Linguistic lateralization in adolescents with Down syndrome revealed by a dichotic monitoring test

Linguistic lateralization in 10 adolescents with Down syndrome (average age: 15.7 years), 15 adolescents with intellectual disabilities of unknown etiology (average age: 17.8 years), 2 groups of children without disabilities (11 children, average age: 4.7 years; 10 children, average age: 8.5 years), and 14 adolescents without disabilities (average age: 18.7 years) was examined, using a dichotic monitoring test (DMT). Different Japanese words with 2 consonant–vowel syllables were presented to each ear simultaneously. Participants pressed a button when they heard the target word. The younger children without disabilities and the adolescents with intellectual disabilities exhibited a right-ear advantage, whereas the adolescents with Down syndrome showed the reverse pattern, i.e., a left-ear advantage. These results suggest that there is atypical linguistic lateralization in adolescents with Down syndrome.