Mick Couper really likes pictures. He not only takes a lot of them he also has had an ongoing interest in how incorporating pictures into Web surveys affects how people answer questions. Way back in 2004 he and his colleagues showed that the frequency with which respondents reported certain types of events (shopping, going to sporting events, etc.) varied significantly depending on the picture displayed with the question. Pictures of infrequent events (shopping in a department store) depressed reports of shopping frequency while pictures of more frequent events (shopping in a grocery store) increased the number of shopping trips people reported. In subsequent research he and his frequent collaborators (Roger Tourangeau and Fred Conrad) showed that respondent reports of their health status varied when the question was accompanied by a picture of a healthy woman jogging versus a sick woman in a hospital bed. While the 2004 research showed assimilative effects (pictures with more frequent events led to higher frequency reporting) the second experiment showed how pictures sometimes can have contrast effects (people reporting being less healthy when a picture of an obviously fit person exercising is shown). So while it's clear that respondents react to pictures the direction of that reaction and its impact on how they answer survey questions is unpredictable.
In the current issue of POQ Mick has an article co-authored with Vera Toepoel that looks at whether verbal instructions can overcome the influence that pictures generate. Their research shows that well written questions with clear instructions can obviate the influence of pictures, even when the two are inconsistent. In other words, there seems to be a hierarchy of features in which Web respondents give much greater weight to verbal instructions and cues than they do to pictures and graphical images. In an additional analysis they find no evidence that including pictures in Web surveys creates a more respondent friendly survey, that is, respondents do not report a more positive survey experience with pictures than without.
As if we needed it, this is one more bit of evidence that there is no substitute for clear, concise, and well written questionnaires. Further, using pictures or other graphical images to try to increase engagement may well come at cost that is hard to predict or measure.