Methods

Participants

A total of 70 Catalan–Spanish (CS)-speaking children (22 girls and 48 boys), 35 children with developmental language disorder (DLD-CS, MAge = 8;9) and 35 chronological age- and sex-paired-wise-matched typically development children with normal language (TD-CS, MAge = 8;9) participated in Experiment 1. The children with DLD-CS were recruited from institutions, organizations and schools around Catalonia. Children with DLD-CS were identified with the help of the Catalan Center of Resources for Hearing-Impaired People (CREDA), members of the Catalan service for school counselling and guidance (EAP), and Catalan Association of Specific Language Impairment (ATELCA), which work in conjunction with public and private schools throughout Catalonia to identify children with DLD-CS or children with language difficulties. The children with TD-CS were recruited from public schools within the larger Barcelona metropolitan area. All participating families completed an informed consent form and a background information questionnaire. A final report containing the results of all the tests administered to the children was given to the family as a token of gratitude for their commitment and contribution to the study.

All participants met the following inclusion criteria: (1) normal non-verbal intellectual quotient (NVIQ) ≥ 75; (2) normal hearing at 500, 1000, 2000 and 4000 Hz at 20 dB based on the American National Standards Institute (1997); (3) normal or corrected-to-normal vision; (4) normal oral and speech motor abilities by a certified speech–language pathologist; and (5) were native bilingual Catalan–Spanish speakers.1 Children were excluded if parents reported: (1) a neurodevelopmental disorder, (2) emotional or behavioural disturbances, (3) frank neurological signs or (4) seizure disorders or use of medication to control seizures.

The children in the DLD-CS group had a formal diagnosis of language impairment or were in process to be diagnosed and were receiving speech–language services at the time of the study. The TD-CS children were at grade level in school had no history, or diagnosis, of language-learning disability and had never received speech and language services. To confirm participant's language status, standardized testing was completed by two trained researchers at the time of the study and included the Nonverbal Kaufman Brief Intelligence Test (K-BIT; Kaufman & Kaufman, 2004), and Clinical Evaluation of Language Fundamentals—Fourth Edition, Spanish (CELF-4-Spanish; Wiig et al., 2006):2 (1) Core Language score, (2) Expressive Language score and/or (3) Receptive Language score. For the children with DLD-CS, either Core, Receptive or Expressive CELF composite scores were ≥ 1.5 SD below age level expectations. For the children in the TD-CS group, CELF composite scores were all at or above age level expectations (Table 1). Non-verbal IQ was within normal limits for all the participants and the two groups did not differ in age or in the number of females/males per group (22 females, 24 males). In addition, to investigate whether children's SWL is related to their receptive and expressive vocabulary, all children also completed the Peabody Picture Vocabulary Test, Third Edition, Spanish version (PPVT-III; Dunn et al., 2006), and the expressive vocabulary portion of the Spanish version of the Kaufman Brief Intelligence test (K-BIT-Voc; Kaufman & Kaufman, 2004).

TABLE 1. Age and standardized scores for language and cognitive assessment measures for Catalan–Spanish (CS)-speaking children with developmental language disorder (DLD-CS) and typically developing (TD-CS) children DLD-CS (n = 35) TD-CS (n = 35) Comparison Variable Mean SD Range Mean SD Range t(68) p-value Age (months) 105.34 21.27 66–155 107.80 21.26 67–153 –0.48 0.63 K-BIT (IQ)a 99.08 11.69 82–119 103.51 9.76 88–125 –1.72 0.09 CELF-CLSb 72.57 10.89 45–89 108.74 6.09 95–125 17.14 < 0.01 CELF-ELSc 73.22 8.77 52–87 108.45 8.11 89–128 –17.43 < 0.01 CELF-RLSd 77.45 10.19 59–97 105.82 5.55 94–118 14.45 < 0.01 Concepts & Directionse 5.80 2.30 1–10 11.66 1.71 8–15 –12.09 < 0.01 K-BIT vocf 77.14 11.65 53–96 106.40 10.20 83–127 –11.17 < 0.01 PPVT-IIIg 77.80 11.87 55–105 106.25 12.59 83–127 –9.72 < 0.01 Note: aK-BIT IQ: Kaufman Brief Intelligence, Spanish version: Non-verbal intelligence score (Kaufman & Kaufman, 2004) Scaled scores (M = 100, SD = 15). bCELF-4 CLS = Spanish Clinical Evaluation of Language Fundamentals, 4th Edition: Core Language score (Wiig et al., 2006). Scaled scores (M = 100, SD = 15). cCELF-4 ELS = Spanish Clinical Evaluation of Language Fundamentals, 4th Edition: Expressive Language score (Wiig et al., 2006). Scaled scores (M = 100, SD = 15). dCELF-4 RLS = Spanish Clinical Evaluation of Language Fundamentals, 4th Edition: Receptive Language score (Wiig et al., 2006). Scaled scores (M = 100, SD = 15). eClinical Evaluation of Language Fundamentals (Wiig et al., 2006): Oral Directions Receptive Subtest Score (M = 10, SD = 3). fK-BIT vocabulary = Kaufman Brief Intelligence, Spanish version: Expressive vocabulary score (Kaufman & Kaufman, 2004) Scaled scores (M = 100, SD = 15). gPPVT-III = Peabody Picture Vocabulary Test, Third Edition, Spanish version (Dunn, Dunn & Arribas, 2006) Scaled scores (M = 100, SD = 15). Significance of the p-values is shown in bold.

Stimuli

Because the goal of the present study was to extend the findings from Evans et al. (2009) to a group of Catalan–Spanish children, the stimuli for the present study was the tone language used by Evans et al. (2009) and tone language 1 from Saffran et al. (1999). The tone language consisted of 11 pure tones taken from the same octave (starting at middle C within the chromatic set A, B, C, C#, D, D#, E, F, F#, G, G#). Each pure tone was created using the SoundEdit 16 sine wave generator (Adobe, San Jose, CA, USA) and was 0.33 s in duration. The tones were combined to create a total of six, three-syllable tone words. The tone words did not conform to rules of standard melodic or musical composition. Some tones appeared in only one word whereas other tones occurred in more than one word. For example, D occurred in four of the tone words whereas G# only occurred in one of the tone words (Table 2).

TABLE 2. Transitional probability of tone words and non-words Stimuli Internal transitional probability Tone words GG#A 1.0 CC#D 0.75 D#ED 0.65 FCF# 0.50 DFE 0.42 ADB 0.37 Tone non-words AC#E 0.0 F#G#E 0.0 GCD# 0.0 C#BA 0.0 C#FD 0.0 G#BA 0.0

The six tone words were combined in a random order with no silent junctures between the words to create a 21-min continuous stream of tones where an individual tone word never occurred twice in a row. The transitional probability within the tone words ranged from 0.37 to 1.00, whereas the transitional probability across the tone word boundaries ranges from 0.05 to 0.60. This overlap in the transitional probabilities within and across the word boundaries occurred three times in the 30 across-word tone pairs resulting in this across word probability of 0.60. This 0.60 probability occurred when the tone word GG#A was followed by the tone word DFE, as the cross-boundary sequence AD also occurred in the tone word ADB. In addition to the six tone words, six tone non-words were created (Table 2). These non-words were made up of the same tones from the language tone inventory, but because they never occurred in that order during the exposure the internal transitional probability of the non-words was 0.0.

The same two-alternative forced choice (2AFC) test as in Evans et al. (2009) was used to measure children's ability to use transitional probability to discover the boundaries of the tone words within the stream of tones. The six tone words and non-words listed in Table 2 were paired exhaustively to generate a 36-item test. Each test trial consisted of a tone word plus non-word pair. The tone word occurred as the first member of the pair for half of the test items and as the second member of the pair for the remaining test items. The order of test items with the tone word as the first item in the pair was counterbalanced across the trials and the order of the trials was randomized. The test items were recorded onto a digital recorder and presented in the same fixed random order to all the participants.

Procedure

Similar to Evans et al. (2009), the children listened to the continuous stream of tones while colouring pictures. To avoid potential ceiling effects, the Catalan–Spanish study was designed to mirror that of Saffran et al. (1999), and the children heard the exposure stimuli for a total of 21 min. Prior to the task, children were told:

You are going to have about 20 min to colour. While you are colouring, some weird computer music will be playing in the background, but I would like you to focus on painting. When the music has finished, I will ask you some questions.

The examiner sat quietly behind the children during the task to ensure they were focused on the colouring task and were not distracted. At the end of the 21 min of exposure, children completed the test trials. Children were instructed to choose the sound sequence that sounded most familiar to the word tone stream from among two alternatives.

Prior to the testing phase, children completed a series of practice trials. Practice trials consisted of pairs of short melodies created from familiar Catalan–Spanish children's songs in a correct and incorrect order (e.g., the tune, without words, from ‘Quan les oques van al camp’ versus ‘les van camp al quan oques’). For the practice trials children were told:

Now you are going to hear two sets of sounds and I want you to choose the set of sounds that sounds most like the weird computer music. If you do not know, it is ok to guess. First, we will practice. We're going to hear two different sets of sounds. I want you to tell me verbally if the ‘one’ set or the ‘two’ set sounds more like the song you know.

After completing the practice phase children completed the test trials. All the children completed all the practice trials successfully and no children were excluded from the study because they were unable to understand the task.