Does presentation matter? : an analysis of images and text in a choice experiment of green roofs

The use of images in choice experiment surveys has been increasing over time. Research on the impact of complex graphical displays of information on respondent comprehension and the quality of preference estimates yields mixed results. We contribute to this literature by leveraging a split-sample design for a choice experiment concerning green roofs in Portland, Oregon, to investigate the effects of including high-quality static images in the survey instrument and in the choice cards. We find that respondents who completed the 'image' version of our survey had a significantly higher total willingness to pay (TWTP) to support a new green roof program than respondents who completed the 'text only' version of the survey. We explore the relationship between respondent characteristics and TWTP and find that respondents with little knowledge about green roofs who completed the image survey have a TWTP that is over three times larger than text survey respondents. Our findings support the trend in the literature of using images in choice experiments but also highlight the importance of paying attention to image quality in survey design, using focus groups with mixed previous knowledge for survey refinement, and gathering information in surveys themselves about respondents' prior knowledge about the valuation scenario.