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Brice Brossette
email: brice.brossette@univ-amu.fr

Élise Lefèvre

Elisabeth Beyersmann

Eddy Cavalli

Jonathan Grainger

Bernard Lété

Phonological Decoding and Morpho-Orthographic Decomposition: Complementary Routes During Learning to Read

Keywords: phonology, morphology, reading acquisition

published or not. The documents may come   L'archive ouverte pluridisciplinaire

Introduction

Visual word recognition is a key component of reading proficiency [START_REF] Cutting | Prediction of reading comprehension: Relative contributions of word recognition, language proficiency, and other cognitive skills can depend on how comprehension is measured[END_REF]. In most models of reading acquisition, beginning readers initially have access to the meanings of words by applying spelling-to-sound translation on letters decoded serially [START_REF] Ehri | Phases of development in learning to read words by sight[END_REF][START_REF] Grainger | A dual-route approach to orthographic processing[END_REF][START_REF] Seymour | Foundations of orthographic development[END_REF][START_REF] Share | Phonological recoding and self-teaching: sine qua non of reading acquisition[END_REF][START_REF] Ziegler | Reading acquisition, developmental dyslexia, and skilled reading across languages: a psycholinguistic grain size theory[END_REF]. Each successful decoding through this orthography-phonology-meaning route is assumed to help develop a direct connection between orthography and meaning, which is no longer mediated by using phonological units [START_REF] Share | Phonological recoding and self-teaching: sine qua non of reading acquisition[END_REF]. The emergence of a direct orthography-meaning route is thought to support more automatic word recognition processes for more efficient silent reading for meaning [START_REF] Coltheart | DRC: a dual route cascaded model of visual word recognition and reading aloud[END_REF][START_REF] Diependaele | Fast phonology and the bimodal interactive activation model[END_REF][START_REF] Grainger | Phonology and Orthography in Visual Word Recognition: Effects of Masked Homophone Primes[END_REF][START_REF] Grainger | Watching the Word Go by: On the Time-course of Component Processes in Visual Word Recognition[END_REF][START_REF] Grainger | A dual-route approach to orthographic processing[END_REF][START_REF] Perry | Nested incremental modeling in the development of computational theories: the CDP+ model of reading aloud[END_REF][START_REF] Perry | Beyond single syllables: large-scale modeling of reading aloud with the Connectionist Dual Process (CDP++) model[END_REF]. As described by [START_REF] Grainger | A dual-route approach to orthographic processing[END_REF], automatic visual word recognition is achieved principally via the parallel processing of letter identities and their positions thus delegating phonological decoding to a secondary role.

More precisely, [START_REF] Grainger | A dual-route approach to orthographic processing[END_REF] dual-route model hypothesized that skilled readers process written words using two types of sublexical orthographic representation. On the one hand, a coarse-grained orthographic code enables flexible letterposition coding, which provides fast access to whole-word orthographic representations. A well-known manifestation of this coarse-grained code is the transposed-letter effect which reflects the tendency of skilled readers to confuse, to a larger extent, a base-word with a transposed-letter nonword (e.g., judge with jugde) than with a replacement-letter nonword (e.g., judge with jupte; see [START_REF] Blythe | Reading transposed text: effects of transposed letter distance and consonant-vowel status on eye movements[END_REF][START_REF] Grainger | Cracking the orthographic code: An introduction[END_REF][START_REF] Guerrera | Masked form priming with extreme transposition[END_REF][START_REF] Perea | Can CANISO activate CASINO? Transposed-letter similarity effects with nonadjacent letter positions[END_REF]. In an innovative study, [START_REF] Grainger | Evidence for multiple routes in learning to read[END_REF] investigated the development of the coarse-grained route by comparing the size of the pseudo-homophone (PsH) effect (i.e., participants are more likely to judge that a pseudoword that can be pronounced like a real word is a word, for example, BRANE can be pronounced to sound like the word BRAIN) and the transposed-letter effect (i.e., participants are more likely to judge that a pseudoword created by the transposition of two letters is a word, such as TALBE derived from the word TABLE) in a lexical decision task. Results showed that children exhibit large PsH effects in Grade 1 (44.61 %), which continuously decreased over reading acquisition (16.07% in Grade 5, and only 4.6% in adults). Interestingly, the transposed-letter effect followed the opposite trajectory with the effect increasing as reading level increased (starting at 8.24% in Grade 1 and reaching its maximum -12.88% -in Grade 4). These results were interpreted as evidence for a decreased reliance on phonological decoding (the PsH effect) and an increased reliance on the coarse-grained route (the transposed-letter effect) during learning to read.

The present study builds on one additional assumption in the model of [START_REF] Grainger | A dual-route approach to orthographic processing[END_REF], that the fine-grained code is crucial for precisely encoding not only graphemes but also small morphemic units (i.e., affixes). Morphemes are hypothesized to play a key role in visual word recognition by providing an island of regularity to overcome the arbitrariness of the spelling-meaning relationships [START_REF] Rastle | Morphological and semantic effects in visual word recognition: A time-course study[END_REF]. Prior research has shown that although children already have awareness for morphological structures in their oral language from a pre-school age [START_REF] Treiman | The development of spelling skill[END_REF][START_REF] Treiman | Spelling acquisition in English[END_REF], it takes many years of reading experience for children to develop the kind of automatic, morphological parsing mechanisms that are characteristic of skilled reading (e.g., [START_REF] Beyersmann | Morphological processing during visual word recognition in developing readers: evidence from masked priming[END_REF][START_REF] Beyersmann | The dynamics of morphological processing in developing readers: A cross-linguistic masked priming study[END_REF][START_REF] Dawson | Morphological Effects in Visual Word Recognition: Children, Adolescents, and Adults[END_REF][START_REF] Dawson | Finding the man amongst many: A developmental perspective on mechanisms of morphological decomposition[END_REF][START_REF] Hasenäcker | Morphological Priming in Children: Disentangling the Effects of School-grade and Reading Skill[END_REF][START_REF] Schiff | The Development of the Hebrew Mental Lexicon: When Morphological Representations Become Devoid of Their Meaning[END_REF]. In the present study we tested pseudo-morphemic (PsM) nonwords as the morphological equivalent of PsH nonwords. More precisely we used PsM nonwords composed of a real stem and affix such as the English example farmity composed of the stem farm and the suffix ity.

A variety of different tasks have been used to tease apart the different component processes involved in reading PsM nonwords, such as masked priming (e.g., [START_REF] Beyersmann | Effects of reading proficiency on embedded stem priming in primary school children[END_REF][START_REF] Hasenäcker | Masked morphological priming in German-speaking adults and children: Evidence from response time distributions[END_REF][START_REF] Hasenäcker | Morphological Priming in Children: Disentangling the Effects of School-grade and Reading Skill[END_REF], lexical decision (e.g., [START_REF] Casalis | How language affects children's use of derivational morphology in visual word and pseudoword processing: Evidence from a crosslanguage study[END_REF][START_REF] Dawson | Morphological Effects in Visual Word Recognition: Children, Adolescents, and Adults[END_REF]Hasenäcker et al., 2017;[START_REF] Quémart | Exploring the Role of Bases and Suffixes When Reading Familiar and Unfamiliar Words: Evidence From French Young Readers[END_REF] and reading aloud [START_REF] Colé | Stem and derivational-suffix processing during reading by French second and third graders[END_REF][START_REF] Mousikou | Orthographic consistency influences morphological processing in reading aloud: Evidence from a cross-linguistic study[END_REF]. What is typically seen in unprimed lexical decision, which was the task of choice in the current study, is a stepwise pattern showing that it is harder to reject a nonword when it is exhaustively decomposable into two morphemic subunits (farmity: i.e., PsM nonwords) than nonwords containing just one embedded morpheme (e.g., farm in farmald or ity in falmity), which in turn are harder to reject than non-morphemic control items (falmald). This so-called morpheme interference effect [START_REF] Crepaldi | Morphemes in their place: Evidence for positionspecific identification of suffixes[END_REF][START_REF] Taft | Lexical storage and retrieval of prefixed words[END_REF] has been observed in mid-primary school children (in Italian: [START_REF] Burani | How Early Does Morpholexical Reading Develop in Readers of a Shallow Orthography?[END_REF]in French: Casalis et al., 2015;[START_REF] Quémart | Exploring the Role of Bases and Suffixes When Reading Familiar and Unfamiliar Words: Evidence From French Young Readers[END_REF]in English: Dawson et al., 2018), with a tendency of becoming more robust throughout reading development [START_REF] Dawson | Morphological Effects in Visual Word Recognition: Children, Adolescents, and Adults[END_REF].

A related approach was used by Hasenäcker and Schroeder (2017) to investigate the developmental trajectory of the use of syllabic structure and morphological structure during learning to read. In a lexical decision task in German, the functional units of mono-and multimorphemic words and nonwords were highlighted using a colon (:), and their position either respected syllable or morpheme boundaries. For example, the word FAHRER was disrupted at the syllable boundary (FAH:RER) in the syllable-congruent condition and the morpheme boundary (FAHR:ER) in the syllable-incongruent/morpheme-congruent condition. Results

showed that children rely on different functional units over reading development. On the one hand, second graders showed a preference for syllabic units regardless of lexicality or morphological complexity. On the other hand, fourth graders exhibited the same reliance on syllabic units except for multi-morphemic nonwords, which were harder to reject when the presentation format highlighted morphological units (HELB:ER) rather than syllabic units (HEL:BER). Interestingly, the emphasis on either syllabic or morphological units no longer affected adult word recognition performance. These results are consistent with the hypothesis that phonological processes (influenced by syllabic structure) have an early influence, whereas morphological processing requires more reading experience.

The present study builds on this prior theoretical and empirical work in an investigation of the time-course of phonological and morphological processes during reading acquisition in three groups of developing readers (from Grade 1 to Grade 5) and one group of adults. To this end, we investigated the learning trajectory of PsH and PsM interference effects following the same experimental design as used by [START_REF] Grainger | Evidence for multiple routes in learning to read[END_REF], but this time replacing the transposed-letter nonwords with PsM nonwords. We predicted that phonological effects (i.e., PsH interference) should be strong for novice readers and then gradually diminish as reading expertise increases, which means that novice readers will be more likely to judge a pseudo-homophone non-word as a real word. On the other hand, we expected morphological effects (i.e., PsM interference) to take longer to emerge and gradually increase as reading expertise increases, which means that skilled readers will be more likely to judge a pseudomorphemic non-word as a real word. Although we instructed our participants to respond as rapidly as possible (in order to increase error rates), given the large variability in response times in young readers (e.g., [START_REF] Grainger | Evidence for multiple routes in learning to read[END_REF] we used error rates supplemented with signal detection theory to analyze our results.

Methods

Participants

One hundred and ninety-four children from public elementary schools were tested at the end of their school year in May: 36 were 1st Graders, 49 were 3rd Graders, and 59 were 5th Graders. All participants were native French speakers with normal or corrected-to-normal vision. Informed consent was provided by the participant's caregivers prior to experimentation. Ethical approval for this study was granted by the Comité de Protection des Personnes SUD-EST IV (No. 17/051). The experiment was performed in accordance with relevant guidelines and regulations and in accordance with the Declaration of Helsinki. An additional group of 50 adult students was tested at the University of Lyon. They were between 18-and 30-years age (mean age = 22 years and 11 months, SD = 2 years and 11 months). All participants were pre-tested for their reading fluency using a French standardized test [START_REF] Lefavrais | L'A ouette-R[END_REF]

Design and Stimuli

Thirty base-words (mean word frequency per million = 172.32, SD = 209.60) were used to construct 120 nonwords divided into four conditions: 30 pseudo-homophones (PsH), 30 pseudo-homophone controls (PsHc), 30 pseudo-morphemes (PsM), and 30 pseudomorpheme controls (PsMc). Base-word frequencies were obtained from the Manulex database [START_REF] Lété | MANULEX: a grade-level lexical database from French elementary school readers[END_REF]. All base-words occurred in Grade 1 texts in the Manulex corpus, meaning that these words are regularly encountered by beginning readers1 .

Pseudo-homophone nonwords

Pseudo-homophones (PsH) were obtained by substituting one grapheme of the baseword by another one of the same length associated with the same phonological representation (e.g., base-word: visage, PsH: visaje). The substitutions were made according to substitution rules described by Farioli et al. (2011). Then, pseudo-homophone controls (PsHc) were obtained according to the same principle but by using a grapheme that differs from the original phonological representation (base-word: visage, PsHc: visape). Thus, pseudohomophones were not associated with a valid orthographic representation stored in the lexicon (visaje is an incorrect spelling in French), while pseudo-homophone controls had both incorrect orthographic and phonological representations. Pseudo-homophones and their controls were matched on number of syllables, number of letters, orthographic similarity (as measured by the Orthographic Levenshtein Distance 20; [START_REF] Yarkoni | Moving beyond Coltheart's N: A new measure of orthographic similarity[END_REF], the mean consistency of grapho-phonological associations as computed on words in ManulexInfra [START_REF] Peereman | Manulex-infra: Distributional characteristics of grapheme-phoneme mappings, and infralexical and lexical units in child-directed written material[END_REF], and bigram frequency.

Pseudo-morphemic nonwords

Pseudo-morphemic (PsM) nonwords were obtained by adding an existing legal French suffix to the base-word (base-word: visage, PsM: visageable). Then, pseudo-morphemic nonword controls (PsMc) were obtained according to the same principle but by adding a nonaffix ending of the same length and of the same number of syllables as the suffix ending (base-word: visage, PsMc: visagealle). Non-morphological endings were obtained by substituting one letters of the suffix in the PsM condition to have a high degree of orthographic overlap between PsM and PsMc nonwords. PsM and PsMc nonwords were matched on number of syllables, numbers of letters, orthographic similarity, and bigram frequency.

Filler words

For the purpose of the lexical decision task, 120 words were selected from the Manulex database [START_REF] Lété | MANULEX: a grade-level lexical database from French elementary school readers[END_REF]. Half were high-frequency words (mean word frequency per million = 136.24, SD = 243.20) and the other half were low-frequency words (mean word frequency per million = 4.08, SD = 7.07). For each frequency class, half of the words were mono-morphemic, and the other half were morphologically complex. Thus, we obtained: 30 high-frequency monomorphemic words, 30 low-frequency monomorphemic words, 30 highfrequency morphologically complex words, and 30 low-frequency morphologically complex words. Filler words were matched with the critical nonword stimuli on length in letters and number of syllables. The complete set of stimuli are available in the Supplemental Materials.

Procedure and apparatus

Participants were seated in front of a 14-inch laptop computer running OpenSesame software [START_REF] Mathôt | OpenSesame: an open-source, graphical experiment builder for the social sciences[END_REF] at a viewing distance of approximately 60 cm. The stimuli were displayed in black lowercase in 24-point Courier font on a gray background with a resolution of 1280 x 720 px. Participants were tested in groups of two. The main experiment (lexical decision) lasted around 20-minutes.

Each trial began with a fixation cross for 1000 ms. Then, the fixation cross was replaced by a target stimulus at the center of the screen until the participant's response.

Participants were instructed to decide as quickly and as accurately as possible using the "M" key if the stimulus was a legal French word and the "Q" key otherwise on an AZERTY keyboard where the Q and M keys occupy the left and right extremes of the central row of letters (for left-handed participants the response keys were reversed). Stimuli were divided into five counterbalanced blocks of 24 experimental trials. Blocks and trials within blocks were presented in a randomized order. A practice block of 24 trials was also presented before experimental blocks. To avoid fatigue, a break was offered between each block.

Children were tested in groups of four to six by three experimenters in the same room.

Results

The final data set retained for analysis consisted of 23,280 observations. As acknowledged by [START_REF] Grainger | Evidence for multiple routes in learning to read[END_REF], the high percentage of errors for young readers in most developmental studies on reading acquisition makes the use of reaction time data unreliable2 . Analyses reported below were therefore only performed on the error data. We completed the error rate analyses with a signal detection analysis.

Error data analyses

Error data were analyzed using generalized linear mixed effects (lme4 package in R, version 1.1.31; [START_REF] Bates | Fitting Linear Mixed-Effects Models Using lme4[END_REF]. The GLME analysis was conducted using Group (Grade 1, Grade 3, Grade 5, and Adults), Type of Manipulation (pseudo-homophone vs. pseudomorpheme) and, Type of Condition (experimental vs. control) as fixed factors. The maximal random structure model that successfully converged was used. We tested the significance of the effects using Type III sum of squares and χ 2 Wald tests. Post-hoc contrasts were calculated using the emmeans package [START_REF] Lenth | emmeans: Estimated Marginal Means, aka Least-Squares Means (R package version 1[END_REF]. Full model outputs are given in the Online Supplemental Materials.

Prior to the analyses, we excluded two participants (one adult and one 5th Graders) with a reading level exceeding +/-2.5 SD from the mean of their group. In addition, four items were removed after data collection because of material defects 3 . The analyses revealed significant main effects of Group (χ 2 = 156.99, p < .001), Type of Manipulation (χ 2 = 34.52, p < .001), and Type of Condition (χ 2 = 111.83, p < .001). Most importantly, the three-way interaction between Type of Condition, Type of Manipulation and Group was significant (χ 2 = 124.14, p < .001). This three-way interaction reflects the distinct learning trajectories for pseudo-homophone and pseudo-morpheme effects. The pseudo-homophone effect decreased with age and was no longer significant in Adults (∆ER = 2.67%, z = 1.88, p = .060), which highlights the fact that more skilled readers are less likely to judge a pseudo-homophone as a real word. On the contrary, the pseudo-morpheme effect, which was already significant in Grade 1 (∆ER = 3.29%, z = 2.04, p = .042) increased with age, which highlights the fact that more skilled readers are more likely to judge a pseudo-morphemic non-word as a real word.

(see planned comparison and effect sizes reported in Table 1). 's d) of these differences were also reported.

Table 1. Mean percentage of error for pseudo-homophones (PsH), pseudo-morphemes (PsM), and their respective controls (PsHc, PsMc) across participant groups (standard errors in parentheses). The difference between PsH and controls reflects the size of the pseudohomophone effect, whereas the difference between PsM and controls reflects the size of the pseudo-morpheme effect. The significance (p-value computed with emmeans package) and the effect size (Cohen

Condition Group

Grade

Signal Detection Theory Analysis

We conducted a Signal Detection Theory (SDT; [START_REF] Swets | Decision processes in perception[END_REF] analysis to ensure that the different learning trajectories for pseudo-homophone and pseudo-morpheme effects were not due to a shift in the strategy used by participants to complete the lexical decision task, and more precisely, to possible changes in response bias across grades. Although the proportion of correct responses is affected by both sensitivity (i.e., the difficulty in discriminating words from pseudowords) and bias (i.e., the extent to which one response is more probable than another), SDT provides two distinct measures for these components. Crucially, for the present purposes, the sensitivity measure (d') provided by SDT provides a measure of participants' accuracy in classifying pseudo-homophones and pseudo-morphemes as pseudowords while controlling for response bias. Thus, accuracy data were used to calculate sensitivity (d') based on the percentage of hits (correct rejection of pseudowordsthe critical stimuli in our experiment) and false alarms (incorrect classification of words as pseudowords). Sensitivity (d') was analyzed using an ANOVA based on the same factorial design as used in the mixed model analysis: Group (Grade 1, Grade 3, Grade 5, and Adults) as a between-participants factor, and Type of Manipulation (pseudo-homophone vs. pseudo-morpheme) and Type of Condition (experimental vs. control) as within-participant factors. Post-hoc contrasts were calculated using the emmeans package (version 1.8.4.1;[START_REF] Lenth | emmeans: Estimated Marginal Means, aka Least-Squares Means (R package version 1[END_REF].

The sensitivity analysis was coherent with the error rate analysis, showing significant main effects of Group (F(3, 188) = 100.61, p < .001), Type of Manipulation (F(1, 188) = 100.80 p < .001), and Type of Condition (F(1,188 = 334.71, p < .001). Most importantly, the threeway interaction between the Type of Condition, Type of Manipulation and Group was also significant (F(3, 188) = 24.94, p < .001). Decomposition of this three-way interaction revealed only one significant divergence with respect to the error rate analysis. When this dependent measure was controlled for response bias (i.e., using d'), the pseudo-morpheme effect increased with age, but it became significant only in Grade 3 (∆ER = -.5, t = 5.72, p < .001). The trajectory of the pseudo-homophone effect remained unchanged. All the planned comparisons are presented in Table 2.

Table 2.

Sensitivity (d') measures for pseudo-homophones (PsH), pseudo-morphemes (PsM), and their respective controls (PsHc, PsMc) across participant groups (standard errors in parentheses). The difference between PsH and controls reflects the size of the pseudo-homophone effect, whereas the difference between PsM and controls reflects the size of the pseudo-morpheme effect. The significance (p-value computed using the emmeans package) of these differences is also reported.

Discussion

The present study investigated the learning trajectory of phonological and morphological processes during reading acquisition, with children in grades 1, 3 and 5, and adults. We did so by examining error rates in a lexical decision task to two types of nonword and their corresponding controls all derived from the same base-word (VISAGE in these examples): 1) pseudo-homophone (PsH) nonwords that can be pronounced like a real word (e.g., visaje) and the corresponding orthographic controls (e.g., visape); 2) pseudo-morphemic (PsM) nonwords that are formed by an illegal combination of a legal stem and suffix (e.g., visageable) and the corresponding controls where the suffix ending was changed to a nonsuffix ending (e.g., visagealle). The results showed that the PsH interference effect (i.e., pseudo homophone nonwords elicited more errors than their orthographic controls) decreased during reading acquisition and was non-significant in adults. On the other hand, the PsM interference effect (i.e., pseudo-morphemic nonwords elicited more errors than their orthographic controls) increased during reading acquisition and was larger in adults.

Crucially, a signal detection analysis of the present data revealed practically the same pattern of results with the measure of sensitivity (d') that controls for potential response biases.

These findings align well with previous work on the learning trajectories of the role of phonology and morphology when learning to read. More specifically, the PsH effect shown in our study showed the same learning trajectory as reported by [START_REF] Grainger | Evidence for multiple routes in learning to read[END_REF] and therefore further confirms the importance of phonological decoding during the early stages of reading acquisition. The progressive decrease of phonological decoding marks its gradual replacement by a process that enables a more efficient access to meaning from print [START_REF] Grainger | Evidence for multiple routes in learning to read[END_REF][START_REF] Wesseling | The transient role of explicit phonological recoding for reading acquisition[END_REF]. Although part of this more efficient reading route involves direct access to meaning from orthographic representations, a key role is also played by morpho-orthographic representations (e.g., [START_REF] Grainger | Orthographic processing: A "mid-level" vision of reading: The 44th Sir Frederic Bartlett Lecture[END_REF]. This increasing reliance on morphological processing during reading development has been documented in numerous developmental studies [START_REF] Burani | How Early Does Morpholexical Reading Develop in Readers of a Shallow Orthography?[END_REF][START_REF] Casalis | How language affects children's use of derivational morphology in visual word and pseudoword processing: Evidence from a crosslanguage study[END_REF][START_REF] Dawson | Morphological Effects in Visual Word Recognition: Children, Adolescents, and Adults[END_REF][START_REF] Quémart | Exploring the Role of Bases and Suffixes When Reading Familiar and Unfamiliar Words: Evidence From French Young Readers[END_REF]. A more surprising result is the small but significant PsM effect on error rates observed in Grade 1. Indeed, on the basis of prior work we expected the PsM effect to occur later. However, this prior work tested older children (mostly from Grade 3). Our results therefore suggest that including younger children in these studies is necessary in order to provide a complete developmental picture of PsM effects. Nevertheless, the PsM effect observed in Grade 1 should be interpreted with caution since it was not significant in the signal detection analysis. This discrepancy could be due to the smaller sample size of Grade 1 children compared to the sample size of other groups, which are close to meeting the recommendation of [START_REF] Brysbaert | Power Analysis and Effect Size in Mixed Effects Models: A Tutorial[END_REF].

The key result of the present study, however, is the demonstration of these opposing learning patterns in the same participants (children in grades 1, 3, and 5, and one group of adults). The decreasing effect of phonological processing and the increasing effect of morphological processing across these four groups is likely due to the development of their language skills and their increasing exposure to written language. At the early stages of reading development, children rely heavily on phonological processing, which involves recognizing and manipulating the sounds of language [START_REF] Castles | Ending the Reading Wars: Reading Acquisition From Novice to Expert[END_REF]. As children become more proficient readers, they start to rely more on the orthographic analysis of meaningful units of language, such as prefixes, suffixes, and stem morphemes [START_REF] Rastle | The place of morphology in learning to read in English[END_REF].

This shift in processing strategies may be due to the fact that children's language skills are rapidly developing as they are exposed to more complex vocabulary and sentence structures.

Recognizing the morphological structure of words helps children derive meaning from unfamiliar words. Morphological processing therefore represents the perfect tool to decompose unfamiliar words into smaller, familiar morphemic chunks [START_REF] Beyersmann | The dynamics of morphological processing in developing readers: A cross-linguistic masked priming study[END_REF]. For example, Hasenäcker et al. (2017) reported that German speaking children with a high vocabulary level benefitted earlier (i.e., Grade 2) and from various types of morphological structure (compounds, suffixed and prefixed words) compared to children with a lower vocabulary level. For children with a low vocabulary level, the presence of a suffix or a prefix was found to be detrimental for word recognition. This is in line with the hypothesis that, as readers become more experienced, they rely more on lexical and morphological processing, which involves accessing the meaning of words and morphemes directly from whole-word and morpheme representations in long-term memory [START_REF] Beyersmann | Morphological processing during visual word recognition in developing readers: evidence from masked priming[END_REF][START_REF] Beyersmann | The Role of Embedded Words and Morphemes in Reading[END_REF][START_REF] Grainger | Edge-Aligned Embedded Word Activation Initiates Morpho-orthographic Segmentation[END_REF]. This not only explains the increased reliance on morphological segmentation, but also explains why more experienced readers are less likely to rely solely on phonological processing when recognizing words, which is consistent with the present findings. However, it should be acknowledged that the present study did not assess children's vocabulary knowledge nor their prior knowledge of the base-words used to generate the PsH and PsM nonwords. We did select the base-words on the basis that they should be known by Grade 1 children according to Manulex [START_REF] Lété | MANULEX: a grade-level lexical database from French elementary school readers[END_REF].

Nevertheless, the prior knowledge of these base-words in the sample of children that we tested was not assessed. Therefore, one important addition for future work on this topic is to pretest the participants on their ability to read the base-words used to generated the critical nonword stimuli.

The present study points to the general interest, for future research, of studying pseudo-homophone and pseudo-morpheme effects in order to better understand the development of reading skills in children. It is possible that learning to read in highly productive morphemic languages may involve an even greater reliance on morphological representations relative to non-morphological phonological representations (i.e., phonemes and possibly syllables). Indeed, Finnish children appear to show greater reliance on morphemic compared to syllabic processing, even in a silent reading task [START_REF] Häikiö | Syllables and inflectional morphemes in early Finnish readers: evidence from eye-movements[END_REF]. Finnish first-and second-grade children read sentences with embedded inflected target words that had either syllable-congruent or syllable-incongruent hyphenation, while their eyemovements were registered. The study found that Finnish children in Grades 1 and 2 relied more on inflectional morphemes than syllables in their reading, suggesting that morphological processing plays an important role in the acquisition of Finnish reading skills. As an agglutinative language, Finnish clearly has a rich inflectional morphology, which therefore provides an interesting contrast to the current findings in French. Cross-linguistic studies therefore offer an important avenue for future research on the evolution of phonological and morphological processing during reading development.

Conclusions

The present study investigated the use of phonological decoding and morphoorthographic decomposition strategies during the course of learning to read. French speaking children would appear to use both strategies in the initial stages of learning to read. After that, phonological decoding becomes less important and eventually had a non-significant impact on the performance of adult participants in the present study (at least for the measure used in the present study), while the impact of morphological decomposition increased. This demonstrates how different sublexical representations are used to read words during learning to read silently for meaning, and how their impact changes over the course of learning.

  The lexical decision task was explained by an experimenter who gave the children examples of words and nonwords written on paper and asked them to respond together and orally if the letter string was a word or a nonword. The experimenter let the children express their opinion before providing the correct response. Examples were given until the experimenter believed that children had correctly understood the lexical decision task. During the practice trials, experimenters carefully controlled children's seating position and their correct use of the keyboard.

The mean word frequency per million for selected-based words was 172 (SD =

210); therefore, they could be considered highly frequent in the children's corpus. The detailed word frequency values for each base word are available in the online supplementary material.

In our experiment, the pseudo-homophone condition elicited more than 50% of the errors, which makes the use of reaction times less reliable (see also[START_REF] Goswami | Pseudohomophone effects and phonological recoding procedures in reading development in English and German[END_REF] for another example).

The pseudo-homophone control "cuje" built on the base-word "cage" was not built on a single substituting operation based on the critical grapheme "g." Hence, we took the decision to remove all items associated with the base-word "cage" : caje, cuje, cagitule, cagitude.

Acknowledgments

We thank Rachel Auroy and Mathilde Deglesne for their assistance in data collection during their research's internship. Funding B.B. was supported by a PhD scholarship from the co e orma e u érieure (ENS) of Lyon for the conceptualization, the methodology development, the data collection/analysis and by the pilot centre for research in education Ampiric, funded by the France 2030 Investment Program, as part of the action "Territories of Educational Innovation" operated by the Caisse des Dépôts for writing. J.G. was supported by the European Research Council (ERC 742141).

E.L. and E.C. was supported by the research grant "DYSsuccess" (ANR-18-CE28-0006).

Data availability

All data, materials, and code are available at the Open Science Framework (https://osf.io/n7qjk/?view_only=7b16a2e5d1034fbeb9c13dfc57c7e391)

Author contributions

Conceived and designed the experiment: BB, EC, EL, BL. Performed the experiment: BB, EL. Analyzed the data: BB, EL. Wrote the manuscript: EB, BB, EC, JG, EL, BL.

BB and EL contributed equally to this work.

Competing interests

The author(s) declare that there are no potential conflicts of interest with respect to the research, authorship, and/or publication this article.


F Dacquait

L Guinard

S Taunier

J L Bretelle

A Rocher

Auxiliary System Contamination in French PWRs

In order to study the impact of design and operating parameters on French PWR contamination, the CEA, by request of EDF, has been performing in-situ gamma spectrometry measurements using the so-called EMECC device for 37 years. These measurements have allowed researchers to characterize contamination levels accurately (surface activities by radionuclide), mainly in primary systems, but also in some reactor auxiliary systems such as the Chemical and Volume Control System (CVCS), the Residual Heat Removal System (RHRS), the Nuclear Sampling System (NSS) or the Fuel Pool Cooling and Cleanup System (FPCS).

Based on EMECC campaigns performed in different standardized plant series, this paper shows that the contamination of nuclear auxiliary systems presents differences in comparison to the contamination of the primary system:

-The 58 Co and 60 Co deposited activities on the CVCS, RHRS, NSS and FPCS are generally lower. On the other hand, the 110m Ag contamination is higher with a considerable recontamination resulting during cold shutdowns. -The dose rates around the auxiliary systems are generally higher.

-The 58 Co contribution and especially the 110m Ag contribution are both higher. For auxiliary systems that do not operate for several months, the 60 Co contribution emerges as the major one. -The nuclear auxiliary systems are the only circuits that allow us to measure the 51 Cr surface activities. These characteristics are due to different design and operating conditions, particularly the following : the presence of heat exchangers and lower fluid temperature, different flow rates, thinner thickness of pipes and of exchanger shells, the presence of filtering systems and operations during a short period.

A final observation is that, the peculiar behavior of 110m Ag inside the NSS generally results in a poor estimation of the 110m Ag volume activity in the primary coolant.

INTRODUCTION

In order to study the impact of design and operating parameters on the French PWR contamination by Activated Corrosion Products (ACP), the CEA, by request of EDF, has been performing in-situ gamma spectrometry measurements using the so-called EMECC device [START_REF] Eimecke | Ensemble de Mesures et d'Etude de la Contamination des Circuits[END_REF] for the past 37 years. These measurements have allowed researchers to characterize the contamination levels accurately (surface activities by radionuclides), mainly in primary systems [START_REF] Dacquait | Status of primary system contamination in French PWRs[END_REF] but also in some nuclear auxiliary systems. Knowledge of the contamination levels and their types in these systems is important for many reasons:

-The maintenance work carried out in the vicinity of these systems can influence the dosimetry greatly.

-Some radionuclides contaminate these systems preferentially. Thus, they can highlight a peculiar contamination, which could not be pinpointed by the EMECC measurements of the primary system.

-The surface activities of radionuclides emitting low energy gamma rays can only be measured in these systems.

-It contributes to studies on corrosion product transfer in PWR systems. This paper will present:

the surface activities in some auxiliary systems and their comparison to those in the primary system, the reasons for the contamination differences between auxiliary systems and the primary system, and the explanation of the peculiar behavior of 110m Ag.

EMECC CAMPAIGNS OF NUCLEAR AUXILIARY SYSTEMS

In this paper, nuclear auxiliary systems are defined as systems, other than the primary system, in which primary coolant circulates. These systems are thus contaminated and in particular by ACP. The surface activities of the components in these circuits (piping, heat exchangers, valves…) are measured by gamma spectrometry measurements using the EMECC device.

The background noise and the volume activities are taken into account for each EMECC measurement in order to determine the surface activities. Usually, the primary system contamination is the main interest of EMECC campaigns but some of them focus on the auxiliary system contamination. The main auxiliary systems analyzed are:

-CVCS : Chemical and Volume Control System -RHRS : Residual Heat Removal System -NSS : Nuclear Sampling System -FPCS : Fuel Pool Cooling and Cleanup System The measurement points are determined according to the probability of contamination changes: the presence of heat exchangers and lower fluid temperature, the presence of filtering systems, operation during a short period… Two EDF PWR cases are presented below: a 900 MWe PWR (Reactor A) and a 1300 MWe PWR (Reactor B).

Reactor A

This 900 MWe PWR is equipped with steam generator tubing in alloy 600TT. A boron-lithium coordinated chemistry at pH 7.0 was applied until cycle 3 and since then the aimed pH has been 7.2 at 300°C.

Several EMECC campaigns of the nuclear auxiliary system contamination were carried out in this PWR at cycle 11: a. During the power operation, 4 months before the refueling outage, b. Before the primary system oxygenation at the beginning of the refueling shutdown, c. After the primary system oxygenation, d. At the end of the shutdown.

Surface activities and dose rates

The list of the EMECC measurement points and their dose rates measured in contact with components of the CVCS, RHRS and FCPS is presented in Table 1. The values of dose rates in italics were measured with a shielded probe to mitigate the ambient dose rates. The EMECC measurement points of the Reactor Coolant System (RCS) are also indicated in this table.

Figure 1, Figure 2, Figure 3 and Figure 4 present the 58 Co, 60 Co, 51 Cr and 110m Ag surface activities in the RCS, CVCS and RHRS respectively; and Figure 5 in the FPCS. The 58 Co/ 60 Co surface activity ratio in the circuits is described in Figure 6.

Comments

Compared to the primary system, the dose rates of the CVCS are higher, those of the RHRS are similar and those of the FPCS are generally lower except for the pipe upstream from the heat exchanger. The surface activities of the CVCS and the RHRS are similar or lower than those of the RCS except for the 110m Ag contamination, which is higher in the CVCS. Thus, when compared to the RCS, the higher or similar dose rates in the CVCS and the RHRS (see Table 1) are due to the lessened thickness of piping or to the higher 110m Ag contamination level.

In the CVCS, downstream from the regenerative heat exchanger, the 58 Co deposited activities are less than those upstream (factor about 2) and they are much lower downstream from the particle filter (factor about 200) (see Figure 1). Downstream from the charging pump and therefore the ion exchanger resins, the ACP surface activities are higher than upstream. This could be attributed to the saturated ion exchanger or to the fact that the ion exchanger bypass valve was not closed properly.

The 60 Co surface activities tend to decrease along the CVCS (factor 10) particularly downstream from the particle filter (factor about 40) (see Figure 2).

The 58 Co/ 60 Co ratios increase along the CVCS, particularly in the regenerative heat exchanger and the pipe downstream (see Figure 6). They are higher than the ratios of the primary system.

The 51 Cr surface activities decrease by a factor of 3 in the non-regenerative heat exchanger and are not detectable downstream from the particle filter (see Figure 3).

On the other hand, during the shutdown before the primary system oxygenation, the 110m Ag deposited activities are practically constant along the CVCS up to the particle filter (see Figure 4). Downstream from the filter, they are lower by a factor of about 10.

The EMECC measurements in the nuclear auxiliary building (from the pipe upstream from the non regenerative heat exchanger) show that the surface activities have increased during power operation except for the 110m Ag contamination which tends to decrease.

The primary system oxygenation by injection of H 2 0 2 has not led to a change in the contamination level of 58 Co (peak of 100 GBq/t) and 60 Co (peak of 0.62 GBq/t) in the CVCS nor in the RCS, thanks to the oxygenation temperature of 80°C [START_REF] Dacquait | Corrosion Product Transfer in French PWRs during Shutdown[END_REF]. On the other hand, the 110m Ag surface activities have decreased upstream from the nonregenerative heat exchanger and have increased by a factor of 5 in this exchanger (with a measured maximum value of 110m Ag volume activity after oxygenation of 0.63 GBq/t).

In the RHRS, before its startup, the ACP surface activities on the pipe upstream from the main four valves are similar to those on the primary system since the primary coolant circulates in this part of the RHRS during power operation. After its startup, the 58 Co and 51 Cr contaminations tend to decrease (probably, erosion of a deposit enriched in 58 Co and 51 Cr) and the 60 Co surface activity is constant (see Figure 1, Figure 2 and Figure 3). It should be noted that in the second half of cycle 11, the 58 Co and 51 Cr volume activities under particle form have increased. These particles have formed a deposit not very adhesive that could be eroded with flow rate changes. Downstream from the main four valves, before their opening, the very low or undetectable contamination level of short radioactive half-life radionuclides ( 58 Co: 70.8 days, 51 Cr: 27.7 days) shows that this contamination is old and formed during the previous unit outage (the primary coolant did not circulate in the RHRS during the reactor power operation). On the other hand, after its startup, the RHRS parts downstream from the main valves are recontaminated. However, the contamination levels in the RHRS remain low compared to the primary system, but with a similar 58 Co/ 60 Co ratio (see Figure 6). The 58 Co, 60 Co and 51 Cr surface activities are lower and lower along the RHRS particularly in the heat exchanger. However, it is the opposite case for the 110m Ag: after the H 2 O 2 injection, the deposited activity is higher in the heat exchanger (see Figure 4).

In the FPCS (see Figure 5), during reactor power operation, the main radionuclide is 60 Co due to its long radioactive half-life (5.27 years) so the contamination is old. The contamination levels are practically constant in the different parts of the system except in the cooling line upstream from the heat exchanger, which is also downstream from the main FPCS tank and in which radioactive water circulates. During the refueling shutdown, due to the filling of the refueling cavity and the shifting of fuel in the spent fuel pit, the ACP contamination increases in the FPCS, particularly the 110m Ag contamination, which has become predominant.

At the end of the refueling shutdown, the 58 Co/ 60 Co ratio in the FPCS is similar to the ratio in the RCS.

What must be pointed out is that generally the 51 Cr surface activities can not be measured in the RCS due to its low gamma energy of 320 keV and the great thicknesses of the primary coolant pipes and steam generator shell. Thanks to a "nuclear auxiliary system", the steam generator bypass, the EMECC measurement of this thin pipe provides the 51 Cr surface activity of the primary system (see Figure 3).

Reactor B

This 1300 MWe PWR is equipped with steam generator tubing in alloy 600TT. A boron-lithium coordinated chemistry at pH 7.0 was applied until cycle 5 and since then the aimed pH has been 7.2 at 300°C.

An EMECC campaign of the nuclear auxiliary system contamination was performed in this PWR at cycle 10 at the beginning of the refueling shutdown before and after the primary system oxygenation.

Surface activities and dose rates

The list of the EMECC measurement points and their dose rates measured in contact with components of the CVCS, RHRS and NSS is presented in Table 2. The values of dose rates in italics were measured with a shielded probe to mitigate the ambient dose rates. The EMECC measurement points of the Reactor Coolant System (RCS) are also indicated in this table.

Figure 7 and Figure 8 present the 58 Co and 60 Co surface activities in the RCS, CVCS, RHRS and NSS respectively. The radionuclide contributions to the dose rates around the systems are presented in Figure 9 before the H 2 O 2 injection and in Figure 10 after the primary system oxygenation.

Comments

Compared to the primary system, the dose rates of the CVCS and NSS are generally higher while those of the RHRS are similar. The 58 Co surface activities of the CVCS pipes up to the particle filter are similar to those of the RCS. Those of the RHRS and the NSS are lower, as is also the case of the 60 Co deposited activities. Thus, compared to the RCS, the higher dose rates in the auxiliary systems are due to either the lessened thickness of the piping or to the higher 110m Ag contamination level (see Figure 9 and Figure 10).

During the shutdown procedure ( 58 Co peak of 48 GBq/t), the 58 Co contamination has increased by a factor 2 to 8 in the NSS and it is practically constant in the other systems except for the pipe upstream from the pumps of the RHRS. The 60 Co surface activities are constant in all the circuits and the 110m Ag contamination has increased in some cold parts of the RHRS, CVCS and NSS (with a measured maximum value of 110m Ag volume activity after oxygenation of 39 MBq/t).

Figure 9 and Figure 10 show that the main radionuclides contributing to the dose rates around the auxiliary systems are 58 Co, 60 Co and 110m Ag.

In the RHRS, before its startup, the main radionuclides are 60 Co and 110m Ag because of their long half-life, the RHRS does not operate during reactor power operation. After oxygenation, the 110m Ag contribution increases in the cold parts; it reaches about 70% in the heat exchanger.

In the CVCS, upstream from the filter, the two main contributors are 58 Co and 110m Ag, with the 110m Ag contribution increasing after the oxygenation. The contribution upstream from the regenerative heat exchanger is similar to the one of the primary system (close conditions): 58 Co and 60 Co are the two main contributors. Downstream from the filter, the two main contributors are 60 Co and 110m Ag.

In the NSS, 58 Co, 60 Co and 110m Ag are the three main contributors to the dose rates. The 58 Co contribution increases after oxygenation.

DISCUSSION

The EMECC campaigns carried out in different standardized plant series allow us to define the principal characteristics of the contamination of the main auxiliary systems.

The 58 Co and 60 Co deposited activities on the CVCS, RHRS, NSS and FPCS are generally lower than those on the primary system. They can be similar, especially in the upstream parts and they do not decrease inevitably along the circuits. Of course, they decrease downstream from the CVCS purification system (particle and mixed bed filters) unless there is an opened bypass valve or a problem such as a saturated filter.

The 58 Co and 60 Co contaminations of the CVCS and NSS build up essentially during reactor power operation, but the 58 Co contamination can also increase during the oxygenation. The RHRS and FPCS contaminations occur during the shutdown, when these systems operate or are particularly requisite. Before their operation, they are contaminated by ACP with long radioactive half-life, mainly 60 Co. During their operation, they are contaminated by ACP with short half-life. Thus, the RHRS is contaminated after its startup during cold shutdown and the FPCS during the refueling shutdown due to the filling of the refueling cavity and the shifting of fuel in the spent fuel pit. The comparison of the 58 Co/ 60 Co ratios of deposited activities on the primary system and on auxiliary systems shows that the types of contamination are different: different because of their thermal hydraulic conditions, their components or their operation.

Sometimes during shutdown, the 58 Co and 51 Cr contaminations or those of the 60 Co decrease in the auxiliary systems. This is due to the movement of particles that were deposited and that have been swept away by the flow rate changes.

The nuclear auxiliary systems are the only circuits that allow us to measure the 51 Cr deposited activities. The thicknesses of primary pipes or steam generator shells are generally too great (more than about 7 cm) for the 320 keV gamma emitted by 51 Cr. In order to know the 51 Cr surface activity in the primary system, the SG bypass pipe, when it exists (in 1450 MWe PWRs, there is not any SG bypass), or the CVCS letdown pipe upstream from the regenerative heat exchanger (thickness of about 1 cm) are measured with an EMECC device. As the contamination levels by the other radionuclides of the primary pipes and of these parts of auxiliary systems are similar, the 51 Cr contamination level can be extrapolated to the primary system.

One main characteristic of the nuclear auxiliary systems, which is not shared with the primary system, is its potentially high recontamination by 110m Ag during the primary system oxygenation.

Silver is soluble in oxidizing conditions and its solubility increases with temperature. Thus, during oxygenation, it dissolves in the primary coolant from the deposits on the primary surfaces (e.g. the 110m Ag deposited activities on the primary pipes and SG tubes decrease during oxygenation, see Figure 4 and Figure 12), then it precipitates on the cold parts of the auxiliary systems, in particular on the heat exchangers of the RHRS and the NSS and on the non-regenerative heat exchanger of the CVCS and the pipes downstream. The 110m Ag surface activity can become the highest one, e.g. in the FPCS at the end of the refueling shutdown of reactor A (see Figure 5).

The fact that silver precipitates on the cold parts, particularly on the NSS, can lead to an underestimation of the 110m Ag volume activity for some hours after the oxygenation and then an overestimation. Figure 11 illustrates this behavior. This figure presents the variations of the 110m Ag and 58 Co deposited activities on the second heat exchanger of the RCS sampling line, the 110m Ag and 58 Co volume activities sampled with this line and the primary system temperature of an EDF unit (Reactor C).

Figure 11 : Reactor C -Deposited activities on the second heat exchanger of the RCS sampling line Generally, the 110m Ag volume activity variation can be described in 4 steps:

1. Just after the H 2 O 2 injection, the 110m Ag surface activity increases in the heat exchanger 1 , whereas the 110m Ag volume activity sampled downstream from this exchanger has not yet increased. This means that the 110m Ag precipitates on the sampling line before its sampling at the end of this line. 2. Then, when the deposits become more and more saturated by silver, the sampling begins to show an increase in the 110m Ag volume activity. 3. Gradually, the 110m Ag deposited on the sampling line dissolves which leads to a plateau of 110m Ag volume activity. This dissolution compensates the decrease in the volume activity of the primary coolant. 4. Finally, the decrease in the 110m Ag volume activity is observed, the dissolution does not compensate any more. In step 3, one might think that the CVCS purification system efficiency is poor, the 110m Ag volume activity remaining constant. This seems to be confirmed by the 110m Ag volume activity sampled downstream from the mixed bed demineralizers which tends to increase. In fact, this increase is due to the silver dissolution deposited on the pipe downstream from the ion exchangers, as it can be observed in Figure 12. This figure presents the 110m Ag surface activities before and after the primary coolant oxygenation in the CVCS of reactor C.

The silver contamination of this pipe occurs during power operation since silver can be under a colloidal form and poorly trapped by the purification system [START_REF] Bretelle | Study of Various Chemical Species Behaviour for Contamination Risk[END_REF]. 1 thereby proving that the 110m Ag volume activity is increasing. One can note that this issue concerns 110m Ag and not the other ACP (see Figure 11). The 58 Co volume activity has increased just after the H 2 O 2 injection and the 58 Co deposited activity on the heat exchanger remains constant.

Because of the peculiar behavior of silver, 110m Ag is often the major contributor to the dose rates around the auxiliary systems, sometimes at a level greater than 90%. Even in the 1300 MWe PWRs, which is less affected by this kind of pollution, its contribution is not negligible and can be the major one (see Figure 10) but the dose rates are relatively low.

The dose rates around the auxiliary systems are generally higher than those around the primary system. There are two main reasons for this: the lesser thickness of pipes and exchanger shells and the high 110m Ag contamination level.

Last it would be worthwhile to point out that the 58 Co contribution to the dose rates in comparison to the 60 Co contribution is higher around the auxiliary systems than it is around the primary system. It is still due to the lesser thickness of the pipes and exchangers (see Figure 9). However, for the auxiliary systems which do not operate for several months, 60 Co becomes the major contributor owing to its long radioactive half-life.

CONCLUSION

Based on EMECC campaigns carried out in different standardized plant series, this paper shows that the contamination of the nuclear auxiliary systems presents differences in comparison to the contamination of the primary system:

-The 58 Co and 60 Co deposited activities on the CVCS, RHRS, NSS and FPCS are generally lower. On the other hand, the 110m Ag contamination is higher with a great recontamination during cold shutdowns. -The dose rates around the auxiliary systems are generally higher. -The 58 Co contribution and especially the 110m Ag contribution are higher. For the auxiliary systems that do not operate for several months, the 60 Co contribution becomes the major one. -The nuclear auxiliary systems are the only circuits that allow us to measure the 51 Cr surface activities. These differences are due to different design and operating conditions, in particular the presence of heat exchangers and lower fluid temperature, different flow rates, lesser thickness of pipes and exchanger shells, the presence of filtering systems, operations carried out during a short period.

Last the peculiar behavior of 110m Ag inside the NSS generally results in a poor estimation of the 110m Ag volume activity in the primary coolant.

Figure 6 :

 6 Figure 4 : Reactor A -Cycle 11 -110m Ag surface activities in RCS, CVCS and RHRS

Figure 8 :

 8 Figure 8 : Reactor B -Cycle 10 -60 Co surface activities in RCS, CVCS, RHRS and NSS

Figure 12 :

 12 Figure 12 : Reactor C -110m Ag surface activities in CVCS During step 1 and perhaps step 2 as well, the sampled 110m Ag volume activity is underestimated. On the other hand, during steps 3 and 4, it is overestimated.One can note that this issue concerns 110m Ag and not the other ACP (see Figure11). The 58 Co volume activity has increased just after the H 2 O 2 injection and the 58 Co deposited activity on the heat exchanger remains constant.Because of the peculiar behavior of silver, 110m Ag is often the major contributor to the dose rates around the auxiliary systems, sometimes at a level greater than 90%. Even in the 1300 MWe PWRs, which is less affected by this kind of pollution, its contribution is not negligible and can be the major one (see Figure10) but the dose rates are relatively low.The dose rates around the auxiliary systems are generally higher than those around the primary system. There are two main reasons for this: the lesser thickness of pipes and exchanger shells and the high 110m Ag contamination level.Last it would be worthwhile to point out that the 58 Co contribution to the dose rates in comparison to the 60 Co contribution is higher around the auxiliary systems than it is around the primary system. It is still due to the lesser thickness of the pipes and exchangers (see Figure9). However, for the auxiliary systems which do not operate for several months, 60 Co becomes the major contributor owing to its long radioactive half-life.

Table 1 :

 1 EMECC measurement points and dose rates

		EMECC Points	a	Dose rates (mSv/h) b c	d
			CVCS
		Letdown line / Upstream Regenerative heat exchanger		2.7	3.0
		Regenerative heat exchanger		2.1	2.5
		Upstream Non-regenerative heat exchanger	1.4	2.4	2.4
		Non-regenerative heat exchanger	2.7	11	20
		Upstream Filter		1.8	6.0
		Downstream Filter		0.65	1.2
		Downstream Charging pump	1.2
			RHRS
		Upstream Main valves		1.5	1.0
		Upstream Pumps			0.21
		Heat exchanger Bypass
		Heat exchanger			0.58
		Downstream Heat exchanger		0.64
			FPCS
		Cooling/Downstream Spent fuel pool	0.03	0.09
		Cooling/ Upstream heat exchanger	0.19	0.26
		Cooling/Downstream Heat exchanger	0.02	0.08
		Cleanup/Upstream Filter	0.03	0.10
		Cleanup/Downstream Filter	0.06	0.10
			RCS
		Hot leg			0.84 0.78
		SG tubing			0.32 0.32
		Crossover leg			0.23
		SG bypass
		Reactor A -Cycle 11 -	58 Co surface activities	Operation Shutdown -Bef. O2
		100			Shutdown -Aft. O2
		RCS	CVCS		RHRS
		10
	GBq/m²	0.1 1
		0.01
		0.001
		H o t le g S G tu b in g C r o s s o v e r le g S G B y p a s s L e t. /U p . R e g . h e a t e x c h . R e g e n e r a ti v e h e a t e x c h . U p . N o n r e g . h e a t e x c h . N o n r e g . h e a t e x c h . U p s tr e a m F il te r D o w n s tr e a m F il te r D o w n . C h a r g in g p u m p U p s tr e a m M a in v a lv e s U p s tr e a m P u m D p s H e a t e x c h . B y p a s s H o w n s tr e a m H e a t e x c h a n g e r e a t e x c h .
		Figure 1 : Reactor A -Cycle 11 -58 Co surface activities
		in RCS, CVCS and RHRS

Table 2 :

 2 EMECC measurement points and dose rates

						Reactor B -Cycle 10 -	60 Co surface activities	Bef.O2 Aft. O2
						10	RCS
						Dose rates	1	CVCS	RHRS	NSS
			EMECC Points CVCS	(mSv/h) Before O 2 After O 2	GBq/m²	0.001 0.01 0.1
		Letdown line / Upstream Regenerative heat exchanger Upstream Non-regenerative heat exchanger Non-regenerative heat exchanger Upstream Filter	0.45 0.76 0.95 0.32	1.0 1.0 0.51	0.0001 H o t le g S G tu b in g C o ld le g S G b y p a s s L e td o w n /U p . R e g . h e a t e x c h . U p N o n r e g e h e a t e x c h . N o n r e g . h e a t e x c h a n g e r U p s tr e a m F il te r U p s tr e a m C h a r g in g p u m p C h a r g ./ D o w n . R e g . h e a t e x c h . U p s tr e a m P u m p s H e a t e x c h a n g e r H D o w n s tr e a m H e a t e x c h a n g e r H o t le g /U p . 1 s t h e a t e x c h . H o t le g /2 n d h e a t e x c h . o t le g /D o w n . 2 n d h e a t e x c h . U U p . fi lt r a ti o n /U p . H U p . F il t. /D o w p . fi lt r a ti o n /H n . H e a t e x c h . e a t e x c h . e a t e x c h .
		Upstream Charging pump		0.070	0.046
		Charging line / Downstream Regenerative heat exchanger		0.090	0.11
				RHRS
		Upstream Pumps			0.20	0.35
		Heat exchanger			0.090	0.14
		Downstream Heat exchanger		0.12	0.52
				NSS
		RCS Hot leg / Upstream First heat exchanger	0.15	0.095
		RCS Hot leg / Second heat exchanger	0.70	1.1
		RCS Hot leg / Downstream Second heat exchanger	0.15	0.20
		CVCS Upstream filtration / Upstream Heat exchanger	0.29	0.35
		CVCS Upstream filtration / Heat exchanger	0.46	0.9
		CVCS Upstream filtration / Downstream Heat exchanger		0.14	0.25
				RCS
		Hot leg				0.39	0.22
		SG tubing			0.10	0.090
		Cold leg				0.22	0.22
		SG bypass			0.69
			Reactor B -Cycle 10 -	58 Co surface activities	Bef.O2
						Aft. O2
		10	RCS	CVCS
		1				RHRS	NSS
	GBq/m²	0.01 0.1
		0.001
		0.0001
		H o t le g S G tu b in g C o ld le g S G b y p a s s L e td o w n /U p . R e g . h e a t e x c h . U p N o n r e g e h e a t e x c h . N o n r e g . h e a t e x c h a n g e r U p s tr e a m F il te r U p s tr e a m C h a r g in g p u m p C h a r g ./ D o w n . R e g . h e a t e x c h . U p s tr e a m P u m p s H e a t e x c h a n g e r D o w n s tr e a m H e a t e x c h a n g e r H o t le g /U p . 1 s t h e a t e x c h . H o t le g /2 n d h e a t e x c h . H o t le g /D o w n . 2 n d h e a t e x c h . U p . fi lt r a ti o n /U p . H e a t e x c h . U p . fi lt r a ti o n /H U p . F il t. /D o w n . H e a t e x c h . e a t e x c h .
	Figure 7 : Reactor B -Cycle 10 -58 Co surface activities
			in RCS, CVCS, RHRS and NSS

Proceedings of the International Conference on Water Chemistry of Nuclear Reactors Systems, 15-18/09/08, Berlin (Germany),L11-4, 2008

Co-58 Vol. act.

Ag-110m

Vol. act. RCS samp.

Co-58 Surf. act.

Ag110m

Surf. act.

Reactor C -Surface activities on the second heat exchanger of the RCS sampling line


Ludovic Seifert

Dominic Orth

Jérémie Boulanger

Vladislavs Dovgalecs

Romain Hérault

Keith Davids

Seifert Ludovic

Cetaps -Ea

Climbing skill and complexity of climbing wall design: Assessment of Jerk as a novel indicator of performance fluency

Keywords: Movement jerk, climbing, hip translation, hip orientation, inertial measurement unit, fluency

This study investigated a new performance indicator to assess climbing fluency: smoothness and orientation of the hip trajectory of a climber using normalized jerk coefficients. To analyse performance fluency, 6 experienced climbers completed 4 repetitions of two 10-m high routes with similar difficulty levels, but varying in hold graspability (hold with one edge vs. hold with two edges). An inertial measurement unit was attached to the hip of each climber to collect 3D acceleration and 3D orientation data in order to compute jerk coefficients. Results showed high correlations (r = 0.83, p<0.05) between the normalized jerk coefficient of hip translation and hip oscillation. Results showed higher normalized jerk coefficients for the route with two graspable edges, perhaps due to more complex decision making and action regulation. This effect decreased with practice.

Introduction

Previous research has revealed that the jerk coefficient (third time derivative of position or the rate of change of acceleration) is a valid indicator of multi-joint limb movement smoothness [START_REF] Flash | The coordination of arm movements: an experimentally confirmed mathematical model[END_REF][START_REF] Hogan | An organizing principle for a class of voluntary movements[END_REF]. An assumption in this previous work is that maximizing arm movement smoothness may be modelled by minimizing the mean-square jerk, reducing energy cost. The validity of this minimizing jerk hypothesis has been investigated in various tasks involving upper-limb movements such as pointing [START_REF] Goldvasser | High curvature and jerk analyses of arm ataxia[END_REF][START_REF] Klein Breteler | An evaluation of the minimum-jerk and minimum torque-change principles at the path, trajectory, and movement-cost levels[END_REF], throwing [START_REF] Yan | Normalized Jerk: A Measure to Capture Developmental Characteristics of Young Girls' Overarm Throwing[END_REF], reaching [START_REF] Wininger | Spatial resolution of spontaneous accelerations in reaching tasks[END_REF] and drawing [START_REF] Richardson | Comparing Smooth Arm Movements with the Two-Thirds Power Law and the Related Segmented-Control Hypothesis[END_REF], as well as d in lower-limb tasks such as walking [START_REF] Young | Acquisition of a multi-articular kicking task: Jerk analysis demonstrates movements do not become smoother with learning[END_REF] and kicking [START_REF] Young | Acquisition of a multi-articular kicking task: Jerk analysis demonstrates movements do not become smoother with learning[END_REF].

Contrasting results have emerged, suggesting, for instance, that high curvature analysis was more convenient than jerk computation to distinguish healthy and cerebellopathy patients performing pointing tasks [START_REF] Goldvasser | High curvature and jerk analyses of arm ataxia[END_REF]. It was also observed that quantifying spontaneous accelerative transients within a movement when performing reaching tasks provided more reliable information on regional movement impairments than recording the jerk coefficient [START_REF] Wininger | Spatial resolution of spontaneous accelerations in reaching tasks[END_REF].

The sport of rock climbing involves both upper and lower-limbs for reaching and grasping holds, and climbing up a rock surface with the feet. It is particularly valuable to assess the validity of the minimizing jerk hypothesis as a potential indicator of fluency in climbing performance. A previous study exploring self-handicap factors on successful climbing performance highlighted that competitive climbers exhibited performance anxiety through rigid posture and jerky movements which could limit performance by reducing movement fluency [START_REF] Ferrand | Self-Handicapping in Rock Climbing: A Qualitative Approach[END_REF]. Rock climbing involves interspersed periods of maintaining body equilibrium on a more or less vertical climbing surface [START_REF] Bourdin | Postural constraints modify the organization of grasping movements[END_REF][START_REF] Bourdin | High postural constraints affect the organization of reaching and grasping movements[END_REF][START_REF] Testa | 3D analysis of posturo-kinetic coordination associated with a climbing task in children and teenagers[END_REF][START_REF] Testa | Effects of the type of holds and movement amplitude on postural control associated with a climbing task[END_REF], with combining upper and lower limb movements to ascend these surfaces rapidly (Boschker et al., 2002;[START_REF] Nougier | Kinematic modifications of the manual reaching in climbing: Effects of environmental and corporal constraints[END_REF][START_REF] Sibella | 3D analysis of the body center of mass in rock climbing[END_REF]. During performance, the alternation of periods dedicated to postural regulation and to quadruped displacement on a vertical surface, might lead to a drop in measures of climbing fluency that is fundamental to quantify. Previous studies have assessed the fluency of climbing movements by: (i) implementing a harmonic analysis of the acceleration of the hips [START_REF] Cordier | Harmonic analysis of a complex motor behaviour[END_REF], by quantifying the duration of a static position as any point throughout the climb where the hips were not in motion [START_REF] Billat | Energy specificity of rock climbing and aerobic capacity in competitive sport rock climbers[END_REF][START_REF] Sanchez | Efficacy of pre-ascent climbing route visual inspection in indoor sport climbing[END_REF]Seifert et al., 2013b); and (ii), by measuring the geometric entropy index value from the displacement of the hips (Boschker and Bakker, 2002;[START_REF] Cordier | Entropy as a global variable of the learning process[END_REF][START_REF] Cordier | Entropy, degrees of freedom, and free climbing: a thermodynamic study of a complex behavior based on trajectory analysis[END_REF][START_REF] Sanchez | Pre-performance psychological states and performance in an elite climbing competition[END_REF][START_REF] Sibella | 3D analysis of the body center of mass in rock climbing[END_REF]. Harmonic analysis is a tool for observing the structure of the dynamics of a movement. Using Fourier transformation, Cordier and colleagues [START_REF] Cordier | Harmonic analysis of a complex motor behaviour[END_REF]conducted a harmonic analysis revealing that the expert climbing performance could be characterized by a pendulum oscillating as a mass-spring system that works like a dissipative system, i.e., a system where dissipation of energy is minimized by harmonic movements.

Although very promising, the study of [START_REF] Cordier | Harmonic analysis of a complex motor behaviour[END_REF] only considered the displacement of the hips in 2D (i.e., movement projection in the vertical plane), whereas recent studies have highlighted the prevalence of antero-posterior and lateral sway during climbing performance [START_REF] Sibella | 3D analysis of the body center of mass in rock climbing[END_REF][START_REF] Zampagni | Idiosyncratic control of the center of mass in expert climbers[END_REF], supporting the importance of 3D movement analysis. Similar limitations emerge from the use of the geometric entropy index, (Boschker and Bakker, 2002;[START_REF] Cordier | Entropy as a global variable of the learning process[END_REF][START_REF] Cordier | Entropy, degrees of freedom, and free climbing: a thermodynamic study of a complex behavior based on trajectory analysis[END_REF][START_REF] Sanchez | Pre-performance psychological states and performance in an elite climbing competition[END_REF][START_REF] Sibella | 3D analysis of the body center of mass in rock climbing[END_REF]. The geometric index of entropy (H) was calculated by recording the distance covered by the body (L) and the convex hull (c) according to the following equation: H = log n 2L/c [START_REF] Cordier | Entropy as a global variable of the learning process[END_REF][START_REF] Cordier | Entropy, degrees of freedom, and free climbing: a thermodynamic study of a complex behavior based on trajectory analysis[END_REF]. According to [START_REF] Cordier | Entropy as a global variable of the learning process[END_REF], 1993), geometric entropy measures reveal the amount of fluency/curvature of a curve: the higher the entropy, the higher the disorder of the system; therefore, a low entropy value was associated with a low energy expenditure and greater climbing fluency. Regardless, geometric entropy index remains a spatial analysis of the body motion that does not consider the displacement of the hips over time. This is an omission since both hip translations and oscillations in 3D should be considered to assess climbing fluency. The aim of this study was to explore whether the computation of jerk coefficient values could provide an indicator of climbing fluency, achieved by computing the jerk of hip trajectory and hip orientation and examining their correlation. We also sought to investigate whether jerk is minimized with practice and modifications to climbing wall design (simple vs. complex hold grasping patterns).

Methods

Participants

Eight students of a Faculty of Sport Sciences voluntary participated to this study (mean age:

21.4 ± 2.4 yr; mean height: 170.1 ± 9.5 cm; mean weight: 69.9 ± 5.5 kg). These climbers had climbing experience of 4.1 ± 2.1 yr, trained for 3.4 ± 1.9 hours per week and had a rock climbing ability of 6a on the French Rating Scale of Difficulty (F-RSD) [START_REF] Delignières | A psychophysical study of difficulty rating in rock climbing[END_REF], which corresponds to an intermediate level of performance [START_REF] Draper | Self-reported ability assessment in rock climbing[END_REF].

Climbing ability was defined as the most difficult ascent by top rope [START_REF] Delignières | A psychophysical study of difficulty rating in rock climbing[END_REF].

Protocol

Each climber participated in four testing sessions (separated by two days of rest), each consisting of two different route ascents. Participants were randomly allocated to climb two routes of a similar grade rated 5c on the F-RSD. Each route was identifiable by colour and was set on an artificial indoor climbing wall by two certified route setters who ensured that they matched intermediate climbing levels). The routes had the same height (10 m) and were composed of 20 hand holds each, located at the same place on the artificial wall. Only the orientation of the hold was changed between the two routes: the first route was designed to allow horizontal edge hold grasping, while the second route was designed to allow both horizontal and vertical edges hold grasping (Fig. 1). This design allowed us to examine whether the level of grasping uncertainty could constrainclimbing fluency. Participants were instructed to self-pace their ascent, to climb fluently and to climb without falling. Each route was top-roped, i.e., routes were climbed with the rope anchored above the climber at all times.

Each ascent wa preceded by 3 minutes of route preview, as pre-ascent visual inspection is a key climbing performance parameter [START_REF] Sanchez | Efficacy of pre-ascent climbing route visual inspection in indoor sport climbing[END_REF]. The protocol was approved by the local University ethics committee and followed the declaration of Helsinki. Procedures were explained to the climbers, who then gave their written informed consent to participate.

Data collection

In line with previous studies, climbing fluency was assessed through recording hip displacements [START_REF] Cordier | Entropy as a global variable of the learning process[END_REF][START_REF] Cordier | Entropy, degrees of freedom, and free climbing: a thermodynamic study of a complex behavior based on trajectory analysis[END_REF][START_REF] Sanchez | Pre-performance psychological states and performance in an elite climbing competition[END_REF][START_REF] Sibella | 3D analysis of the body center of mass in rock climbing[END_REF]. The original feature of our study was to collect body acceleration data from an IMU located at the hip, in order to compute jerk. Previous studies have used piezoelectric accelerometers for this purpose [START_REF] Minami | A comparison between jerk-cost derived from a jaw-tracking system with that from an accelerometer[END_REF][START_REF] Minami | Measurement of jerk-cost using a triaxial piezoelectric accelerometer for the evaluation of jaw movement smoothness[END_REF]. In our study, an IMU corresponded to a combination of a tri-axial accelerometer (±8G), tri-axial gyroscope (1600°.s -1 ) and a tri-axial magnetometer (MotionPod, Movea©, Grenoble, France). Data collected from the IMU (with MotionDevTool, Movea©, Grenoble, France) were recorded with North magnetic reference and at a 100 Hz sample frequency.

Data collection and analysis methods

The first step towards computation of jerk coefficients was to compute hip orientation in

Earth reference frame and follow its orientation changes. Raw accelerometer readings cannot be used directly to compute the jerk coefficient due to orientation changes during ascent. The solution to this problem was found by tracking sensor orientation by using the complementary filter based algorithm [START_REF] Madgwick | An efficient orientation filter for inertial and inertial/magnetic sensor arrays[END_REF][START_REF] Madgwick | An efficient orientation filter for inertial and inertial/magnetic sensor arrays[END_REF], which integrated the three sensor information sources (i.e., accelerometer, gyroscope and magnetometer). The gyroscope measured precise angular changes at very short time durations but could not be used to track the angle changes by integration due to the problem of drift. The accelerometer provided absolute, albeit noisy, measurements of hip acceleration and the Earth's gravitational force at the same time. By combining the two sensor information sources it was possible to reduce drift of the gyroscope for hip orientation tracking. When magnetometer information was added, it was possible to compute orientation of the sensor with respect to the fixed frame of Earth reference (magnetic north, East and gravity directions) [START_REF] Madgwick | An efficient orientation filter for inertial and inertial/magnetic sensor arrays[END_REF][START_REF] Madgwick | An efficient orientation filter for inertial and inertial/magnetic sensor arrays[END_REF].

Second, the accelerometer readings were always expressed with respect to the sensor frame and it was necessary to separate hip acceleration, of interest for jerk computation, and constant acceleration of gravity. Let 𝑅 𝑡 ∈ 𝑆𝑂(3) be the current sensor orientation at time 𝑡 in the Earth frame of reference, 𝑎 𝑡 𝑆𝐹 the measured acceleration of hip in the sensor frame, then the acceleration of hip at time 𝑡 in the fixed Earth reference frame can be expressed as

𝑎 𝑡 𝐺𝐹 = 𝑅 𝑡 𝑎 𝑡 𝑆𝐹 .
The third step consisted of assessing smoothness of the hip trajectory by computing the jerk coefficient from processed 3D accelerometer signals 𝑎 𝑡 𝐺𝐹 . Jerk is a measure of the lack of smoothness of a joint or limb segment during performance. For a smooth trajectory 𝑥 𝐺𝐹 ∈ 𝒞 3 , the jerk 𝐽 𝑥 𝐺𝐹 (𝑡) was defined as:

𝐽 𝑥 𝐺𝐹 (𝑇) = 𝐶 ∫ ‖𝑥 𝑠 𝐺𝐹 ⃛ ‖ 2 𝑇 0 𝑑𝑠
where 𝐶 was a normalization constant to make the quantity dimensionless [START_REF] Hogan | Sensitivity of smoothness measures to movement duration, amplitude, and arrests[END_REF]. In practice instead of computing 𝑥 𝑡 𝐺𝐹 (position on the wall) from 𝑎 𝑡 𝐺𝐹 with successive integration, the term 𝑥 𝑠 𝐺𝐹 ⃛ was replaced by 𝑎 𝑡 𝐺𝐹 ̇. By derivation of 𝑎 𝑡 𝐺𝐹 , the constant gravity acceleration was removed, leaving only the hip acceleration component.

It is noteworthy that the jerk was minimized when 𝑥 𝑡 𝐺𝐹 is a fifth degree polynomial, corresponding to the smoothest possible hip trajectory. The integral was computed between time 0 and time 𝑇 which corresponded to a given final position 𝑥 𝑇 𝐺𝐹 . The constant 𝐶 can be chosen such that 𝐶 = 𝑇 5

(Δ𝑥 𝐺𝐹 ) 2 , where Δ𝑥 𝐺𝐹 was the climbing height and 𝑇 the time needed to reach it. It should also be noted that the current position 𝑥 𝑡 𝐺𝐹 was not available from IMU sensor data and, therefore, jerk could be computed for an arbitrary position interval. The only height information was the total height of the ascent; therefore, the jerk coefficient could be computed for the whole ascent but not for a local displacement path. Thus, the normalized jerk coefficient was computed by differentiating the processed accelerometer signal and integrating its squared norm.

A second indicator of climbing fluency consisted of computing jerk coefficient measuring hip orientation smoothness. Indeed, as stated previously, hip displacements of climbers not only correspond to 3D translations, but also to 3D orientation oscillations [START_REF] Cordier | Harmonic analysis of a complex motor behaviour[END_REF][START_REF] Sibella | 3D analysis of the body center of mass in rock climbing[END_REF][START_REF] Zampagni | Idiosyncratic control of the center of mass in expert climbers[END_REF]. These results highlighted the interest of studying jerk now defined from hip orientation 𝑅 𝑡 ∈ 𝑆𝑂(3). In this case the previous equation could not be used directly and some technical adjustments were required. Due to the structure of 𝑆𝑂(3), orientation acceleration could not be obtained by directly considering successive derivation of 𝑅 𝑡 as a 3x3 matrix. The solution to this problem in our study consisted of constructing a process 𝑧 𝑡 ∈ ℝ 3 such that its velocity was the angular velocity of 𝑅 𝑡 , which can be differentiated easily (note that 𝑧 𝑡 and 𝑅 𝑡 are of the same dimensionality). We define

𝑧 𝑡 as 𝑧 𝑡 ̇= 𝑅 𝑡 ̇𝑅𝑡 -1
where 𝑅 𝑡 -1 = 𝑅 𝑡 𝑇 which is due to orthogonality of the elements of 𝑆𝑂(3). If 𝑅 𝑡 has an angular velocity 𝜔 𝑡 , then 𝑧 𝑡 ̇= 𝜔 𝑡 . Therefore, working on 𝑧 𝑡 allowed us to eliminate all the non-linear issues inherent to 𝑆𝑂(3) and work in instead, where derivative was carried out simpler than in 𝑆𝑂(3). In practice, due to the discretization of observations of 𝑅 𝑡 with a sampling time 𝛿𝑡 , the process 𝑧 𝑡 was approximated by 𝑧 𝑘 ̃≈ 𝑧 𝑘𝛿𝑡 , with 𝑧̃ recursively computed as 𝑧 𝑘+1 ̃-𝑧 𝑘 ̃= 𝑙𝑜𝑔(𝑅 (𝑘+1)𝛿𝑡 𝑅 𝑘𝛿𝑡 -1 ) where 𝑙𝑜𝑔 was the inverse application of the matrix exponential. In our study, jerk of orientation was defined as 𝐽 𝑧 (𝑇).

The last indicator computed in our study related to elucidating climbing skill of participants (e.g., the capability of traversing an ascent quickly) through differentiating the relationship between touched holds (exploratory movements) and grasped holds (performatory movements) [START_REF] Pijpers | The Role of Anxiety in Perceiving and Realizing Affordances[END_REF]. Indeed, Pijpers and colleagues (2006) distinguished exploratory and performatory movements according to whether a potential hold on a climbing wall was touched, with or without it being used as support. According to this ratio, [START_REF] Sibella | 3D analysis of the body center of mass in rock climbing[END_REF] reported that skilled climbers can move quickly by using fewer than three holds, signifying that they had touched fewer than three surface holds before grasping the functional one.

Statistical analysis

After the computation of the jerk from 𝑧 𝑡 for each session, differences of jerk coefficients between sessions and route designs were compared by two-way repeated measures ANOVA (practice across four sessions (4) and climbing wall design across two different routes (2) )

using SPSS Statistics 20.0. Sphericity was verified by the Mauchly test [START_REF] Winter | Statistical analyses in the physiology of exercise and kinanthropometry[END_REF].

When the assumption of sphericity was not met, the significance of F-ratios was adjusted according to the Greenhouse-Geisser procedure. Then, Helmert contrast tests enabled us to compare each session with the performance mean of the other sessions, in order to determine whether jerk reduced with practice and whether route design influenced jerk values. Here it was predicted that routes providing double edges (vertical and horizontal) grasping patterns would be associated with more jerk compared to the route where only horizontal grasping was afforded. Partial eta squared (η P 2 ) statistics were calculated as an indicator of effect size, considering that η P 2 = 0.01 represents a small effect, η P 2 = 0.06 represents a medium effect and η P 2 = 0.15 represents a large effect [START_REF] Cohen | Statistical power analysis for the behavioral science (2nd Edition)[END_REF]. Pearson correlation tests were also performed to examine the relationships between jerk of hip trajectory 𝐽 𝑥 (𝑇) and jerk of hip orientation 𝐽 𝑧 (𝑇). For all tests, the level of significance was fixed at p < 0.05.

Results

Significantly higher values of normalized jerk for hip trajectory emerged in the double edges holds route in comparison to the horizontal edge holds route (4.48E+11 ± 1.77E+11 vs.

9.65E+10 ± 4.44E+10; F 1,7 = 6.14, p = 0.03, η P 2 = 0.463). Similar results were observed for normalized jerk of hip orientation; this latter measure was higher for the double edges holds route in comparison to horizontal edge holds route (776846 ± 434836 vs. 155590 ± 96743;

F 1,7 = 6.22, p = 0.028, η P 2 = 0.442).

To examine session effect, Mauchly's test indicated significant sphericity (χ2 (5) = 38.55, p = 0.01), so the Greenhouse-Geisser correction was applied and showed significant differences of normalized jerk of hip trajectory between sessions (session 1: ± 2.93E+11, session 2:

2.13E+11 ± 9.11E+10, session 3: 8.92E+10 ± 2.18E+10, session 4: 7.93E+10 ± 1.83E+10; F 1.05,7.348 = 5.18, p = 0.034, η P 2 = 0.428). According to the outcomes of the Helmert contrast tests, significant differences occurred between the first session and the others (F 1,7 = 5.14, p = 0.038, η P 2 = 0.424), and between the second session and the last two sessions (F 1,7 = 5.08, p = 0.041, η P 2 = 0.413). Mauchly's test indicated significant sphericity (χ2 (5) = 64.94, p = 0.01) when differences of normalized jerk of hip orientation were analysed between sessions. Thus, the Greenhouse-Geisser correction was applied, revealing significant differences between sessions (session 1: 1314799 ± 575210, session 2: 414744 ± 244049, session 3: 72651 ± 19323, session 4: 62678 ± 18922; F 1.013,7.092 = 5.34, p = 0.027, η P 2 = 0.436). According to the Helmert contrast tests, significant differences emerged between the first session and the others (F 1,7 = 5.27, p = 0.032, η P 2 = 0.428), and between the second session and the last two sessions (F 1,7 = 5.18, p = 0.034, η P 2 = 0.417). Figure 2 illustrates the differences of normalized jerk of hip trajectory between sessions for the two routes and Figure 3 illustrates the differences of normalized jerk of hip orientation between sessions for the two routes. A significant positive correlation appears between the normalized jerk of hips trajectory smoothness and normalized jerk of hips orientation (r = 0.83, p < 0.05) (Figure 4). This finding signifies that the jerk of the trajectory can be measured via the jerk of its orientation or equivalently: both measures provide a similar measure of smoothness, the only difference being the scale of the two coefficients. Last, our results showed improvement in climbing skills as climbers decreased the number of exploratory movements with practice in the simple and complex route designs (Table 1).

Discussion

High correlation values were observed between the normalized jerk values of hip trajectory and hip orientation revealing that both 3D translations and 3D oscillations of the hips can be used to assess climbing fluency. Our results showed that the normalized jerk values of hiptrajectory and orientation decreased with practice and were lower for the simple route design (i.e., horizontal edge holds grasping), confirming the usefulness of measuring jerk as an indicator of climbing fluency.

Relationships between climbing fluency and climbing wall design

Climbing the route with horizontal edge holds resembled the action of grasping the rungs of a ladder, explaining how lower normalized jerk values of both hip trajectory and orientation emerged in the simple route than rather the complex route. Horizontal edge hold grasping led to a 'face-to-the-wall' body orientation, whereas vertical edge hold grasping induced a 'sideto-the-wall' body orientation (Seifert et al., 2013a). Therefore, the complex route design with holds offering dual edge orientations invited the climbers to explore two types of grasping patterns and body orientations (Seifert et al., 2013a) and involved higher jerk in both 3D

translations and 3D oscillations of the hips. Indeed, moving between a right-orientated vertical edge hold to a left-orientated vertical edge hold would lead the body to oscillate like a door, a performance feature particularly well captured by recording the jerk of hip orientation.

Previous studies have already shown how route design influences the kinematics of climbers, notably the value of movement time during hold grasping [START_REF] Nougier | Kinematic modifications of the manual reaching in climbing: Effects of environmental and corporal constraints[END_REF] and the entropy measure of hip displacement [START_REF] Sanchez | Pre-performance psychological states and performance in an elite climbing competition[END_REF]. More precisely, complexity of manual grips (2 cm vs. 1 cm depth) and posture difficulty (low vs. high inclination of the foot holds) led to shorter movement time of grasping; in particular, longer times to reach the maximum acceleration and shorter times to reach the maximum deceleration were observed [START_REF] Nougier | Kinematic modifications of the manual reaching in climbing: Effects of environmental and corporal constraints[END_REF]. Moreover, complex hold grip and difficult posture emerged occasionally during the route that corresponded to a 'crux' (i.e., most difficult section of the route) or all over the route [START_REF] Phillips | Optimizing rock climbing performance through sport-specific strength and conditioning[END_REF]. It was found that the crux led to a higher entropy value for hip displacement and higher movement time for skilled climbers than for less skilled climbers [START_REF] Sanchez | Pre-performance psychological states and performance in an elite climbing competition[END_REF], supporting the utility of computing jerk as precisely as possible by taking into account both the hip trajectory and orientation.

Relationships between climbing fluency and practice

Our results showed a critical drop of jerk between the first and remaining three sessions, with stabilization emerging between the last two sessions. These results clarify contradictory data from previous studies that analysed the effect of practice on jerk minimization [START_REF] Schneider | Jerk-cost modulations during the practice of rapid arm movements[END_REF][START_REF] Young | Acquisition of a multi-articular kicking task: Jerk analysis demonstrates movements do not become smoother with learning[END_REF]. When arm movements were trained at different speeds, Schneider and Zernicke [START_REF] Schneider | Jerk-cost modulations during the practice of rapid arm movements[END_REF] showed that jerk decreased for the slowest hand movement with practice. Conversely, when learning to kick, participants [START_REF] Young | Acquisition of a multi-articular kicking task: Jerk analysis demonstrates movements do not become smoother with learning[END_REF] revealed different jerk values for movements with similar trajectories, which did not support the jerk minimizing hypothesis with practice. In our study, high standard deviation values of jerk for hip trajectory and orientation (i.e., inter-individual variability) emerged in the first practice session, which could have been due to absence of prior knowledge of route finding that may have led to a search process in participants [START_REF] Cordier | Entropy, degrees of freedom, and free climbing: a thermodynamic study of a complex behavior based on trajectory analysis[END_REF]. Indeed, it is commonly accepted that performance could vary according to prior knowledge of routes [START_REF] Phillips | Optimizing rock climbing performance through sport-specific strength and conditioning[END_REF][START_REF] Sanchez | Efficacy of pre-ascent climbing route visual inspection in indoor sport climbing[END_REF], which could explain the increase in climbing fluency observed between the first and second session in our study. In fact, three different conditions of practice may influence climbing fluency:

on-sight climbing involves successful climbing with no prior knowledge of the climb; flash climbing means successful climbing at the first attempt after receiving prior knowledge of the climb; red-point climbing signifies successful climbing without falling after previous unsuccessful attempts [START_REF] Phillips | Optimizing rock climbing performance through sport-specific strength and conditioning[END_REF]. These assumptions have been confirmed by a recent study that showed significant reductions in the number and duration of stops when climbing with a route preview [START_REF] Sanchez | Efficacy of pre-ascent climbing route visual inspection in indoor sport climbing[END_REF]. To consider the possible effects of previewing on climbing fluency, three minutes of previewing were allowed in our study.

However, route previewing does not appear to be the main constraint on climbing fluency.

Improvement in route finding (i.e., interpretation of the ever-changing structure of the climbing wall design [START_REF] Cordier | Entropy as a global variable of the learning process[END_REF]) could further explain the drop of jerk values and the decrease in the number of exploratory movements with practice. Indeed, [START_REF] Cordier | Entropy as a global variable of the learning process[END_REF][START_REF] Cordier | Entropy, degrees of freedom, and free climbing: a thermodynamic study of a complex behavior based on trajectory analysis[END_REF] have already reported that practice can lead to a lower number and duration of stops, less exploration during route finding and lower entropy values of hip displacement, imputing greater climbing fluency. To summarise, the computation of jerk of hip trajectory and orientation in this study provided two complementary indicators of climbing fluency that seemed to provide a valuable contribution to understanding the effects of practice and route design on climbing performance.

Figure 1 .

 1 Figure 1. Orientation and shape of the holds for the two routes. The arrow indicates the

Figure 2 .Figure 3 .

 23 Figure 2. Differences of normalized jerk of hip trajectory between sessions for double edges

Figure 4 .

 4 Figure 4. Correlation between jerk of hip trajectory (x-axis) and jerk of hip orientation (y-

Table 1 .

 1 Sum of number of exploratory movements for the six climbers on the simple and

	complex routes
		Session 1	Session 2	Session 3	Session 4
	Simple route design	4	3	1	1
	Complex route design	9	5	5	3