British Journal of Developmental Psychology (2012), 30, 326–343 C 2011 The British Psychological Society
The British Psychological Society www.wileyonlinelibrary.com
Differences between girls and boys in emerging language skills: Evidence from 10 language communities M˚arten Eriksson1 ∗ , Peter B. Marschik2 , Tiia Tulviste3 , Margareta Almgren4 , Miguel P´erez Pereira5 , Sonja Wehberg6 , Ljubica Marjanoviˇc-Umek7 , Frederique Gayraud8 , Melita Kovacevic9 and Carlos Gallego10 1
Faculty of Health and Occupational Studies, University of G¨avle, Sweden Institute of Physiology, Center for Physiological Medicine, Medical University of Graz, Austria 3 Institute of Psychology, University of Tartu, Estonia 4 University of the Basque Country, Vitoria-Gasteiz, Spain 5 Department of Developmental and Educational Psychology, University of Santiago de Compostela, Spain 6 Institute of Language and Communication, University of Southern Denmark, Denmark 7 Department of Psychology, University of Ljubljana, Slovenia 8 Dynamics of Language, University of Lyon, France 9 Laboratory for Psycholinguistic Research, University of Zagreb, Croatia 10 Department of Psychology, Complutense University of Madrid, Spain 2
The present study explored gender differences in emerging language skills in 13,783 European children from 10 non-English language communities. It was based on a synthesis of published data assessed with adapted versions of the MacArthur-Bates Communicative Development Inventories (CDIs) from age 0.08 to 2.06. The results showed that girls are slightly ahead of boys in early communicative gestures, in productive vocabulary, and in combining words. The difference increased with age. Boys were not found to be more variable than girls. Despite extensive variation in language skills between language communities, the difference between girls and boys remained. This suggests that the difference is caused by robust factors that do not change between language communities.
Correspondence should be addressed to Associate professor M˚arten Eriksson, Faculty of Health and Occupational Studies, University of G¨avle, SE-801 76 G¨avle, Sweden (e-mail: [email protected]
Differences between girls and boys in early language
Girls and boys are similar at birth in that neither gender talk. In their well-known review of gender differences in cognitive functioning, Maccoby and Jacklin (1974) concluded that girls matured more rapidly in verbal abilities than boys but did not find solid evidence for this divergence before the age of 11 years. Hyde and Linn (1988) reported a small girl advantage but no developmental trend in a meta-analysis of gender differences in verbal ability including the studies of Maccoby and Jacklin (1974) as well as later ones. No child younger than 3 years was included in these studies and participants were restricted to those living in the United States or Canada. In a more recent study Bornstein, Hahn, and Haynes (2004) reported that American girls scored higher than American boys on a multitude of language measures, including spontaneous speech, caregiver reports, and formal testing from age 2 to 5 years. Thus, although many studies indicate that girls are slightly ahead of boys in verbal skills, there seems to be some confusion about the timing when girls start to outperform boys. Further, the majority of research on early child language acquisition has been carried out in a mono-language, mono-cultural setting (English/American). Such studies are particularly vulnerable to confounding variables in questions of nature versus nurture. Therefore, comparative studies of child language in multiple linguistic and cultural settings are considered to be of special value (Bornstein, 2002; Bornstein et al., 2004). The present study extends previous research on gender differences in language by investigating emerging language skills in a large sample of children from 10 non-English language communities, thereby making it less vulnerable to cultural and linguistic biases. Both differences in mean language skills and differences in variability between girls and boys will be studied.
Gender differences in language for children before age 3 Comprehensive studies on gender differences in verbal ability for children below the age of 3 years have mainly been performed with parent report instruments, such as the MacArthur-Bates Communicative Development Inventories (CDIs) (e.g., Fenson et al., 1994, 2007). Based on the CDI norming study, Fenson and colleagues (1994, 2007) reported a girl advantage that accounted for about 1–2% of the variance in a study that included 2,550 American children aged 0.08–2.06 (year; months). The girl advantage concerned gestures as well as vocabulary comprehension and vocabulary production. However, an interaction between gender and age (the difference increasing with age) was only reported for vocabulary production and only in children aged 0.08–1.04. The scarcity of reported interactions between gender and age on language skills is surprising because gender differences are recurrently reported and an interaction with age is to be expected for any emerging skill in which girls and boys are going to differ. In another large-scale study based on a short version of the CDI, Galsworthy, Dionne, Dale, and Plomin (2000) found a girl advantage in a study of over 3,000 2-year-old British children that accounted for about 3% of the variance in vocabulary production. Thus, metaanalyses and large-scale parental reports suggest that there is a consistent girl advantage in early language acquisition, at least for children acquiring English. This advantage has only been reported occasionally to interact with age. The CDI instrument has been adapted and normed for several non-English cultures and languages. The results from these norming studies are complex concerning differences between girls and boys. Many reported a girl advantage for at least one language skill, primarily word production (for Danish, Bleses et al. 2008; for Estonian, Tulviste, 2007; for French, Kern, 2007; for Slovene, Marjanoviˇc-Umek, Fekonja, Kranjc, & Bajc, 2008; for Spanish, Gallego & Mariscal, 2008), more rarely for word comprehension (for Basque, Garc´ıa, Ezeizabarrena, Almgren, & Errarte, 2005; for Danish, Bleses et al.,
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2008) and gestures (for Danish, Bleses et al., 2008; for Swedish, Eriksson & Berglund, 1999). In contrast, no gender difference was reported by Jackson-Maldonado and colleagues among children acquiring Mexican-Spanish (Jackson-Maldonado, Thal, Bates, Marchman, & Gutierrez-Clellen, 1993), by Berglund and Eriksson (2000) for Swedishspeaking children or by Kern & Gayraud (2007) for preterm children acquiring French. However, some of these studies are limited by small sample size and the inclusion of age is inconsistent (different age intervals are used, if age is included at all). Because age explains a major part of the variance in children’s language skills, it is crucial to include age in a consistent way in statistical models. Few cross-linguistic and cross-cultural studies on early language acquisition have been performed in relation to gender differences. In one such rare study, Bornstein and Cote (2005) reported that girls aged 1.08 had larger vocabularies than boys of the same age across languages as well as urban and rural settings. The study was conducted in three countries comparing children from the United States, Argentina, and Italy. Social explanations to gender differences in language Many theories of gender differences (e.g., the gender role socialisation theory by Jacklin & Baker, 1993 or the social role theory by Eagly, Wood, & Diekman, 2000) stress the influence of the social environment on various cognitive domains, including language. For example, parents typically choose gender-typed toys even for very young children (Fagot, 1995). Caldera, Huston, and O’Brian (1989) argued that the action-oriented toys, more likely bought for boys, do not stimulate language in the same way as the more caring-oriented toys normally bought for girls. In response to action play, parents mainly produced animated sounds and verbal corrections as compared to caring play in which parents produced more verbal interactions in forms of comments and questions. Similarly, Bornstein and colleagues, (Bornstein, Haynes, Pascual, Painter, & Galperin, 1999; Suizzo & Bornstein, 2006) found that mothers of boys in Argentina, France, and the United States engaged in more exploratory play than did mothers of girls, and mothers of girls engaged in more symbolic play than did mothers of boys. Corresponding differences were also found in the amount of exploratory and symbolic play girls and boys themselves engaged in. This is important because several studies have shown that amount of symbolic play in children is highly related to more advanced language (e.g., Bates, Benigni, Bretherton, Camaioni, & Volterra, 1979; Lyytinen, Poikkeus, & Laakso, 1997). Hence, there is a multitude of social factors that may contribute to different acquisition of language among girls and boys. Because the particular mix of these factors is expected to vary among different language communities (Best & Williams, 1997), gender differences in early language skills are consequently also expected to vary among language communities if caused by the social environment. (The term language community is used throughout this paper to refer to the specific linguistic forms and structures constituting a specific language as well as language as an expression of culture. Language is the prime medium for a culture to express itself. The independence that languages can have from national borders is also acknowledged by the term.) One purpose of the present study is to test the robustness of the gender effect in language by comparing early language skills between girls and boys in different language communities. The greater male variability hypothesis Since the days of Ellis (Ellis, 1894), it has been argued at times that men are more variable than women in cognitive functioning, which is often referred to as the greater
Differences between girls and boys in early language
male variability hypothesis (i.e., greater variability among males in intelligence). The evidence for this hypothesis varies. Arden and Plomin (2006) found support for greater variance of intelligence among boys at age 3 to 10 but not at age 2. Homogeneity of variance between genders has usually been found for most verbal tests (see Feingold, 1992 for a review). Thus, inconsistent support for the greater male variability hypothesis could either depend on the investigated age period, on the cognitive domain, or both. Knowledge of equal or unequal variance between genders might have important applied consequences in determining cut-offs in screening programs. For example, boys are often over-represented in the lower percentiles when screening for language delay (Law, Boyle, Harris, Harkness, & Nye, 1998). This observation might reflect a lower mean performance in the measured language skills among boys in comparison with girls, a greater variability among boys, or both. Whereas equal means and equal variance between genders would call for unisex norms, findings of equal means and heterogeneous variance, or different means (with or without a difference in variance) would be a more complicated matter. It might indicate that one gender is more vulnerable and, therefore, more in need for special interventions and unisex norms should be kept, or that unisex norms would result in many false positives within the gender with many individuals in the lower tail (boys) and separate norms should be used instead. Long-term follow-ups of girls and boys at the lower tail of each gender would be needed to delineate these alternatives if heterogeneous variance or homogeneous variance and a difference in means are found. Hence, the male variability hypothesis is not only of mere historical interest but also has current relevance for clinical practice. Therefore, another purpose of the present study is to test the hypothesis that boys are more variable than girls in language skills at language onset.
The present study This study extends earlier research on gender differences by merging data from previously published studies on early language skills in girls and boys from 10 nonEnglish European language communities. The inclusion of both language community and age as independent variables in the analyses and in interaction with gender allows us to control for these variables in a coherent way. Variety of differences between girls and boys across the 10 language communities (expressed as an interaction between gender and language community) would be evidence of causes within the language communities, for example in terms of linguistic variables or social variables such as different ways to raise and talk to girls and boys. Neurodevelopmental factors such as earlier brain lateralization in girls (Crow, 1998) do certainly not differ across language communities and could not account for such a result. In summary, this study tests the following four hypotheses: (1) girls are ahead of boys in emerging language skills; (2) the gender difference in language interacts with language community; (3) the gender difference in language interacts with age group; and (4) young boys are more variable in language skills than young girls.
Method This study is a synthesis of normed data from previously published studies (see Language Communities for references). All participants were assessed with adapted versions of the MacArthur-Bates CDI.
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Table 1. Number of girls and boys over two CDI forms and 10 language communities (N = 13,783) Language community
Austrian German Basque Croatian Danish Estonian French Galician Slovene Spanish Swedish Total
Words and gestures
Words and sentences
72 225 125 848 182 275 190 – 223 241 2381
42 217 125 864 190 273 186 – 189 224 2310
266 494 179 1477 325 346 348 443 296 473 4697
147 481 197 1386 314 317 352 484 297 420 4395
Participants In total, 13,783 children from 10 European language communities contributed data to this study. Of these 13,783 children 4,691 were aged 0.08–1.04 and assessed with adapted versions of the Words and Gestures form (W&G) of the CDI. The remaining 9,092 children were aged 1.04–2.06 and assessed with adapted versions of the Words and Sentences form (W&S) of the CDI. The proportion of girls in each age group was 51%. The proportion of girls in the different samples varied at most 3% from the total proportion with the exception of Austrian girls who were considerably over-represented, constituting 63% and 64% for W&G and W&S, respectively (Table 1). Birth order was evenly distributed over girls and boys. In the infant sample (assessed with W&G), 48.3% of the girls and 48.1% of the boys were firstborns. For the toddler sample (assessed with W&S), 53.2% of the girls and 52.8% of the boys were firstborns. Among both infants and toddlers, 11.8% of the girls were bilingual whereas 10.9% of the infant boys and 12.2% of the toddler boys were bilingual.
Measures and procedure Word comprehension and production in infants were assessed with adapted versions of the W&G form and word production in toddlers was assessed using adapted versions of the W&S form. These forms have a checklist format enabling a parent to mark the particular words the child presently understands or produces. The words are grouped by semantic category to facilitate retrieval. In addition, a similar checklist in the adapted W&G forms assessing children’s first communicative gestures was used. Parents’ answer (yes/no) to the question of whether the child combined words was assessed by the adapted W&S forms. The number of items varied in the versions adapted to different language communities. The number of gestures varied between 11 and 13 words, the vocabulary checklist in the adapted W&G form varied between 303 (Spanish) and 688 (Austrian German) words, and in the adapted W&S between 588 and 725 words. A major cause of the difference in length in the adapted W&G forms was that the Austrian infant (W&G) and toddler (W&S) forms consisted of almost identical number of items. Minor causes of differences in length were due to linguistic and cultural characteristics. For example, the number of pronouns and kinship terms differs markedly between
Differences between girls and boys in early language
languages and the relevance of words denoting food items and clothing differs between communities. Adapted versions of the CDI were distributed to parents with children of the relevant ages. The main method of contact across language communities was in cooperation with educational and paediatric institutions. Some parents were contacted through random selection from population registers (e.g., Denmark and Sweden). Most of the parents returned the instrument by mail. Girls and boys were recruited in the same way within each language community.
Language communities The sample consists of 10 European language communities covering the following languages: three Germanic languages: Austrian-German, (Marschik, Einspieler, Garzarolli, & Prechtl, 2007), Danish (Bleses, Vach, Wehberg, Faber, & Madsen, 2007), and Swedish (Berglund & Eriksson, 2000; Eriksson & Berglund, 1999); three Romance languages: French, (Kern, 2007), Galician (P´erez-Pereira, 2008; P´erez-Pereira & Garc´ıa-Soto, 2003; P´erez-Pereira & Resches, 2011), and Spanish (L´ opez Ornat et al., 2005; Mariscal, L´ opez Ornat, Gallego, Karousou, & Mart´ınez, 2007) two Slavic languages: Croatian (Kovacevic, Jelaska, Kuvac, & Cepanec, 2005) and Slovene (Marjanoviˇc-Umek et al., 2008); one Finno-Ugric language: Estonian (Tulviste, 2007); and one non-Indo-European language: Basque (Barre˜ na, Ezeizabarrena, & Garc´ıa, 2008; Barre˜ na et al., 2008). The children acquiring a Germanic, or Slavic language as well as Estonian, or French were predominantly monolinguals. About 20–25% of the Spanish participants, 30 (toddlers)–50% (infants) of the Basque participants, and 66% of the Galician participants were bilingual. The bilingual children were assessed in their dominant language only.
Statistics Effects of gender, age, and language community on the early use of gestures, as well as on receptive and expressive vocabularies were explored by a multivariate analysis of variance (MANOVA) and analyses of variance (ANOVAs) in full factorial models using SPSS software. A logistic regression analysis was performed to explore the same independent variables on whether a child had started to combine words. Age was scored in 3-month intervals for both infants and toddlers. Because the number of CDI items varied between versions, all analyses were recalculated with the percentage of the particular measure as the dependent variable. The present authors’ comments are offered when this procedure yields results differing from the analyses using the transformed raw data. Using raw data assumes that each form is exhaustive, while using percentages assumes that each form is equally exhaustive. Neither is correct and the truth lies somewhere in between. Adaptations with longer CDI forms received higher scores by the first procedure, whereas adaptations with shorter CDI forms, concentrating on the items expected to be most prominent, are favoured by the second procedure. Means and standard deviations (SDs) are given in raw scores. As is often the case in field research, data did not meet all assumptions upon which classic parametric tests such as ANOVA rest. The scales for word comprehension and word production were transformed by the square root (word comprehension in infants and word production in toddlers) and by a natural logarithm function, LN (word production in infants) to approach normal distributions. The difference in number of children from each language community has been handled by the use of the type III
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SS option in the ANOVAs. No deviance from homogeneity could be found for gender. A level of significance of 1% was used to safeguard against type I errors. With these precautions, and as the samples were unusually large, it was considered safe to calculate MANOVAs and ANOVAs. Because differences in distributions between groups are not revealed by statistics based on means, analyses based on central tendencies will be complemented with analyses of distributions for girls and boys separately. The distribution of scores for girls versus scores for boys will be indexed using the variance ratio (VR), that is the variance of the boys’ score over the variance of the girls’ score (Feingold, 1992). A VR of 1.00 indicates homogeneity of variance; a greater VR indicates greater variability among boys and a VR less than 1.00 indicates greater variability among girls. The tail ratio (TR) (Halpern, 2000) is another measure of variability that concentrates on the number of girls and boys at the extreme ends of the distribution. It can be expressed as the percentage of boys in the tail of all boys in the sample over the percentage of girls in the tail of all girls in the sample. Thus, a TR over 1.00 indicates that boys are over-represented in the particular tail and a TR under 1.00 indicates that girls are over-represented. An equal distribution of girls and boys but with a difference in means results in an overrepresentation of the low-performing group in the lower tail and an under-representation of the same group in the upper tail. TRs, after adjustment for age, are also reported in this study and the tails are set at the top and bottom 5%.
Results Infants (W&G) Communicative gestures, word comprehension, and word production were moderately correlated with each other (r varied between .38 and .59) and used as dependent variables in a MANOVA with gender, age group, and language community as fixed factors. The analysis revealed main effects of all factors. Girls (Wilks’ ␥ = .99, F[3, 4546] = 9.895, p < .01, 2 = .006) and older infants (Wilks’ ␥ = .55, F[6, 9092] = 534.886, p < .01, 2 = .261) were reported to use and understand more types of communicative items than boys and younger infants. The effect of language community (Wilks’ ␥ = .76, F[24, 13185] = 54.660, p < .01, 2 = .09) showed that the infants’ language skills varied among communities. An interaction was found between age and language community, indicating that the increase in language skills by age differed among language communities (Wilks’ ␥ = .97, F[42, 13486] = 3.267, p < .01, 2 = .010). No other interactions were found. Calculations using the percentage of mastered items, comprehended as well as produced, relative to the number of items in the instrument of each adaptation yielded the same results regarding significant contributions of the independent variables, although all interactions now turned out significant.
First communicative gestures A separate univariate ANOVA revealed main effects of age, gender, and language community on children’s first communicative gestures. Girls (F[1, 4548] = 26.79, p < .01, 2 = .006) were reported to use more types of communicative gestures than boys and older infants were reported to use more types of communicative gestures than younger infants (F[2, 4548] = 1227.19, p < .01, 2 = .35). See Table 2 for means and SDs. The increase with age was slightly more pronounced among girls between the first (8–10-month-olds) and second (11–13-month-olds) age groups. In contrast, the
Differences between girls and boys in early language
Table 2. Mean (SD) number of first communicative gestures, word comprehension, and word production for girls and boys (aged 0.08–1.4 [year; months]) and word production (aged 1.04–2.06) in relation to age groups Girls Age
2.50 2.13 1.94
695 771 864
4.07 6.90 8.42
2.34 2.22 1.90
659 795 814
Word comprehension (W&G) 0.08–0.10 year 32.51 0.11–1.01 year 80.1 1.02–1.04 year 145.8
40.8 66.176 85.2
704 776 865
31.49 79.45 135.37
41.87 69.87 84.79
678 798 814
Word production (W&G) 0.08–0.10 year 1.5 0.11–1.01 year 8.0 1.02–1.04 year 24.5
3.14 13.19 36.83
704 776 901
1.46 6.39 18.89
3.43 11.00 29.14
678 798 834
First communicative gesture (W&G) 0.08–0.10 year 4.46 0.11–1.01 year 7.46 1.02–1.04 year 8.85
Word production (W&S) 1.04–1.06 year 57.4 1.07–1.09 year 136.3 1.10–2.00 year 248.5 2.01–2.03 year 367.2 2.04–2.06 year 445.4
76.1 120.4 156.5 154.9 143.9
791 896 1132 889 939
49.6 101.0 203.7 301.3 405.0
70.9 101.8 147.5 161.7 160.1
718 853 1039 886 899
differences between girls and boys decreased at the oldest age group (14–16-month-olds), most likely because of a ceiling effect for girls (F[2, 4548] = 4.88, p < .01, 2 = .002) (Figure 1). There was a main effect of language community (F[8, 4548] = 50.96, p < .01, 2 = .08), and there was an interaction between age group and language community, (F[14, 4585] = 3.008, p < .01, 2 = .009) indicating that children used more types of gestures at an earlier age group in some language communities as compared with others. There was no interaction between gender and language community. Calculations using the proportion of communicative gestures yielded similar results (data not shown). The VR ratio for communicative gestures was .96, indicating a very similar overall distribution of scores for girls and boys. TR in the lower tail (5.4%) was 1.21, which means that there
10 8 6
2 0 0;08-0;10
Age (years; months)
Figure 1. Number of communicative gestures among girls and boys (aged 0.08–1.04) in relation to age (N = 4,598).
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30 25 20
15 10 5 0 0;08-0;10
Age (years; months)
Figure 2. Number of words produced among girls and boys (aged 0.08–1.04) in relation to age (N = 4,598).
are 121 boys for every 100 girls in the lower tail of the distribution. TR among the top 8.1% was .69, indicating there are 69 boys for every 100 girls in this tail. Thus, despite an extremely small effect size for gender, the difference between girls and boys on mean number of communicative gestures had a clear impact on the tails.
Word comprehension A corresponding ANOVA on word comprehension revealed main effects of age and language community. Older infants (F[2, 4585] = 1186.617, p < .01, 2 = .34) were reported to understand more words than younger infants and the number of words children comprehended varied for different language communities (F[8, 4585] = 82.278, p < .01, 2 = .12). See Table 2 for means and SDs. However, the effect of gender was not statistically significant (p = .034); nor were there any interactions between gender and age group or gender and language community, although there was an interaction between age group and language community, (F[14, 4585] = 2.825, p < .01, 2 = .009) indicating that children comprehended more words at an earlier age group in some language communities as compared with others. Calculations that used the proportion of words understood yielded similar results (data not shown). VR for word comprehension was .93, with TR for the lower tail (5.1%) at 1.19 and TR for the upper tail (5%) at 1.03. Thus, while VR based on means indicated a slightly greater variability among girls, the analysis based on the tails gave the opposite result. As the differences are small, a fair conclusion is that the variability between girls and boys in word comprehension is about the same.
Word production The same type of ANOVA revealed main effects of gender, age, and language community on children’s early word production. Girls (F[1, 4641] = 16.023, p < .01, 2 = .003) were reported to use more types of word than boys and older infants more types of word than younger infants (F[2, 4641] = 977.488, p < .01, 2 = .296). See Figure 2 and Table 2 for means and SDs. The effect of language community (F[8, 4641] = 59.364, p < .01, 2 = .093) indicated that the number of words children from different language communities produced varied. No interactions were significant. Calculations using the proportion of word production yielded significant contributions of main effects as well as for all interactions (data not shown). The VR for spoken words was .61, indicating that girls were more variable than boys. However, because the sample was not normally
Differences between girls and boys in early language
Mean number of words produced
500 450 400 350 300
250 200 150 100 50 0 1;04-1;06
Age (years, months) Figure 3. Mean number of words produced by girls and boys (aged 1.04–2.06) in relation to age (N = 9,012).
distributed, the VR value of .61 should be interpreted with caution. The proportion of children from which no word was reported was 29%. The bottom TR was 1.13, indicating slightly more boys in the bottom tail. About 5% of the children produced more than 43 words. The TR for these children was .65, indicating that there were considerably more girls among the top 5%. To sum up the effects of gender on infants’ communicative gestures, word comprehension, and word production as reported in the W&G form, the acquisition of all three skills varied among language community and with the age of the children. Significant differences were observed between girls and boys on communicative gestures and early word production. There was one exception from a general girl advantage in word production. Austrian boys produced more words than their female peers. We have no explanation at hand for this but note that the sample of Austrian infant boys (42) was the smallest group of all (Table 1). No significant difference was found between girls and boys in comprehension. The greater male variability hypothesis received no support. On the contrary, variability was comparable for both genders on the first two skills and noticeably higher for girls in early word production. The TR analyses confirmed the analyses based on mean estimates.
Toddlers (W&S) Word production An ANOVA that included gender, age group, and language community as fixed factors revealed main effects of all three variables. Girls (F[1, 8942] = 127.337, p < .01, 2 = .014) were reported to use more types of word than boys and older toddlers used more types of word than younger toddlers (F[4, 8942] = 1633.699, p < .01, 2 = .422). See Table 2 for means and standard deviations. The difference between girls and boys increased with age, (F[4, 8942] = 3.895, p < .01, 2 = .002, Figure 3). The effect of language community (F[9, 8942] = 36.600, p < .01, 2 = .036) indicated that the number of words children from different language communities produced varied. There was also an interaction between age group and language community, (F[36, 8942] = 2.790, p < .01, 2 = .011) indicating that children produced more words at an earlier age
M˚arten Eriksson et al. 100 90
80 70 60
50 40 30 20 10 0 1;04-1;06 1;07-1;09 1;10-2;00 2;01-2;03 2;04-2;06
Age (years, months) Figure 4. Mean percentage of girls and boys reported to combine words (aged 1.04–2.06) in relation to age (N = 8,829 children, p < .05 for all age groups).
group in some language communities as compared with others. However, no interaction between gender and language community was found. Calculations using the proportion of words relative to the number of items in each adaptation of CDI did not change these results. Girls from all language communities, including the Austrian toddlers, produced now more words than the boys. The VR for these somewhat older children was .91, indicating that the distribution was similar among girls and boys. As expected from the difference in means, boys dominated the lower tail (4.9%, TR = 1.28) and girls dominated the upper tail (5%, TR = .70). Onset of early two-word utterances Differences in the onset of early two-word utterances between girls and boys were investigated by parent reports of first-word combinations. These reports showed that more girls (75.0%) combined words than boys (69.3%). These differences held across all age groups but were most prominent between the ages 1.07 and 2.03, indicating a ceiling effect in the oldest age group (Figure 4). A hierarchical logistic regression analysis with age group, gender, and language community entered in a first block and the interactions between age group and gender and between language community and gender in a second block confirmed this difference. The analysis revealed main effects for all variables in the first block (Wald statistics was 1812.98 for age group, 59.69 for gender, and 136.08 for language community, B = 1.19 and SE = .028 for age group and B = .44 and SE = .058 for gender, all ps < .01). Girls had started to combine words to a higher degree than boys. None of the interactions in the second block were significant. In sum, there were significant differences between toddler girls and boys on word production, differences that increased with age. Although word production varied among children from different language communities, this did not affect the differences between girls and boys. The distribution of spoken words was rather similar among girls and boys and the tail ratios confirmed the analysis based on means. A similar but less clear pattern was found for word combinations. Gender differences across language communities Previous analyses have shown main effects of language community for both infants (on gestures, word comprehension, and word productions) and toddlers (word production
Differences between girls and boys in early language
Table 3. Partial contribution (2 ) of gender in gender × age group ANOVAs and the correlation coefficient (rho) for each language community and the total Infants
Language Gestures Word Word Word Word comprehension (2 ) production (2 ) production (2 ) combinations (rho) community (2 ) Austria Basque Croatian Danish Estonian French Galician Slovenian Spanish Swedish Total
.010 .025 .000 .012 .013 .030 .003 — .000 .029 .011
.006 .014 .001 .000 .009 .004 −.004 — .000 .002 .001
−.004 .002 .012 .002 .041 .013 −.001 — .000 .002 .004
.001 .005 .034 .025 .055 .017 .021 .030 .020 .011 .020
.052 .064 .061 .099 .138 .110 .064 .118 .023 .044 .083
Note. ‘−’ indicates that boys scored higher than girls.
and onset of first word combinations). It is beyond the scope of the present study to analyse the causes to these differences, some of which are likely to depend upon variables we do not have control over. Instead, our interest concerned the issue whether the emerging difference in early language skills between girls and boys differ between language communities, disregarding the causes of these differences. Analyses so far have not found any evidence of such interactions, although we have noticed a few deviant cases where boys from one language community scored higher than the girls from that particular community. Table 3 gives an overview of this pattern by showing the effect sizes of the differences between girls and boys for each language community and assessed language skill. Effect sizes (2 ) for gestures, word comprehension, and word production were computed by a gender by age group ANOVA for each language community (in contrast to the previous analyses in which language community was included as a factor). Partial correlations were computed between gender and onset of word combinations controlling for age. Analyses based on percentages did not result in any essential change. All effect sizes were small. Austrian and Galician infant boys deviated from the general pattern and scored higher than infant Austrian and Galician girls on word production. Galician boys scored also higher than Galician girls in word comprehension. Word comprehension was the only language skill in which no general difference between girls and boys was found. The girl advantage was without exceptions for toddlers and the effect sizes were slightly larger for this group, although still small.
Discussion The study has investigated gender differences in emerging language skills across 10 non-English language communities. Support was found for the hypotheses that girls are generally ahead of boys in emerging language skills and that this difference increases with age up to 2.06. Little support was found for the hypotheses that this gender difference
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in language varies across language communities or that young boys are more variable in language skills than young girls. Infant girls were reported to use more types of communicative gestures than infant boys and both infant and toddler girls produced more words than same-aged boys. Toddler girls were also ahead of boys in first word combinations. This finding is in accord with that of other large-scale studies on English-speaking children (Bornstein et al., 2004; Fenson et al., 2007; Galsworthy et al., 2000). In contrast to Fenson et al. (2007), no difference between girls and boys was found in word comprehension. This absence of a difference cannot be explained by floor or ceiling effects since comprehension precedes production. Instead, we believe that the comprehension part of the CDI is a less precise measure than the production part and, therefore, makes this difference unstable and hard to assess. In fact, it was already suggested by Tomasello and Mervis (1994) in the initial scientific publication on the CDI that parents are more uncertain in judging their child’s comprehension as compared with production. If Tomasello and Mervis are right, the uncertainty in parental reports on comprehension would leave more room for parental expectations than reports on productions. However, as no difference between girls and boys was found in comprehension, parental expectations do not seem to be responsible for the differences between genders in gestures, word production, and word combinations. In conclusion, Hypothesis 1 received support from data on gestures; word production and onset of word combinations but not from the data on word comprehension. There were also main effects of language community in all five measures (for infants in gestures, word comprehension, and word productions, for toddlers in word production and word combinations), indicating a variation in the social and linguistic environments. The variation in levels of language skills between language communities is important because it indicates that the difference between girls and boys is robust. There was no significant interaction between gender and language community. Thus, Hypothesis 2 received no support. On the contrary, no interaction between gender and language community is precisely what we would expect if neuropsychological differences (e.g., differences in rate of brain lateralization or hormone release) were responsible for the girl advantage in early language skills. However, a pattern of consistent differences between girls and boys in language skills and consistent differences between language communities but no interaction between gender and language community would be compatible with social explanations to the girl advantage if the values and customs related to gender roles are particularly robust with little variation between societies. Examples would be if parents offered gender-typed toys (Fagot, 1995) or encouraged more language towards their daughters (Leaper, Andersson, & Sanders, 1998) to exactly the same extent in all the language communities investigated. It was beyond the scope of the present study to collect data on gender norms in different communities. However, many of the language communities in the present study were also included in Hofstede’s (2001) comparison of values on several of dimensions across nations. His masculinity index is of particular interest as it measures how distinct gender roles are in one society as compared with another society. Slovakia was reported with a top masculinity score of 110. Austria was also reported to score high on masculinity (79), while gender roles in Denmark (16) and Sweden (5) were more or less overlapping. This suggests that the studied language communities included substantial variation in their distribution of gender roles. It has been pointed out as a problem the fact that the population was not homogeneous regarding demographic variables such as socioeconomic status (SES),
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birth order, or exposure to a second language. We agree that this would be a problem if girls and boys were exposed differently to these factors. However, as girls and boys were recruited in the same way within each community, and the sample was unusually large, there is no reason to believe that these variables have favoured one sex over the other. (The same assumption is regularly made for intelligence when not controlled for, which it rarely is). Moreover, the only possible bias differences in SES and inclusion of bilingualism could cause, would be to somewhat artificially increase the difference in child performance between some language communities, not between genders. Large differences between language communities would also increase the likelihood to obtain significant interactions between language community and gender. Yet, we have not focused on differences between language communities per se, but only intended to investigate whether variation among language communities also affected the difference between girls and boys. Furthermore, a main result in the study is that no interactions between language community and gender were obtained. Hence, we cannot see that incomplete control over SES, birth order, and inclusion of bilingual children has biased the result in any interesting way. On the contrary, because bilingualism is so frequent in the world, we think it is important to include such children in the study and show that the girl advantage found for monolingual children also applies to bilingual children. For number of communicative gestures and word production in both infants and toddlers, the difference between girls and boys increased with age confirming Hypothesis 3. A ceiling effect, however, prevented the detection of this difference in first word combinations. As neither girls nor boys speak at birth, any difference between genders at a later point in time is expected to interact with age. However, interactions with age have not been consistently reported in the literature. One reason for this inconsistency is probably that age has been measured in small units such as months (e.g., Fenson et al., 2007), which results in correspondingly more degrees of freedom between groups than the present 3-month period and hence a lower F-value. How age is measured is naturally a matter of convention but we stress that it should be categorized in a statistical model in a way that gives expected effects a fair chance to be detected. Because VR never was over 1, the greater male variability hypothesis (Hypothesis 4) received no support. On the contrary, girls were consistently more variable than boys. In particular, VR for spoken words among infants was .61. However, this difference in variability can be explained by a floor effect among boys, something that is very clear for word production among infants. A large proportion of the boys (30%) had not started to use words productively at this age and VR for word production among toddlers increased rapidly to .91. Except for word comprehension, the TR analyses showed that boys were consistently over-represented at the lower end of the distributions and that girls were over-represented at the top. Taken together, this indicates basically uniform distributions with a small difference in means between girls and boys in gestures and spoken words and confirms the analyses based on means. Equal variance in language skills for girls and boys below the age of 3 years is compatible with the findings of both Arden and Plomin (2006) and the review of Feingold (1992). However, the VR for older children would have to support one or the other indicating either that a greater male variability in language skills emerges from the age of 3 in accord with general intelligence (Arden & Plomin, 2006), or that the variance between genders in language skills departs from that found for general intelligence and remains equal (Feingold, 1992). Merging of actual data in a re-analysis has the advantage over conventional metaanalyses based on effect size in that it allows not only the investigation of main effects but also interactions between variables and exploration of distributions. However, analysing
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already collected data also imply certain drawbacks such as a lack of control over sample sizes, of the applied instruments and in choosing what background information to include. Another limitation of the present study, shared with all parent report instruments, is that it is based on indirect measures of children’s performance. However, parent reports on early language skills have proved to be valid in several studies (see Fenson et al., 2007 for a review) and are particularly useful for depicting emergent phenomena. Unique features of the present study are its comprehensiveness in including over 13,000 girls and boys from 10 different language communities assessed with adaptations of the same instrument. It must be noted that the effect of gender on parent assessment of infants’ and toddlers’ language skills was small (gender accounted for around 1% or less of the variability in children’s early language skills). Such small effect sizes are often said to be of no importance (e.g., Hyde, 2005). However, the difference between girls and boys corresponded to .7 gesture and 1 spoken word at 1.00 and 57 spoken words at 2.00. At least at the age of 2.00, a difference of this size have important implications for issues of screening for language delay. It indicates either that one gender is more vulnerable and therefore more in need for special interventions and unisex norms should be kept, or that unisex norms would result in more false negative girls and more false positive boys as compared with a situation in which different norms are used. That would make the screen costly and be disadvantageous towards girls in the sense that it is worse to be in need of help but not receive it than to receive help without needing it. Separate long-term follow-ups of girls and boys at the lower tail would be needed to delineate these alternatives.
Acknowledgements We would like to express our sincere gratitude to all participants of all countries and to our colleagues of the European Network on Communicative Development Inventories for their support and input during our meetings. Parts of this study were supported by the Austrian Science Fund (FWF; P19581-B02), the City of Graz, the Lanyar Foundation (P325), the Croatian National Grant (MZOS 0013 002), and the Estonian Research Competency Council (grant No. SF0180025s08). The study has also received financial support from the University of G¨avle.
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