Research Update: Dr. Naomi Caselli’s Team Extends Investigation into Language Deprivation in Deaf Children

“We already know that a lot of deaf kids are at risk for language deprivation, but this grant will give us the tools necessary to figure out how many children are actually falling behind and by how much, and that can have a tremendous impact on policies that are put in place to address it.” –Dr. Naomi Caselli, February 2017

Last winter, we reported on a newly awarded National Institute of Health grant that would support Dr. Naomi Caselli’s research into the factors that predict sign language vocabulary acquisition in children who have been exposed to a sign language from birth. Her goals in this study include establishing a benchmark that can be used to better understand language development in deaf children who have had early exposure to fluent ASL speakers. This benchmark could then be used widely to assess language development in deaf children who are at risk of language deprivation.

Dr. Caselli and her team, which includes Wellesley College’s Dr. Jennie Pyers, Wheelock professor Dr. Amy Lieberman, Wheelock doctoral student Anna Lim Franck, , and a crew of Wheelock staff and graduate students, have since developed the three ASL vocabulary tests that will help them identify that key benchmark.

Two of these tests are conducted in-person, on young children who have had early exposure to ASL. The first aims to determine the child’s ability to produce signs while the second assesses their ability to recognize signs. Through direct observation in these sessions, Dr. Caselli and her team determine the child’s level of vocabulary acquisition, which, Dr. Caselli notes, is a probable early indicator of progress toward language acquisition.

The third test is an online survey filled out by parents of deaf children. This online test has the potential to be used widely as an assessment tool. But first, Dr. Caselli and her team must determine its reliability.

To do so, they’ve given a subset of participants all three tests, generating data that can help confirm the accuracy of the online test. “Our goal right now is to validate this online test,” says Dr. Caselli. “The in-person tests are, by nature, slower to norm because you have to be with the children when you administer it. This online version could be distributed nationally and gather data quickly.”

An important aspect of the online test is its capacity to provide a detailed picture of a child’s vocabulary; in-person tests have to be short enough that young children with limited attention spans can manage them. The team has collected close to half of the data needed to assess their online test, and the early evidence suggests that the data gathered in-person tests matches closely with data gathered online. This indicates that parents completing the online test seem able to reliably report on their children’s vocabulary.

Halfway through their data-collection process, Dr. Caselli and her team have gained strong evidence about how vocabulary acquisition in deaf children works. In an article published in the journal Psychological Science, Dr. Caselli and Dr. Pyers took a close look at the kinds of signs that kids who are not at risk for language deprivation learn first. They asked whether iconicity–how closely a sign relates visually to the concept it represents–overshadows two other factors knows to affect spoken language acquisition: neighborhood density (the number of “rhyming” signs in the ASL lexicon) and lexical frequency.

This study was only possible by using ASL-LEX, a complete and searchable database of the ASL lexicon developed by Dr. Caselli and researchers from Tufts University and UC San Diego. The study showed that deaf children use not only iconicity but also other phonological and lexical properties of signs to help them learn new words. This matches how hearing children acquire spoken language, and indicates that even though the mode of communication is different between the two groups (speaking versus signing), the process for children is quite similar.

Two further articles from the team are currently under review and the data-gathering process for ASL vocab-acquisition benchmarking will extend into the coming months. The team’s next challenge involves recruiting enough parents and children to take the online test and complete the data set. Boston University’s Institutional Review Board has approved the following call for participants:

We are looking for parents that use ASL and have children under the age of 5 years old to participate in a research study. The study is all online, and there are three parts that take 1 hour each. You can complete the study at your own pace over the course of one week. If you participate, you would earn $25 for each part, and an extra $15 if you complete the whole thing.

If you or someone you know is interested, please have them contact us at