Frédérique Gayraud

Melissa Barkat-Defradas

Mohamed Lahrouchi

& Mahé

Ben Hamed

Development of phonetic complexity in Arabic, Berber, English and French (children's productions, targets, Child Directed Speech, and 50 randomly selected words in the adult language)

The goal of this study is to provide crosslinguistic data on the acquisition of phonetic complexity among children acquiring four different languages: Tunisian Arabic, Berber, English, and French. Using an adaptation of Jakielski's (2000) Index of Phonetic Complexity (IPC), we carried out an analysis to assess phonetic complexity of children's early vocabulary in the four languages. Four different samples from each language were analyzed: 50 words selected from an adult dictionary of each language, 50 words from child directed speech, 50 words targeted by the child, and the child's actual pronunciations of those 50 words. Globally, we hypothesized that children's early productions would be shaped by universal articulatory constraints, but also by the language they are exposed to, depending on its phonological complexity. Our findings show that Arabic and Berber display higher degrees of complexity compared to English and French, and that children acquiring Arabic and Berber target and produce more complex words than children learning English and French.

Children typically produce their first words around 12 months of age. However, the full mastery of an adult-like sound system is not achieved before 8 [START_REF] Sander | When are speech sounds learned?[END_REF] or even 10-12 years of age [START_REF] Smith | Articulatory movement characteristics of labial consonant productions by children and adults[END_REF]. In English for instance, some phonemes such as /s/ or consonant clusters such as /spl/ are not acquired before 7 and 9 years of age [START_REF] Smit | The Iowa Articulation Norms Project and its Nebraska Replication[END_REF]. This extended period required for the mastery of the speech sound system of the adult language is due to the fact that young children are neither endowed initially with an adult-like vocal tract configuration nor with the neuromuscular control for producing the range of sounds of their ambient language [START_REF] Kent | Acoustic features of infant vocalic utterances at 3, 6, and 9 months[END_REF]; [START_REF] Green | The sequential development of jaw and lip control for speech[END_REF][START_REF] Stoel-Gammon | Phonological development[END_REF]. These anatomical and neurophysiological constraints result in a restriction on children's early phonetic inventories [START_REF] Green | Some organization principles in early speech development[END_REF][START_REF] Nip | Early speech motor development: Cognitive and linguistic considerations[END_REF]).

Children's phonetic inventory is initially composed of sounds produced primarily by the jaw [START_REF] Macneilage | The motor core of speech: A comparison of serial organization patterns in infants and languages[END_REF], on which they have a better muscle control compared to the motion of lips and tongue movements [START_REF] Green | The sequential development of jaw and lip control for speech[END_REF]. As a consequence of these biological universal constraints, children acquiring different languages show a similar restricted inventory of sounds [START_REF] Locke | Phonological acquisition and change[END_REF][START_REF] Locke | The child's path to spoken language[END_REF]. Indeed, babbling and first-word productions demonstrate universal patterns: children show a preference for labials and coronals, stops, nasals and glides, open syllables, short utterances, few consonant clusters (and if any, they tend to be homorganic), and more reduplication than variegation [START_REF] Macneilage | Origin of serial-output complexity in speech[END_REF][START_REF] Oller | Speech-like vocalizations in infancy: An evaluation of potential risk factors[END_REF][START_REF] Vihman | From babbling to speech: A re-assessment of the continuity issue[END_REF]. Furthermore, these preferences have been shown to influence the words that children select to produce. Thus, the inventory of children's early vocabulary is not composed of randomly selected words. Rather, it has been suggested that children select words with phonetic characteristics that are already present in their own phonological systems [START_REF] Ferguson | Words and sounds in early language acquisition[END_REF][START_REF] Schwartz | Attempted sounds are sometimes not: An expanded view of phonological selection and avoidance[END_REF][START_REF] Vihman | From babbling to speech: A re-assessment of the continuity issue[END_REF]. Other studies on lexical selectivity have shown that children attempt more complex words targets according to age (Dobrich & Scarborough, 1992). An Index of Phonetic Complexity (henceforth IPC) based on the phonetic regularities observed in the babbling and the first-word period, was proposed to assess children's phonetic development [START_REF] Jakielski | A new method for measuring articulatory complexity[END_REF][START_REF] Jakielski | Quantifying phonetic complexity in words: An experimental index[END_REF][START_REF] Jakielski | Acquisition of phonetic complexity in children 12-36 months of age[END_REF]. The IPC has proven to be a valuable tool for different purposes such as assessing phonological skills in toddlers [START_REF] Morris | Test-retest reliability of independent measures of phonology in the assessment of toddler's speech[END_REF], comparing speech acquisition in bilingual vs. monolingual children [START_REF] Gildersleeve-Neumann | English speech acquisition in 3-to 5-year-old children learning Russian and English[END_REF], or exploring the relationships between phonetic complexity and stuttering [START_REF] Howell | Phonetic difficulty and stuttering in English[END_REF][START_REF] Howell | Phonetic complexity and stuttering in Spanish[END_REF]. The IPC, which considers productions composed of less preferred segments and segment associations as more complex, permits one to measure the development of phonetic complexity in both targeted and produced words by children. [START_REF] Ward | Measuring word target and production articulatory complexity in children 12-24 months of age[END_REF] documented a lexical selectivity bias in children aged 16 to 24 months through the phonetic complexity of targeted words. In addition, it was shown that IPC scores at 12 months predicted speech and language skills at 18 months [START_REF] Furey | The growth of early phonological and lexical development: A longitudinal investigation[END_REF]. Biomechanical constraints of the production system [START_REF] Macneilage | Acquisition of speech production: Frames, then content[END_REF]) and lexical selectivity are both universal tendencies.

Crosslinguistic studies hence provide support for a strong determination of early phonetic inventories by biological constraints. However, they do not rule out an influence of the ambient language. Languages differ to a large extent in terms of their phonological inventories and phonotactics, making the input more or less difficult to acquire for children. Crosslinguistic analysis of diverse languages enables us to distinguish between potentially universal and language-specific patterns (Stoel Gammon, 2012). In fact, previous analyses have shown that segmental development, namely word shapes and CV co-occurrences, are influenced by input frequency in the ambient language [START_REF] Saffran | Incidental language learning: Listening (and learning) out of the corner of your ear[END_REF], as well as by the functional load of segments in the language, i.e. how much use a language makes of its available contrasts [START_REF] Stokes | Articulatory complexity, ambient frequency, and functional load as predictors of consonant development in children[END_REF]. As languages vary on those parameters, previous findings suggest that some languages may be acquired at a faster rate than others. For instance, [START_REF] So | The acquisition of phonology by Cantonese-speaking children[END_REF] showed that Cantonese children acquire phonology at a faster rate than English-speaking children as they master the contrastive use of tones and vowels by two years and that few phonological errors occur after age four. Similarly, [START_REF] Caselli | A crosslinguistic study of early lexical development[END_REF] observed that Italian children were slower in vocabulary acquisition compared to English-speaking children: Italian children lag behind the English group in total vocabulary size at most ages between 8 and 16 months. Another crosslinguistic study, comparing L1 vocabulary growth at 16-30 months of age, found that Galician children produce fewer words than Basque, French and Mexican-Spanish-learning children [START_REF] Pérez-Pereira | Crosslinguistic comparisons between Basque and Galician[END_REF]. In brief, phonetic development seems to be strongly influenced by universal biological constraints but also by the characteristics of the ambient language.

However, considering the ambient language, one must keep in mind that the type of language to which children are exposed (referred to as Child Directed Speech, henceforth CDS) differs in several important ways from the adult language. When addressing children, caregivers adjust their language by simplifying and clarifying the linguistic material [START_REF] Ferguson | Baby talk in six languages[END_REF] in order to engage children's attention and facilitate language acquisition [START_REF] Snow | Mothers' speech research: From input to interaction[END_REF][START_REF] Werker | Infant-directed speech supports phonetic category learning in English and Japanese[END_REF]

CDS is characterized by simplified syntax, shorter utterances, restricted vocabulary, repetitions, phonetic modifications [START_REF] Kuhl | A new view of language acquisition[END_REF] increased variations in fundamental frequency and longer pauses [START_REF] Albin | Stressed and word-final syllables in infant-directed speech[END_REF][START_REF] Andruski | The acoustic structure of vowels in mothers' speech to infants and adults[END_REF][START_REF] Ferguson | Baby talk as a simplified register[END_REF][START_REF] Papoušek | The meanings of melodies in motherese in tone and stress languages[END_REF]. Moreover, this specific register used by parents to promote infants' language learning has been shown to be almost universal [START_REF] Ferguson | Baby talk in six languages[END_REF][START_REF] Kitamura | Universality and specificity in infant-directed speech: Pitch modifications as a function of infant age and sex in a tonal and non-tonal language[END_REF][START_REF] Kuhl | Cross-language analysis of phonetic units in language addressed to infants[END_REF][START_REF] Monnot | Function of infant-directed speech[END_REF].

The current study aims at examining the phonetic complexity of words produced by children acquiring four different languages: Arabic (Tunisian vernacular), Berber (Tashlhiyt variety), English (American) and French. These languages show different phonetic and phonological characteristics of interest for early language development, such as word length, word complexity (syllable types, consonant clusters) and phonemic inventory diversity. For example, the Arabic lexicon, which is largely derived from basic consonantal roots, includes many polysyllabic words. In terms of syllable types, French shows a strong preference for open syllables (76%), English exhibits mostly closed syllables (60%) (Delattre, 1965) and Arabic displays 49,92% of closed vs. 50,08% of open syllables (Hamdi, Ghazali & Barkat-Defradas, 2005). These languages also differ in consonant cluster2 requirements: in Berber, clusters are only possible in word initial position and in Arabic, they are hardly found in word final position. In French both positions are permitted but a bias towards word initial position is attested. Phonemic inventories are also quite diverse. Indeed, when computing the consonant/vowel ratio, two groups emerge: Berber and Arabic are highly consonantal languages [START_REF] Fougeron | Schwa elements in Tashlhiyt word-initial clusters[END_REF]Hamdi, Ghazali & Barkat-Defradas, 2002) whereas vowels are more frequent than consonants in French and, to a lesser extent, in English, Berber and Arabic display a significant proportion of fricatives as compared to English and French. Moreover, the phonological inventories of Arabic and Berber put forward a large number of back consonants (i.e. uvulars, pharyngeals and glottals) that are known to be acquired rather late [START_REF] Omar | The acquisition of Egyptian Arabic as a native language[END_REF]. In sum, this study aims to provide informative contribution comparing the phonetic development in four languages including Berber and Arabic Studies, languages in which studies of phonetic development are rare.

We elaborated six interrelated hypotheses for our crosslinguistic study:

H1. The different languages should display different degrees of complexity. The dictionary words in Berber and Arabic, which are highly consonantal languages, should have higher complexity scores compared to the more vocalic English and French.

The following IPC parameters are of special interest for our cross linguistic analysis: a. Place of articulation: More complexity expected in Arabic, due to the many back (i.e. dorsal) consonants, and in French, due to the frequent /ʁ/ [START_REF] Gromer | Apprendre à lire[END_REF]. f. Variegation (Place): More variegation is expected in Arabic, due to the non-homorganic consonantal rule, which constrains the root-skeleton.

g. Variegation (Manner): in Arabic the non-homorganic consonantal rule which constraints the root-skeleton leads to expect this language will attest more variegation than the others.

h. Rhoticity4 will contribute to complexity in American English only.

H2. In each language, we expect the words that mothers use when addressing their children (CDS) to be less complex than the words used in the "adult" language (i.e. represented here through dictionary words).

H3. According to the lexical selectivity hypothesis, children should attempt words (targets) that are less complex to produce than many other words in the adult language (Dictionary).

H4. Given the biomechanical constraint hypothesis, we expect children's actual productions to be less complex than the targets they attempt.

H5. However, we expect an effect of the ambient language: children acquiring a phonologically more complex language should target and produce more complex forms. Hence, we expect Arabic-and 3 When consonant articulation occurs at the same time as another articulation is being made at a different place in the vocal tract, the consonant is said to form a complex articulation.

Berber-speaking children's IPC scores to be higher than those observed for English-and Frenchspeaking children.

H6. In sum, if a complex parameter is frequent in the ambient language, children should use it or attempt it more often than if it is not present in the ambient language. Sophie Kern). The French data are part of the French Kern corpus [START_REF] Kern | From babbling to first words in four languages: Common trends across languages and individual differences[END_REF], and the English data comes from the Providence Corpus [START_REF] Demuth | Word-minimality, epenthesis and coda licensing in the early acquisition of English[END_REF].

Procedures

The children were recorded in natural settings at home in interaction with their mother. The recording sessions took place twice a month from the onset of first word production until a few months after the lexical spurt. As [START_REF] Jakielski | Quantifying phonetic complexity in words: An experimental index[END_REF] recommend to use 50 words to compute the IPC, four lists of 50 words were analyzed for each language: (i) the first 50 words actually produced by each child (hereafter referred to as Actual), (ii) the targets corresponding to these first 50 words, (iii) 50 words randomly extracted from CDS produced by each mother and (iv) 50 words from the adult language randomly selected from dictionaries (See APPENDIX 1 to 4 for an illustration). For each list, an adaptation of the Index of Phonetic Complexity [START_REF] Jakielski | Quantifying phonetic complexity in words: An experimental index[END_REF] was computed (see Table 2). The IPC is based on the phonetic regularities observed during the babbling and the first-words periods.

Vocal outputs that are composed of the less preferred segments (or segment associations) in early development are rated as more complex in the IPC. This allows measuring the development of phonetic complexity in both word targets and words actually produced by the children. The IPC consists of eight parameters: consonants by place and manner, vowels by class, word shape and word length (in syllable type and number), singleton consonants by place variegation, contiguous consonants and cluster by type (i.e. homo-vs. hetero-organic). However, as this measure was initially designed to capture the phonetic complexity of English, it must be adapted for crosslinguistic comparison in order to account for other determining features of phonetic complexity exhibited in the 4 languages under examination..

Data analysis

In order to take into consideration the typological peculiarities of our linguistic sample, we [START_REF] Omar | The Acquisition of Egyptian Arabic as a Native Language[END_REF].

We therefore added 1 point for such complex segments, that are typical of Afro-asiatic languages [START_REF] Hetzron | The Semitic Languages[END_REF]. The same rationale was applied for labialization, which consists of adding lip rounding to the principal articulation. We considered radical consonants (i.e. pharyngeals) as particularly complex in terms of the consonant by place class, since they are, on the one hand, even more posterior than dorsals (that are themselves considered as complex in the original IPC model) and, on the other hand, since the mastery of production for these consonants is reported to occur rather late [START_REF] Amrayeh | A normative study of the acquisition of consonant sounds in Arabic[END_REF]Amrayeh & Dyson, 1998). Lastly, considering the fact that consonantal clusters are frequent in the Western varieties of colloquial Arabic, under the influence of Berber, and can thus be very long (up to seven contiguous consonants), we decided to add up to 2 points when more than two consonantal segments are contiguous. Our purpose here is to compare the total phonetic complexity of children's production crosslinguistically, as well as the contribution of each of the parameters accounting for it. Translating each word into a phonetic sequence in which each element is described (as a vowel, a consonant, or a secondary articulation, with consonants being identified in terms of place and mode of articulation), we can identify and compute each parameter, and the IPC as their total sum. Table 3 provides an example of IPC scoring for four dictionary words in each language.

Commenté [DC1]:

It = ? The production or the complexity?

French fork fuʁʃɛt 0 1 1 1 0 0 1 1 1 1 7 English mixture mɪkstʃər 0 1 3 1 1 0 1 1 2 1 11 Berber girl tafruxt 0 1 2 0 1 1 1 1 2 2 11 Arabic he fell sqətˤ 1 1 1 0 1 0 1 1 1 1 8

Results

The dictionary sample is a window on the expected mean word phonetic complexity of the languages under study. The sample being rather small, we also computed the confidence interval of the mean with a 5% type I error by bootstrapping the sample to estimate the interval of values for the mean phonetic complexity for the dictionary as a whole. Figure 1 shows that the 4 languages have indeed different mean word IPCs, with a decreasing decline from Arabic > Berber > English >

French. As expected given the sample size the 95% confidence intervals are large, but they still support this complexity decline. Since the IPC is computed as the sum of 10 phonetic parameters, depending on the language, this overall complexity can be attributed to different parameters. Figure 2 shows the individual contribution of each parameter to the overall IPC for the dictionary sample. Contributions are computed as the difference between the proportion of the overall complexity (that is, the IPC the parameter actually accounts for), and what would be expected from a uniform contribution of all parameters. Since there are ten of those, the uniform contribution null hypothesis would set each parameter's contribution at 10 %. Specific parameter contributions will thus vary between -0,1-0,9. word length is computed as the number of vowels, assumed to act as syllabic nuclei (except for Berber, where, null syllabic nuclei were also identified, using [START_REF] Dell | Syllables in Tashlhiyt Berber and in Moroccan Arabic[END_REF] syllabification algorithm). For this parameter, all four languages exhibited less than the 10% contribution anticipated if all of the parameters make an equal contribution Complexity measures on the dictionary samples provide the baseline against which children's production and lexical selectivity, but also Child Directed Speech (CDS) can be analyzed. Figure 3 shows the mean IPC values for the different lists in the various languages. Although the general tendency is that of a decreasing complexity decline from Dictionary/adult language to CDS to Target to Actual child productions, major differences exist between languages.

For instance, CDS in Arabic and English shows the highest complexity compared to the dictionary sample, but Berber, while showing a lower mean IPC for CDS, also exhibits comparable levels of phonetic complexity between CDS and the targets selected by children for production. Moreover, Arabic and Berber show similar Target complexity and an Actual-to-Target complexity differential.

But while English and French display lower Target complexity, they also display larger Actual-to-Target complexity differentials, with lower achieved complexity in children's actual production, especially for French.

However, these Actual-to-Target complexity differentials do not necessary translate into Actual-to-Target accuracy. Given that the individual parameters focus primarily on consonants, we computed the Actual-to-Target accuracy in the realization of consonants for the 4 languages (Figure 4). These results suggest that typological characteristics of the language indeed play a role in the acquisition process and call for a detailed examination of the individual contribution of each parameter to the overall IPC score of children's actual production, as compared to the language (dictionary) parameter contribution landscape.

Figure 5 shows that not all parameters contribute in the same way to the mean IPC of the child's actual production, depending on the language, with respect to how they contribute in the other samples, and especially, the Dictionary. For instance, Arabic Actual shows an enhanced tendency for children to produce closed final syllables, irrespective of what is displayed in either the Target or the CDS, thus mirroring more of the dictionary tendency than these two latter samples do. On the other hand, clusters, which contribute to different extents to the IPC of Berber, Arabic and English (dictionary), do not in any of the other samples, suggesting that both CDS and Targets selected by the children tend to misrepresent clusters during this phase of acquisition, thereby reducing the complexity of their production.

A tendency that appears common to all languages, however, is the large contribution of manner of articulation in CDS with respect to Dictionary which is reflected for Arabic and Berber in the Target selected by children for production, while French, where this is not the case, displays an enhanced contribution of manner in the Actual production of the children. Place of articulation also displays a trend common to all languages, with enhanced contributions in Actual production, irrespective of their contribution in the other samples. However, whereas place and manner contribute the most in French to actual production, their variegation contributes the least, contrary to all three other languages.

Discussion

Using an adaptation of [START_REF] Jakielski | Quantifying phonetic complexity in words: An experimental index[END_REF] Index of Phonetic Complexity (IPC), we carried out an analysis to assess phonetic complexity of children's early vocabulary in four languages: Arabic, Berber, English and French. Globally, we hypothesized that children's early productions would be shaped by universal articulatory constraints, but also by the language they are exposed to, depending on its phonological complexity.

Considering language-specific aspects, we observed that as hypothesized, some languages of our samples, namely Arabic and Berber, show higher IPC scores (complexity) than English and especially French (H1). The different IPC parameters contribute differently to complexity. Manner and place of articulation contribute significantly to complexity in all four languages, and not only in Arabic and French as predited by H1a. In other words, children in these languages do not systematically avoid fricatives or liquids, which are frequent in the ambient language. Similarly for Place of articulation, although children prefer labials and coronals to dorsals in the early period of production, they are able to produce posterior consonants (like dorsals and/or pharyngeals) when required by the ambient language (i.e. typically in Arabic and Berber where they are rather frequent).

However, some parameters clearly differ across languages. Clusters are significant contributors to phonetic complexity in Berber, and, to a lesser extent, in Arabic and English (H1b.). As for final consonant, French is confirmed to be easier than the other languages, as expected as predicted by

H1e. In contrast, some other parameters that were expected to play a role in complexity scores (H1 c., d., f. g. h.), in particular word length and complex articulation (H1 c. and d.), do not seem to contribute significantly to the global complexity score. In sum, we found a decreasing complexity:

Berber < Arabic < English and we hypothesized that these differences in phonetic complexity in the adult languages would influence phonetic development in children acquiring these languages. An obvious assumption is that a phonetically complex language such as Berber would take longer to acquire, and would be more challenging to reach accuracy. Nevertheless, our findings suggest that this is not the case. Although our sample is too small to draw solid conclusions, our data indicate that Berber infants are not delayed in the timing of first words production, given that first words are produced as early as 7 months of age in one of our subjects. Similarly, children acquiring Arabic and Berber show the best accuracy scores compared to the a priori easier languages, English and French.

Turning to universal aspects of phonetic development (H2, H3 & H4), our findings are in line with previous work underlying the universal tendency for caregivers to modify their speech when addressing children (H2) [START_REF] Ferguson | Baby talk in six languages[END_REF][START_REF] Ferguson | Talking to Children: A search for universals[END_REF][START_REF] Kitamura | Universality and specificity in infant-directed speech: Pitch modifications as a function of infant age and sex in a tonal and non-tonal language[END_REF][START_REF] Kuhl | Cross-language analysis of phonetic units in language addressed to infants[END_REF][START_REF] Monnot | Function of infant-directed speech[END_REF]. Some studies had investigated motherese in Arabic and Berber and cultural differences have been documented in the range of modifications of CDS [START_REF] Ferguson | Arabic Baby Talk, For Roman Jackobson[END_REF], Gumperz & Hymes, 1964[START_REF] Bynon | Berber nursery language[END_REF][START_REF] Omar | The Acquisition of Egyptian Arabic as a Native Language[END_REF][START_REF] Haggan | Self Reports and Self Delusion regarding the use of Motherese: implications from Kuwaiti adults[END_REF][START_REF] Al-Shatty | Differentiating between the interactive styles of two types of caregiver with 11-21 months kuwaiti children[END_REF][START_REF] Ferguson | Talking to Children: a search for Universals[END_REF] and the fact that caregivers use a special register to address young children remains indisputable cross-linguistically.

The vast majority of CDS studies are focused on semantic, syntactic or prosodic characteristics. Fewer address the phonetic characteristics of CDS, but [START_REF] Kuhl | Cross-language analysis of phonetic units in language addressed to infants[END_REF] for instance showed that mothers in different languages (American English, Russian and Swedish) produce vowels that are acoustically more extreme when addressing their young children, thus providing information about the sound system of the infant's native language in an exaggerated form. CDS thus promotes language learning by separating sounds into contrasting categories. The present study did not focus on potential modifications of segments in CDS, but our findings show that caregivers use words that are less complex than in the adult language. This suggests the operation of lexical selectivity in CDS just as lexical selectivity is hypothesized in children's productions. Thus, one can assume that caregivers reduce the gap between children's restricted articulatory capacities and the necessary capacities to produce phonetically complex words of the adult language.

As predicted by H3, children also seem to select the words they produce or attempt to produce depending on their phonetic complexity [START_REF] Ferguson | Words and sounds in early language acquisition[END_REF][START_REF] Schwartz | Attempted sounds are sometimes not: An expanded view of phonological selection and avoidance[END_REF][START_REF] Vihman | From babbling to speech: A re-assessment of the continuity issue[END_REF]. Indeed, in the four languages under study, we observed that words attempted (Target) or produced (Actual) by children have lower complexity scores than CDS or adult words (H3 and H4). Finally, the fact that in all the four languages, actual productions show reduced complexity compared to attempted (and obviously CDS or adult) words illustrates the fact that during this early period of first word productions, children's early phonetic inventories are strongly limited by anatomical and neurophysiological constraints [START_REF] Green | The sequential development of jaw and lip control for speech[END_REF][START_REF] Green | Some organization principles in early speech development[END_REF][START_REF] Macneilage | The motor core of speech: A comparison of serial organization patterns in infants and languages[END_REF][START_REF] Stoel-Gammon | Phonological development[END_REF].

Looking at the detailed parameters that children either produce or avoid depending on the language, our findings show a mixed influence of language specificity and neurophysiological constraints. Globally, children's actual productions tend to reflect the tendencies displayed in adult productions (H5 and H6). The fact that children's use of closed syllables (Actual) in Arabic mirrors the adult language (dictionary words) but not targets nor CDS remains to be explained. However, clusters, which are strong contributors of complexity in Berber (and to a lesser extent in Arabic and English), seem to be avoided by children acquiring these languages. This finding is not surprising, as consonant clusters appear to be especially challenging for children. Indeed, they are not produced before age 2 and their acquisition is one of the longest-lasting aspects of speech acquisition in normally developing children [START_REF] Mcleod | Normal acquisition of consonant clusters[END_REF]. In sum, the different IPC parameters are not equally difficult for children to produce: while some (such as producing fricatives or dorsals) can be overcome by children even at a very early age in spite of biological constraints, others (such as consonant clusters) need more time to master.

APPENDIX

  b. Clusters: More complexity expected in Berber and Arabic, in which clusters are more frequent. c. Complex articulation 3 should contribute to complexity in Berber and Arabic. d. Word length: More complexity on this parameter is expected in Arabic, which shows many polysyllabic words due to the insertion of vocalic patterns and affixes into the root for lexical derivation. e. Final Consonant: Less complexity is expected in French, due to its preference for open syllables.

Figure 1 .

 1 Figure 1. Mean word IPC showing a decreasing decline from Arabic > Berber > English > Vertical bars show the 95% confidence interval for the means for the dictionary as a whole.

Figure 2 :

 2 Figure 2: Specific parameter contribution with respect to the uniform contribution null hypothesis.Values range from -0,1 to 0,9 for each of the 10 parameters composing the IPC.

Figure 3 .

 3 Figure 3. Mean word IPC and 95M confidence intervals for the Dictionary/adult language, CDS, actual child production and target for Arabic, Berber, English and French

Figure 4 .

 4 Figure 4. Mean Actual-to-Target accuracy in consonant production for Arabic, Berber, English and French. Vertical bars display the 95% confidence interval

Figure 5 .

 5 Figure 5. Mean parameter contribution by sample (Dictionary, CDS, Target and Actual) and by language(Arabic, Berber, English, French)

Table 1

 1

		. recapitulates the different hypotheses
	H1	Dictionary	Globally, Berber and Arabic should show higher complexity because they
			are highly consonantal languages

a. More complexity in Arabic and French for place of articulation b. More complexity in Berber and Arabic for clusters c. More complexity in Berber and Arabic for complex articulations d. More complexity in Arabic for word length e. Less complexity in French for final consonant f. More complexity in Arabic for variegation (Place) g. More complexity in Arabic for variegation (Manner) h. More complexity in English for Rhoticity H2 CDS Less complexity in CDS compared to Dictionary H3 Targets Less complexity in Targets compared to Dictionary H4 Actual Less complexity in Actual compared to targets H5 Targets & Actual Targets and Actual in Berber and Arabic should be more complex than in French and English H6 Targets & Actual Targets and Actual should reflect the ambient language Table 1. Predictions for Dictionary, CDS, Target and Actual words in the four different languages Method Participants Sixteen children from four linguistic communities: Arabic (Tunisian vernacular), Berber (Tashlhiyt variety), American English and French were included in the study. The parents did not report any concerns about the children's language development, hearing status, or general development. The Arabic and Berber data are part of The PREMs Project 5 (Principal Investigator:

Table 2 .

 2 Participants' demographic information

	Language	n	Sex	Age Range (months;days)
	Arabic	4	2M/2F	8;09 -24;06
	Berber	4	2M/2F	7;21 -18;12
	English	4	2M/2F	11;27 -20;05
	French	4	3M/1F	9;09 -22;22

  first had to integrate into the original IPC model a new parameter relative to consonantal articulation. We called it consonant by articulation class in reference to Jakielski's first two

parameters (i.e. Consonant by place and manner class and Consonant by place class). This new parameter was created in order to discriminate between simple vs. complex articulations (see n.1). In Arabic and Berber, two types of secondary (or complex) articulation are phonemically attested: pharyngealization (both in Arabic and Berber) and labialization (in Berber only). Basically, during the realization of a pharyngealized consonant (for example [t ʕ , d ʕ , ð ʕ ]), the pharynx is constricted and the root of the tongue is retracted. Such consonants, which require a skillful control of the back of the vocal tract

[START_REF] Barkat-Defradas | Mécanismes articulatoires et corrélats acoustiques de l'emphase en arabe et en berbère : un état de l'art[END_REF]

, are acquired very late in development

Table 2

 2

	recapitulates the different parameters

Table 3 .

 3 Index of Phonetic Complexity Scoring for 4 words in each language

	Language	Item	IPA Transcription	Consonant by	articulation	class	Consonant by	place class	Consonant by manner class class Vowel by class	Word shape class	Word length in syllables	Consonants by place variegation Consonants by manner variegation Contiguous consonants	Cluster by type	Total IPC

  1. Examples of ARABIC data

	pxːu af	nan:i buxːuʃ wɛt ʒiʁaf	sleep ! here's the insect ʕasˤfuːra wet ˈjunɪˌkɔrn bird ħawa giraffe telekomɑd remote control ynite aθat cow tirmt unicorn taɪm	unit	furniture food thyme
	Actual IPA Target IPA Translation 47 ʔahu ʔahuwa here it is ! 48 ʃːaʔ ʃː eat 49 pʌpo pʌrpəl purple 46 ɔuː ʃosyʁ shoe	CDS IPA matibkiːʃ waeks hawhaw dog Translation hurry up (don't cry) mədwəd Dictionary IPA azur wax ˈtraɪəl dəbu stand ɔnɔʁe honor	Translation nursery terrace trial
	1 2 3 4 5 48 tat: mɛm:ae itaejj pae dae ʔi APPENDIX 2. Examples of BERBER data mama mommy tˤɑːħ tˤɑj Peek a boo ʔiːʒae papa daddy tˤɑtˤɑ la: no ʔaħħaeː ʔɛj yes kiχχae APPENDIX 3. Examples of ENGLISH data jtat:ti (he) beats kifaeːʃ 49 sːasːa sħsːa be quite 50 dʒiː triː tree ˈjɛloʊ tˤanun to fall he comes tata ouch ! eew ! how ? yogourt yellow 47 bubeː pubɛl trash nuʁityʁ food 49 raejae mraejae mirror nhizz bring 50 adːa tdːˤrˤ she felt down tiʒiʒ:it meat 48 dadaː salad salad kanaj raffish 50 stan:ae ʔistana wait ! suːq market 49 ʁoːgwɛ dekʁoʃe pick up pubɛl trash 50 apiː apɥi press mɑʒe eat	ʕəʃb ħuku:m ħi:la farləχla msisa rqi:q izgr voʊg dərbuka xdmn ʕilaqa seʁɔm etɛ̃ kɑ̃ kɑtɔnad	medical monopole ruse bracelet fieldmouse he crossed vogue menu they worked drum serum off camp Coat rack No one in particular
	6 7 8 9 10 ʔɛjʒi taeːħ baej aem baeħ 11 bɛj 12 tɛdː 13 ʔaeħː 14 hup 15 ʒaʒae 16 ħibɛʃ 17 ktib 18 ka 19 taeːʕi 20 bebe 21 kak:ae 22 tat:a 23 tatae 24 ħutae: 25 bab 26 na:n 27 naehnae 28 mae mae 29 kaek 30 tae:ħ 31 taw taw 32 daeb:u:sae dab:uzae tˤɑːħ bah mam:i baħ ʔiʒa baj baj ʃi:d: ʔaħː ħutˤː ʤaːʒa maenħibɛʃ I don't want ʔaʕmil it fell quːl ok naeħħiː mum ʔahajjaeː It disappeared wiːni come here ! ʃuː bye-bye dadduːʃ hold ! jɛzzi ouch ! traeh put down ! baːħ chicken alo ʔiktibli write (to me) haeːt kask your helmet laeː mtaeːʕi mine ʔɛj bebe baby χuː kaka poo kaka batˤːɑ canard jimʃi tˤɑtˤɑ beat ! sˤɑħiːt ħutaː fish ʔaqɛf dub ours baeʕ ħsˤaːn horse ʒi:b lihnae here haeðɪka mae: water tħutˤ qird monkey ʔistannae muftaeːħ key ʔaelʕib taw:a now ʃʕaer bottle mtaʕ 33 ʃbi:k ʃbi:k what happens to you ? sˤɑfiq 34 ʔuxdaen ʔuxzur watch ! ʃnuwae 35 kas:ar tkas:ir you broke bismilah 36 baez xubz bread ʕaquːla 37 fasu: ʕasˤfuːra bird ʔaʕtˤi 38 tax:a kix:a eew ! matmissiʃ 39 ʕam ʕamːi my uncle ʔuqʕud 40 ku:ra ku:ra ball ɣaːdi 41 di haði this one ʃbiːk 42 tiz:a hizha lift it up nrakablik 43 laħda laħðˤa one minute please tkallim 44 kuja xuja my brother nχabbiːh 45 ku: qu:m get up ! ħsˤɑːn Actual IPA Target IPA Translation Actual IPA Target IPA Translation CDS IPA CDS IPA tell remove here it is where is it ? what is it ? walk stop ! show me ! gone (nothing !) hello do put no go ! brother poo he goes thank you up ! bèè (bleat noise) bring this one place wait play hair his applaud ! what bless you nice give don't touch sit down ! there what happens I'll put it together talk I hide horse Translation Translation Dictionary IPA Translation ħəwəl to try qa:l tell mraħħəm marble zra:ʕi: agricultural mdˤəl straw mudˤif stewart butˤa-in ventricule dəħʃ baby donkey wəsχ fouling səqqa:t gourmet kursi saddle ʕrəq sweat ħadd fence rijja:ga bib qəm estimate məstəɣəl profiteer bəlɣa oriental slipper ʃkara bag bəqra:ʒ tea pot ħɛ:l weather sˤəffa clarify məllɛ:ħ seller da-ijəb melting qəfza jump da:r home ma:t perish rʒaʕ take back tˤbi:b doctor faħħəm explain hdər argue sqətˤ fall ɣri:b unheard-of bətˤtˤəl idle mʕalləm expert səndu:q coffin hənd magnet qəmr moon qəsma part stəχbər be informed ʒəʕʕada spatula Dictionary IPA Translation 1 bːabːa bajbaj goodbye d:aħ hit (have a pain) ara 1 dʌˈbɛ bʌmbəl ˈbi: bumble-bee ˈaekrəˌbaet acrobat əˈsiːtəs acetous APPENDIX 4. Examples of FRENCH data give 2 babaː baba dad ʕaw noise aman 2 daeˈdeɪ daediː daddy əˈdɔr adore ˈɑrʧˌduk archduke water 3 amːaː mama mom aratid give it to me afus 3 əˈzi dʌrtiː dirty aent ant ˈbaekɪs bacchus Actual IPA Target IPA Translation CDS IPA Translation Dictionary IPA Translation hand 4 hbːa sːˤbːatˤ shoes ixʃ it is bad (thing) ilm 4 dʌwɪ dɑɡiː doggie əˈslip asleep ˈbaesʧən bastion 1 maːma mamɑ̃ mummy ʁəɡaʁd look ɑtɔʁs sprain skin 5 ajalːa lalːa auntie tit:i sit down krf 5 dʌdi dʌkiː duckie ˈbeɪbiˌsɪtər babysitter ˈbaetəl battle 2 paː papa daddy komɑse start bʁutij trinket tie 6 haːh hak take x:iʃ it is bad (thing) adr 6 ɑbwiː beɪbiː baby ˈbaetəl battle klaeʃ clash 3 toχto toeː dodo sleep pas think ɑtuzjasme get enthusiastic press 7 manːama lmunika toy ʃaʃːa a donky rgl 7 hʌ kaʊ cow ˈbɪskət biscuit kɔɪn coin 4 paː pɛ̃ bread vjɛ̃ come eʁezi heresy close 8 qːaqːa ʁika like this fuf:u hot/fire ifta 8 dʌ dɑt dot ˈkɛrfəl careful kʌm come 5 toedeː tete suck tɛlmɑ̃ so much ʁətʁɛ withdrawal he went 9 tːa xtːa this one (fem.) baʕːa sheep usin 9 hʌbu lɑbstər lobster ʧɑk chalk cyclin cyclin 6 taːte taʁtin sandwich ivɛʁ winter tʁuve find they took 10 bːaħ bːaħ disappeared b:aħ It's over awid 10 ʌmɛ mɑmiː mommy ˈdɑrlɪŋ darling daelˈmeɪʃən dalmatian 7 daːdaː ɡato cake dusmɑ̃ slowly kʁəvɛzɔ̃ flat bring! 11 məməm mumːu toy (generic) d:aw walk / go inijas 11 mʌm muːn moon ˈdɪfərənt different dɛd dead 8 oebiː abɛj bee pø can kanaʁ duck tell him 12 hatːi hatːi here it is (fem.) dajd:a fall down ufiɣ 12 bəˈbɛ pʌpiː puppy ˈizi easy dɪsˈgrʌntəld disgruntled 9 bɛbeː bebe baby dədɑ̃ inside duluʁø painful I found 13 ajːaː tajːaː another one (fem.) baʕːatin sheep lkmɣ 13 ʊˈwʌ bɑl ball ɛnˈʤɔɪ enjoy ˈɛsʧuˌɛri estuary 10 teːte tɛte head ɡʁɑ̃ big libeʁalism liberalism I arrived 14 ʃɛʃ ʃaʃːa horse (baby talk) ʃt:i grandfather tamːnt 14 ɛ aɪ eye fɑrm farm ˈfrizɪŋ freezing 11 tataː tata auntie fɛ do pʁɔvizjɔ̃ supply honey 15 bːɛħbːa aħbːudˤ tummy kak:a chocolate takurtː 15 ɑtʃi ɑntiː auntie ˈfɪlθi filthy fjuz fuse 12 bibiː bottle baby vwala here ʒødi Thursday ball 16 bula bula this is a light bulb et:ej move ! agrzam 16 kizɪ kɪtiː kitty ʤəˈraef giraffe heɪz haze 13 ɔp ɔp hop kɔm like kʁist Christ lion 17 mna magana this is a watch buʕːu monster tafruxt 17 aeː rɔr roar gɜrl girl ˈhɛvi heavy 14 awoː alo hello atɑ̃ wait avaʁi damage girl 18 qaqːa kukuʕːu cock (baby talk) tinxarin nose afrux 18 diθhɪ tiːʧər teacher greɪt great ˈhaɪbərˌneɪt hibernate 15 kukuː kuku hello lezaʁ lizard ɑɡaʁ shed boy 19 alaqa alqːaʕ sheep tabat:ˤaħt foot imi 19 dʌʔdae baekpaek backpack gɪˈtɑr guitar ˈɪnˌsɛst incest 16 apoː pɔpje fireman dakɔʁ okay ʁɑzwaʁ razor mouth 20 aːlaː ara give me tafust hand argaz 20 bɑ bɛr bear ˈhɛvi heavy ɪnˈtoʊn intone 17 poː po pot ale go tɑ̃ time man 21 baʕpːɛʕ lbanan banana tamz:ˤuxt ear tamɣart 21 peɪ bai bye hɔrs horse ˈlɑgər lager 18 kokoe tɔtɔ̃ uncle aʁiv arrive ataʁde linger woman 22 tːɛtetːe ʁid here tagaj:ut head amadl 22 dʌkʰ stʌk stuck ˈɪnˌsɛkt insect lɪv live 19 apeː papje paper avɑtaʒ advantage kuʃe lying hill 23 tʃtiʃk juʃkad he came timimit mouth amdlu 23 bu bluː blue ˈɪʧi itchy maeʧ match 20 oemaːʁoeː kameʁa camera mwɛ̃ less maʁʃɑ̃ seller cloud 24 aːpbː ibːi it is ripped tiwalin eyes skr 24 bɑk boʊt boat ˈʤaekət jacket ˈmɛntəl mental 21 teteː tete sucking dɑ̃ in səkwe shake do 25 acaːca agajːu head mimiʃ mouth fl 25 bʊk bʊk book ˈʤʌgəlɪŋ juggling ˈmɪksʧər mixture 22 kokɛː elikɔptɛʁ helicopter pɔʁtik crossbar tʁiko knitting let 26 memːe ʕmti my aunt tabit:u eyes ls 26 bo baʊ bow ˌkaeŋgəˈru kangaroo ˈpeɪpəl papal 23 ɔvaː oʁəvwaʁ bye bye pusɛ̃ chick vɑ̃ wind wear 27 handbːa andːu we are going tidˤudˤin fingers gn 27 bu bruːm broom kaɪt kite ˈroʊmən roman 24 tatɔː klakson horn amne brought deʁeɡle upset sleep 28 ʃu ʃuf look ʃk:ata eat (it) izˤuran 28 ɡʊˈkeɪ kʊkiː cookie ˈleɪtər later rul rule 25 baː bal ball ʁapɛl remember dɛʁm dermis veins 29 neːnːe ninːi sleep (baby talk) tas:awalt trousers azˤalim 29 duʃ ʃuːz shoes liv leave ˈskɛrsli scarcely 26 baː bɛ̃ bath ʒø games ɔtɔmatik automatic onion 30 aʃːe adʃːʁ I will eat banana banana tiwit 30 bu bʌrd bird ˈlɪkɪŋ licking taeb tab 27 apaː lapɛ̃ rabbit butɔ̃ button ɑɡɔse constrain you took away 31 ajːiː hajːi here I am biʒ:u baby tabrat 31 bɑk blaek black lʌv love ˈtaekəl tackle 28 biːboː bibʁɔ̃ bottle tele TV ɔfʁiʁ offer letter 32 haʃtʃkːa iʃqːa it is tough tˤrʃt break smun 32 pɪˈteɪ pɪɡlət piglet ˈmaegnət magnet ˈviəməns vehemence 29 guː leɡo lego komɑ̃ how vəly hairy pick up 33 ʃual ʃuwːr slow down ʕan: car knu 33 bu buːts boots min mean ˈvɜrʤənəl virginal 30 mɔː mɔʁ bite lɛs let velɛ vellum paper lean 34 anana wijnːa mom's one babat shoes kru 34 bʌˈbaʊwɪs bʌbəlz bubbles ˈmʌŋki monkey vəˈsɪfərəsli vociferously 31 maː mal hurt lynɛt glasses ɛʁb grass rent 35 ʃaʃaː matˤeʃa tomatoes fuf:u fire/ hot igawr 35 boː bʌɡ bug neɪm name ˈwikli weekly 32 neːne mimi cute aplɛ called defile parade he sit down 36 bakːaʔ baraka that's enough ak:ik give / Show tkʃmt 36 keɪk keɪk cake ˈnɛkləs necklace waɪld wild 33 apoː ʃapo hat pwasɔ̃ fish kale wedge you entered 37 ʁːa ʁwːa this one baja biscuits ssnkr 37 kɑː kɑr car naɪs nice kaerɪdʒ carriage 34 ameː fɛʁme closed penibl tiresome kɔtʁəpɛtʁi spoonerism wake 38 alti xalti my aunt st:ii grandfather udm 38 kɑk klɑk clock ˈɔrənʤ orange tɛkst text 35 bɛ tɔb fall vaʃ cow epanwiʁ blooming face 39 mamiandːu manisrandːu where ħmal donkey idamːn 39 flɛlɑ flawər flower ˈpeɪntɪŋ painting bɑks box 36 puː pul hen ɛtɛʁdi forbidden dɔsil docile blood 40 d adˤadˤ finger ʕːu fermented milk aɣrum 40 fuː fuːd food ˈpɪkʧər picture ˈaʊtˌlaɪn outline 37 fwɑ fʁwa cold ʃosɛt socks ʃɑs chance bread 41 mimːi amuʃː cat daʕ also juda 41 kik kɪk kick ˈreɪni rainy paekt pact 38 vyː pyl jumper ɡaʁsɔ̃ boy apsɑ̃ absent it's enough 42 bwa iswa he drank x:ix:iʃ dirty izra 42 mu muːs moose rɔr roar pʊt put 39 kaː kask helmet pətit small aspik aspic he saw 43 jːah jah yes kukuʕːu cok alim 43 pik pɪŋk pink ˈsaendi sandy riˈpʌblək republic 40 pyː py stink kat four fam woman straw 44 ːufːuʔ sfːuʁt get him out ħaħ:a boho / cut afunas 44 doʃ stɑrz stars ˈskrʌbɪŋ scrubbing raɪt right 41 afaː paʁfoẽ perfume pʁɛ ready manifɛstasjɔ̃ demonstration bull 45 fːufːu ifːuʁ he went out d:aħ:ati hit (me) ajdi 45 sɛː sʌn sun sit seat ˈsaednəs sadness 42 nɔːne koksinɛl ladybird tabl table. peje pay dog 46 mːam imːim it's tasty b:ˤatˤ shoes ngr 46 fwi θriː three spəˈgɛti spaghetti snaep snap 43 aneː fɛʁme close aspiʁatoeʁ vacuum cleaner sɛ̃ saint between 47 tos toʊz toes ˈtɪkət ticket skwiz squeeze 44 buː bul ball mɔtʁ show tiʁɑjoeʁ infantryman

However, some studies suggest that CDS is not necessary facilitating as it introduces more variability in input(Benders,

2013),[START_REF] Dilley | Acoustic-phonetic variation in word-final alveolar consonants in infant-directed speech over the first two years[END_REF],[START_REF] Dodane | An acoustic comparison of vowel systems in adult directedspeech and child-directed speech: evidence from French, English & Japanese[END_REF], and[START_REF] Sundberg | Voice onset time in speech to infants and adults[END_REF]

In the present study, the term 'cluster' refers to consonant sequences that occur both within and across syllables.

Rhoticity in English (the pronunciation of the historical rhotic consonant /r/) is one of the most prominent features distinguishing varieties of English. Here we studied the acquisition of American English, which belongs to the rhotic varieties.

http://www.ddl.ish-lyon.cnrs.fr/projets/prems/index.asp?Langue=EN&Page=Presentation


Carole Delenne

Jean-Stéphane Bailly

Antoine Rousseau

Renaud Hostache

Olivier Boutron

Jean-Stephane Bailly

Endorheic waterbodies delineation from remote sensing as a tool for immersed surface topography

  L'archive ouverte pluridisciplinaire

Introduction

Endorheic and temporarily submerged natural or man-made areas (wetlands, deltas, reservoirs...) are a vital resource for ecosystems, agrosystems and populations. Hydraulic models may be used for their study and management (see e.g. [START_REF] Boutron | An Unstructured Numerical Model to Study Wind-Driven Circulation Patterns in a Managed Coastal Mediterranean Wetland: The Vaccarès Lagoon System[END_REF][START_REF] Haque | development of a time-varying modis/ 2d hydrodynamic model relationship between water levels and flooded areas in the inner niger delta, mali, west africa[END_REF]); but if bidimensional models are powerful tools for shallow water flows representation, they require precise knowledge of the topography of the modelled domain. The extent, heterogeneity and the generally very little marked or evolving topography of such submerged area, make practical models application difficult. Proven interpolation methods are most often applied, using point surveys carried out in the field. Ideally, higher resolution LIDAR data could be available but their acquisition and processing cost remains prohibitive.

These interpolations are therefore inaccurate and can quickly turn out to be obsolete when annual floods change the system's geometry. Indeed, during a flood period, the sediments carried by surface water modify the geometry of natural rivers and become blocked in water reservoirs, leading to a reduction in storage capacity [START_REF] Albergel | Sediment budgets on hill reservoirs of small catchments in North Africa and the Middle East[END_REF]. Reservoirs geometry is also an essential factor in the modelling of their hydrological functioning [START_REF] Bouteffeha | A water balance approach for quantifying subsurface exchange fluxes and associated errors in hill reservoirs in semiarid regions[END_REF]. Bathymetric monitoring is the standard method for monitoring reservoir geometries but it remains an expensive method, and given the tidal range, especially in semi-arid areas, alternatives are possible [START_REF] Ogilvie | Combining landsat observations with hydrological modelling for improved surface water monitoring of small lakes[END_REF][START_REF] Tseng | Integrating Landsat Imageries and Digital Elevation Models to Infer Water Level Change in Hoover Dam[END_REF].

Remote sensing data from optical or radar images are now widely accessible and available at high spatial resolution and high temporal repeatability. It becomes possible to extract the water limits and their dynamics (e.g. floods limits [START_REF] Ogilvie | Decadal monitoring of the Niger Inner Delta flood dynamics using MODIS optical data[END_REF], seasonal tidal ranges [START_REF] Soti | Assessing optical earth observation systems for mapping and monitoring temporary ponds in arid areas[END_REF][START_REF] Ogilvie | Combining landsat observations with hydrological modelling for improved surface water monitoring of small lakes[END_REF], or long-term changes [START_REF] Xu | Surface-Water-Level Changes During 2003-2019 in Australia Revealed by ICESat/ICESat-2 Altimetry and Landsat Imagery[END_REF]) and use them for calibrating or validating hydraulic/hydrologic models (e.g. [START_REF] Ogilvie | Decadal monitoring of the Niger Inner Delta flood dynamics using MODIS optical data[END_REF][START_REF] Hostache | Assimilation of spatially distributed water levels into a shallow-water flood model. Part II: Use of a remote sensing image of Mosel River[END_REF][START_REF] Schumann | Deriving distributed roughness values from satellite radar data for flood inundation modelling[END_REF]) or to retrieve water elevation [START_REF] Hong | Multitemporal Multitrack Monitoring of Wetland Water Levels in the Florida Everglades Using ALOS PALSAR Data With Interferometric Processing[END_REF]. In the event of scarce field observation, it appears interesting to take advantage of these dynamics of water surfaces, which in endorheic areas form isovalue curves, in order to improve the estimation of the topography. Recent papers have been published [START_REF] Xu | Surface-Water-Level Changes During 2003-2019 in Australia Revealed by ICESat/ICESat-2 Altimetry and Landsat Imagery[END_REF][START_REF] Getirana | deriving three dimensional reservoir bathymetry from multi-satellite datasets[END_REF] to derive bathymetry for dynamic waterbodies using information on land elevation and long temporal series of water surfaces provided by satellite data. However, these studies are applied on very large areas only, since they uses high resolution images combined to radar altimeters. The bathymetry is recovered with an overall accuracy of several meters, which may be unsuitable for smaller waterbodies, while these represent the majority of the stored volume in European regions [START_REF] Messager | Estimating the volume and age of water stored in global lakes using a geo-statistical approach[END_REF]. Moreover, if remote sensing make the geolocation of the isovalue curves always possible, it generally does not allow to directly assign them a value, i.e. an elevation, except for areas under altimeter tracks, which represents a very small part of continental areas.

The approach proposed in this paper aims to find an interpolated field which takes into account several measurement points and the information from a few number of unvalued isovalue curves. It is based on the optimisation of an objective function in two parts: a "classical part", representing the distance of the interpolation to the measurement points, and an additional part integrating the information from the contour lines. A difficulty here is that the elevation itself of each curve is not known. The elevation of the contour lines is consequently computed in the proposed optimisation algorithm and is then defined as a parameters of the interpolation functions. The following section presents the proposed methodology applied first in a controlled environment to an artificially generated elevation field and next in a real-world experiment to the Rascaillan pond (Rhône delta, France), presented in section 3. Section 4 analyses the accuracy of the proposed approach with respect to the parameter settings for the artificial test case and provides numerical results for both the artificial and real application test cases.

Methodology

Input data

Let a domain D containing N punctual records, defined by their coordinate vectors:

s k =   x k y k z k   , k = 1, . . . , N (1)
and L contour-lines (i.e. L sets of points with the same elevation):

C l = s l = x l , y l , z l T | z l = a l , l = 1, . . . , L (2)
where the points x l , y l = X l are known since the shape of the contour-line is supposed to be extracted from remote sensing data, but the actual elevation a l of the contour-line is not known.

Approximation function

The approximated elevation Z(X) for each point X of the domain D is defined as a sum of radial functions:

∀ X ∈ D, Z(X) = Nϕ c=1 λ c ϕ c ( X -X c ) (3)
where X c is the centre of function ϕ c and N ϕ is the number of functions ϕ chosen.

The interpolation function chosen in this study is a sum of Thin Plate Splin (TPS), introduced by Duchon in [START_REF] Duchon | splines minimizing rotation-invariant semi-norms in sobolev spaces[END_REF]. TPS has a natural representation in terms of radial basis functions, and can be written on its normalized form as:

ϕ c (r) = r 2 R 2 ln r 2 R 2 (4)
where r is the Euclidian distance from the spline node (or center) c. According to [START_REF] Rabut | B-splines polyharmoniques cardinales : interpolation, quasiinterpolation, filtrage[END_REF], we compute the parameter R as follows:

R = 1 2 max k ( X c -G ) ( 5
)
where G is the barycenter of all the center points X c .

The main advantage of TPS on other radial functions such as Gaussian or inverse multiquadratic functions is that it does not depend on the scale of the topographic map of interest and has also good properties concerning the minimization of the overall curvature of the generated surface (see e.g. [START_REF] Bookstein | Principal warps: Thin-plate splines and the decomposition of deformations[END_REF][START_REF] Meinguet | Surface spline interpolation: Basic theory and computational aspects[END_REF]) as well as the speed of convergence towards the desired surface [START_REF] Buhmann | Multivariate cardinal interpolation functions[END_REF][START_REF] Powell | The Uniform Convergence of Thin Plate Spline Interpolation in Two Dimensions[END_REF]. However, any other interpolation function may be used in the proposed approach. For example, the classical inverse-distance function was tested and lead to similar results.

Minimisation problem

The problem can be expressed as follows: determine an approximation function Z (X; p), where X = (x, y) stands for any points of the domain and p stands for the possible parameters of the function Z.This would classically be defined as a minimisation problem with the following cost function (Mean Square Error):

J 1 (p) = 1 N N k=1 [Z(X k ; p) -z k ] 2 (6)
The purpose of this study is to introduce another information based on the contour-lines that can be visible on aerial or satellite images, via the following cost function:

J 2 (p) = 1 l L l=1 1 N l N l i=1 Z(X l i ; p) -ãl 2 (7)
where N l is the number of points X l i chosen on each contour-line C l and ãl the estimation of the contour-line level a l . Indeed, the particularity of this approach is that the elevation a l of each contour-line is not known and will be assessed along with the parameters p during the minimisation process.

The two following approaches will thus be compared in this paper:

• Approach 1 (A1): minimisation based only on the measurement points using cost function J 1 (p) defined by equation ( 6).

• Approach 2 (A2): minimisation based on measurement points and contourlines with unknown levels using cost function J 12 (p) = J 1 (p) + J 2 (p), defined by equations ( 6) and [START_REF] Cordeiro | Automatic water detection from multidimensional hierarchical clustering for Sentinel-2 images and a comparison with Level 2A processors[END_REF].

Resolution

The optimisation function depends on N φ + L parameters, i.e. the chosen number of interpolation functions plus the number of contour-lines whose elevation is unknown. The approximation Z(X) given by equation ( 3) is computed for each measurement point s k and each point on the contour-lines s l i . Starting from a random set of initial parameters values, a quasi-Newton approach [START_REF] Shanno | Conditioning of quasi-Newton methods for function minimization[END_REF] is used to find parameters minimising the cost function given by equations (6-7).

Data

Academic test case

The proposed methodology is first applied on an academic test case, for which all input values are controlled, for a better parametric analysis. A random Gaussian field is generated to simulate a smooth and realistic topography used as reference for the validation test case. The domain extent is 1000 m×1000 m with a 10 m spatial resolution; the model used to generate this 2D field is a Gaussian model with a 150 m practical range, a 0 m nugget and a 1/36 sill in order to get a smooth field with elevation values ranging from -0.5 m to 0.5 m (see Fig. 1).

Contour-lines, such as those that could be obtained by remote sensing approaches, are extracted from this field (see an example Figure 1-right). All the elevation pixels falling on a contour-line are selected to constitute the C l set of points defined by equation [START_REF] Belkin | Does data interpolation contradict statistical optimality[END_REF].

In order to better compare the two approaches, several numbers of punctual measurements are selected with the following random stratified method. The domain is divided into d 2 subdomains in which one point is randomly selected, with d varying from 1 to 5 hereafter (see Figure 2). The minimisation process is run 100 times for each number of points and for each of the two approaches.

The TPS radial functions ϕ used in this test case are defined on a regular grid which density is also studied.

The results will be assessed via the classical Root Mean Square Error (RMSE) computed between the "real" topography and its estimation by the two ap- 3.2 Real test case: the Rascaillan pond

Study area and validation data

The Rascaillan is a pond located in the Rhone delta, south of France, as part of the UNESCO's Man and Biosphere reserve of Camargue (Figure 3). It comprises an area of c.a. 420 ha, and is a shallow pond (average water depth of 0.6 m at a water level of 0.5 m NGF (General Leveling of France). It is subject to very strong evaporation rates [START_REF] Boutron | An Unstructured Numerical Model to Study Wind-Driven Circulation Patterns in a Managed Coastal Mediterranean Wetland: The Vaccarès Lagoon System[END_REF], which can result in a partial drying up. Figure 4 shows the real bathymetry of the pond obtained by a topo-bathymetric LIDAR survey carried out in September 2016 with the Optech Titan DW600 of Nantes and Rennes Universities platform and processed by D. Lague [START_REF] Lague | Chapter 2 -topo-bathymetric airborne lidar for fluvial-geomorphology analysis[END_REF]. The spatial resolution is 0.5×0.5 m. The vertical resolution is 0.01 m, with a vertical accuracy of 0.05 m.

Remote-sensing data and water extent extraction

To extract varying waterbody extents of the Rascaillan pond, we processed a series of Synthetic Aperture Radar (SAR) images acquired by the Sentinel-1 satellite constellation. These images were acquired in Interferometric Wide swath mode with a pixel spacing of 10 m, corresponding to an average resolution of 20 m. The images were calibrated and re-sampled at 20 m pixel spacing. The waterbody extent was retrieved based on the method proposed in [START_REF] Giustarini | Probabilistic flood mapping using synthetic aperture radar data[END_REF].

Results

Academic test case

Figure 5 shows an example of application with three different contour-lines selected at -0.1 m, 0 m and 0.1 m, 9 punctual records (red points) and 100 interpolation functions (one each 10m). In this particular test case, the RMSE between the reconstructed field and the real one is equal to e 1 = 0.32 m for Approach 1 corresponding to a relative error of 30%. Approach 2 enables a drop of the error to e 2 = 0.10 m (9.87%). It is first noticeable that the use of the contour-lines in the optimisation process reduces the error by three. Moreover, the approach enables the estimation of the contour-lines level with a RMSE equal to 4.7cm only. A parametric analysis is then performed with these generated data. Each of the following tests has been repeated 100 times with a random selection of measurement points.

The density of interpolation functions has first been tested on the classical approach with 3 contour-lines (selected at -0.1 m, 0 m and 0.1 m) and 9 punctual records. It can be seen (see Figure 6) that the distance between two ϕ centres should be of the same order of magnitude than the field range of spatial correlation. The following results are thus obtained with 7 × 7 functions (e.g. about 15 m apart from each other).

The influence of the number of measurement points have then been assessed, with the three same curves. As expected, it is first noticeable that for both approaches, the result accuracy increases with the number of interpolation points. What is more interesting is that the use of contour-lines extracted from remote sensing enables a very significant gain in accuracy with few measurement points (see Figure 6 right). Indeed the RMSE obtained by Approach 2 with only one measurement point and the three curves is between the ones obtained using 9 and 16 points in the classical approach.

The last parameter of interest here is the number of contour-lines available, taken from 2 to 6. At each of the 100 repetitions, the nine measurement points are randomly selected as explained before and the contour-lines are also ran- domly selected, with levels ranging between -0.4 m and 0.4 m. It can be seen (Figure 7) that the benefit of adding contour-lines rapidly drops (best results are obtained with four curves). Moreover, although adding curves slightly enhance the altitude assessment on the whole domain on average, local biases degrade the estimates of each contour-lines level. This result shows that we face a biasvariance tradeoff which has been also observed for other spatial regularization problems [START_REF] Belkin | Does data interpolation contradict statistical optimality[END_REF].

Real case application

Figure 8 shows two contourlines extracted from Sentinel 1 images (using approach presented in [START_REF] Giustarini | Probabilistic flood mapping using synthetic aperture radar data[END_REF]) at dates with different water levels (2017-11-03 and 2016-09-16) and an example of 8 punctual records selected with stratified random procedure from Lidar data. As for the academic case, several tests were run with contourlines number varying from two to four and with punctual records number from 5 to 10. The results are assessed through the RMSE between the estimated and Lidar topographies. The standard approach based on records yields error ranging from 0.22 m to more than 0.6 m depending on the number and position of the randomly selected points. However, the proposed approach provides systematically better results with errors generally between 0.18 m and 0.22 m. Moreover, using more than two contourlines does not increase accuracy. This may be due to the uncertainty of the contourlines extracted from sentinel images as can be seen in Figure 8-right, that enable the comparison of the estimated contourlines to the real topography. Several factors may be in cause, such as image resolution, variation of topography between Lidar and images acquisition, or wind that often inclines the pond surface elevation in this area (several centimeters of difference from one side to the other). Figure 9 shows an example of results obtained for the Rascaillan pond using the classical approach with five punctual records interpolation and the proposed abled a parametric study with many repetitions. The results show a substantial reduction of the RMSE error when adding only a few contourlines (up to 4), whereas additional isolines do not seem to provide any useful information. The real-case application to the Rascaillan pond shows that this approach can easily be implemented using widely available data such as Sentinel images, yielding a large decrease of the root mean square error between the interpolated topography and the reference LIDAR acquisition, even using only two satellite images.

Depending on the study area and the available data, other methodologies may be used to extract waterbodies contourlines such as the ones presented in [START_REF] Yang | Monthly estimation of the surface water extent in france at a 10-m resolution using sentinel-2 data[END_REF] or [START_REF] Cordeiro | Automatic water detection from multidimensional hierarchical clustering for Sentinel-2 images and a comparison with Level 2A processors[END_REF].

Figure 1 :Figure 2 :

 12 Figure 1: Generated topography for the validation test case (left) and example of the 0 m contour-line (right)

Figure 3 :

 3 Figure 3: Situation of Rascaillan pond, south of France.,

Figure 4 :

 4 Figure 4: Real bathymetry of Rascaillan pond obtained from lidar survey

Figure 5 :Figure 6 :

 56 Figure 5: Example of application. a) Real field, with 3 contour-lines and 9 punctual records (red crosses). Results obtained using b) punctual records only (red crosses) and J 1 cost function, c) punctual records plus contour-lines (red crosses) and J 12 cost function.

Figure 7 :

 7 Figure 7: RMSE (m) as a function of number of curves for the proposed approach (A2). Left: computed on the whole field; Right: computed on contour-lines points only.

[b]. 5

 5

Figure 8 :

 8 Figure 8: a) Example of two contourlines (red crosses) extracted from Sentinel 1 images (the probability for each pixel of beeing water is given in gray scale), and b) five punctual "records" selected from lidar data (red points) along with contourlines (black crosses) and lidar topograhy (in color).

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approach that accounts for the two contourlines extracted from Sentinel 1 images provided in Figure 8. The RMSE obtained here for the first approach is 0.42 m whereas it drops to 0.17 m using the two contourlines.

Conclusion

In this study we evaluate the impact of adding topography contourlines to traditional point-wise measured altitudes in a global topography reconstruction. The location of the isolines is an available information from remote sensing data, whereas their altitude remains unknown. Indeed, the approach takes benefits of widely accessible optical or radar images and, since the contourlines altitudes are assessed by the optimisation process, it does not require more rarely available altimeters information. The application on generated data en-


Frédérique Gayraud

Isabelle Simoes Loureiro

Camille Frouin

Cynthia Collette

Laurent Lefebvre

Melissa Barkat-Defradas

Isabelle Simoes Loureiro²

Cynthia Collette²

Laurent Lefebvre²

Lexical deterioration in Alzheimer's disease

Keywords: retrogenesis, Alzheimer's disease, semantic knowledge, lexical access

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Lexico-semantic network is the result of a progressive construction across lifespan. During childhood, the features of objects and their verbal labels are progressively stored to build our semantic knowledge and language. In AD, both sides, language and semantic knowledge, can be affected as demonstrated by word finding difficulties, circumlocutions, paraphasia and/or semantic errors. The specific aim of this research is to analyze whether the understanding of lexico-semantic knowledge constitution in childhood brings clarification about its deterioration in AD. Retrogenesis theory [START_REF] Reisberg | Functional staging of dementia of the Alzheimer type[END_REF] suggests that the earlier an ability is developed, the stronger it will resist to aging and to degenerative processes such as AD. Thus, one can expect a retrogenic trajectory of lexico-semantic aspects in AD manifested by the loss of semantic knowledge following a path opposite to their acquisition. Some studies have highlighted results suggesting that this hypothesis of retrogenesis should be considered (e.g. [START_REF] Mello | Involution of categorical thinking processes in Alzheimer's disease: Preliminary results[END_REF]. The results of these studies show that the lexico-semantic aspects that are acquired later in development are also the most vulnerable in AD. The goal of the present study was then to test the retrogenic hypothesis by applying it to the lexicosemantic deterioration in normal aging and in AD.

Study 1: Semantic knowledge

Our first study aimed to investigate the development of semantic knowledge about objects in children aged from 5 to 9 years old and to compare this acquisition to the semantic loss in Alzheimer's disease.

Method

A total of 191 French native speakers were enrolled in the experiment. 93 children were allocated into 3 age groups: 5-year-olds (n=30, 17 girls); 7year-olds (n=30, 20 girls) and 9-year-olds (n=33, 19 girls). 32 healthy elderly and 66 AD patients were also tested. AD patients were divided into three groups depending on their global cognitive deterioration measured by their performance at the Mini-Mental State Examination (MMSE): Mild (AD1: MMSE>20, n=20); Moderate (AD2: 16<MMSE<19, n=16), and Advanced stages (AD3: MMSE<16, n=30). No difference of age and sociocultural level appeared between the four elderly groups (p<.05). The Semantic Knowledge Questionnaire (SKQ) was used for all participants. Initially proposed by [START_REF] Laiacona | Perceptual and associative knowledge in category specific impairment of semantic memory: A study of two cases[END_REF], this tool was revised and adapted in French for children (Simoes Loureiro & Lefebvre, 2015a) and for AD patients (Simoes Loureiro & Lefebvre, 2015b). SKQ contains 120 questions about 30 objects with different levels of hierarchy and attributes in semantic memory (Q1: questions about general superordinate aspects, e.g. Is the ostrich an animal, a plant, or an object?; Q2: questions about intracategorical aspects, e.g. Is the ostrich a four-legged animal, a bird, or an insect?; Q3: questions about perceptual attributes, e.g. Is the ostrich's neck longer than a rooster's neck? ; Q4 : questions about thematical/functional attributes, e.g. Does the ostrich run, walk, or swim?).

Results and discussion

ANOVA on repeated measures were carried out using the errors to each type of question (Q1, Q2, Q3, Q4) as 'within subject factor,' and the groups as 'between subject factor'. Results indicated a group effect, (F=43.884; p< .001) demonstrating a decrease of the total number of errors to SKQ in childhood and an increase with the stages of AD, a type of question effect (F=230.083; p<.001) demonstrating fewer errors at the superordinate level (Q1+Q2) than at the subordinate level (Q3+Q4) and an interaction effect (F=23.066; p< .001) (for a more detailed description of the results, see Simoes Loureiro & Lefebvre, 2016).

Those results demonstrate an evolution/deterioration of the different levels of hierarchy of semantic knowledge with a slight improvement of general and intracategorical superordinate information from 5 to 9 years old and a slight deterioration in AD, contrary to the subordinate level (perceptual and thematic/functional), with a later formation in childhood and an earlier deterioration in AD. These results sustain the hypothesis of [START_REF] Reisberg | Functional staging of dementia of the Alzheimer type[END_REF]. Indeed, we observed that for the knowledge tested in this study, the earlier the children acquired concepts, the later the AD patients lost it. Study 2 will consider the importance of the developmental trajectory of semantic knowledge by considering the age of word acquisition as a factor in anchoring this knowledge.

Study 2: Naming task

The purpose of study 2 was to compare naming performances of children and patients with AD. Based on the assumption that early acquired words are more robust than late acquired ones, we predicted that the scores of patients at different stages of the disease and those of children at different developmental stages should show a mirror pattern, especially for late acquired words.

Method

A total of 160 participants: 80 AD patients, 60 children and 20 elderly controls participated in the study. The AD group was split into four subgroups depending on the MMSE scores: mild (MMSE = 20-25), moderate (MMSE = 16-19), moderately severe (MMSE = 10-15), and severe (MMSE < 10). Similarly, the children were divided into 3 subgroups: early childhood (MMSE = 10-15, from 3 to 5 years old), middle childhood (MMSE = 16-19, from 5 to 7 years old) and late childhood (MMSE = 20-25, from 8 to 10 years old). For the naming task, 24 pictures were selected from [START_REF] Rossion | Revisiting Snodgrass and Vanderwart's object pictorial set: The role of surface detail in basic-level object recognition[END_REF]: 12 pictures depicted words acquired early (mean AoA = 1,8 years), and 12 pictures corresponded to words acquired later (mean AoA = 2,8 years). Words in both lists were controlled for frequency, name agreement, word length, phonological neighborhood and visual complexity.

Results and discussion

We found a significant effect of group (p<.0001), AoA (p<.0001), as well as a significant interaction (p=.001). Patients with AD showed lower scores compared to other participants, early acquired words displayed higher scores than late acquired words, especially for children and AD patients. Focusing on early acquired words, Post hoc Tuckey analysis showed no significant differences between subgroups except for severe AD patients, who showed significantly lower scores (p<.0001). Turning to late acquired words, the results showed a mirror pattern between the subgroups of AD patients and children.

Globally, our findings are in line with the retrogenesis hypothesis. We also found a strong AoA effect, which had however, a more detrimental effect in AD patients than in children.

Conclusion

Our findings suggest that globally, the retrogenesis hypothesis is relevant and useful for a better understanding of language decline in AD, since developmental changes in the child are better known than changes occurring in AD. Nevertheless, it is also important to take into accounts the specificities of each population, as AD patients benefit from a cumulative life experience that should not be ignored [START_REF] Moos | Humour, irony and sarcasm in severe Alzheimer's dementia-a corrective to retrogenesis?[END_REF].