In three experiments, we investigated Hebb repetition learning (HRL) differences between children and adults, as a function of the type of item (lexical vs. sub-lexical) and the level of item-overlap between sequences. In a first experiment, it was shown that when non-repeating and repeating (Hebb) sequences of words were all permutations of the same words, HRL was slower than when the sequences shared no words. This item-overlap effect was observed in both children and adults. In a second experiment, we used syllable sequences and we observed reduced HRL due to item-overlap only in children. The findings are explained within a chunking account of the HRL effect on the basis of which we hypothesize that children, compared with adults, chunk syllable sequences in smaller units. By hypothesis, small chunks are more prone to interference from anagram representations included in the filler sequences, potentially explaining the item-overlap effect in children. This hypothesis was tested in a third experiment with adults where we experimentally manipulated the chunk size by embedding pauses in the syllable sequences. Interestingly, we showed that imposing a small chunk size caused adults to show the same behavioral effects as those observed in children. Departing from the analogy between verbal HRL and lexical development, the results are discussed in light of the less-is-more hypothesis of age-related differences in language acquisition.

A large sample study (n = 513) was conducted to investigate executive control performance in pupils following an immersion education program. We recruited 10-year-old children (n = 128) and 16-year-old adolescents (n = 127) who were enrolled in English or Dutch immersion education in French-speaking Belgium for at least 4 school years. They were compared to non-immersed children (n = 102) and adolescents (n = 156) on a number of executive control tasks assessing inhibitory control, monitoring, switching and attentional abilities. Several control variables such as receptive vocabulary, nonverbal intelligence, socioeconomic status and other potentially relevant background variables were also considered. Our results show significant gains in foreign-language proficiency for the immersed compared to the non-immersed participants. These gains were however not associated with any measurable benefits on executive control. Our findings make a unique contribution to understanding how language and cognition develop through formal education methods that promote bilingualism.

There is currently much controversy surrounding the cognitive advantages that are often associated with bilingualism, especially regarding the so-called executive control advantage.Recently, it has been suggested that bilingualism emerging from immersion education may not lead to an advantage in executive control, but rather to an improvement specifically at the level of attentional abilities. In order to test this hypothesis, the current large sample study involving over 500 participants investigated whether foreign-language immersion education can be associated with an advantage in attentional functions. We recruited 12-year-old children and 18-year-old adolescents enrolled in immersion education in French-speaking Belgium for at least 6 years. They were compared to non-immersed children and adolescents on tasks assessing auditory sustained attention, auditory and visual selective attention and divided attention. Several control variables such as nonverbal intelligence, socioeconomic status and other potentially relevant background variables were also considered. The results indicate no measurable difference between the immersed and the non-immersed participants, for none of the examined attentional abilities. These findings are discussed in the light of the cognitive implications of becoming bilingual through a formal education experience.