The purpose of this study was to investigate the comprehension of questions beginning with different wh- question words presented in two referential conditions to individuals with intellectual disability (ID). Thirty-nine school-age participants completed a battery of who, what, where, when, why, and how questions with and without a picture referent. Students generally answered more questions correctly in the no referent condition. Across conditions the rank ordering of correct responses for each question word was: what, who, where, how, why, when. While logistic regression analysis revealed a finding of no overall statistical significance between the probability of answering questions correctly between referential conditions, there were important qualitative differences in the way students answered certain wh- questions based on referential condition. The questions presented were grouped and compared based on conceptual complexity with who, what, where categorized as concrete and when, why, how as abstract. Participants answered 89% of concrete and 56% of abstract questions correctly across both conditions. A statistically significant difference between the probability of answering correctly concrete and abstract questions was found. There was also a statistically significant relationship between receptive vocabulary and the probability of answering all questions correctly. Additionally, logistic regression models revealed that receptive vocabulary ability may be more related to answering abstract questions than concrete questions. Analysis of incorrect answers showed that 85% of errors could be meaningfully categorized. Of these responses, 25% were categorically related to the particular wh- question word that was targeted. Further, 10% would have been correct if a different question word was substituted for the target. Additionally, 27% of the responses were related to the topic of the question and the remaining were either I don't know/No responses, repetitions, or unrelated. The categories were generally the same across conditions. Students did, however, produce more of these incorrect responses that were related to the topic in the picture condition. The results of this study point to the importance of learning more about ways to support question comprehension and answering to help individuals with ID answer all types of questions more effectively
