Persuasive Advertising - J. Scott Armstrong [10]
Experimental evidence comes in two types: laboratory experiments and field experiments. The former allows for tighter control, while the latter are more realistic.
Some people believe that laboratory studies (which will simply be referred to as lab experiments for the rest of this book) cannot be used to generalize to realworld problems. To address this issue, leading researchers were asked to compare findings from laboratory experiments with those from field experiments in 11 areas of human and organizational behavior; the findings were similar (Locke 1986). In addition, an analysis of 40 studies on sources of communication found similar effects from field and laboratory studies (Wilson and Sherrell 1993).
Exhibit A provides a summary, starting with the weakest evidence and moving toward the strongest. The weak forms are adequate only for the principles that have few conditions and where advertisers receive good feedback on effects.
The best evidence—and the source of much of the evidence provided in this book—is the meta-analysis, which involves a formal collection and analysis of all relevant evidence on a given principle, especially when the evidence involves laboratory and field experiments. Meta-analyses provide full disclosure on how the researchers searched for studies, coded the results, and summarized the findings. Findings from meta-analyses are more valid than those from traditional reviews (Beaman 1991). The meta-analyses are of particular value when the conditions are well specified.
Exhibit A Types of evidence (listed from weak to strong)
Casual observation
Typical practice
Expert advice
Empirical evidence
Non-experimental data
Quasi-experimental data
Experimental data
Lab experiments
Field experiments
Meta-analyses of experimental findings
Not all principles are based on evidence. Some seem so obvious that no one has bothered to study them. An example of an obvious principle from another area is “ensure that the computer is plugged in before calling tech support.” I provide some obvious principles because they are an important part of the checklist. For example, I have seen ads that, by mistake, omit critical information about how to obtain a product or when an advertised event will take place.
The book is organized so that you can easily skip the evidence as these sections are flagged by sub-titles. But I do not advise doing that, especially if a principle conflicts with your beliefs – and some will. It is not wise to change one’s opinion without seeing the evidence.
The various studies can help you to understand how to apply the principle to a given situation. They allow the reader to see the nature and strength of the evidence for each principle. Some of the studies might be of particular relevance to your problem, so I provide the sources. In doing so, Persuasive Advertising follows a convenient academic convention: author name and publication year, such as “(O’Keefe 1999),” typically placed at the end of the description of the evidence. Thanks to the Internet, the studies are easy to track down. For example, most papers are in full text on the Internet so that one only needs to enter a few words from the title into a Google Advanced Search.
Barriers to the use of evidence-based principles
A survey of 40 respondents from the ten largest advertising agencies in Norway found that these advertisers were largely ignorant of the research literature on advertising (Helgesen 1994). For example, none of the advertising agencies vying for Subaru’s U.S. account used prior research on advertising in their proposals (Rothenberg 1994).
Advertisers might question the value of using findings from empirical research, preferring instead to rely on their judgment. Of course, there are potential