The evolution of the exponent versus child age (in months): .

<p>The major classes of roles, i.e. target children (blue), mothers (green), investigators (red) and fathers (black), are shown. Length normalization by prefix with is used. Swedish lacks the class ‘investigator’.</p

Analysis of the variation the value of the exponent : .

<p>Observed vocabulary size normalization by prefix with is used. The remainder of the methods and the format are the same as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053227#pone-0053227-t004" target="_blank">Table 4</a>.</p

The evolution of the maximum rank versus child age (in months):.

<p>The major classes of roles, i.e. target children (blue), mothers (green), investigators (red) and fathers (black), are shown. Length normalization by prefix with is used. Swedish lacks the class ‘investigator’.</p

Proportion of words produced within each role class as a function of language.

<p>Role classes without words are omitted.</p

The dependency between and age: length normalization by prefix with .

<p>Analysis of the correlation between and age from two perspectives: the sign of the correlation and the significance of the correlations. Four language categories, i.e. All (all languages mixed), Dutch, English, German and Swedish, are considered. is the number of individuals analyzed for a given role class and language category that had at least different points of time (the minimum number of points needed to show a significant correlation between a parameter and age through a two-sided correlation test at a significance level of 0.05, see the Methods section). This filter was applied for consistency between the analysis of the sign of the dependency and its significance. For each individual, the Spearman rank correlation <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053227#pone.0053227-Conover1" target="_blank">[24]</a> between age and a certain parameter of the right-truncated distribution was computed. In the analysis of the sign of the correlation, two counts are provided, namely and , for each role class and language category. and are, respectively, the number individuals with a positive and negative correlation (regardless of the sign of the correlation). In the analysis of the significance of the correlation, three counts are provided, namely , and , for each role class and language category. and are the number individuals with a statistically significant positive and negative correlation, respectively. is the number of individuals with a correlation that is not significant. Significance was decided by a two-sided Spearman rank correlation test <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053227#pone.0053227-Conover1" target="_blank">[24]</a> at a significance level . and indicate counts that are, respectively, significantly high or significantly low according to a binomial test (see Methods).</p

The dependency between and MLU: length normalization by prefix with .

<p>Methods (other than the normalization and the target variables) and format are the same as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053227#pone-0053227-t002" target="_blank">Table 2</a>.</p

The dependency between and age: length normalization by prefix with .

<p>Methods (other than the normalization) and format are the same as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053227#pone-0053227-t002" target="_blank">Table 2</a>.</p

The MLU (in words) versus : .

<p>The major classes of roles, i.e. target children (blue), mothers (green), investigators (red) and fathers (black), are shown. Length normalization by prefix with is used. Swedish lacks the class ‘investigator’. In order to facilitate the visual inspection of the series, the few points with MLU above 15 or above 2 are not shown (this concerns English and German).</p

The dependency between and age: length normalization by prefix with .

<p>Methods (other than the target parameter) and format are the same as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053227#pone-0053227-t002" target="_blank">Table 2</a>.</p

The dependency between and MLU: length normalization by prefix with .

<p>Methods (other than the target variables) and format are the same as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053227#pone-0053227-t002" target="_blank">Table 2</a>.</p