Sesma, Mahone and colleagues extended this view in a 2009 study, noting that while some children have difficulty with reading comprehension because they have chronic difficulty in decoding and accurately reading single words, there are others who struggle with reading comprehension despite their having adequate ability to decode and accurately read single words. These researchers did a study with 60 children aged 9 to 15 years with deficits in reading comprehension to test the hypothesis that executive functions would be significantly associated with reading comprehension skills, but not with single word reading accuracy in children with word reading deficits, reading comprehension deficits, and ADHD.