Longitudinal tracking of vocabulary development in neurodevelopmental and genetic disorders using Communicative Development Inventories (CDIs)

Parent-report instruments have transformed the study of early language and communicative development since the mid-1990s, offering insights into the acquisition of gestures, vocabulary, grammar, and communication from infancy onward (Fenson et al., 1994). Among them, the MacArthur–Bates Communicative Development Inventories (CDIs) are the most widely used tools which have been adapted for use in many languages (https://mb-cdi.stanford.edu/; e.g., Bleses et al., 2008; Bornstein et al., 2004; Eriksson et al., 2012). In addition to characterizing typical development, CDIs have also been used to detect “red flags” for language delay (e.g., Guinchat et al., 2012; Herlihy et al., 2015). Furthermore, CDIs have since been applied in studies of children with neurodevelopmental conditions and genetic syndromes, often beyond the age range CDIs were designed for (e.g., Luyster et al., 2007). These studies span clinical screening, developmental monitoring, outcome prediction, and the exploration of condition-specific developmental profiles (e.g., Rescorla, 2011; Can et al., 2013; Tager-Flusberg et al., 2009). In this vignette, we focus on a specific subset of CDI applications in clinical populations: studies using longitudinal designs with repeated CDI assessments to track expressive vocabulary growth over time. We aim to evaluate their utility in mapping developmental trajectories, report developmental progress or regression and informing tailored intervention.