Speech and language development is essential in following up children's wellbeing. Assessment of active early childhood vocabulary gives information about language development. Parents' assessment is reliable until about 2 years. Studies show that children aged 1 year 6 months have an average active vocabulary of dozens of words. Though individual variation is wide, most children possess far more than a few words. Current screening practice may miss children with language disorders. Support given from early on in child's own environment diminishes challenges and prevents potential later problems, e.g. difficulties in learning and in social relationships.