For their study, scientists at the University of Colorado-Boulder tested four possible explanations for the connection between shyness and delayed speech:
The research team, from CU-Boulder’s Institute for Behavioral Genetics and the Department of Psychology and Neuroscience, found consistent evidence to support only one hypothesis: Shy toddlers were delayed in speaking, but not in understanding.
“Behaviorally inhibited children who may not be speaking much shouldn’t be underestimated,” said Soo Rhee, an author of the study and an associate professor of psychology and neuroscience.
“Parents and teachers should be aware that they may need to be encouraged more in their expressive language development.”
For the study, the researchers looked at data collected on 408 sets of twins at 14, 20, and 24 months of age, when language skills are rapidly expanding. The data came from parent reports and researcher observations.
Notes were made both of the child’s ability to repeat sounds and answer questions, as well of the child’s ability to follow directions, the researchers noted.
The researchers looked for patterns in how the children’s behavior changed over time noting, for example, whether an increase in shyness followed or preceded a delay in speech.
The result — that shy toddlers understand more than they indicate through talking — is both good news and bad news, according to Rhee.
“It’s good news that the children are not delayed in language acquisition,” she said. “But not being willing to speak may still have consequences.”
“Past studies have shown that delayed speech can lead to a number of negative outcomes later in life, including poor self-regulation and social difficulties,” she noted.
The study was published in the journal Child Development.