imagery. However, to establish that imaginal processing was, in fact, the cause of any observed effects, manipulation and process checks are required. Several issues arise in this regard. Some researchers have argued that imagery may not be adequately captured through written responses, as sensory experiences may be difficult to verbalize (Morris & Hampson, 1983). Further, all retrospective measures (be they written responses or scales) are criticized on the grounds that they measure only respondents' memory for images and not the images themselves. On the other hand, concurrent measures interrupt subjects while they are engaged in imaginal processing. Researchers also need to be sensitive to the issue of demand effects while constructing their manipulation and process check measures. In other words, the measures should not lead subjects to falsely indicate that they engaged in imagery simply in order to provide an “acceptable” response. Thus, an important avenue for future research is the development of more refined and nonintrusive measurement techniques to obtain evidence of imaginal processing.
The purpose of this chapter was to review and reconcile the body of evidence relating to the role of imagery instructions in persuasion. We began by clarifying the concepts of mental imagery and imagery instructions and exploring the mechanisms implicated in their use. We then described the inconsistent findings regarding the impact of imagery instructions and identified circumstances under which instructions to imagine might be persuasive. Thus, we explored various issues in the provision of the instructions that might influence their capacity to enhance persuasion. We also suggested that imagery instructions might be persuasive in conjunction with other imagery-eliciting strategies or facilitating factors. Finally, we discussed some issues relating to the measurement of mental imagery evoked through instructions to imagine. In each section, we described relevant findings from a recent study and identified possible avenues for future research in the area.