Cognitive Sequelae of Atypical Sign Language Development

Language is a unique human capability and its impact on cognitive development is largely unknown. In the past, researchers have relied on the rare cases of feral children, who experience language deprivation, to understand the relationship between language and cognition. Recently, researchers began to look at the deaf community to understand this relationship. Over 95 percent of deaf children are born to hearing parents who have no fluency in a signed language. Many of these children are raised in improvised language environments and experience significant language delays. The other percentage of deaf children are raised by deaf parents who already are able to make language accessible to their children at home. These children experience typical language development and achieve language developmental milestones similar to hearing children.

This study investigated how the language deprivation experienced by deaf children of hearing parents has an impact on higher order cognitive abilities compared to those raised by deaf parents. This study focused on the executive functions that are responsible for optimal learning and social behavior. The Color Trails Test was administered to deaf children and adults. This test required them to connect numbered circles sequentially while alternating the circles’ colors (line from a pink circle with the number 1 to a yellow circle with the number 2 while ignoring the pink circle with the number 2 and so on). The task requires cognitive flexibility to shift attention while inhibiting distractors. The time it took participants to complete the task was recorded.

The results illustrated that deaf children and adults raised in language improvised environments and are not exposed to a signed language until after the age of 3 or older perform worse on this executive function task compared to deaf individuals who were raised by parents who are fluent in a sign language. These results highlight the importance of high quality language experiences early in life for optimal cognitive development later in life. The results also have practical implications for early intervention programs for deaf infants and toddlers.