"When interpreting the information in an advertisement, consumers may use either imagery processing or analytical processing," explain Debora Viana Thompson and Rebecca W. Hamilton (University of Maryland). Imagery processing occurs when, "a consumer is imagining herself using the advertised product," as opposed to analytical processing, or "weighing [of] the positive and negative characteristics of the product."
The authors found that ads comparing two brands are effective when people use analytical processing, but not as effective when people use imagery processing. The opposite was true for non-comparative ads.
"Imagery processing encourages consumers to focus on a single brand rather than dividing their attention among two or more brands," explain the authors. "Analytical processing encourages consumers to compare product characteristics across brands, and comparative ads provide explicit comparisons among brands."
The authors also used specific features of sample ads, such as vivid ad text and matrix tables, to influence subjects to use one type of processing over the other. When perception types were induced, they again found that comparative ads are much more effective when analytical processing is used than when imagery processing is used.
Debora Viana Thompson And Rebecca W. Hamilton. "The Effects of Information Processing Mode on Consumers' Responses to Comparative Advertising." Journal of Consumer Research. March 2006.