The DD model (Barcroft & Sommers, 2005) is an emergentist (usage-based) model that posits that acoustically varied input (of a phonetically relevant nature) leads to increasingly more robust developing lexical representations and, in this way, improves early vocabulary learning. Conditions of no variability, as depicted by six instances of input with no variability, lead to stronger representations that are less distributed or robust in nature. Conditions of moderate and high variability, on the other hand, lead to increasingly more distributed or robust representations even if individual nodes for exemplars becomes increasingly weaker.
Note. Adapted from Barcroft & Sommers, 2005.