Psychology / Attention / Adolescent / Williams Syndrome / Executive Function / Down Syndrome / Space perception / Gait / Humans / Female / Male / Young Adult / Developmental disabilities / Adult / Public health systems and services research / Short Term Memory / Verbal Learning / Down Syndrome / Space perception / Gait / Humans / Female / Male / Young Adult / Developmental disabilities / Adult / Public health systems and services research / Short Term Memory / Verbal Learning