Persuasive effects of story and statistical evidence.

• Author: Baesler, E. James

Facts and opinions, when offered in support of a communicator's claim, constitute the domain of factual evidence (Reinard, 1988), which can be subdivided into report evidence,(1) such as a story narrative, and statistical evidence, defined as numerical representations of events.

Cognitive response theory (see Petty, Ostrom, & Brock, 1981 for a review) would suggest that if an agent attempted to support a persuasive claim with evidence, then a target would generate cognitive responses (CRs) to the message. Petty and Cacioppo (1986) found that high quality message arguments produce more favorable and fewer unfavorable cognitive responses (UCRs) than low quality arguments. These favorable cognitive responses (FCRs), in turn, are positively correlated with persuasive outcomes.

Petty and Cacioppo do not address the characteristics of the message arguments that may be related to CRs or persuasive outcomes. Thus, two evidence issues that might increase our understanding of persuasion remain unaccounted for by current CR models: (a) What characteristics distinguish story from statistical evidence? and (b) Which of these discriminating characteristics are positively correlated with persuasive outcomes?

INVOLVEMENT, CREDIBILITY, AND VIVIDNESS

Persuasive effects of evidence are moderated by at least three variables not subsumed by any one persuasion theory, but nonetheless that need to be accounted for when attempting to explain effects of evidence. First, higher degrees of topic involvement facilitate the persuasive effects of evidence when compared to low topic involvement apparently because of systematic processing of central message cues (Stiff, 1986). Second, communicator credibility interacts with involvement, such that as involvement increases, the effect of credibility on persuasion increases to some point beyond which further increases in involvement decrease persuasiveness (Stiff, 1986). Third, several studies have shown support for the persuasive advantage of vivid when compared to nonvivid evidence types of evidence (e.g., Kazoleas, 1993; Baesler & Burgoon, 1994); other research has not revealed support for the vividness hypothesis (e.g., Iyengar & Kinder, 1987; see review by Taylor & Thompson, 1982). This study attempted to control these potentially confounding variables by creating messages that are comparable on topic involvement, communicator credibility, and message vividness.

CHARACTERISTICS OF STORY AND STATISTICAL EVIDENCE

In a social influence context, given sufficient target motivation (such as an involving message topic), story evidence may be easier to argue against than statistical evidence. A persuader's use of a story narrative could be refuted by the target's recall of a single contradictory story. This is not the case for arguing against statistical evidence. Typically, only experts in particular knowledge domains would routinely have access to statistical data in memory, whereas most individuals have a storehouse of stories on many topics. Thus, it would be difficult for most adults to marshal statistical data to counterargue a claim, but story data, since they are based on one's personal experience or the experience of others that is readily accessible, would be the preferred mode of arguing against both story and statistical claims.

Other features of evidence that distinguish story from statistical evidence, and might also be related to persuasiveness, include readability, complexity, personalness, and scientificness.(2) Since the numerical representation of statistics is encountered less frequently in everyday life than in stories, and since statistics are more difficult to interpret than a story, statistics are expected to be less readable and more complex than stories.

Personalness and scientificness of evidence were included in this study since they are characteristics unique to a particular type of evidence. The content and structure of the story, with characters engaged in a dialogue, are inherently more personal than statistics; statistics, by including numerical data based on some type of research, are often perceived as inherently more scientific than stories.

Given the review of evidence characteristics and persuasion, the following hypotheses and research questions were posed:

H1: Story and statistical types of evidence should be persuasive in: (a) changing beliefs in the direction advocated in a message and (b) producing a greater number of favorable than unfavorable cognitive responses.

H2: Statistical evidence, when compared to story evidence, generates: (a) greater belief change in the direction advocated by the message and (b) fewer unfavorable cognitive responses.

RQ1: Are there differences in perceptions of the readability, complexity, personalness, and scientificness of story and statistical evidence?

RQ2: Given differences in evidence characteristics, do any of these...