Studies on persuasive arguments have generally found that claims supported by high-quality evidence are better accepted than claims supported by low-quality evidence. However, an experiment by Hoeken and Hustinx (2007) demonstrated that this effect was only observed in short texts (a claim with evidence), but not in longer texts (where information unrelated to the evidence was added at the end of the text). The present experiment was conducted to examine whether this effect of text length could be explained by distraction (the additional text at the end distracts the reader) or by dilution (the additional text makes the fragment less diagnostic for claim evaluation). Participants (N = 629) read two texts with a claim supported by high-quality or low-quality (anecdotal, statistical, or expert) evidence. The text was presented in one of the three versions: (1) short, (2) long with additional information at the end, or (3) new in comparison to Hoeken and Hustinx (2007) – long with additional information at the start. The data found support for the distraction explanation. An effect of evidence quality on claim acceptance was observed in two conditions: in the short text, and in the longer text with additional information at the start. The effect of evidence quality was not found in the longer text with additional information at the end.
- Hornikx, J. (2016). Evidence quality variations and claim acceptance: An experimental investigation of the role of distraction and dilution. Paglieri, F., Bonelli, L., & Felletti, S. (eds.), The psychology of argument: Cognitive approaches to argumentation and persuasion (pp. 211-222). London: College Publications. [paper book]