Teaching shape bias to increase the expressive vocabularies of late talkers
Clinical Archives of Communication Disorders
By the age of two, children's expressive semantic skills are rapidly expanding. These highly skilled word learners typically produce 200−300 different words, combine words into phrases, and use a variety of word types, such as nouns, verbs, adjectives, pronouns, and location words  . Not all two-year-olds, however, master these skills at the same rate. The term Late Talkers (LTs) describes children between the ages of 18 and 36 months who, a) have receptive language abilities that are
... ly age appropriate, b) do not have any obvious sensory, cognitive, or neurological deficits, but c) produce fewer words and word combinations than expected for their chronological age  . The criteria used for defining the low expressive vocabulary skills of LTs are typically cutoff scores based on the child's expressive vocabulary size (e.g., 50 words or less for a 24-month-old) or standard scores on expressive vocabulary measures (e.g., below the 10th percentile). Successful interventions for LTs have primarily focused on increasing vocabulary exposure, providing contextual supports, and directly teaching target vo-Purpose: Shape bias is a lexical principle that suggests shape is the primary feature by which concrete noun labels apply to other objects. It helps children generalize the labels of newly encountered words to other referents. Shape bias typically develops around two years of age and has been linked with increases in expressive vocabulary. Smith et al.  , for example, found significant increases in 17-month-olds' noun vocabularies following an intervention that taught shape bias. Methods: The present investigation, a non-randomized pilot study, applied an eight-week shape bias-based intervention to Late Talkers who were between the ages of 23 and 34 months. The eight participants were exposed to novel objects, associated nonsense spoken labels, and objects that did and did not match their shape. Pre-and post-treatment expressive vocabularies were measured using the MacArthur-Bates Communicative Development Inventory  . Results: The participants increased their expressive vocabularies by 24 to 119 words, adding more new nouns than other word types. Conclusions: These results, along with lessons learned about implementing the treatment, support larger-scale research on teaching shape bias to positively influence the expressive vocabularies of Late Talkers.