The 'Strong' theory of advertising receives widespread support and is characterized by the beliefs that advertising increases peoples' knowledge, changes peoples'attitudes and, as a result, is capable of persuading people who have not previously bought a particular brand to start buying it and to persuade others who already buy it to do so with greater frequency and in preference to other brands on offer. Advertising is seen as being capable of increasing sales not only of brands but also of complete product categories and is a prime mover in the capitalist system. There is another theory, the 'Weak' theory, developed especially in Europe and strongly rooted in empiricism. Derived from Andrew Ehrenberg's Awareness-Trial-Reinforcement hypothesis, the 'Weak' theory argues that advertising is capable of increasing peoples' knowledge but actually communicates not very much: advertising is not strong enough to convert people whose beliefs are different from those championed in an advertisement: most advertising is employed defensively: members of the public frequently claim that they are not influenced by advertising and they are probably right. In general, according to the 'Weak' theory, consumers are apathetic and rather intelligent. The two theories are at opposite ends of the spectrum. It is easy to produce a great deal of circumstantial evidence to demonstrate that the Strong theory of advertising does not accord with reality. Research can make a major contribution towards providing the evidence which will help us all to better understand how advertising really works.
This paper is in three parts. Part 1 introduces and describes the Strong and Weak theories. Outside observers (both protagonists and antagonists of advertising) and many practitioners believe in the Strong theory. This paper introduces facts suggesting the likelihood that the Strong theory is not universally or even generally valid. The paper hypothesizes that for "high involvement" products and for the small proportion of successful new brands in "low involvement" product fields, advertising works according to the Strong theory. By contrast, in the cases of established brands in "low involvement" product fields, advertising is more likely to operate according to the Weak theory. Taking account of the large but unquantified amount of advertising that has no effect at all, it is estimated very approximately that more than three-quarters of all advertising works (or fails to work) according to the Weak theory. Part II argues that the almost universal belief in the Strong theory has contributed to considerable waste. American universities are imbued with the Strong theory, so that most new entrants into the advertising business are indoctrinated with it. The resultant attitude and practice of over-promise and under-delivery have had malevolent effects. Part III argues that research has an important role in any evaluation of the Strong and Weak theories. Case-by-case study depends on our ability to relate advertising exposure to a longitudinal tracking of penetration and purchase frequency. This is a practicable albeit difficult procedure. A final point relates to advertising research. Quantitative copy testing employing measurements of intrusiveness, recall and persuasion - procedures widely practiced in the United States - is predicated on the implicit assumption that advertising is working according to the Strong theory. Qualitative creative development research (strongly associated with London agencies) is more harmonious with the Weak theory: and is often flexible enough also to give fair treatment to advertising that works as a strong force.