Child Neuropsychology A Journal on Normal and Abnormal Development in Childhood and Adolescence

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Auditory orienting of attention: Effects of cues and verbal workload with children and adults Marion Phélip, Julien Donnot & Jacques Vauclair To cite this article: Marion Phélip, Julien Donnot & Jacques Vauclair (2015): Auditory orienting of attention: Effects of cues and verbal workload with children and adults, Child Neuropsychology, DOI: 10.1080/09297049.2015.1041368 To link to this article: http://dx.doi.org/10.1080/09297049.2015.1041368

Published online: 02 Jun 2015.

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Date: 06 November 2015, At: 19:00

Child Neuropsychology, 2015 http://dx.doi.org/10.1080/09297049.2015.1041368

Auditory orienting of attention: Effects of cues and verbal workload with children and adults Marion Phélip1, Julien Donnot2, and Jacques Vauclair1

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Center for Research in the Psychology of Cognition, Language and Emotion (PsyCLE), Aix-Marseille University, Aix-en-Provence, France 2 French Air Force Research Center, Department of Human Factors and Operational Environment, Center for Research in the Psychology of Cognition, Language and Emotion (PsyCLE), Salon Air, France The use of tone cues has an improving effect on the auditory orienting of attention for children as for adults. Verbal cues, on the contrary, do not seem to orient attention as efficiently before the age of 9 years. However, several studies have reported inconsistent effects of orienting attention on ear asymmetries. Multiple factors are questioned, such as the role of verbal workload. Indeed, the semantic nature of the dichotic pairs and their load of processing may explain orienting of attention performance. Thus, by controlling for the role of verbal workload, the present experiment aimed to evaluate the development of capacities for the auditory orienting of attention. Right-handed, 6- to 12year-olds and adults were recruited to complete either a tone cue or a verbal cue dichotic listening task in the identification of familiar words or nonsense words. A factorial design analysis of variance showed a significant right-ear advantage for all the participants and for all the types of stimuli. A major developmental effect was observed in which verbal cues played an important role: they allowed the 6- to 8-year-olds to improve their performance of identification in the left ear. These effects were taken as evidence of the implication of top-down processes in cognitive flexibility across development. Keywords: Dichotic listening; Orienting of attention; Development; Verbal workload; Verbal cues.

Dichotic listening has mostly been used for assessing auditory laterality effects. In effect, by presenting at the same time two different stimuli, one in the left ear and one in the right ear, this paradigm measures lateralized differences in performance and thus gives access to hemispheric specialization (e.g., Bryden, 1988; Kimura, 1961, 1967; Obrzut, 1988). Studies using dichotic listening have shown that adults and children reported verbal stimuli presented to the right ear faster and more accurately than that presented to the left ear (Kimura, 1961; Studdert-Kennedy & Shankweiler, 1970; Wexler & Halwes, 1983). This right-ear advantage (REA) may result from a lefthemisphere specialization for verbal information processing. Conversely, auditory No potential conflict of interest was reported by the authors. Address correspondence to Marion Phélip, Center for Research in the Psychology of Cognition, Language and Emotion (PsyCLE), Aix-Marseille University, PSYCLE EA 3273, 13621, Aix-en-Provence, France. E-mail: [email protected]

© 2015 Taylor & Francis

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emotional stimuli are preferentially recognized via the left ear (left-ear advantage; LEA), presumably reflecting a right-hemisphere specialization for auditory emotional processing (Erhan, Borod, Tenke, & Bruder, 1998; Ley & Bryden, 1982; Mahoney & Sainsbury, 1987). Although auditory laterality effects have proven to be mostly reliable in previous research to put forward hemispheric specializations, attentional factors may also influence the apparent variability of performance in the two ears (Asbjørnsen & Hugdahl, 1995; Obrzut, Boliek, & Obrzut, 1986; Voyer & Flight, 2001). By attempting to identify verbal stimuli, participants may pre-activate their left cerebral hemisphere and thus facilitate stimuli processing in the right ear (Kinsbourne, 1970). To control as much as possible for the effect of these attentional biases, Treisman and Geffen (1968), followed among others by Bryden, Munhall, and Allard (1983) and Hugdahl and Andersson (1986), proposed to refine the dichotic listening situation by introducing attentional instructions with verbal cues that solicit a voluntary orientation of attention (M. Andersson, Llera, Rimol, & Hugdahl, 2008; Gadea & Espert, 2009; Hiscock & Beckie, 1993; Hugdahl, Carlsson, & Eichele, 2001; Obrzut, Boliek, & Asbjørnsen, 2006; Techentin & Voyer, 2005; Voyer & Flight, 2001). In their protocol, participants were directly forced to detect and correctly report stimuli heard in the orally indicated right or left ear. In comparison to a non-forced condition, this requirement always led to an amplification of the REA when adult participants had to report verbal stimuli heard in the right ear. Results from a forced-left (FL) condition were more contrasted, leading either to an attenuation of the REA (M. Andersson et al., 2008; Hiscock & Beckie, 1993; Hiscock, Inch, & Kinsbourne, 1999; Techentin & Voyer, 2005), or to the same amplification of the REA (Asbjørnsen & Hugdahl, 1995). Data collected from studying children (Hugdahl et al., 2001; Obrzut, Horgesheimer, & Boliek, 1999) reported that verbal cues were effective in efficiently orienting attention toward the indicated ear with children of at least 9 years of age. Below this age, children would be unable to efficiently use verbal cues. This deficiency in cognitive flexibility and inhibition processing is certainly due to an immature development of their frontal cortex (Kanemura, Aihara, Aoki, Araki, & Nakazawa, 2003; Li, Gratton, Fabiani, & Knight, 2013). However, the efficiency of verbal cues raises some questions (Mondor & Bryden, 1991, 1992). Based on research in the visual domain (Posner, 1980; Yantis & Jonides, 1990), Mondor and Bryden (1991) called into question the use of verbal cues for capturing attention. These authors considered that verbal cues, which solicit a voluntary orientation of attention like push cues (Posner, 1980; Posner & Petersen, 1990), selectively pre-activate the left hemisphere (Kinsbourne, 1970) and may additionally interfere with the observed effects of attention on ear asymmetries. Their proposition to orient attention with tone cues, which are less asymmetrically processed and solicit a more automatic orientation of attention like pull cues (Posner, 1980; Posner & Petersen, 1990), was designed to counterbalance the possible effects of these voluntary strategies. With adults, the results of a verbal recognition task led to an efficient orientation of attention with tone cues: not only was the REA amplified in forced-right (FR) trials compared to non-forced trials, but above all, observations showed an increasing LEA in FL trials from 150 ms to 450 ms stimulus-onset asynchrony (SOA, the time period between the onset of the cue and the onset of the stimulus; see Gadea & Espert, 2009; Obrzut et al., 2006; Voyer & Flight, 2001). Consequently, a 450 ms SOA, introduced between the onset of the tone cue and the onset of the trial, appeared to be an optimal delay for orienting attention automatically.

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Even if studies conducted in the visual domain (Leclercq & Siéroff, 2013; Müller & Rabbitt, 1989; Pearson & Lane, 1990; Posner, 1980; Wainwright & Bryson, 2002, 2005; Yantis & Jonides, 1990) showed a systematic control of time intervals with both central and peripheral cues, no such evaluations of time intervals have been undertaken with verbal cues in past auditory past research. To the authors’ knowledge, only one study, conducted with children of 10 years of age, controlled for the effect of a unique 450 ms SOA between the onset of verbal cues and the onset of trials (Obrzut et al., 2006) and it revealed a beneficial influence of verbal cues on the performance of orienting attention. Therefore, it is still not clear whether tone cues are more effective than verbal cues for orienting attention across development. Using consonant–vowel (CV) syllables, Hugdahl et al. (2001) showed that the REA could not be shifted into a significant LEA with verbal instructions until the ages of 10 to 15 years. However, Obrzut and his colleagues showed that, from around 6 years of age, children can efficiently direct their attention with verbal cues (and verbal instructions) to identify CV syllables as well as words spoken in four different emotional tones (Obrzut, Bryden, Lange, & Bulman-Fleming, 2001; Obrzut et al., 2006). Indeed, in the recent research of Donnot, Phélip, Blättler, and Vauclair (2014), children from 7 to 8 years of age were able to efficiently orient their attention with verbal cues when having to identify sentences made up of nonsense words and spoken in three different emotional tones. Thus, as suggested by Obrzut, Mondor, and Uecker (1993, p. 1415), “further investigation should assess both types of cueing procedures with the same group of subjects”. Indeed, previous studies as cited here suggest that, with the use of verbal cues, children from 10 years of age are able to control and orient their attention (Donnot et al., 2014; Obrzut et al., 2006). In other words, verbal cues may help these children to efficiently control their attentional resources. Nonetheless, these previous studies also point out another major factor influencing lateralized performance; the nature of the stimuli proposed in dichotic listening studies, namely the workload, has an impact on children’s performance. Dichotic tests administered with words, digits and CV syllables with children from 3 to 12 years of age have shown a decrease in magnitude of the REA with words and digits but not with CV syllables. Single syllables were thought to involve the highest verbal workload, and thus a more important verbal processing that amputated the allocation of attentional resources to the indicated channel (Lamn & Epstein, 1997; Moncrieff, 2011). The Control of Attention and the Nature of Stimuli Several studies have demonstrated that performance of identification differed among the types of semantic stimuli proposed in the dichotic trials (e.g., Moncrieff, 2011; Obrzut et al., 1986). Indeed, performance is highly based on the participants’ capacity to process these stimuli, which can refer to their level of difficulty or their lexical content (Findlen & Roup, 2011). Findlen and Roup (2011) rightly observed that young adults use lexical cues when processing speech in complex listening situations. Consequently, in general, digits, sentences and CVC words are all easier to identify than CV syllables because of their higher lexical content (Findlen & Roup, 2011; Moncrieff, 2011). Thus, Findlen and Roup observed in an adult population that, in both directed right and directed left conditions, overall performance was significantly poorer with nonsense CVC syllables than with CVC words, while the identification of CVC words led to a larger REA in FR trials and a larger LEA in FL trials. Similarly, dichotic listening performance may be due to the frequency or familiarity of the

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stimuli; frequent and/or familiar stimuli are easier to perceive than infrequent and/or unfamiliar stimuli (Techentin & Voyer, 2011). Consequently and more importantly, the classic REA can be modified by the lexical content or the level of familiarity of the semantic stimuli. When a dichotic pair includes a highly familiar or frequent stimulus only presented in the left ear, the REA can be considerably lowered and even replaced by an LEA. Therefore, to control for any effect of lexical content and familiarity on performance, the present study introduced two different types of words: familiar words and nonsense words. As a matter of fact, familiar words and nonsense words show a much higher lexical content than CV syllables, but differ in terms of familiarity. In addition, with our study being focused on children, we intended to propose stimuli that were not too arduous for this population: word stimuli have been proven to be easier to detect by children than CV syllables (Moncrieff & Black, 2008). In our experiment, we thus expected that children would obtain better dichotic listening performance—that is to say a higher accuracy raw score—with familiar words than with nonsense words. More specifically, in our “oriented” dichotic listening paradigm, we expected a larger REA with nonsense words than with familiar words; we hypothesized that children would more easily orient their attention toward the indicated left ear to create an LEA with familiar words. Concerning the cueing conditions, we expected that verbal cues would facilitate more allocation of attention toward the indicated ear with the two types of stimuli. We thus waited for better performance in the two ears in the verbal cues/familiar words condition and poorer performance in the tone cues/nonsense words condition. In fact, we intended in our study to investigate the unique role of the orientation of attention on performance. To this end, we chose to control as much as possible the factors that might also influence the allocation of attention by creating dichotic pairs with the same voice-onset time (VOT) (see more in the method section below; see also Rimol, Eichele, & Hugdahl, 2006; Techentin & Voyer, 2011). With a focus on children’s competence, the aim of the present study was thus to evaluate the development of the auditory orienting of attention. To this end, we not only compared the effect of the two cueing conditions (tone cues and verbal cues) on the capacity to orient attention, but we also controlled for the influence of verbal workload (with the use of familiar words and nonsense words). Participants were composed of two groups of children, and adults: the two groups consisted of a group of 6- to 8-year-olds, the age range of which should be typical of immature attentional capacities, and a group of 10- to 12-year-olds, the members of which should have developed the required cognitive resources to efficiently orient their attention (M. Andersson et al., 2008; Hiscock & Beckie, 1993; Mondor & Bryden, 1991, 1992; Techentin & Voyer, 2005). According to the conclusions obtained in the literature, we firstly expected that the 10- to 12-year-olds and the adults would both give a better performance of identification than the younger group for both types of cues. Tone cues were thought to be more efficient than verbal cues for orienting the 6- to 8-year-olds’ attention. Indeed, only children above 9 years of age should be able to efficiently orient their attention using verbal cues and control it as adults do (M. Andersson et al., 2008; Hugdahl et al., 2001). Below this age, children should have more accurate detection rates for tone cues (Obrzut et al., 1999). Secondly, we hypothesized that the identification of familiar words would lead to better performance in the two ears for all the participants than the identification of nonsense words in the two cuing conditions.

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METHOD

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Participants A total of 170 participants volunteered to take part in this study. Adults, whose age range varied from 18 to 55 years (N = 49), were recruited at the Aix-Marseille University, Aix-en-Provence, France. Children aged from 6 to 8 years of age (N = 65) and 10 to 12 years of age (N = 56) were recruited from regular education classrooms in two French elementary schools (Leonard de Vinci and Emilie de Rodat in Toulouse, France). The headmasters of each elementary school gave their formal consent to run the study and written consent was obtained from all participants (including the children’s parents). Participants’ handedness was controlled with a revised version of the Oldfield Edinburgh Handedness Inventory (Donnot & Vauclair, 2007; Oldfield, 1971); only right-handers took part in the study. Teachers were also asked to participate in the selection of participants by only considering children whose school performance was not deviant. Prior to the experiment, auditory acuity was assessed (a) by asking participants and their parents to declare any present or prior history of auditory problems or impairments, and (b) by conducting a familiarization phase in which all the stimuli were presented binaurally and at the same intensity for each participant. Participants who were unable to distinctively identify the stimuli heard in the familiarization phase were excluded. This procedure led to the exclusion of two participants: one child in the youngest age group and one adult. All the remaining participants (N = 168) completed the test phase, that is, 64 6- to 8-year-olds (mean age = 7.07, SD = 0.58, 33 boys, 31 girls), 56 10- to 12-yearolds (mean age = 10.67, SD = 0.34, 24 boys, 32 girls) and 48 adults (mean age = 25.65, SD = 9.99, 17 men, 31 women). Stimuli and Cues Stimulus material. The experimental material consisted of two different types of stimuli: familiar words and nonsense words. Participants performed either the familiar word task or the nonsense word task. In short, participants were only asked to identify one type of stimuli. [PARA]The first set of stimuli consisted of six familiar French disyllabic words, chosen for their high familiarity at 6 years of age (Lété, Sprenger-Charolles, & Colé, 2004), namely the words panier [panjεʀ] (basket), papier [papje] (paper), paquet [pakε] (parcel), bague [bag] (ring), balai [balε] (broom), and bateau [bato] (boat). The particularity of these stimuli results in the voicing of the syllables, a phonological concept that describes the vocal cord vibration during the articulatory process. The three consonants /b/, /d/, and /g/ are voiced, whereas the three consonants /p/, /t/, and /k/ are unvoiced. Rimol et al. (2006) found that when combined together within a dichotic pair, unvoiced syllables dominate over-voiced syllables, whatever the ear indicated. These results demonstrate that VOT significantly affects ear-advantage and plays a greater influence on dichotic listening performance than the classic REA effect. Thus, as a methodological precaution, dichotic pairs of words and nonsense words were not formed randomly. Instead, stimuli were associated among a phonemic similarity rule: dichotic pairs were made of stimuli with the same VOT consonant. Six dichotic pairs were created with the words bague, balai and bateau, and six other pairs were created with the words panier, paquet, and papier. In total, twelve

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different dichotic pairs were administered. Durations of stimulus presentation varied from 0.45 s to 0.60 s. The last set of stimuli was made up of six disyllabic nonsense words, bonin [bonε]̃ , bolin [bolε]̃ , bovan [bovɑ̃ ], damon [damɔ̃], darou [daRu], and daveau [davo]. As for the familiar word pairs, dichotic pairs were made up of words with the same VOT (Rimol et al., 2006). Their durations varied from 0.48 s to 0.55 s. A French male voice synthesizer recorded all our stimuli; the sampling rate was 22 kHz with 32-bit resolution. Stimuli were presented on a Dell laptop computer running DMDX (Forster & Forster, 2003), and were played through Sennheiser HD headphones. Cues. Participants were instructed to report the stimulus heard in the ear indicated either by a monaural tone cue or by a binaural verbal cue. Tone cues were recorded at a sampling rate of 44 KHz with 32-bit resolution, and their duration was of 100 ms (Mondor & Bryden, 1991). Verbal cues consisted of the words “left” or “right” (in French in the experiment) that instructed participants to report the stimulus heard in the indicated ear. Their duration was 550 ms and cues were recorded at the same sampling rate and resolution as before. Because we used two types of cues, which have different durations in the current study, it seemed appropriate to control for the interstimulus interval (ISI) instead of the SOA, that is the time interval between the end of the cue and the beginning of the stimulus. Two different ISIs of 400 ms and 1000 ms were chosen. The 400 ms ISI was considered an optimal duration for orienting attention both with tone cues and verbal cues, whereas the 1000 ms ISI suggested a larger engagement of voluntary attention (Camus, 1996; Obrzut et al., 1999, 2006; Siéroff, 1998, 2001). Procedure As mentioned earlier, our experimental paradigm included two different orienting conditions (tone cues or verbal cues) as well as two different types of stimuli (familiar words or nonsense words), creating four different experimental dichotic tests: tone cues with familiar words, tone cues with nonsense words, verbal cues with familiar words, and verbal cues with nonsense words. Participants only completed one of these four conditions. The two variables Nature of stimuli (familiar words and nonsense words) and Cueing conditions (verbal cues and tone cues) were designated as between-subjects variables. Similar instructions were given regardless of the type of stimuli and orienting condition. Participants were told that they should only identify the stimulus heard in the cued ear. Each participant performed 48 trials featuring the different combinations of forced ear (right, left), dichotic pairs (twelve pairs available for each task), and ISIs (400 ms or 1000 ms). In order to maximize the mobilization of attentional resources in the younger children, we divided the test into two parts, each comprising 24 trials, with a short 5minute break in between. Within these two parts, trials were randomized across participants and separated by a 4-s inter-trial interval. Children were tested individually at school in a quiet, empty room, whereas adults completed the test in a laboratory room at the AixMarseille University. Responses were gathered orally. Results were analyzed in terms of mean correct responses and raw scores.

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Prior to the test, we administered a familiarization phase where participants had to (a) correctly identify all the corresponding stimuli heard binaurally (this procedure was repeated twice) and then (b) perform six oriented dichotic practice trials (approximate duration: 10 minutes).

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RESULTS Given the wide range of adult participants (18 to 55 years of age), a preliminary analysis was conducted to examine the possible correlations between age and mean overall accuracy responses. No significant correlations were found (r(46) = −.07, p > .05). Moreover, an omnibus analysis of variance (ANOVA), excluding the adults older than 40, did not reveal changes in the results. As a consequence, it was not necessary to exclude any adult participants from further analyses. A second preliminary ANOVA with repeated measures also aimed to control for the possible effects of gender. No simple effect of gender (F(1, 141) = 0.01, p = .91, η2 = .001) was found, and there were no two-way interaction effects with ear (F(1, 141) = 2.89, p = .09, η2 = .02) or age (F(2, 141) = 2.71, p = .07, η2 = .04). Consequently, we ran our analyses without taking these factors into account. An omnibus ANOVA mixing the within-subjects variables Ear of target (left or right) and ISIs (400 ms or 1000 ms) and the between-subjects variables Nature of the stimuli (familiar words or nonsense words) and Cueing condition (tone cue or verbal cue) was performed. A simple effect of age was obtained, F(1, 156) = 60.72, p < .001, η2 = .44 (M = 0.83, SD = 0.14 for adults; M = 0.76, SD = 0.14 for 10- to 12-year-olds; M = 0.71, SD = 0.16 for 6- to 8-year-olds). Dunn-Bonferroni post hoc t tests showed that performance of the 6- to 8-year-olds was weaker than that of their older peers, t(118) = 6.53, p < .001, η2 = .26, and that of the adults, t(110) = 8.61, p < .001, η2 = .41. However, the adults and the 10- to 12-year-olds gave a similar performance, t(102) = 2.41, p > .05, η2 = .05. It also appeared that the participants identified nonsense words less easily than familiar words (M = 0.80, SD = 0.16 for familiar words; M = 0.63, SD = 0.16 for nonsense words), according to the observed simple effect of stimulus type, F(2, 156) = 74.46, p < .001, η2 = .32. Figure 1 shows the mean percentage of correct responses by task as a function of age.

Figure 1 Mean accuracy responses in percentages (and SDs) by age as a function of stimulus type.

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Figure 2 Mean accuracy responses in percentages (and SDs) by age as a function of cue condition and ears of target (LE = left ear; RE = right ear).

Moreover, the identification of both types of stimuli led to a significant REA, F(1, 156) = 16.26, p < .001, η2 = .09, which was compromised by an Age × Ear of target interaction, F(2, 156) = 5.24, p = .006, η2 = .06. A trend interaction effect between the Ear of target and the Nature of stimuli is also noted, F(1, 156) = 3.59, p = .06, η2 = .02. As a consequence, we observed a three-way interaction between the age of participants, Ear of target and Cueing condition, F(2, 156) = 3.55, p = .03, η2 = .04, as seen in Figure 2. These results indicate that, in the tone cue condition, the younger children displayed a major REA. Indeed, while verbal cues yielded similar performance in both ears for all the participants, even the youngest ones [t(31) = −1.46, p = .15, η2 = .006 for the 6- to 8year-olds; t(27) = −0.58, p = .56, η2 = .006 for the 10- to 12-year-olds; t(23) = −1.27, p = .22, η2 = .01 for the adults], Dunn-Bonferroni post hoc t tests showed that, with the use of tone cues, performance of identification of the 6- to 8-year-olds was higher in the right cued ear than in the left cued ear [t(31) = −4.64, p < .001, η2 = .15 for the 6- to 8year-olds; t(27) = −0.11, p = .91, η2 = .0001 for the 10- to 12-year-olds; t(23) = −1.63, p = .12, η2 = .01 for the adults). Finally, a simple effect of ISIs, favoring the longer delays, was found. Participants tended to improve their performance of identification when more time was given to orient their attention toward the indicated ear (M = 0.70, σ = 0.018 for a 400 ms ISI; M = 0.72, σ = 0.016 for a 1000 ms ISI). However, this effect did not generate an ISIs × Cueing condition interaction effect, F(1, 156) = 0.08, p = .77, η2 < .001. DISCUSSION The main aim of the present study was to evaluate the development of auditory orienting of attention abilities. To this end, we intended to extend and clarify the findings of previous studies (e.g., Hiscock & Beckie, 1993; Hugdahl et al., 2001; Mondor & Bryden, 1991, 1992) by evaluating within the same study the role of tone cues and verbal cues on the performance of orienting attention. Our paradigm allowed controlling for time interval effects both with tone cues and verbal cues. Observations had so far shown that, before 9 years of age, tone cues are more efficient for orienting attention and modulating the REA reported during verbal tasks. However, after this

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age, these cues would seem to be as efficient as, or even less efficient than, verbal cues for orienting attention across the two ears. Results showed a major developmental effect in which verbal cues play a particular role in the ability to efficiently orient attention compared to tone cues. Indeed, by contrast to past dichotic listening studies using verbal stimuli (Hugdahl & Andersson, 1986; Hugdahl et al., 2001), we observed that children younger than 9 years of age were fully able to efficiently orient their attention onto the left non-advantaged ear with verbal cues. These conclusions happened to be independent of any time interval effect. In order to deepen our research, we also controlled for the impact of verbal workload on orienting attention capacities. Here, if the verbal processing of familiar words happened to effectively be less demanding than the processing of nonsense words, it did not impact the allocation of resources required for orienting attention. Firstly, it occurred that the global performance of the younger children was significantly lower than that of the older children and the adults. Global performance rate showed, in effect, a major developmental effect. The 6- to 8-year-olds did not succeed in identifying the stimuli presented in their left and right ears as easily as their older peers and the adults did. This finding is the line with several past studies where performance of identification has been shown to improve with age (e.g., B. Andersson & Hugdahl, 1987; M. Andersson et al., 2008; Donnot et al., 2014; Hugdahl et al., 2001). By leaning on neuroanatomical studies (Kanemura et al., 2003; Li et al., 2013), our results anticipated a lack of cognitive flexibility and inhibition in children under 9 years of age. Certainly because their frontal cortex is not yet fully developed, young children may lack the cognitive flexibility and the inhibition necessary to orient their attention as efficiently as older children and adults. Secondly, we observed that only the 6- to 8-year-olds did not succeed in overcoming the REA induced by the identification of verbal stimuli (Asbjørnsen & Hugdahl, 1995; Mondor & Bryden, 1991; Obrzut et al., 1999), when their attention was oriented automatically via tone cues. Whereas the 10- to 12-year-olds and the adults obtained comparable performance between the two ears in the two cueing conditions, the 6- to 8-year-olds showed a significant REA with tone cues. These results are in agreement with the study of Obrzut et al. (1999), conducted on a population of children of around 8 years of age. In contrast to the adults, who demonstrated an attenuation of the REA when sufficient opportunity to orient attention to the left ear was available (Mondor & Bryden, 1991), Obrzut et al. (1999) showed that children are not able to attenuate the magnitude of the REA to the left ear when attention is oriented with tone cues. Notwithstanding, orienting auditory attention with verbal cues in our study allowed the youngest children to identify the verbal stimuli similarly between both ears. In FL conditions, the engagement of a voluntary orientation of attention with verbal cues led to a reduction of the magnitude of the REA observed with tone cues. The 6- to 8-year-olds mostly benefited from verbal cues than tone cues for efficiently orienting their attention towards their left non-advantaged ear to identify the corresponding stimuli. Even though these last observations counter the conclusions of a major part of the literature, they also are supported by some former data. Sexton and Geffen (1979) proposed that the ability to focus and divide attention to dichotically presented linguistic stimuli, with the use of verbal cues, is established before the age of 7 years. B. Andersson and Hugdahl (1987) demonstrated an increase of the LEA in FL attention conditions with 8-year-olds. Hiscock and Beckie (1993) even suggested that 7- to 10-year-olds are able to modify the REA when instructed to do so. Thus, the comparison within the same study of the effects of

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verbal cues and tone cues, as suggested by Obrzut et al. (1993), allowed us to clarify the enhancing effect of verbal cues over tone cues on capacities for orienting attention, especially for children below 10 years of age. To us, this specific role of verbal cues results from the larger pre-activation of the top-down processes that they engage, in contrast to tonal cues, and which are essential for efficiently controlling attention in forced-attention conditions. Indeed, as suggested by Westerhausen and Hugdahl (2010), the observed modulation of the REA in FL conditions, which is not seen in (FR) conditions, is linked to cognitive control functions related to executive processes. When using verbal stimuli like CV syllables in FR conditions, participants are required to report the stimulus that is preferred, because of a left-hemisphere advantage for verbal stimuli. In contrast, in FL conditions, the top-down attentional cues have to overcome the structural preference for the right ear. Therefore, whereas FR conditions only call for the selection of the bottom-up salient stimulus, FL conditions require the ability to inhibit the salient stimulus heard in the other ear and to report the weaker left-ear stimulus. As mentioned earlier, verbal cues solicit a voluntary orientation of attention that is conveyed by top-down processes. In FL conditions, we assume that verbal cues increase the performance of identification by massively pre-activating the topdown processes needed to control attention (Hugdahl, 2000; Hugdahl et al., 2009; Westerhausen et al., 2010, 2011). Tone cues, which solicit an automatic orientation of attention, are far less conveyed by these top-down processes and did not lead to the same observations. The recruitment of top-down processes, activated by the frontal cortex, appears to constitute a major difficulty for children under the age of 9 (Hwang, Velanova, & Luna, 2010; Li et al., 2013). In effect, in our study, 6- to 8-year-olds did not succeed in controlling their attention as efficiently with tone cues as with verbal cues. According to the neuro-developmental research of Falkenberg, Specht, and Westerhausen (2011), the activation of top-down processes, which play a major role in cognitive flexibility, seems to be largely dependent upon the frontal cortex. Thus, for 6- to 8-year-olds showing a still immature development of the frontal cortex, verbal cues might have more easily solicited the top-down processes implicated in cognitive flexibility than tone cues. We also controlled for the implication of time intervals on orienting attention performance, both with tone cues and verbal cues. In reference to past studies, we expected a differential effect of ISI depending on the cueing condition. We thought that the short 400 ms ISI would favor the orientation of attention with tone cues better than the longer 1000 ms ISI (Gadea & Espert, 2009; Mondor & Bryden, 1991, 1992; Obrzut et al., 1999). As for verbal cues, hypotheses were not that clear; we only expected correct performance with the 400 ms ISI (Obrzut et al., 2006). As a matter of fact, all our participants showed significantly higher performance of identification with the 1000 ms ISI than with 400 ms ISI, and this was the case for both types of cueing condition. Long time intervals allowed participants, even the youngest ones, to orient their attention more efficiently toward the indicated ears and to more efficiently identify the corresponding stimuli. Previous studies did not suggest such an enhancing effect of longer time intervals. For adults as for children, it appeared that performance of the identification of CV syllables was not improved by longer time intervals (beyond 450 ms SOA). This absence of consensus upon the impact played by time intervals on orienting attention capacities leaves the debate open. Our study, which is the first to propose controlling for time

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intervals with verbal cues, will need to be replicated and refined in order to provide clearer and more conclusive results. As a final point, we observed that all three groups of participants more easily identified the familiar words than the nonsense words (Findlen & Roup, 2011; Lamn & Epstein, 1997; Moncrieff, 2011). However, contrary to our predictions, the verbal workload of the two kinds of stimuli did not impact on the magnitude of the REA. We expected a reduction of the magnitude of the REA with familiar words, and thus a stronger advantage for the right ear with nonsense words. Nevertheless, performance of identification in the right and left ears was similar between the familiar words condition and the nonsense words condition. As stated earlier, the results showed that the 10- to 12-yearolds and the adults more easily identified both types of stimuli with the right ear than with the left ear. As for the 6- to 8-year-olds however, the observed REA was not attenuated by the nature of the words. Contrary to Findlen and Roup (2011), we found that the verbal workload of stimuli had no effect on the setting of auditory orienting of attention across development. We intend to explore this point in greater depth in future studies, in order to investigate the relations between the processing of stimuli and the capacity for orienting attention. Limits of the Present Study It should be noted that the present study did not include a non-forced attention condition. Observations were only based upon forced attention conditions (FL and FR attention conditions). Several former studies that have investigated cerebral laterality effects and attentional biases with dichotic listening situations have reported that the identification of verbal stimuli led to an automatic REA for non-forced attention conditions (e.g., Asbjørnsen & Hugdahl, 1995; Mondor & Bryden, 1991; Obrzut et al., 1999). In these non-forced conditions, the results of past studies have indicated that adults and children always manifest an REA during the identification of words or nonsense words such as CV syllables, digits, CVC words, and CVC nonsense words (Findlen & Roup, 2011; Hiscock et al., 1999; Moncrieff & Black, 2008; Obrzut et al., 1986; Saetrevik, 2012). A French study using monosyllabic and disyllabic words with children aged from 3 to 6 years even revealed an REA that was independent of the stimuli’s nature (Michel, Labourel, Canonge, Rochefort, & Elliot, 1980). By leaning on this major consensus, we stated in this study that our verbal stimuli would be preferentially identified in the right ear by all our participants as opposed to the left ear, and decided not to propose a non-forced condition. The purpose of the present research was not to demonstrate once again the advantage of the right ear in verbal dichotic listening tests but rather to compare the effects of verbal cues and tone cues on the capacities for orienting attention. Although we chose to only compare the effect of tone cues over verbal cues on the capacity for orienting attention, we do not dismiss their mutual role as attentional biases of laterality asymmetries. Thus, we intend to include non-forced conditions in future studies. We intended, in this research, to create a test well suited to younger children’s attentional resources, and thus we did not want the duration of any protocol to overload their attentional capacities and thus form a bias. As we had concerns about the creation of the dichotic listening test, we made experimental choices that limited our observations; we only proposed 48 trials and we manipulated the cueing conditions as a between-subjects variable. We are completely aware of the limits that these choices represent. An increasing

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number of trials would have strengthened the stability of our results and a within-subjects set-up would have been better for comparing performance under different experimental conditions. It is obvious that future studies will be enhanced by increasing the number of trials and by manipulating the cueing conditions as a within-subjects variable in order to optimize performance comparison. Original manuscript received November 17, 2014 Revised manuscript accepted April 10, 2015 First published online June 1, 2015

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