Apart from literacy, Bialystok and Codd (1997) found that four and five year-old bilinguals were ahead of monolinguals in developing concepts of number (cardinality of number) owing to their higher levels of attentional control. Bilingual children need to be attentive to which language is being spoken, by whom, where and when. This attentiveness appears to give advantages in early number work, when attention to the symbolic nature of number is needed.