Christophe Pallier

WORD RECOGNITION: DO WE NEED PHONOLOGICAL REPRESENTATIONS?

Under what format(s) are spoken words memorized by the brain? Are word forms stored as abstract phonological representations? Or rather, are they stored as detailed acoustic-phonetic representations? (For example as a set of acoustic exemplars associated with each word). We present a series of experiments whose results point to the existence of prelexical phonological processes in word recognition and suggest that spoken words are accessed using a phonological code.

INTRODUCTION

Linguistics makes a strong case for the psychological reality of phonological representations. It is important to assess how and when phonological representations are used by the brain. Some have argued that phonological representations may be used in speech production but not in speech perception [START_REF] Klatt | Lexical representations for speech production and perception[END_REF][START_REF] Pisoni | Some thoughts on "normalization" in speech perception[END_REF][START_REF] Goldinger | Words and Voices: implicit and explicit memory for spoken words[END_REF]. They propose, instead, that word recognition involves a "direct" mapping from an acoustic representation of the input to the lexical representations. The series of experiments presented in this paper address whether phonological representations can be spared in speech perception.

LANGUAGE-SPECIFIC REPETITION PRIMING

The first experiment was designed to test whether the metrics of comparison between two word forms are universal or language-specific [START_REF] Pallier | Phonological representations and repetition priming[END_REF]. Indeed, theories postulating phonological prelexical processes naturally predict that an incoming spoken word is represented in a languagespecific manner. However, one may argue that strong forms of the "direct acoustic access" hypothesis posit that word forms are represented and compared using a universal acoustic format. We tested two groups of people who spoke two dialects of the same language, that is they shared the same vocabulary, yet they had different phonemic systems. Actually, the first group of subjects consisted of native speakers of Catalan, while the second group consisted of Spanish speakers who were highly fluent in Catalan, as a result of a long and intensive exposure to Catalan starting around 5 years of age. In previous work [START_REF] Pallier | A limit on behavioral plasticity in speech perception[END_REF], we demonstrated that, roughly speaking, those two groups do not have the same phonemic systems, as assessed by phonetic categorization and discrimination tasks.

The present experiment is based on the repetition effect, that is the fact that the processing of a stimulus is facilitated when it is repeated. Participants had to perform an auditory lexical decision task, with lists of words that contained some words repeated verbatim, and also some words repeated with one phonetic feature changed. Crucially, the phonetic feature alternation was phonemic for one population but not for the other. The question was whether the repetition effect would be depend on each subject's phonemic system or not.

The results were unambiguous (see fig 1): the repetition effect is modulated by the phonemic system of the listener.

Figure 1: Average reaction times for the first and second occurrences of words, as a function of the relationship between the first and the second member of the pair ('same token' or 'feature change'). The repetition effect is measured by the difference in RT between the 2 nd and the 1 st occurrence. The fact that word recognition is language-specific is not necessarily problematic for direct access models: the acoustic records obviously depend on the history of the listeners and, therefore, on the language. If the Spanish have heard many "distorted" Catalan words, then it is not surprising that they have different representations for these words. It would be important to know whether or not they have heard a lot of "broken" Catalan. This seems very unlikely according to our Catalan informants. If one accepts that the two populations (Spanish and native Catalan) have been exposed to roughly similar samples of Catalan speech, this result then clearly poses a threat for direct acoustic access models with universal metrics of comparison.

Catalan-dominant:

ON-LINE ELABORATION OF THE SYLLABIC STRUCTURE

Phonological representations, as postulated by linguists, usually possess a hierarchical structure: a word is not just a simple concatenation of phonemes: these phoneme appear within a syllabic frame. For example, the word "caprice" can be represented as "[ka] [pris]" and the word "capture" as [kap] [ture]". In both cases, [p] is the third phoneme, but it belongs to the first or to the second syllable, respectively. The next experiment was designed to assess whether the perceptual system is sensitive to the syllabic position of phonemes [START_REF] Pallier | Attentional allocation within the syllabic structure of spoken words[END_REF]. Subjects had to perform a phoneme monitoring task in lists of words. In these lists, we had biased the probabilities that the target phoneme appeared either in the first or in the second syllable. The outcome, displayed in figure 2, revealed that the subjects had (implicitly) become "attuned" to the most probable syllabic position (see also [START_REF] Finney | Attentional allocation to syllables in American English[END_REF][START_REF] Pitt | Syllabic effects in word processing: evidence from the structural induction paradigm[END_REF]). Interestingly, other experiments have revealed that participants have become attuned, not to the whole syllable, but to a precise phoneme slot inside the syllabic struc-ture [START_REF] Pitt | Attentional allocation during speech perception: How fine is the focus?[END_REF][START_REF] Pallier | Phonemes and syllable in speech perception: size of the attentional focus in French[END_REF]. We also showed that it is not possible to train people to attend to phoneme position defined purely sequentially (e.g. to the third phoneme of utterances) [START_REF] Pallier | Rôle de la syllabe dans la perception de la parole: études attentionnelles[END_REF]. These data suggest that the brain elaborates a syllabically structured representation of the stimuli, even in a task that does not require explicit manipulation of the syllable. 1 These results, and the previous ones, lead to the notion that the perceptual system builds a language-specific representation that specifies the syllabic structure. We proposed that the syllabic structure plays the role of a corrector code: by imposing syllabic well-formedness constraints, the perceptual system may solve ambiguous or incomplete phonetic analyses. This idea was tested in the next experiment.

PHONOLOGICALLY INDUCED PERCEPTUAL CORRECTION

Japanese is a language whose phonology places strong constraints on admissible sequences of phonemes: most syllables are of CV type and the number of possible clusters of consonants is quite limited. If a Japanese speaker listens to an illegal sequence of consonants, this may trigger an "error signal" in his speech decoding system, which may then try to "correct" the stimulus to make it conform to the phonology of the language. Indeed, when asked to repeat a stimulus containing an illegal consonant cluster, Japanese speakers will typically insert a vowel "u" between the consonants, producing an utterance that respects the phonology of their language. The task of repeating a stimulus involves both perceptual and production processes. Does the "correction" take place at the production stages, or is it performed at the perceptual stages? We examined this question by presenting Japanese listeners with illegal stimuli of the form VCCV, where the CC clusters were not admissible in Japanese [START_REF] Dupoux | Epenthetic vowels in japanese: A perceptual illusion?[END_REF]. More precisely, we built series of stimuli ranging from VCCV to VCuCV by increasing the duration of the middle vowel. The participants listened to the stimuli and had to report whether they heard a "u" in between the consonants or not. Their performances are plotted on figure 3, along with the results from a control group of native French speakers. These data suggest that Japanese "hear" the vowel "u", even when there is no acoustic correlates of it in the signal. This conclusion was strengthened by other experiments which used the ABX task: they showed that Japanese listeners had significant difficulties discriminating "VCCV" from "VCuCV" stimuli.

These results are compatible with the notion that the perceptual system tries to elaborate a phonological representation of incoming speech.

It is not immediately clear how direct access models could predict these results. Yet, one may try and argue that these effects result from the acoustic similarity between ¢¡ One problem to note, however, with phoneme detection ex- periments, is that is it not clear to what extend they taps prelexical processes French the stimuli and items stored in the mental lexicon: If a stimulus like "ebzo" is presented and there are words like, for example, "ebuza", "ibuzo"... in the mental lexicon of the Japanese listeners, these words may conspire to yield a "u" response. This hypothesis was tested, and refuted, by Dupoux et al. [START_REF] Dupoux | Prelexical locus of an illusory vowel effect in japanese[END_REF]. We will give here only a simplified description of their experiment. They created pseudo words from real Japanese words by deleting the middle vowel which could be "u" or a "a"; e.g. sokudo -> sokdo and mikado -> mikdo. The main finding is that, in a lexical decision task, Japanese listeners made many false alarms on "u"type pseudo-words but not on "a"-type ones; that is, they answered "word" to items like sokdo, but not to items like mikdo. If the acoustic distance between the stimulus and the items in the lexicon was all that mattered, there should have been no difference between the two types of pseudo-words. These results, however, are expected if the perceptual system inserts a "u" between two consonants at a prelexical stage.

CONCLUSION

Theories postulating that the brain elaborates phonological representations of spoken stimuli straightforwardly predict the outcomes of the experiments presented in this paper (see also [START_REF] Marslen-Wilson | Phonological variation in lexical access: Ab-stractness, inference and English place assimilation[END_REF]). It may be possible to tweak acoustic models to yield the same results (in particular, they are generally vague enough about the metrics of comparison between acoustic exemplars). We would certainly not claim that the debate between the two classes of theories is settled. For example, a wealth of data exists that suggest that sub-phonetic information can percolate up to the lexicon (e.g. [START_REF] Andruski | The effect of subphonetic differences on lexical access[END_REF]). To explain this, phonological models have to introduce the notion of graded phonological representations, and then, one must admit, the distinction between acoustic and phonological models starts to blur...

Figure 2 :

 2 Figure 2: Average phoneme detection times, as a function of the target's position, of two groups of Ss induced to attend to coda and onset syllabic positions, respectively

Figure 3 :

 3 Figure 3: Percentage of detection of a vowel "u" as a function of the duration of the "u" within VCuCV stimuli; comparison between native Japanese and native French listeners


Christophe Pallier
email: pallier@lscp.ehess.fr

PHONEMES AND SYLLABLES IN SPEECH PERCEPTION: SIZE OF ATTENTIONAL FOCUS IN FRENCH

. In the present study, we adapted Pitt & Samuel's phoneme detection experiment to French and found that French subjects behave exactly like English subjects: they too can focus attention on a precise phoneme. To explain both this result and the established sensitivity to the syllabic structure, we propose that the perceptual system automatically parses the speech signal into a syllabically-structured phonological representation.

INTRODUCTION

Both the phoneme and the syllable have often been proposed as the "primary unit of speech perception" [START_REF] Savin | The nonperceptual reality of the phoneme[END_REF][START_REF] Massaro | Perceptual units in Speech Recognition[END_REF][START_REF] Mehler | The role of syllables in speech processing: Infant and adult data[END_REF][START_REF] Dupoux | Prelexical processing: the syllabic hypothesis revisited[END_REF][START_REF] Decoene | Testing the speech unit hypothesis with the primed matching task: phoneme categories are perceptually basic[END_REF][START_REF] Segui | The syllable: A basic perceptual unit in speech perception ?[END_REF]. Though this notion -which has rarely been clarified -has become less fashionable with the advent of "continuous" models of word recognition [e.g. 9], the controversy has generated many intriguing observations. One of these observations is the differential sensitivity of French and English listeners to the syllable [START_REF] Cutler | The syllable's differing role in the segmentation of French and English[END_REF]. The results of a series of studies, using syllable and phoneme detection tasks, were taken to indicate that French listeners, but not English listeners, use syllabic units to represent the speech signal [START_REF] Norris | The relative accessibility of phonemes and syllables[END_REF][START_REF] Segui | The role of the syllable in speech segmentation, phoneme identification and lexical access[END_REF].

The evidence for the use of the syllable by French native speakers stems from the "syllable congruency effect" [START_REF] Mehler | The syllable's role in speech segmentation[END_REF]: when asked to monitor for BA or BAL in words like BA#LANCE or BAL#CON (the '#' indicating the syllable boundary), French subjects are faster if the target precisely matches the first syllable of the stimulus. For example BAL is detected faster than BA in BAL#CON, while the opposite is observed for BA#LANCE. When English subjects are tested with the very same material, however, they do not display sensitivity to the syllable boundary [START_REF] Cutler | The syllable's differing role in the segmentation of French and English[END_REF][START_REF] Cutler | A language specific comprehension strategy[END_REF].

A very different approach has been used to suggest that the phoneme is the unit of perception for English speakers. One way to characterise a "perceptual unit" is to show that it can be the object of focal attention [START_REF] Neisser | Cognitive Psychology[END_REF]. Following such a logic, Pitt & Samuel [START_REF] Pitt | Attentional Allocation during Speech Perception: How fine is the focus?[END_REF] tried to determine whether auditory attention could be focused on a unit as small as the phoneme. They had groups of subjects perform a generalised phoneme detection task with a list of CVCCVC words. In this experimental paradigm, subjects carry out a series of trials consisting of the presentation of a written phoneme followed by a spoken word; their task is to press a button, as quickly as possible, if they hear the target phoneme in the incoming word. Their reaction times are then measured. In Pitt & Samuel's study, the probability of occurrence of the target phoneme in the different consonant positions was manipulated: for four groups of subjects out of five, the target was more likely to occur in one consonant position than in the others (1st C for group 1, 2nd C for group 2...) . Thus, the subjects were effectively "conditioned" to expect the target in a precise sequential location. All groups shared some target-word pairs so that their detection times could be compared for all four consonant positions. The fifth group was a "control group" for which the four consonant positions had the same probability of occurrence. Each "experimental" group could be compared with this control. The results were clear: each group showed an advantage when the target occurred precisely at the location which was the most probable. Notably, this advantage did not extend to the other consonant inside the same syllable. That attention could be focused on the phoneme, the authors argued, demonstrated that the phoneme was in fact the unit of speech perception, at least for English speakers.

An important question in this study concerns the property used by the subjects to detect the regularity in the position of the target. It may be (as the authors seem to implicitly assume) that this property was the sequential position of the phoneme in question. However, a feature of the words used in Pitt & Samuel's study was that most had a "CVC#CVC" structure; thus subjects expecting, say, the third consonant, may in fact have been focusing on the onset of the second syllable; and subjects trained to detect the second consonant may have been focusing on the coda of the first syllable, and so on. Put differently, the relevant properties on which attention was focused may have been a position defined in terms of the syllabic structure rather than in terms of sequential phonemic position. This hypothesis was tested by Pallier et al. [START_REF] Pallier | Attentional allocation within syllabic structure of spoken words[END_REF]. In their study, there were two groups of subjects: the first had to detect phonemes that occurred more often in the coda of the first syllable (e.g. P in caP#ture), and the second had to detect phonemes that occurred more often in the onset of the second syllable (e.g. P in ca#Price). The results proved that this manipulation indeed affected detection times on test words shared by the two groups: the first group was faster for codas of first syllables, and the second was faster for onsets of second syllables. This demonstrated that subjects could focus attention on a precise position in the syllabic structure of the stimuli [START_REF] Pallier | Attentional allocation within syllabic structure of spoken words[END_REF].

The fact that syllabic structural position can be used does not rule out the possibility that sequential position cannot play a role. However, Pallier [START_REF] Pallier | Rôle de la syllabe dans la perception de la parole: études attentionnelles[END_REF] showed that it was not possible to induce subjects to attend to a sequential position when the structural status of the target was varied. That is, subjects could not take advantage of the fact that a phoneme target was more often in the third sequential position when it was as likely to be a coda (caP#tif) than an onset (ca#Price). This fact demonstrates that sequential position is simply not a psychologically relevant property: subject do not automatically "count" phonemes.

Nevertheless, whereas Pitt and Samuel used American English listeners, the studies by Pallier et al. were conducted with French and Spanish subjects. In light of the previous studies concluding that French, but not English, relied on the syllable, one alternative explanation for the results is possible: French subjects may have been focusing attention on the whole syllable. The present study, an adaptation to French of the Pitt & Samuel study, was designed to assess this hypothesis.

EXPERIMENT

This experiment is a replication, with French subjects, of Pitt and Samuel's (1990) experiment 1: we compared four groups of Ss who were induced to attend respectively to the first, second, third and fourth consonantal position of CVC#CVC words.

Method

Material

One hundred and forty seven CVC#CVC French words were selected, providing four potential consonant locations for the targets (C1, C2, C3 and C4, corresponding to the sequential position inside the word). Four lists of 147 word-target phoneme trials were then constructed. The lists differed only in the target phonemes: the words and their order were the same in the four lists. Sixteen different types of phonemes were used for the targets. There were three categories of trials: Tests, Fillers and Foils. There were forty "Tests" trials: ten for each of the consonant location condition (C1, C2, C3 and C4). Care was taken that the phoneme sets were the same in the four conditions. Only the 70 Fillers distinguished the four lists: in the first list, the target phoneme was always the first consonant of the word; in the second list it was the second consonant, and so on. The 37 "Foil" trials were distracters for which the target did not occur in the word. The Test trials were always preceded by one or two Filler trials. Finally, we insured that two successive trials never contained the same phoneme target.

Procedure

The subjects were tested individually in a quiet room. They were seated in front a portable PC Toshiba 5200 that controlled the progress of the experiment (the stimuli were stored as 16 bit files on the computer and played back at 64 kHz by an OROS AU22 sound board). After reading the instructions explaining the generalised phoneme detection task, the subjects performed a short (unbiased) training with 7 trials. Then, the experiment proper started. The subjects were not informed that the phoneme target would occur more often in one location than in the other. Each trial began with the presentation of an upper case letter representing the phoneme target for 800 ms. The screen was then cleared, and one second later, a word was played in the headphones. The subject had to press a morse key when he detected the target (he had 2.5 sec from stimulus onset to answer). The reactiontime was measured from the target phoneme onset. The next trial started 5 sec after the beginning of the previous one, except when the subject had made a mistake (false alarm or miss). In such a case, a warning message was displayed for 2.5 second and the same trial was started again (only the first trial was considered for analysis, that is, as an error; this change in the original procedure aimed at diminishing the effects of errors on subsequent trials).

Several departures from Pitt & Samuel's original design are notable:

• in our case 75% (vs. 50% in the P&S study) of the words contained the target, and we used half as many test words, ending up with a lists of 147 stimuli rather than 480. This reduced the duration of the experiment from 45 minutes to 15 minutes.

• we used a go/no go paradigm rather than a yes/no decision. Our aim was to speed up response times and decrease error rates.

• we had only 4 groups of subjects and no control group. This is because a between-subjects design would have required many more subjects than the within-subject design that we planned for this experiment (see results section).

Subjects

Forty students from various universities in Paris participated in the experiment for which they received 20 FF. All were native speakers of French with no known auditory defect. Ten were randomly assigned to each of the four lists, yielding four groups.

Results

Mean detection times and error rates were computed for each subject. Table 1 displays the data averaged over groups and consonantal positions. Table 2 shows costbenefit figures computed from the reaction time data by removing the mains effects of group and consonant position from each cell.

We performed two two-way analyses of variance on the mean reaction times, the first with subjects and the second with items as the random factor. The two factors were (a) (consonantal) "Position" (within-subjects and between-items) and (b) "Group" (between-subjects and within-items). Position yielded a significant effect (F 1 (3,108)=109; p<.001 and F 2 (3,35)=20; p<.001), as did the global interaction Group × Position (F 1 (9,108)=8.7; p<.001 and F 2 (9,105)=9.6; p<.001). We then examined, for all pairs of groups, the interactions Group × Position: All were significant at the .05 level both in the subject-based and in the item-based analysis.

Discussion

First and foremost, each group had the largest benefit when the phoneme target occurred in its expected position (see diagonal of Table 2). This was statistically significant as attested by the significance of all two by two interactions. We thus reproduce the main result of Pitt & Samuel, but this time with French subjects. Second, our subjects were faster (460 ms) than Pitt & Samuel's (701 ms) and the error rates were quite low (false alarms: 2.7%; missed targets: 1.3%). Three differences between their study and ours can be invoked to try to explain the difference: (a) we used a go/no-go paradigm rather than yes/no decision (b) we gave feedback on errors (c) our experiment was much shorter (about 15 min) than theirs (about 40 min).

Finally, we observe that the reaction times substantially decrease as the position of the target phoneme approaches the end of the word. We think that several factors may conspire to bring this about: (a) coarticulation information before the target phoneme can help the response (b) with position, the potential influence of lexical knowledge increases [START_REF] Frauenfelder | Lexical Effects in Phonemic Processing: Facilitatory or Inhibitory ?[END_REF][START_REF] Frauenfelder | Phoneme monitoring and lexical processing: Evidence for associative context effects[END_REF] (c) subjects response "threshold" may decrease with time (It is a general fact that detection time decreases as the serial position of the target in a list of stimuli increases (see ref. [START_REF] Luce | Response times: Their role in inferring elementary mental organization[END_REF]) (d) the end of the stimulus can act as a go signal.

CONCLUSION

This experiment replicates with French subjects the pattern of results previously obtained with American subjects: French listeners too can focus their attention on a unit as small as a phoneme. This result adds to the ones reported in [START_REF] Pallier | Attentional allocation within syllabic structure of spoken words[END_REF][START_REF] Finney | Attentional Allocation to Syllables in American English[END_REF]: together they demonstrate that listeners can focus attention on phoneme-sized units whose position is defined in terms of the syllabic structure of the stimulus.

Most models of speech perception make the assumption that the brain extracts a linear string of units (phonemes, syllables, etc.) from the speech signal. The data presented here are better interpreted by supposing that the speech processing system elaborates, in real-time, a hierarchical, syllabically-structured representation of the stimulus [START_REF] Pallier | Rôle de la syllabe dans la perception de la parole: études attentionnelles[END_REF].

Table 1 . Mean reaction-times (in ms) and error-rates (in percents) of each group according to the consonantal position.

 1

	Group		Consonantal position
		C1	C2	C3	C4
	Gr1	503 1 596 3 488 2 344 1
	Gr2	494 0 436 1 439 1 353 7
	Gr3	527 1 502 2 404 0 350 4
	Gr4	640 0 590 3 505 1 290 1
	Each cell is the mean of 100 measures (10 Ss × 10
	items). The pooled standard deviation is 57.6 ms by
	subjects and 53.4 ms by items.

Table 2 . Costs/Benefits computed from the reaction- times.

 2

	Group		Consonantal position
		C1	C2	C3	C4
	Gr1	-54*	49	13	-7
	Gr2	-11	-59*	16	55
	Gr3	7	-8	-34*	36
	Gr4	59	19	6	-84*
	Each cell is obtained from the corresponding one in table
	1 by computing (y ij = x ij -x i. -x .j +x .. ). (*= expected position)

ACKNOWLEDGEMENTS

The author was supported by grants from the Direction Générale des Études et Techniques and from the Fyssen Foundation.


C Pallier
email: pallier@lscp.ehess.fr

S Dehaene

J.-B Poline

D Lebihan

A.-M Argenti

E Dupoux

J Mehler

Brain imaging of language plasticity in adopted adults: can a second language replace the first?

Do the neural circuits that subserve language acquisition lose plasticity as they become tuned to the maternal language? We tested adult subjects born in Korea and adopted by French families in childhood; they have become fluent in their second language and report no conscious recollection of their native language. In behavioral tests assessing their memory for Korean, we found that they do not perform better than a control group of native French subjects who have never been exposed to Korean. We also used event-related fMRI to monitor cortical activations while the Korean adoptees and native French listened to sentences spoken in the Korean, French, and in other unknown foreign languages. The adopted subjects did not show any specific activations to Korean stimuli relative to unknown languages. The areas activated more by French stimuli than by foreign stimuli were similar in the Korean adoptees and in the French native subjects, but with relatively larger extents of activation in the latter group. We discuss these data in light of the critical period hypothesis for language acquisition.

: a lag of even a few years in first exposure to a language can result in subtle but significant deficits in the com-

mand of its phonology, morphology or syntax [START_REF] Pallier | A limit on behavioral plasticity in speech perception[END_REF][START_REF] Johnson | Critical period effects in second language learning: The influence of maturational state on the acquisition of english as a second language[END_REF][START_REF] Weber-Fox | Maturational constraints on functional specializations for language processing: Erp and behavioral evidence in bilingual speakers[END_REF]. These facts have often been taken to support the existence of a critical, or sensitive, period for language learning in humans, similar to that observed in non-human species in other domains [START_REF] Doupe | Birdsong and human speech: common themes and mechanisms[END_REF].

One explanation attributes this to a progressive loss of plasticity of the neural circuits that subserve language learning. The change in plasticity may result from age-related maturational processes [START_REF] Lenneberg | Biological foundations of language[END_REF][START_REF] Penfield | Speech and brain mechanisms[END_REF], or from the act of learning itself [START_REF] Bever | Normal acquisition processes explain the critical period for language learning[END_REF][START_REF] Flege | Age constraints on second-language acquisition[END_REF]. However, this interpretation, henceforth "the crystallization hypothesis", is controversial: some late learners of a second language apparently become perfectly fluent speakers, and it remains an unsettled issue whether or not, provided adequate environment and training, the human brain has the potential to reach native-like command of a second language [START_REF] Long | Maturational constraints on language development[END_REF][START_REF] Harley | The critical period hypothesis: Where are we now?[END_REF][START_REF] Macwhinney | Second language acquisition and the competition model[END_REF][START_REF] Birdsong | Ultimate attainment in second language acquisition[END_REF][START_REF] Werker | The organization and reorganization of human speech perception[END_REF]Strange, 1995).

The crystallization hypothesis predicts that the later a second language is learned, the more the cortical representations of the second and the first languages will differ. This prediction, however, has received only mixed support. In an fMRI study of sentence production in bilinguals, consistent with the hypothesis, the patterns of activation elicited by internal production in L1 and L2 in Broca's area overlapped completely in early bilinguals, but differed in late bilinguals [START_REF] Kim | Distinct cortical areas associated with native and second languages[END_REF]. However, in a subsequent study of single-word production, highly overlapping activations were found in early and late bilinguals (Chee, Tan, & Thiel, 1999). In comprehension tasks, the ultimate level of proficiency in L2, more than the age of acquisition, seems to predict whether the cortical representations of L1 and L2 match [START_REF] Dehaene | Anatomical variability in the cortical representation of first and second languages[END_REF][START_REF] Perani | The bilingual brain. profiency and age of acquisition of the second language[END_REF]Chee et al., 1999). In low-proficiency bilinguals, activations when listening to L2 vary greatly from one individual to another and often differ from those elicited by L1 [START_REF] Dehaene | Anatomical variability in the cortical representation of first and second languages[END_REF]. However, in a PET study of an exceptional subset of late bilinguals who nevertheless managed to become extremely fluent in L2, the cortical representations of L1 and L2 were indistinguishable and similar to those of native speakers [START_REF] Perani | The bilingual brain. profiency and age of acquisition of the second language[END_REF]. The latter findings seem at odds with the crystallization hypothesis. However, such a group study using PET may not be sensitive enough to detect subtle changes in the organization of language areas. Furthermore, it could be argued that the highly proficient participants, several of whom were professional simultaneous translators, were exceptional individuals.

Another prediction of the crystallization hypothesis is that exposure to the first language should leave long-lasting traces in the neural circuits subserving language processing. In the present study, we explore this issue by using fMRI to study the cerebral bases of speech comprehension in a special group of subjects: children adopted from foreign countries who have ceased to use their first language and speak only the language of their new parents. When tested as adults, they are apparently fluent in their second language and report having completely forgotten their first language [START_REF] Maury | Les mécanismes intrapsychiques de l'adoption internationale et interraciale. l'adoption des enfants coréens en france[END_REF]. Has L2 completely replaced L1? According to the crystallization hypothesis, exposure to L1 during the first 3-8 years of life should have left traces. Exposing adopted subjects to sentences in their original language should elicit some remnant activity in language areas. If, on the other hand, the brain circuits for language remain plastic then learning a new language may have completely overridden the traces laid down by the first.

To our knowledge, this is the first behavioral and neuroimaging study that uses evidence from adopted children to examine the plasticity of language acquisition when the child's main language suddenly ceases to be used.

Materials and Methods

Subjects

To identify adopted subjects, we contacted several organisms in charge of foreign adoption in France, and sent mail to several hundreds of adopted subjects from various countries. From the answers we got back, the only sufficiently large group was formed of people of Korean origin. After excluding those who had had contacts with Korean since their arrival, and those would could not participate in the fMRI experiment for various reasons, we ended up with eight individuals for whom we had all good evidence of sudden and definitive isolation from the initial maternal language (2 female, 6 male ranging in age from 20 to 32, mean=26.8; the ages of adoptions were 3, 3, 5.5, 5.5, 5.5, 7, 7.5 and 8 years). All claimed to have completely forgotten their native language, as is generally the case for children adopted from foreign immigration [START_REF] Maury | Les mécanismes intrapsychiques de l'adoption internationale et interraciale. l'adoption des enfants coréens en france[END_REF]. When interviewed about their skills in French, only one (who arrived at 5.5) reported significant problems in learning to speak French. The others reported having learned French rather quickly, and had no perceptible foreign accent in French.

Given their history of adoption, a concern is the extent to which those subjects' initial language acquisition was normal and, in particular, whether they had received sufficient inputs in the Korean language. Though we have little information on their individual history, the adopting organisms informed us that, in the orphanages they come from, they had interaction not only with other children but also with Korean speaking adults. Older children went to Korean school. Thus, it is likely that they received a normal exposure to Korean.

The control group comprised eight native monolingual French speakers (2 female, 6 male ranging in age range from 22 to 28, mean=23.5), who had had no exposure to any Asian language. All subjects were right-handed according to the Edinburgh questionnaire.

All subjects participated to two behavioral tests out of the scanner, and one test inside the scanner.

Behavioral test 1: Language identification

The subjects listened to a total of sixty sentences, twelve in each of five languages unfamiliar to French subjects (Korean, Japanese, Polish, Swedish and Wolof). Sentences were read by three different female native speakers. After each sentence, the subject had to provide, on a scale from 1 to 7, a degree of confidence that the sentence was in Korean or not: '7' meant that he/she was sure the sentence was in Korean; '1' meant that he/she was sure that the sentence was not in Korean; 4 indicated a complete lack of confidence.

Behavioral test 2: Word recognition

The experiment consisted in a series of twenty-four trials that started with the display of a word (written in French) followed by the auditory presentation of two Korean words. The task was to decide which of the two Korean words was the correct translation of the word displayed. Subjects could replay the Korean words as often as they wanted before responding.

fMRI design and acquisition

Brain imaging was performed using event-related fMRI while the participants listened to a total of 128 sentences in four different languages: French, Korean, Japanese and Polish. Japanese and Polish were both unknown to our subjects, and thus served as a control for French and Korean sentences. In addition, Japanese was more similar to Korean than Polish, as attested by our pre-test. We were interested in assessing whether this difference in similarity would show up on the cortical activations.

Sentences were selected from recordings by three female native speakers of each language. The sentences were selected from a corpus of sentences from various languages, all translated from the same original French sentences. All recordings were made in the same sound-proof room (sampling-rate 64Khz; low-pass 20Khz; 4x undersampling). The sentences, read with natural intonation, were 16 to 21 syllables long. They were selected so that the distributions of durations were similar across languages (average=2.9 sec). The mean energies (rms) of the stimuli were also equated.

To ensure that the subjects paid attention to the sentences, they were required to perform a fragment detection task. Following each sentence, after a 500 msec delay, a 400 msec fragment was played. The subject had to indicate, by pressing one of two response buttons, whether this fragment had appeared in the sentence or not. Before scanning, subjects performed a practice run of 12 trials on this task.

The auditory stimulations (playout of one sentence followed with a probe) had a mean duration of four seconds and occurred every 19.6 seconds, during time-windows where the read-out gradients were disabled, which greatly decreased the noise in the scanner. After each stimulation, six whole-brain scans were acquired (T2 * -weighted echo-planar imaging, 3.75 x 3.75 x 5 mm, 22 slices, TR=2.4 sec, on a Bruker 3-Tesla magnet). The stimuli were administered in four 10-minute blocks, each comprising 32 trials. Languages, speakers and side of response were evenly distributed within each block. The instruction (respond 'present' with the right or with the left hand) was switched between the second and third block. The sentences were presented in a different randomized order for each subject. A total of 128×=768 functional images were acquired for each subject. High resolution T1 anatomical scans (3D gradient-echo inversion-recovery sequence, TI = 700 ms, TR = 1600 ms, FOV = 192 x 256 mm2, matrix = 256x128x256, slice thickness = 1.2 mm) were also acquired.

fMRI data analyses fMRI data were processed using SPM99 software, starting with slice timing, spatial realignment (correction for movements), spatial normalization and smoothing with a 5 mm Gaussiankernel. For the statistical analyses, we generated a linear model by defining six categories of events: French, Korean, Japanese or Polish stimulations, and right or left motor responses (Friston, K. J. and Holmes, A. P. and Worsley, K. J. and Poline, J.-B. and Frith, C.D. and Frackowiak, R. S. J., 1995). These categories were crossed with indicator variables for the four sessions, yielding a total of twenty-four onset vectors, which were convolved by an ideal heamodynamic impulse response and its derivative (included to model small temporal shifts). Both individual analyses and group analyses were performed; the group analyses consisted in t-tests using the individual contrast images smoothed at 8 mm (one image per subject). Unless otherwise indicated, the individual and group results were examined at the voxelwise threshold of p<0.001 uncorrected for multiple comparisons and the p<0.05 threshold on clusters' extent.

Results

Behavioral tests

In the sentence identification test, the native Korean subjects failed to recognize Korean sentences. Rather, their ratings were identical for Korean and Japanese sentences (4.09 and 4.04 respectively: t(7)=0.30, p=0.70) and were higher for those languages than for the other three languages presented: Polish, Swedish and Wolof (t(7)=5.0, p=0.001). An analysis of variance indicated that this pattern of performance did not differ significantly from that observed in the group of native French participants (group × language interaction: F(4,56)=1.60, p=0.17; Fig. 1a). In the second test, where subjects were asked to select the translation of a written French word from two spoken Korean words, again, the Korean and the control groups performed similarly (56% and 52% success respectively, t(14)=0.98, p=0.30; see Fig. 1b). Finally, in the speech segment detection task performed during fMRI scanning, performance did not differ between the two groups (group × language interaction: F(3,14)=1.5, p=0.22). Both Korean and control subjects showed better performance for the only language that they could understand (French) than for the other three languages In the "Korean sentence identification" test (panel a), subjects listened to sentences in five different languages and rated their confidence that the sentences were in Korean (7= 100% sure it is Korean; 4=totally unsure, 1= sure it is not Korean). In the "Word recognition test" (panel b), the subjects saw a French word and had to select the correct translation amongst two spoken Korean words. In the "segment detection task" (panel c), subjects had to decide whether a short sound excerpt belonged or not to a sentence they had just heard. In all tests, the Koreans' performance did not differ from that of the control group (error bars display 95% C.I.)

(t(7)=6.65, p<0.001 and t(7)=6.77, p<0.001; Fig. 1c). Inspection of individual data in the three tests showed that none of the Korean adoptees performed markedly differently from the control group.

Brain-imaging

Our first analysis aimed at identifying the network of areas that are more responsive to French than to other unknown languages. We choose the "Polish" condition as a baseline that was neutral for the two groups, and determined the areas where French stimuli elicited stronger activations than Polish stimuli. The group analyses revealed a network of areas comparable to the one identified in previous studies of sentence listening [START_REF] Mazoyer | The cortical representation of speech[END_REF][START_REF] Schlosser | Functional MRI studies of auditory comprehension[END_REF][START_REF] Dehaene | Anatomical variability in the cortical representation of first and second languages[END_REF][START_REF] Perani | Brain processing of native and foreign languages[END_REF][START_REF] Perani | The bilingual brain. profiency and age of acquisition of the second language[END_REF]. This network comprised the left superior temporal sulcus and neighboring portions of the superior and middle temporal gyrus, the left inferior frontal gyrus (triangularis sector), and, to a lesser extent, the contralateral temporal areas of the right hemisphere. Similar networks were activated in both groups of subjects (see Table 1, Figure 2A and 3): direct comparison of the two groups yielded no significant difference (even when the threshold was decreased to p<0.01 voxelwise uncorrected for multiple-comparisons and the cluster size threshold set to p<0.05). Similar results were obtained when the activations evoked by Japanese sentences, rather than Polish sentences, were used as the baseline (Figure 2B).

Inspection of the individual analyses of the French-Polish comparison (Figure 4) revealed that while the participants in both groups activated similar areas, those from the Korean group had smaller extents of activations than the control group. Counts of voxels above the p<0.001 threshold were submitted to an analysis of variance with the factors 'hemisphere' and 'native language' (see figure 5): both factors were significant (Group: F(1,14)=7.3, p=0.02; Hemisphere: F(1,14)=24.0, p<0.001) but did not interact (F(1,14)=1.6, p=0.23). A similar analysis for counts of voxels above p<0.05 corrected, yielded a similar outcome. Importantly, no such group difference was found when we compared the extents of motor cortex activations associated with left-hand and right-hand key presses (Group: F(1,14)=0.53, p=0.48). This suggests that the lesser extent of activation in Korean subjects during language listening was not due to changes in anatomical organization, head shape, or imaging parameters, but was possibly related to their peculiar history of language acquisition.

French Group

Korean Group Next we examined the presence of activations specific to Korean sentences, again relative to Polish sentences. In the Korean group, no significant difference was found (at p<0.01 or at p<0.001 voxelwise uncorrected for multiple comparisons, and p<0.05 corrected for cluster extent). Furthermore, in the individual analyses, none of the native Korean subject showed any Koreanspecific activations (p<.001 uncorrected). In the group analyses of native French speakers, however, two regions were significantly more activated by Korean than by Polish stimuli: one in the left cerebellum (maximum at -12 -56 -16, T(7)=7.08) and one in the right middle temporal STS (at 44 -12 -12, T(7)=18.24). When the two groups were compared, this right STS region came out significantly when the threshold was lowered at p<.01 (at 48 -20 -12 T(14)=5.35). However, a cluster of activation located about the same region (max. at 48 -4 -8, T(14)=4.74) was also detected in the Korean group in the "Korean-Polish" analysis at the p<0.01 voxel level (but this did not approach the p<0.05 extent threshold). This may be related to differences between Korean and

French Ss

Koreans Ss Polish which were perceptible to the participants (see figure 1a). Yet, similar analyses contrasting Korean and Japanese sentences, and Japanese and Polish sentences did not reveal any significant difference between the languages or the two groups. Finally, we directly compared the activations to French versus Korean sentences (Figure 2C). In the French group, this revealed the same left-hemispheric network identified in the "French>Polish" contrast. If Korean subjects had any remnant trace of having learned Korean as the first language and French as the second, then the French versus Korean difference should be attenuated or even reversed in this group. This was not the case. The French versus Korean contrast was highly significant along the left STS and in left inferior frontal areas in the Korean group, just as in the French group. No brain area showed any group difference in the "French>Korean" nor in the "Korean>French" contrasts.

Discussion

We studied language perception and comprehension using behavioral methods and functional magnetic resonance imaging in a group of Korean adults adopted in their youth by French families, as well as in a control group of native French subjects. Three main results were observed. First, behaviorally, the adopted subjects could not distinguish sentences in their native language from sentences coming from various languages. Nor could they identify Korean words in a forced-choice task, or detect fragments from Korean sentences better than native French controls. Second, the fMRI data revealed no differences in brain activation when the adopted subjects listened to Korean relative to an unknown language such as Polish or Japanese. Third, the cortical regions that responded more to the known language, French, than to other foreign languages were similar in the adopted subjects and in the native French control group. However, the observed activations in this comparison had a broader extent in the native French subjects than in the adopted subjects.

These data do not support a strong version of the crystallization hypothesis. Indeed, this hypothesis led to expect activations specific to Korean in the adopted Koreans, and a differential pattern of activated areas, between the French and Korean groups, while listening to French. Actually, the activation patterns in the Koreans were remarkably similar to those of the native French group, at least in terms of the regions that were activated. Slight differences were detected in the extent and amount of activation; these are further discussed below. In both groups, there was a large activation of left-lateralized temporal and inferior frontal regions when listening to French sentences, but essentially no detectable activation of this network when listening to Korean sentences relative to two other unknown languages. This provides evidence in favor of the reversibility of plastic changes associated with language acquisition in the first few years of life. The subjects in our study had been adopted between 3 and 8 years of age. If the brain circuits that subserve language acquisition had started to crystallize during this time period, we would have expected to see larger differences between the two groups. Our data rather suggest that when a second language is learned early on, this acquisition does not necessarily involve different brain systems than those involved in learning the native language. On the contrary, the second language may become represented in the very areas that normally represent the first language. This conclusion fits with a previous PET study of spoken language comprehension in which late but highly fluent learners of a second language were found to have patterns of activation indistinguishable from those of native speakers [START_REF] Perani | The bilingual brain. profiency and age of acquisition of the second language[END_REF]. Compared to this previous study, the present study has the advantage that the adopted subjects were not selected because they were exceptionally gifted for foreign languages. Our study suggests that any child, if placed in the unusual situation of having to learn a new language between 3 and 8 years of life, can succeed to a high degree, and that they do so using the same brain areas as are recruited for first-language acquisition.

The behavioral observations that we collected also support the adopted subjects' claim that they have forgotten their native language. On a Korean sentence identification test, they did not perform any better than naive French subjects. This was true also in the lexical test which involved selecting the appropriate meaning for common words, and in the speech segment detection test. One limitation of these tests (except possibly of the third) is that they were not designed to test for subtle, implicit, remnants of Korean in the adopted subjects. Early experience with Korean may have left implicit unconscious traces at the level of the microcircuitry of the language processing areas that our behavioral and fMRI methods did not detect. If they exist at all, however, such traces must be small and perhaps take the form of "dormant" synaptic changes that cannot be revealed with classical fMRI subtraction methods. Such traces might be revealed by using a learning paradigm. For example, more extensive retraining experiments (which could not be performed in the half-day visit on the present study), might reveal faster learning of Korean in subjects who had early exposure to Korean relative to control subjects, as has been observed in both animals and humans [START_REF] Knudsen | Capacity for plasticity in the adult owl auditory system expanded by juvenile experience[END_REF]Tees & Werker, 1984;[START_REF] Au | Overhearing a language during childhood[END_REF]. We are in the process of devising such a training test, to assess whether the adopted Koreans can perceive phonetic contrasts that exist in Korean but not in French better than native French listeners.

Our fMRI experiment used natural sentences in order to reveal potential traces of Korean in the adopted subjects at any of different linguistic levels, from phonology to the lexicon, prosody, syntax and semantics. To isolate such traces, we subtracted the activation to Korean stimuli from the activation to stimuli in two foreign languages, Japanese and Polish. This procedure has previously been shown to reveal a large network of activation when processing a known relative to a foreign language [START_REF] Mazoyer | The cortical representation of speech[END_REF][START_REF] Dehaene | Anatomical variability in the cortical representation of first and second languages[END_REF][START_REF] Schlosser | Functional MRI studies of auditory comprehension[END_REF]. However, one difficulty with this subtraction logic is that some areas, particularly those involved in speech decoding and phonological processes, may be subtracted away because they may be equally well activated by known and unknown languages. Indeed, the absence of differential activations in the superior temporal gyrus, which has been associated with speech decoding [START_REF] Hickok | Towards a functional neuroanatomy of speech perception[END_REF], in both the adopted subjects and the control group, might be interpreted as supporting the idea that foreign stimuli engage phonological processes as much as do native stimuli. Thus, the subtractive method may have been suboptimal to identify traces of the first language in the early stages of speech processing.

Although the bulk of our results suggests a high degree of similarity between adopted subjects and native French subjects, we found two differences between the groups worth discussing. First, when listening to French relative to foreign stimuli, although the same anatomical regions were activated, the extent of activation was larger in the native French participants relative to the Korean adopted subjects. This result speaks to the main question that our experiment was designed to address: can the second language replace the first? Results discussed above imply that yes, but this latter finding suggests that such replacement may not be complete. The acquisition of expertise is known to be accompanied by local increases in brain activation [START_REF] Poldrack | Characterizing the neural mechanisms of skill learning and repetition priming: Evidence from mirror reading[END_REF][START_REF] Gauthier | Activation of the middle fusiform 'face area' increases with expertise in recognizing novel objects[END_REF] and an enlargement of cortical maps [START_REF] Elbert | Increased cortical representation of the fingers of the left hand in string players[END_REF] concomitant with a narrowing of cortical tuning [START_REF] Rainer | Effects of visual experience on the representation of objects in the prefrontal cortex[END_REF]. The native French subjects' greater experience with French may have resulted in a widening of the cortical maps for language processing, and/or an increase in their responsivity, in comparison to the Korean subjects. Though we have informally observed that the adopted Koreans have a very good command of French, subsequent research will be needed to assess whether they might differ from native speakers in subtle ways.

Alternatively, the relative difference in the extent of activation between groups, could be due to larger activation in the adopted subjects by the foreign stimuli. Contrary to the control group, which was composed of naïve students from the Paris area, the adopted subjects had accepted to participate in the study because of their adopted status, and were coming to Orsay from other parts of France specifically for this study. Given their natural curiosity for their special status, we cannot exclude the possibility that they deployed greater attention to the foreign language stimuli than the control subjects. It is also possible that their unusual history of language acquisition has caused a greater responsivity of left-hemispheric language areas to any form of linguistic input. At present, we cannot discriminate between the above explanations.

A second difference between the groups was observed in the Korean-Polish subtraction, which revealed an activation in the right superior temporal sulcus that was stronger in the native French group than in the adopted subjects. This unpredicted result may be due to a relative inhibition in the Koreans relative to French group, when listening to Korean. This interpretation raises the issue of the possible role of inhibition in unlearning the first language. However, the fact that the two groups did not differ in the Korean-Japanese and French-Korean substractions, mitigates this interpretation.

We close by considering the possible implications of this research for theories of critical periods in language acquisition. The original hypothesis put forward by [START_REF] Lenneberg | Biological foundations of language[END_REF] stipulats that the critical period for language ends around puberty. Given that the adopted subjects arrived in France when they were less than 8 years of age, our results are not incompatible with Lenneberg's hypothesis. However, another version of the critical period hypothesis holds that there is a gradual loss of plasticity starting much before puberty. This view builds on the fact that language perception becomes attuned to the linguistic environment very early on in life. Developmental research has shown that even children in their first year already show the influence of their surrounding linguistic environment in both their behavior [START_REF] Kuhl | Linguistic experience alters phonetic perception in infants by 6 months of age[END_REF][START_REF] Werker | Developmental changes across childhood in the perception of non-native speech sounds[END_REF][START_REF] Halle | Beginnings of prosodic organization: intonation and duration patterns of disyllables produced by japanese and french infants[END_REF] and their brain activations [START_REF] Cheour | Development of language-specific phoneme representations in the infant brain[END_REF][START_REF] Näätänen | Language-specific phoneme representations revealed by electric and magnetic brain responses[END_REF][START_REF] Dehaene-Lambertz | Electrophysiological correlates of categorical perception in adults[END_REF][START_REF] Dehaene-Lambertz | Speed and cerebral correlates of syllable discrimination in infants[END_REF]. This is consistent with studies of second-language processing, which indicate that in immigrants, even a lag of a few years in the onset of second-language acquisition is associated with perceptible deficits compared to native subjects. Such deficits are most evident in speech production, where a foreign accent starts to be perceptible when a second language is acquired after the age of four years [START_REF] Oyama | A sensitive period for the acquisition of a nonnative phonological system[END_REF][START_REF] Flege | Factors affecting strengh of perceived foreign accent in a second language[END_REF]. Similar studies on speech comprehension also reveal deficits in syntax in Chinese immigrants who arrived in the US in their third year [START_REF] Weber-Fox | Maturational constraints on functional specializations for language processing: Erp and behavioral evidence in bilingual speakers[END_REF].

It is often not realized that empirical findings such as those reported above can be submitted to two radically different theoretical interpretations. It is useful to distinguish between interference and "crystallization" accounts of the critical period hypothesis. Both accounts agree that language acquisition starts very early on, probably guided by genetically driven mechanisms partly dedicated to processing speech inputs. However, they differ in their interpretation of subjects' difficulties in acquiring a second language. According to the crystallization account, a window of brain plasticity is open at birth and progressively closes as the brain networks for language become stabilized, under the possible influence of maturational and/or experiential factors. In this view, plasticity is temporally limited and progressively lost. According to the interference account, on the other hand, the presence of processes and representations attuned to the first language acts as a filter that distorts the way a second language can be acquired. In this view, the loss of plasticity in language areas, if it exists at all, plays only a minor role compared to the interference imposes on the maintenance of a first languagby the processing of the second.

The study of adopted children provides a unique opportunity to address this theoretical distinction. Contrary to immigrants, who usually stay in contact with their home family and local language community, adopted children do not need to maintain any representation of the first language, from which they are suddenly deprived. In this situation, our data tentatively suggest that the native language is, in large part, lost and replaced by the language of the new environment. Even by 7 or 8 years of age, plasticity in language areas is still sufficiently high to promote an essentially complete recovery of normal language. This conclusion fits with lesion studies that found good, if incomplete, recovery from large left hemisphere lesions, or even from left hemispherectomy when performed before the age of 9 [START_REF] Vargha-Khadem | Onset of speech after left hemispherectomy in a nine-year-old boy[END_REF]. Our results complement these studies by showing that this form of plasticity is not limited to exceptional situations of brain insult or intractable epilepsy, but that it also occurs in the normal brain. This view is not incompatible with the notion that puberty is associated with a biologically-determined reduction in language learning ability [START_REF] Lenneberg | Biological foundations of language[END_REF]. Indeed, previous brain-imaging studies have revealed major differences in the cortical representation of the first and second languages in most late learners [START_REF] Dehaene | Anatomical variability in the cortical representation of first and second languages[END_REF][START_REF] Perani | Brain processing of native and foreign languages[END_REF][START_REF] Kim | Distinct cortical areas associated with native and second languages[END_REF]. We might obtain similar results if we could study a population of subjects who had been delocalized to a new country and severed from their home language late in life, after puberty. Nor are our data incompatible with developmental evidence for early brain changes associated with language acquisition. Our results merely indicate that those early changes are not immediately stabilized, but remain plastic and reversible for several years.

FrenchFigure 1 .

 1 Figure1. Performance of the native Korean and the native French subjects on three behavioral tests. In the "Korean sentence identification" test (panel a), subjects listened to sentences in five different languages and rated their confidence that the sentences were in Korean (7= 100% sure it is Korean; 4=totally unsure, 1= sure it is not Korean). In the "Word recognition test" (panel b), the subjects saw a French word and had to select the correct translation amongst two spoken Korean words. In the "segment detection task" (panel c), subjects had to decide whether a short sound excerpt belonged or not to a sentence they had just heard. In all tests, the Koreans' performance did not differ from that of the control group (error bars display 95% C.I.)

Figure 2 .Figure 3 .

 23 Figure 2. Brain renderings displaying the results in the group analyses of the three contrasts comparing French stimuli vs. Polish stimuli (A), Japanese stimuli (B) and Korean stimuli(C).

Figure 4 .

 4 Figure 4. Brain renderings showing, for each of the 16 subjects, the regions where activation due to French sentences was significantly stronger (p<.001) than that due to Polish sentences.

Figure 5 .

 5 Figure 5. Numbers of supra-threshold (p<.001) voxels in individual SPMs for the "French-Polish contrast", split by hemispheres (each line corresponds to one subject).

Table 1 :

 1 Areas where activations were greater for "French" than for "Polish" stimuli, for the French and Korean subjects. We report the coordinates in mm and t-values of the local maxima of activations identified in the group analyses.

	French Ss	x	y	z t-value	Korean Ss	x	y	z t-value
	Left STS anterior	-56	-8 -16	11.94	Left STS anterior	-60 -12 -16	8.69
	"	-60	4 -24	5.28	"	-52	4 -24	11.78
	Left STS middle	-56 -32	-4	10.68	Left STS middle	-52 -36	-8	6.78
	"	-52 -24	-8	6.64	"	-56 -20 -12	7.40
	Left STS posterior	-52 -48	12	9.32	Left STS post.	-60 -56	8	4.68
	"	-44 -60	16	6.51
	"	-40 -48	24	5.83	Left MTG post.	-64 -40	-4	4.64
	Left MTG posterior	-60 -44	-4	8.24	"	-64 -48	-8	3.70
	Left MTG middle	-68 -24 -16	7.01	Left ITG post.	-68 -52 -16	5.00
	"	-64 -20 -12	6.96	Left Temp. Pole	-48	12 -24	10.9
	Left Temp. Pole	-52	12 -20	5.88	Left IFG (pars triang.) -56	24	0	6.24
	Left IFG (pars triang.) -56	24	0	9.16	"	-56	20	12	3.97
	"	-44	20	16	5.87	Right STS middle	52 -28 -12	4.46
	Right STS middle	48 -20 -12	7.55	Right STS anterior	52	4 -20	6.33
	Right STS anterior	52	-4 -16	6.75	Right Temp. pole	48	20 -32	3.82
	Note: thresholds: t 7 >4.8 p<.001; t 7 >3.0 p<.01

We thank the participants and the organizations in charge of foreign adoption who helped us. We thank F. Hennel for help in data acquisition.This work was supported by an ACI grant from the Ministère de la Recherche awarded to C. Pallier and a joint European project of the European Commission, DG XII.

Author note: