  Providing explanations in the context of Visual Question Answering (VQA)
presents a fundamental problem in machine learning. To obtain detailed insights
into the process of generating natural language explanations for VQA, we
introduce the large-scale CLEVR-X dataset that extends the CLEVR dataset with
natural language explanations. For each image-question pair in the CLEVR
dataset, CLEVR-X contains multiple structured textual explanations which are
derived from the original scene graphs. By construction, the CLEVR-X
explanations are correct and describe the reasoning and visual information that
is necessary to answer a given question. We conducted a user study to confirm
that the ground-truth explanations in our proposed dataset are indeed complete
and relevant. We present baseline results for generating natural language
explanations in the context of VQA using two state-of-the-art frameworks on the
CLEVR-X dataset. Furthermore, we provide a detailed analysis of the explanation
generation quality for different question and answer types. Additionally, we
study the influence of using different numbers of ground-truth explanations on
the convergence of natural language generation (NLG) metrics. The CLEVR-X
dataset is publicly available at
\url{https://explainableml.github.io/CLEVR-X/}.
