EX audio interface and an Alesis Multimix 8 mixer device, and all

recordings took place in a soundproof room at the Speech Service of the Autonomous

University of Barcelona.




Data analysis

We conducted two kinds of analyses: 1) an auditory evaluation of each recording in order to

determine whether a) the intended morphological value conveyed by the stress pattern,

whether canonically realised or not, was identifiable and b) the main features of AOS were

audible; and 2) an acoustic analysis of each production.

For the first analysis, five listeners from the same geographic area as the participants (three

phoneticians and two naïve speakers) were asked to independently listen to all the recordings

and indicate whether each word or sentence corresponded to a 1st person present tense or a 3rd

person preterite tense narrative. In addition, in order to check the on-target morphological

value and perceived canonicity of the production, we also asked listeners to assess in a yes/no

task whether one or more of the main features of AOS (effortful speech production with

groping, articulatory imprecision, slowed speech rate, syllable segregation and ‘equal stress’)
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
were audible in each produced word or sentence.2 In both cases, we evaluated inter-listener

agreement by calculating Conger’s exact kappa (Conger, 1980; Fleiss, 1971) using the ‘irr’

package (Gamer, Lemon, Fellows, & Singh, 2015) in R (version 3.1.2) (R Core Team, 2014).

As for the acoustic analysis, each word or sentence production was automatically segmented

into phones and syllables using the EasyAlign plugin under Praat (Boersma & Weenink,

2014; Goldman & Schwab, 2014) and manually corrected. For each syllable we extracted the

duration (in s), the maximum intensity value (in dB) and the mean F0 value of the vowel (in

Hz, using Hirst’s algorithm (Hirst, 2011)). In order to avoid an inter-speaker effect on

duration, F0 and intensity values, we calculated the percentage of variation between the

duration of the last and first syllables (VarDurSyl), mean F0 (VarF0Syl) and maximum

intensity values (VarIntSyl). We then ran separate analyses for each acoustic parameter by

means of several mixed-effects regression models (Baayen, Davidson, & Bates, 2008).

Participants and items were entered as random factors. The predictors were Group (AX vs

N0), Task (sentence picture naming (SN) vs sentence reading (SR) vs word reading (WR)),

Stress Pattern (oxytone (OX) vs paroxytone (PX)) and all their possible interactions. We also

carried out mixed-effects linear regression models with the aim of analysing the co-variation

between VarDurSyl on the one hand and VarF0Syl and VarIntSyl on the other as a function of

Group, Stress Pattern and Task.

In order to identify participants’ idiosyncratic behaviours, we added for the various measures

and for each case-control mixed-effects regression analyses with items entered as a random

factor.

Linear mixed-effects regression models were fitted using the ‘lme4’ package (Bates,

Maechler, Bolker, & Walker, 2015), contrast and comparisons were computed using lsmeans



2
    We thank Reviewer #1 for his/her suggestion.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
(Lenth & Hervé, 2015) and figures were generated with ggplot2 (Wickham, 2009) in R

software (version 3.1.2) (R Core Team, 2014). Significance level was set at 5%.




RESULTS 3

Perceived errors and inter-listener agreement

We carried out several logistic regression mixed models in order to determine if there was any

effect of Group, Task and/or Stress Pattern on the number of perceived errors (see table 1).

When we considered all items (n = 216) classified as an error if the majority of listeners

interpreted them as corresponding to the off-target morphological value, no significant effects

were found (Group: Wald-X2(1) = 3.1111, p = 0.07776; Stress Pattern: Wald-X2(1) = 0.5750,

p = 0.44827; and Task: Wald-X2(2) = 1.7035, p = 0.42667). Similarly, no significant effects

were found when we took into account only those 171 items (78.8% of total productions) for

which there was perfect inter-listener agreement, that is, that were interpreted as

corresponding to either a 1st person present tense or a 3rd person preterite tense narrative by all

the listeners (Group: Wald-X2(1) = 0.0002, p = 0.9885; Stress Pattern: Wald-X2(1) = 0.0574,

p = 0.8106; and Task: Wald-X2(2) = 0.0166, p = 0.9917). Moreover, the comparison of each

aphasic’s productions with those of controls also showed no significant effect. When the

dependent variable included each evaluation of a production by each listener (n = 216 × 5 =

1080), the results showed an effect of Group (Wald-X2(1) = 4.5011, p = 0.03387) and Task

(Wald-X2(2) = 6.2127, p = 0.04476). No other effects were found. As compared to an item

produced by the N0 group in the SN task, the probability of an item being perceived as an

error by a listener was 2.78 times higher in the AX group, and 1.62 times lower for the SR

task (p = 0.163) and 3.09 times lower for the WR (p = 0.014) task. Case-control analysis

showed that the probability of perceived errors was significantly higher for those two specific


3
    See Appendixes B and C (Tables 4 to 15) for a comprehensive overview of the statistical results.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
participants in the AOS group designated respectively AX2 (14.9%) and AX3 (13.8%) as

compared to all controls (N0) (3.2%) as well as the other member of the AOS group,

designated AX1 (2.6%).




Table1: Rate of perceived errors by Morphological value, Group and Task, taking into
account: a) all items classified according to most listeners’ perceived morphological value (n
= 18 items × 2 morphological values × 3 tasks × 2 groups = 216 evaluations), b) the 171 items
with perfect inter-listener agreement, and c) all the items evaluated by each listener (n = 18
items × 2 morphological values × 3 tasks × 2 groups × 5 listeners = 1080 evaluations).


Since the difference between these results might be explained by an articulatory imprecision

in the AX group that resulted in greater inter-listener variability, we decided to calculate

Conger’s exact kappa (Conger, 1980; Fleiss, 1971) for the five listeners not only overall (n =

216) but also separately for each group (n = 108) and participant (n = 36). The results showed

excellent agreement overall (exact-kC = 0.805) following Fleiss’ arbitrary guidelines (Fleiss,

2013). Kappa values varied as a function of Group, being higher for the N0 than the AX

group (exact-kC = 0.883 and 0.726 respectively), Participant (N01: 0.848, N02: 0.900, N03:
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
0.900; AX1: 0.600, AX2: 0.889, AX3: 0.685) and Task (for N0, SN: 0.883, SR: 0.856 and

WR: 1.000; for AX: SN: 0.667, SR: 0.745 and WR: 0.765).

Perceived AOS and inter-listener agreement

As shown in table 2, no word or sentence realisation by any of the participants in the N0

group was perceived to present one or more of the main AOS features. On the other hand,

96.9% of the AX recordings were associated with those characteristics, ranging from 95.5%

(AX3) to 98.3% (AX1 and AX2). Because of the lack of variability in the N0 group and in

some of the tasks as carried out by the AX group, no statistical between-groups analyses

could be conducted. In addition, no effect of Stress Pattern was found. However, a logistic

regression mixed model showed a significant effect of Task on the probability of perception

of AOS characteristics (Wald-X2(2) = 9.259, p = 0.00976): as compared to an item produced

in the SR task, the probability of an item being perceived by a listener as showing AOS

features was significantly lower in the WR task (predicted means: 50.0% and 45.7%

respectively, p = 0.0271). No other significant differences were observed. This result can be

interpreted as resulting from the length of the item listened to (i.e. there were fewer acoustic

cues to help identify atypical speech in words than in sentences; see parallel results in foreign

accent identification in Atagi & Bent, 2017) and/or from a greater difficulty in articulatory

planning of a longer sequence.

Inter-listener analyses by means of Conger’s exact kappa (Conger, 1980; Fleiss, 1971) for the

216 items and five listeners showed excellent agreement overall (exact-kC = 0.950). Kappa

values varied as a function of Task, being higher for the SN and SR tasks than for WR task

(exact-kC = 1, 0.989 and 0.862 respectively).
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155




Table2: Number of items perceived as presenting some of the main AOS characteristics
features by Group and Task, taking into account all the items evaluated by each listener (n =
18 items × 2 morphological values × 3 tasks × 2 groups × 5 listeners = 1080 evaluations).



Overall syllable duration

Concerning syllable duration, the results showed a single significant effect of Group (F(1,

3.9867) = 20.519, p = 0.01066). As shown in Figure 1, syllable duration was twice as short in

the N0 group (0.181 SD 0.069 s) as in the AX group (0.389 SD 0.117 s). As expected, each

AX participant presented longer overall syllable duration (AX1: 0.384 s, AX2: 0.468 s, AX3:

0.316 s) as compared to N0 but the case-control difference was significant only for AX1 and

AX2.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155




Figure 1: Mean syllable duration (in s) as a function of Stress Pattern (OX: oxytone vs PX:
paroxytone) and Group (N0, AX).



Acoustic characteristics of stress contrasts

In the following analyses, we excluded those items (n = 11) considered off-target by at least

three listeners.

For all parameters considered there were significant interaction effects involving Task, and

post hoc analyses showed in all cases differences between those items produced in isolation

(WR) and those included in sentences (SR and SN), which were not significantly different.

This is probably due to the fact that in WR (vs SR and SN) the target word was located at the

final edge of an assertive utterance, which is usually associated with final pre-pausal

lengthening and pitch and intensity decrease.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
Since no differences were found for any of the parameters considered between read and

named sentences, these two tasks were collapsed. Thus we carried out separate analyses for

isolated word production (WR) and for words embedded in sentences (SR + SN).

Intra-word acoustic contrasts: word reading

Results showed a main effect of Stress Pattern and an interaction effect of Stress Pattern and

Group on each parameter considered: VarDurSyl (F(1, 10.158) = 11.4489, p = 0.006809 and

F(1, 51.162) = 10.6283, p = 0.001984), VarF0Syl (F(1, 60.887) = 47.644, p = 3.435e-09 and

F(1, 60.887) = 6.505, p = 0.01329) and VarIntSyl (F(1, 10.259) = 72.261, p = 5.823e-06 and

F(1, 51.943) = 14.865, p = 0.0003199).

Concerning the last vs first syllable duration (VarDurSyl), both groups lengthened the final

syllable in all cases and this lengthening was greater for OX than PX (N0: +94.4% SD 32.5 vs

+33.0% SD 21.8; AX: +58.4% SD 38.4 vs +41.2% SD 43.5). However, this difference was

significant only in the N0 group. Case-control analyses showed that VarDurSyl values did not

differ from those of controls, except for AX1 in OX (+36.0% SD 25.0 vs N0: +94.4% SD

32.5). Contrary to what was observed in the N0 group, none of the AX participants revealed

significant differences as a function of Stress Pattern.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155




Figure 2: Mean syllable duration variation (VarDurSyl) as a function of Stress Pattern (OX:
oxytone vs PX: paroxytone) and Group (N0, AX) in isolated word reading (WR).



As regards the mean F0 of the last vs first syllables (VarF0Syl), as would be expected in final

conclusive intonation, in both groups the last syllable, when unstressed (PX), was

characterised by a decreased F0 mean (N0: -9.2% SD 6.0 and AX: -12.5% SD 25.1), while

VarF0Syl values were positive in OX (N0: +2.1% SD 5.8 and AX: +10.5% SD 15.2). Post

hoc analyses showed that contrasts between OX and PX were significant for both groups and
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
for each participant. Case-control comparisons showed similar VarF0Syl values between AX

and N0 participants, except for AX3, who increased mean F0 in the last syllable even when it

was unstressed (PX: +12.6% SD 22.3). However, this increase was significantly higher in OX

(+34.5% SD 4.2).




Figure 3: Mean syllable F0 variation (VarF0Syl) as a function of Stress Pattern (OX: oxytone
vs PX: paroxytone) and Group (N0, AX) in isolated word reading (WR).
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
With regard to maximum intensity of the last vs first syllables (VarIntSyl), as would be

expected in final assertive intonation, VarIntSyl values were negative for PX (N0: -10.4% SD

5.2 and AX: -7.4% SD 4.3) and almost zero for OX (N0: +3.3% SD 2.8 and AX: -0.9% SD

3.9). Post hoc analyses showed significant differences as a function of Stress Pattern in both

groups. Case-control analyses did not show any significant difference between VarIntSyl

values of any of the AX participants and controls for either OX or PX. However, differences

as a function of Stress Pattern were significant for N0 (PX: -10.4% SD 5.2 vs OX: +3.3% SD

2.8) and AX1 (PX: -10.2% SD 2.5 vs OX: +0.5% SD 5.2) but not for AX2 (PX: -5.0% SD 4.4

vs OX: -0.7% SD 3.9) or AX3 (PX: -6.8% SD 4.5 vs OX: -2.0% SD 2.2).
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155




Figure 4: Mean syllable intensity variation (VarIntSyl) as a function of Stress Pattern (OX:
oxytone vs PX: paroxytone) and Group (N0, AX) in isolated word reading (WR).



Intra-word acoustic contrasts: sentence reading and naming

Results showed a main effect of Stress Pattern (F(1, 21.542) = 6.1271, p = 0.021682) and an

interaction effect of Stress Pattern and Group (F(1, 107.436) = 10.1541, p = 0.001886) on

VarDurSyl. In N0 the final syllable was characterised by substantial shortening in PX (-31.5%

SD 21.6), contrary to what was observed in OX (-1.8% SD 21.3). No such difference was
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
shown by the AX group (PX: +6.5% SD 28.5 vs OX: +6.4% SD 39.1). Case-control analyses

confirmed that none of the AX participants showed significant differences between PX and

OX VarDurSyl values (AX1: +17.3% SD 27.7 vs 28.2% SD 28.7; AX2: +16.6% SD 26.7 vs

+4.4% SD 16.9; AX3: -14.5% SD 19.7 vs -15.5% SD 51.3).




Figure 5: Mean syllable duration variation (VarDurSyl) as a function of Stress Pattern (OX:
oxytone vs PX: paroxytone) and Group (N0, AX) in sentence reading and sentence naming
(SR + SN).
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
Concerning VarF0Syl, there was a single effect of Stress Pattern (F(1, 22.7) = 5.9262, p =

0.02321) and no effect of Group or interaction effect. In OX, the last syllable presented a

higher mean F0 value (+10.4% SD 15.7) than in PX (+3.0% SD 16.5). However, case-control

post hoc analyses showed no significant intra-individual differences between the two stress

patterns in AX, contrary to what was observed in N0.




Figure 6: Mean syllable F0 variation (VarF0Syl) as a function of Stress Pattern (OX: oxytone
vs PX: paroxytone) and Group (N0, AX) in sentence reading and sentence naming (SR + SN).
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
As for VarIntSyl, a main effect of Stress Pattern (F(1, 22.814) = 29.824, p = 1.538e-05) and an

interaction effect of Stress Pattern and Group (F(1, 108.122) = 15.968, p = 0.0001179) were

found. Post hoc analyses showed a significant difference between OX and PX in N0 (+4.2%

SD 4.6 vs -0.8% SD 2.5) but not in AX (-1.6% SD 4.0 vs -0.5% SD 2.5). None of the AX

participants revealed any significant differences as a function of Stress Pattern.




Figure 7: Mean syllable intensity variation (VarIntSyl) as a function of Stress Pattern (OX:
oxytone vs PX: paroxytone) and Group (N0, AX) in sentence reading and sentence naming
(SR + SN).
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
Idiosyncratic relationship between acoustic cues: a compensatory strategy?

Word reading

The results of logistic linear mixed models showed an effect of Group (Wald-X2(1) =

2.6264e+09, p = 2.2e-16), VarDurSyl(Wald-X2(1) = 2.0945e+09, p = 2.2e-16), VarF0Syl (Wald-

X2(1) = 5.3294e+08, p = 2.2e-16) and VarIntSyl (Wald-X2(1) = 1.8254e+12, p = 2.2e-16), and

three interaction effects (Group*VarDurSyl: Wald-X2(1) = 1.1158e+09, p = 2.2e-16;

Group*VarF0Syl: Wald-X2(1) = 1.5431e+10, p = 2.2e-16; and Group*VarIntSyl: Wald-X2(1 ) =

1.7059e+12, p = 2.2e-16) on the probability of stress pattern perception (PX, i.e. 1st person

present tense, vs OX, i.e. 3rd person preterite tense). However, as compared to the N0 group,

significant inter-individual differences were found between AX participants in the way they

combined acoustic parameters in order to create stress contrasts. We will present here only the

most important results.

N0 distinguished PX from OX words by significantly less final lengthening and by a decrease

in F0 and intensity values on the second (unstressed) syllable (in contrast to a slight increase

in OX). Case-control analyses showed that none of the AX participants was able to maintain

durational contrasts: there was a major overlap of VarDurSyl values in OX and PX (AX1,

AX2 and AX3). With the aim of analysing whether the values of VarF0Syl on the one hand

and VarIntSyl on the other could compensate for the atypical values of VarDurSyl in the AX

group in order to make the intended stress pattern identifiable, we carried out mixed effects

linear regression models of VarF0Syl and VarIntSyl as a function of VarDurSyl, Case-Control

(AX1, AX2, AX3 vs all N0), Stress Pattern and Task. The results showed significant effects

on VarF0Syl of Case-Control (F(3, 56.738) = 30.496, p = 7.130e-12) and Stress Pattern (F(1,

13.197) = 41.634, p = 2.009e-05). No effect of VarDurSyl and no interaction effects were

found. As for VarIntSyl, the results showed significant effects of Stress Pattern (F(1,

26.961) = 26.4187, p = 2.1e-05) and RatioDurSyl (F(1, 60.170) = 4.3849, p = 0.040479) and
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
Case-Control*Stress Pattern (F(3, 54.286) = 4.5751, p = 0.006286). No other significant

effects were found.

As can be seen in figure 8, AX1, in whose productions there was a trend towards a greater

final lengthening in PX, cued the stress contrast by means of more substantial final F0

lowering in PX than that observed in controls (VarF0Syl: β = -0.084, p > 0.0273) that tended

to be more important when the second syllable of PX was over-lengthened as compared to

control productions. In addition, VarIntSyl constrasts between PX and OX were similar in N0

and AX1 productions.

Relative to control participants, AX2 cued stress pattern contrasts by means of a slightly

greater (but not significant) F0 lowering in PX and with similar VarIntSyl differences

between OX and PX. Concerning AX3, both OX and PX were associated with a final F0

increase, but, despite some overlapping, this was much greater for OX. No significant

differences between VarIntSyl values of OX and PX were found for this participant.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
Figure 8: Predicted slopes of VarF0Syl (left) and VarIntSyl (right) as a funcion of Stress
Pattern (OX: oxytone vs PX: paroxytone) and VarDurSyl for the N0 group (all participants
combined) and each AX participant (AX1, AX2, AX3) in isolated word reading (WR).



Sentence reading and naming

In sentence production (SR+SN) the logistic linear regression model showed significant

effects of all variables and interactions considered (Group: Wald-X2(1) = 1.8316e+05, p =

2.2e-16; VarDurSyl: Wald-X2(1) = 3.2064e+06, p = 2.2e-16; VarF0Syl: Wald-X2(1) = 1.1541e+08,

p = 2.2e-16 and VarIntSyl (Wald-X2(1) = 1.0711e+09, p = 2.2e-16; Group*VarDurSyl: Wald-

X2(1) = 1.4060e+07, p = 2.2e-16; Group*VarF0Syl: Wald-X2(1) = 6.9720e+07, p = 2.2e-16;

Group*VarIntSyl: Wald-X2(1 ) = 9.5202e+08, p = 2.2e-16; VarDurSyl*VarF0Syl: Wald-X2(1)

= 4.5735e+07; VarDurSyl*VarIntSyl: Wald-X2(1) = 6.3118e+09; VarF0Syl*VarIntSyl: Wald-

X2(1)      =      8.0394e+10;        Group*VarDurSyl*VarF0Syl:                    Wald-X2(1)          =     2.8994e+08;

Group*VarDurSyl*VarIntSyl: Wald-X2(1) = 3.1172e+09; Group*VarF0Syl*VarIntSyl: Wald-

X2(1)      =    4.2532e+11;        VarDurSyl*VarF0Syl*VarIntSyl:                   Wald-X2(1)         =     2.3386e+11;

Group*VarDurSyl*VarF0Syl*VarIntSyl: Wald-X2(1) = 8.0212e+11) on the probability of

stress pattern perception (PX, i.e. 1st person present tense, vs OX, i.e. 3rd person preterite

tense).

As shown in the preceding section, in sentence production (SR + SN), fewer acoustic

differences were detected between OX and PX (see above), especially in the AX group, than

in the word reading (WR) task. While N0 participants tended to produce the second

(unstressed) syllable of PX words shorter and with higher F0 values than the first syllable,

contrary to what was observed in OX, greater inter-individual variability was observed in the

AX group.

The results of mixed linear regression models showed significant interaction effects of Case-

Control (AX1, AX2, AX3 vs all N0), Stress Pattern and VarDurSyl on both VarF0Syl (F(3,
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
106.020) = 3.0834, p = 0.030509) and VarIntSyl (F(3, 106.079) = 3.0173, p = 0.033151). As

can be seen in figure 9, there was a negative relationship between the use of duration and F0

cues in those AX participants that experienced difficulty in shortening the second syllable in

PX: more lengthened second syllables were associated with lower values of VarF0Syl (AX1:

β = -0.101 ± 0.114, AX2: β = -0.292 ± 0.130), contrary to what was observed in OX (AX1:

β = +0.043 ± 0.121; AX2 = +0.060 ± 0.247). Such a behaviour was not observed in AX3, who

was able to shorten the second syllable of OX and whose stress patterns differed also in terms

of VarF0Syl values (see above). Concerning intensity, the slopes of the obtained linear

regression equations were negative in OX and positive in PX for AX1 (β = -0.040 ± 0.033 vs

β = +0.026 ± 0.031) and AX2 (β = -.042 ± 0.068 vs β = +.002 ± 0.036), while the opposite

was observed in AX3 (β = +0.025 ± 0.018 vs β = +0.180 ± 0.046). However, there was a

major overlap of VarIntSyl values in OX and PX for each of the AX participants, contrary to

what was observed in controls, who distinguished OX from PX by higher values of VarIntSyl.




Figure 9: Predicted slopes of VarF0Syl (left) and VarIntSyl (right) as a funcion of Stress
Pattern (OX: oxytone vs PX: paroxytone) and VarDurSyl for the N0 group (all participants
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
combined) and each AX participant (AX1, AX2, AX3) in Sentence Reading and Sentence
naming (SR + SN).



DISCUSSION

The current study sought to investigate stress contrasts conveying verbal morphologic values

in Spanish words produced in isolated disyllabic word reading and sentence reading and

naming tasks by three participants with apraxia of speech but no or very little aphasia

(especially, with no evidence of agrammatism, oral comprehension deficits, asyntactic

comprehension or impairment in phoneme or stress discrimination tasks) and three controls.

The data indicate that, despite the presence of audible features of AOS (effortful speech

production with groping articulatory imprecision, slowed speech rate, syllable segregation

and/or ‘equal stress’) in the overwhelming majority of items (> 99% in SR and SN tasks and

> 92% in WR) by participants with AOS, no significant difference was found between control

(N0) and apraxic (AX) groups in the number of productions perceived as corresponding to the

off-target morphological value. The slightly lower inter-listener agreement with regard to AX

participants’ output (especially for AX2 and AX3) as compared to that of N0 participants is

probably attributable to greater articulatory imprecision. Such results show that AX

participants, despite an obvious ‘atypicality’ in their speech production giving rise to

perceived ‘equal stress’, were essentially able to make the intended stress pattern (and

associated morphological values) identifiable.

Since for both groups there was a significant effect of intonation (conclusive in WR,

characterised by pre-pausal lengthening and pitch and intensity decrease, vs non-conclusive in

SR and SN), we decided to examine isolated word reading (WR) and sentence reading and

naming (SR + SN) separately.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
In isolated word reading (WR), all participants were able to cue the final assertive intonation

by an overall final pre-pause lengthening, both in OX and PX words. This result is consistent

with those of other experiments that have shown relatively spared patterns of acoustic cues to

sentence-level prosody in productions by left-hemisphere-damaged patients (Baum, Pell,

Leonard, & Gordon, 2001; Schirmer, Alter, Kotz, & Friederici, 2001) and does not support, at

least in the tasks we used, the difficulty with the production of pre-boundary syllable

lengthening reported in several other studies (Baum, Pell, Leonard, & Gordon, 1997; Shah,

Baum, & Dwivedi, 2006; Walker et al., 2009).

Interestingly, no effect of task distinguished SR and SN results for either the N0 or the AX

group, which is congruent with the idea that the features of AOS should vary not with the type

of speech task being performed (Galluzzi, Bureca, Guariglia, & Romani, 2015; Ziegler, 2002)

but rather with the length of items and the cognitive complexity they entail (Strand & McNeil,

1996; Vergis et al., 2014). In addition, at least in simple sentences like the ones we used here

(three words, five CV syllables, subject-verb-object), the effect of different linguistic

processes involved in sentence-level picture naming and reading seems not to lead to an

overall different level of simultaneous demand complexity affecting the number of perceived

errors or the acoustic characteristics of stress contrasts.

For the most part, besides the expected overall syllable duration lengthening, the acoustic

characteristics of the intra-word acoustic contrasts between the last versus the first syllable in

OX and PX words did not differ significantly as a function of group. This indicates that AX

participants as a group tended to mark stress using strategies similar to those of N0

participants. The main difference concerned the inability of AX participants to reduce final

(unstressed) syllable duration in PX words in the SR and SN tasks, suggesting that temporal

control deficit in AOS not only affects the overall speech rate, but also somehow impairs the

realisation of the phonological rule of syllable shortening.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
However, the acoustic data was less consistent in the AX group than in the N0 group,

resulting in fewer stress pattern differences (Marquardt et al., 1995; Ross et al., 2013; Walker

et al., 2009), which could be related to the perception of ‘equal stress’. Actually, while N0

participants cued the stress pattern contrasts by each of the acoustic parameters considered

(duration, F0 and intensity) in both isolated words and sentences, none of the AX participants

established statistically significant differences between OX and PX words in terms of intra-

word acoustic contrasts of duration or intensity alone, and consistent differences in VarF0Syl

between OX and PX were only found in the WR task. These results are congruent with those

of several authors (Kent & Rosenbek, 1983; Marquardt et al., 1995; Walker et al., 2009) that

showed fewer inter-syllabic contrasts in apraxia of speech, involving not only duration

(Emmorey, 1987; Gandour, Petty, & Dardarananda, 1988; Ouellette & Baum, 1994), but also

intensity.

Taken together, our findings parallel those of Marquardt et al. (1995) in suggesting that our

participants with AOS have preserved the ability to retrieve the words’ phonological stress

pattern and then to apply different phonological rules for syllable lengthening depending on

the prosodic unit in question (lexical stress or intonational boundaries) and do not support the

hypothesis of a primary prosodic impairment in AOS. Rather, the perception of ‘equal stress’

seems to be related essentially to a basic temporal control deficit that affects speech rate and

the ability to reduce unstressed syllable durations. Possibly related to that are the observed

reduced inter-syllable intensity differences (McClean & Tasko, 2003). In addition, since all

AX participants were able to make the intended morphological value associated with each

stress pattern identifiable by the listeners mostly using acoustic strategies similar to those used

by controls, albeit with less consistent acoustic differences between stress patterns, no specific

deficit in F0 or intensity cue control can be inferred from our data.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
However, the results of examining the relationships between acoustic cues for stress contrast

marking revealed very idiosyncratic behaviours in the AX group and can be interpreted as

related to the idea that speakers with AOS deploy compensatory strategies in order to avoid

the ‘equal stress’ phenomenon (see above), as they correspond to the idea that two acoustic

cues related to the same phonological feature can enter into a compensatory relationship if,

when one cue is weakened (i.e. it presents sub-optimal values), the other is strengthened to

compensate for this (Khasanova et al., 2014). Since these results correspond to words that

were interpreted as corresponding to the on-target morphological value, such spontaneous

developed strategies could be useful for speech therapy.

Of interest is the fact that these possible compensatory relationships between acoustic cues

appeared in those participants whose acoustic characteristics, for a given stress pattern and

task, were very different from those of controls, and this varied according to the task, to wit:

    -    In WR, none of the AX participants was able to distinguish PX from OX in a way that

         resembled the performance of the N0 group in terms of duration. However, each of the

         AX participants preserved stress pattern contrasts by enhancing the difference in

         VarF0Syl, either by lowering the final F0 in PX more than expected (AX1 and AX2)

         or by a disproportionate increase in final F0 in OX (AX3). In addition, AX1 was also

         able to preserve intensity contrasts between OX from PX in a way similar to that of

         controls.

    -    In SR and SN, we observed that, unlike OX, N0 produced PX words with a shortened

         second (stressed) syllable and near zero F0 variation (contrary to OX, in which there

         was a F0 increase on the second syllable). This was also the case of AX3, but not of

         AX1 and AX2, who lengthened PX second (unstressed) syllables and presented higher

         values of F0 variation in OX second (stressed) syllables than in N0. Interestingly, we

         found a negative relationship between these durational and F0 cues in PX words
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
         produced by these participants with AOS: the more they lengthened the second

         (unstressed) syllable, the less they enhanced the F0 increase. In addition, in AX1 we

         observed that F0 contrasts between patterns were preserved by a greater F0 increase in

         PX than in OX. By contrast, no specific effect of intensity was found for any of the

         AX participants.

Given that significant intra-speaker differences were observed between word and sentence

productions, such possibly compensatory behaviours seem to result from online processes,

interacting with other prosodic demands, more than from newly learned articulatory plans.

It is noteworthy, however, that for each participant there were productions that showed similar

values in terms of all the acoustic values considered, but which were interpreted by listeners

as being on-target for different morphological values (and thus stress patterns). Other

parameters, such as sharp intra-syllable F0 variation, sub-syllabic durations or vowel quality

could have contributed to this perception of an on-target stress pattern. Concerning the last of

these three factors, even if there is no phonological vocalic neutralisation in Spanish as a

function of stress, there has been observed an enlarged vowel space area in people with

Broca’s aphasia and concomitant AOS in stressed (vs unstressed) syllables in Spanish (Baqué,

2015). We may suppose that our participants with AOS could have cued their stress patterns

by characteristic modifications of vocalic spectral quality.

There are several possible explanations for the important inter-speaker variability found for

all parameters and interactions considered in the AX group. Besides locus of lesion and time

post-onset, these differences may reflect idiosyncratic behaviours implemented to compensate

for their disability. It is also possible that individuals with tumour-related impairments

restructure their skills differently from post-stroke patients, due to a progressive

reorganisation of the information encoded in the brain during the development of a slow-
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
growing tumour (as opposed to sudden destruction of brain areas; see Anderson, Damasio, &

Tranel, 1990; Davie, Hutcheson, Barringer, Weinberg, & Lewin, 2009).

Thus, further research is needed, not only to validate these results with systematic studies on

larger homogeneous groups and more complex materials, but also to account for other

(combinations of) cues used by participants with AOS in stress pattern marking and their

relative effectiveness in making the intended stress pattern identifiable.




ACKNOWLEDGMENTS

The author would like to thank Anna Marczyk and María-Jesús Machuca for their help with

collecting the data used in this study and the anonymous reviewers for their helpful comments

on earlier versions of this manuscript.

DECLARATION OF INTEREST

The author reports no conflicts of interest.

FUNDING

Support for this research was provided by the Spanish Ministry of Economy and

Competitiveness, National Programme for Fostering Excellence in Scientific and Technical

Research [grant FFI2013-40419-P].



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APPENDIX A
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Table 3. Participant demographic and neuropsychological information. MTBA = Protocolo Montréal-Toulouse-Buenos Aires de examen
lingüístico de la afasia (Labos et al., 2005); COGNIFON= Protocolo de exploración lingüística del proyecto Cognifon. Versión española;
(Baqué et al., 2006), TBR = Test Barcelona Revisado (TBR). Programa Integrado de exploración neuropsicológica (Peña-Casanova, 2005); BA
= Broca’s aphasia; AOS = Apraxia of Speech; SA = unimpaired; + = mild impairment; ++ = moderate impairment; +++ = severe impairment;
NA = not available.
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APPENDIX B. SUMMARY STATISTICS OF THE BETWEEN-GROUP COMPARISONS




Table 4. Summary of statistics of the logistic linear regression mixed models of the number of perceived errors as a function of Group, Task
and/or Stress Pattern in a) all items as perceived by the majority of listeners (n = 216), b) items with perfect inter-listener agreement (n = 171)
and c) all the items as perceived by each listener (n = 2016 x 5 = 1080). Significance codes: ‘***’ <0.001, ‘**’ <0.01, ‘*’ <0.05, ‘.’ <0.10, ‘’
>0.10. When significant, fixed effects statistics for each comparison have been included.
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Table 5: Summary of statistics of the linear regression mixed models of the overall syllable duration as a function of Group. Significance codes:
‘***’ <0.001, ‘**’ <0.01, ‘*’ <0.05, ‘.’ <0.10, ‘’ >0.10. When significant, fixed effects statistics for each comparison have been included.




Table 6: Summary of statistics of the linear regression mixed models of the intra-word acoustic contrasts (VarDurSyl, VarF0Syl and VarIntSyl)
in Word Reading task as a function of Group and/or Stress pattern. Significance codes: ‘***’ <0.001, ‘**’ <0.01, ‘*’ <0.05, ‘.’ <0.10, ‘’ >0.10.
When significant, fixed effects statistics for each comparison have been included.
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Table 7: Summary of statistics of the linear regression mixed models of the intra-word acoustic contrasts (VarDurSyl, VarF0Syl and VarIntSyl)
in Sentence Naming and Sentence Reading tasks as a function of Group and/or Stress pattern. Significance codes: ‘***’ <0.001, ‘**’ <0.01, ‘*’
<0.05, ‘.’ <0.10, ‘’ >0.10. When significant, fixed effects statistics for each comparison have been included.
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Table 8: Summary of statistics of the logistic linear regression mixed models of the perceived stress pattern by the majority of listeners (OX vs
PX) in Word Reading task as a function of Group, VarDurSyl, VarF0Syl and/or VarIntSyl. Significance codes: ‘***’ <0.001, ‘**’ <0.01, ‘*’
<0.05, ‘.’ <0.10, ‘’ >0.10. When significant, fixed effects statistics for each comparison have been included.



                                              Between-group analyses
Predictors                                           Perceived stress pattern by the majority of listeners
Intercept                                                                    ***
                                                                     α=1.146e+01±1.874e-03, z=6116, p<.001
Group                                                                                   ***
                                                                  AX: β=-8.021e-01±1.874e-03, z=--428, p<.001
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VarDurSyl                                                                               ***
                                                                      β=3.356+00±1.874e-03, z=1791, p<.001
VarF0Syl                                                                                ***
                                                                    β=2.014e+01±1.874e-03, z=10743, p<.001
VarIntSyl                                                                               ***
                                                                    β=6.134e+01±1.874e-03, z=32727, p<.001
Group*VarDurSyl                                                                         ***
                                                                    β=-7.028e+00±1.874e-03, z=-3750, p<.001
Group*VarF0Syl                                                                          ***
                                                                    β=-1.565e+01±1.874e-03, z=-8350, p<.001
Group*VarIntSyl                                                                         ***
                                                                    β=5.783e+01±1.874e-03, z=30855, p<.001
VarDurSyl*VarF0Syl                                                                      ***
                                                                     β=1.268e+01±1.874e-03, z=6763, p<.001
VarDurSyl*VarIntSyl                                                                     ***
                                                                    β=1.489e+02±1.874e-03, z=79447, p<.001
VarF0Syl*VarIntSyl                                                                      ***
                                                                    β=8.470e+02±1.936e-03, z=437576, p<.001
Group*VarDurSyl*VarF0Syl                                                                ***
                                                                   β=-3.191e+01±1.874e-03, z=-17028, p<.001
Group*VarDurSyl*VarIntSyl                                                               ***
                                                                   β=-1.081e+02±1.936e-03, z=-55832, p<.001
Group *VarF0Syl*VarIntSyl                                                               ***
                                                                   β=-1.262e+03±1.936e-03, z=-652165, p<.001
VarDurSyl*VarF0Syl*VarIntSyl                                                            ***
                                                                    β=1.340e+03±1.936e-03, z=692137, p<.001
Group*VarDurSyl*VarF0Syl*VarIntSyl                                                      ***
                                                                   β=-1.734e+03±1.936e-03, z=-895610, p<.001
Model summary                                             AIC         BIC       logLik       deviance       df.resid
                                                          73.6       124.8       -18.8         37.6           109
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Table 9: Summary of statistics of the logistic linear regression mixed models of the perceived stress pattern by the majority of listeners (OX vs
PX) in Sentence Naming and Sentence Reading tasks as a function of Group, VarDurSyl, VarF0Syl and/or VarIntSyl. Significance codes: ‘***’
<0.001, ‘**’ <0.01, ‘*’ <0.05, ‘.’ <0.10, ‘’ >0.10. When significant, fixed effects statistics for each comparison have been included.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
APPENDIX C. SUMMARY STATISTICS OF THE CASE-CONTROL COMPARISONS




Table 10: Summary of statistics of the logistic linear regression mixed models of the number
of perceived errors as a function of Case-Control (AX1, AX2, AX3 vs all N0), Task and/or
Stress Pattern in a) all items perceived as perceived by the majority of listeners (n = 216), b)
items with perfect inter-listener agreement (n = 171) and c) all the items as perceived by each
listener (n = 2016 × 5 = 1080). Significance codes: ‘***’ <0.001, ‘**’ <0.01, ‘*’ <0.05, ‘.’
<0.10, ‘’ >0.10. When significant, fixed effects statistics for each comparison have been
included.




Table 11: Summary of statistics of the linear regression mixed models of the overall syllable
duration as a function of Case-Control (AX1, AX2, AX3 vs all N0). Significance codes: ‘***’
<0.001, ‘**’ <0.01, ‘*’ <0.05, ‘.’ <0.10, ‘’ >0.10. When significant, fixed effects statistics for
each comparison have been included.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155




Table 12: Summary of statistics of the linear regression mixed models of the intra-word
acoustic contrasts (VarDurSyl, VarF0Syl and VarIntSyl) in Word Reading task as a function
of Case-Control (AX1, AX2, AX3 vs all N0) and/or Stress pattern. Significance codes: ‘***’
<0.001, ‘**’ <0.01, ‘*’ <0.05, ‘.’ <0.10, ‘’ >0.10. When significant, fixed effects statistics for
each comparison have been included.




Table 13: Summary of statistics of the linear regression mixed models of the intra-word
acoustic contrasts (VarDurSyl, VarF0Syl and VarIntSyl) in Sentence Naming and Sentence
Reading tasks as a function of Case-Control (AX1, AX2, AX3 vs all N0) and/or Stress
pattern. Significance codes: ‘***’ <0.001, ‘**’ <0.01, ‘*’ <0.05, ‘.’ <0.10, ‘’ >0.10. When
significant, fixed effects statistics for each comparison have been included.
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155




Table 14: Summary of statistics of the linear regression mixed models of the intra-word
acoustic contrasts (VarF0Syl and VarIntSyl) in Word Reading task as a function of Case-
Control (AX1, AX2, AX3 vs all N0), Stress pattern and VarDurSyl. Significance codes: ‘***’
<0.001, ‘**’ <0.01, ‘*’ <0.05, ‘.’ <0.10, ‘’ >0.10. When significant, fixed effects statistics for
each comparison have been included.



                                                          Case-control comparisons
Predictors                                 VarF0Syl                                          VarIntSyl
Intercept
                          α=-0.03733±0.04282, df=25.23, t= -0.872,          α=-1.016e-02±2.082e-02, df=3.370 e+00, t= -
                                          p>.10                                           0.488, p>.10
Case-control
                           AX1: β= 0.12699± 0.06210, df= 8.55, t=               AX1: β= -6.481e-03± 3.858e-02, df=
                                        2.045, p<.10                              2.480e+00, t= -0.168, p>.10
                           AX2: β= 0.32980± 0.06498, df= 10.15, t=              AX2: β= 1.660e-02± 3.889e-02, df=
                                       5.076, p<.001                               2.560e+00, t= 0.427, p>.10
                           AX3: β= 0.04005± 0.06430, df= 9.76, t=               AX3: β= -1.384e-03± 3.884e-02, df=
                                        0.623, p>.10                              2.550e+00, t= -0.036, p>.10
Stress pattern                                                                                    **
                           OX: β= 0.10926± 0.04396, df= 75.31, t=                 OX: β= 5.557e-02± 1.184e-02, df=
                                       2.485, p<.05                                 7.735e+01, t= 4.693, p<.001
VarDurSyl
                             β= -0.07340± 0.10022, df= 99.78, t= -           β= 3.616e-04± 2.728e-02, df=9.556e+01, t=
                                        0.732, p>.10                                       0.013, p>.10
Case-                                          ***                                                 *
control*Stress               AX1*OX: β= -0.01870± 0.06846, df=                  AX1*OX: β= -3.824e-02± 1.892e-02,
pattern                          105.63, t= -0.273, p>.10                         df=1.058e+02, t= -2.021, p<.05
                             AX2*OX: β= -0.34676± 0.06887, df=                  AX2*OX: β= -5.270e-02± 1.895e-02,
                                 109.26, t= -5.035, p<.001                        df=1.086e+02, t= -2.781, p<.01
                             AX3*OX: β= 0.01749± 0.06559, df=                   AX3*OX: β= -4.857e-02± 1.813e-02,
                                  105.96, t= 0.267, p>.10                         df=1.061e+02, t= -2.679, p<.01
Case-                                           **                                                **
control*VarDurS             AX1*VDS: β= -0.02776± 0.15200, df=                  AX1*VDS: β= 2.541e-02± 4.155e-02,
                                 107.52, t= -0.183, p>.10                         df=1.047e+02, t= 0.612, p>.10
Pre-print version of :
Baqué, Lorraine (in press). How do persons with apraxia of speech deal with morphological stress in Spanish ? A preliminary
study. Clinical Linguistics & Phonetics. Doi : https://doi.org/10.1080/02699206.2019.1622155
yl                             AX2*VDS: β= -0.21853± 0.15519, df=                  AX2*VDS: β= 1.428e-03± 4.316e-02,
                                       95.37, t= -1.408, p>.10                        df=9.666e+01, t= 0.033, p>.10
                               AX3*VDS: β= 0.66134± 0.18993, df=                   AX3*VDS: β= 1.795e-01± 5.240e-02,
                                      106.86, t= 3.482, p<.001                       df=1.074e+02, t= 3.425, p<.001
Stress                                                                                             *
pattern*VarDurS              OX*VDS: β= 0.16060± 0.11836, df=                   OX*VDS: β= 1.591e-02± 3.221e-02,
yl                               101.88, t= 1.357, p>.10                          df=9.834e+01, t= 0.494, p>.10
Case-                                            *                                                 *
control*Stress              AX1*OX*VDS: β= -0.01606± 0.20476,               AX1*OX*VDS: β= -8.124e-02± 5.591e-02,
pattern*VarDurS                 df= 106.78, t= -0.078, p>.10                    df=1.049e+02, t= -1.453, p<.10
                            AX2*OX*VDS: β= 0.19148± 0.29676,                AX2*OX*VDS: β= -5.957e-02± 8.176e-02,
yl                              df= 107.20, t= 0.645, p>.10                     df=1.075e+02, t= -0.729, p>.10
                            AX3*OX*VDS: β= -0.56984± 0.20992,               AX3*OX*VDS: β= -1.711e-01± 5.785e-02,
                                df= 107.12, t= -2.715, p<.01                    df= 1.078e+02, t= -2.958, p<.01
Model summary              AIC   BIC logLi devianc df.resi                  AIC   BIC logLi devianc df.resi
                                          k          e        d                             k          e         d
                            -      -    114.5      -229.1    108             -      -    272.3      -544.5      108
                           191. 137.                                        506. 452.
                            1     0                                          5      5



Table 15: Summary of statistics of the linear regression mixed models of the intra-word
acoustic contrasts (VarF0Syl and VarIntSyl) in Sentence Naming and Sentence Reading tasks
as a function of Case-Control (AX1, AX2, AX3 vs all N0), Stress pattern and VarDurSyl.
Significance codes: ‘***’ <0.001, ‘**’ <0.01, ‘*’ <0.05, ‘.’ <0.10, ‘’ >0.10. When significant,
fixed effects statistics for each comparison have been included.