Use Amazon Mechanical turk to A/B test different sets of instructions for eliciting captions and descriptions of pictures during the file upload workflow for Upload Wizard.
Research page: Crowdsourced evaluation of Upload Wizard instructions
Conclusions:
Instructions inviting labelers to "Add a one-line explanation of what this file represents, including only the most relevant information" about an image produced better quality captions on average than instructions inviting labelers to add a "short phrase". No differences were observed in the length of captions or descriptions produced under any of the experimental conditions (header text or instruction text). Therefore, we intend to use the phrase "one-line explanation" in the Upload Wizard instructions for eliciting captions.