Arguments: Quality, Quantity, and the Persuasive Power of Three

What matters more when presenting arguments: quality or quantity? Is there an optimal number of arguments to present? Myriad examples exist for a “Rule of Three,” which posits that information presented as a trio, whether spoken or written, is inherently more interesting, memorable, effective, and even persuasive. Examples of these rules abound across a variety of disciplines, including aviation, computer programming, medicinal chemistry, and more. What is it about triads that is so appealing, and how can litigators utilize research on quality and quantity of arguments for their benefit? In a jury trial, persuading jurors via argument is the ultimate job of any trial attorney. Attending to jurors’ motivation and ability to contemplate arguments can strengthen your case, and presenting those arguments as a trio can be powerfully persuasive. 

A prominent psychological theory of how persuasion occurs is the ELM, or Elaboration Likelihood Model (Petty & Cacioppo (1984, 1986)). The ELM posits two routes of persuasion, a central route and a peripheral one. The central route consists of thoughtful consideration of the message, its ideas, logic, and content. With central processing, the message recipient is an active participant in the process of persuasion. This route can only occur when the message recipient has both the motivation and ability to think about the message and its topic. If they do not care about the topic, they will not be motivated. In addition, if they cannot understand because they are distracted, the information is too complex, or they cannot hear you, they will lack the ability to attend to your message. Nevertheless, if you can overcome these obstacles, persuasion via the central route will be more enduring, predictive of future behavior, and resistant to counter persuasion.

With the peripheral route, persuasion is based on unrelated external factors, like message length, the font it is typed in, or the perceived intelligence and/or attractiveness of the speaker. Attitude changes via this route are temporary in nature, less predictive of future behavior, and less resistant to counter persuasion. The model explains how, at times, we can persuade with less substance and more superficiality, or vice versa. Consider a research study where participants served as mock jurors and listened to arguments in a simulated court trial (Calder et al. (1974)). The study was setup so that one side presented many more arguments than the other did. The verdicts demonstrated that an increased number of arguments determined which side the mock jurors favored. The key in persuading, then, lies with knowing your audience. If they do not have the motivation or ability to think about the message they will likely fall back to using peripheral cues, where quantity wins out over quality and more arguments are better regardless of whether they are strong or weak. For messages without persuasive intent, quantity is also king (Shu & Carlson (2014)).

Take the example of a jury trial involving a complex matter that lasts for many weeks or even months. Here, when it comes to the jurors, the central route is preferred due to the lasting attitudinal change it can evoke, especially since jurors will deliberate long after the beginning of the proceedings. Given the more effortful processing with the central route, stronger arguments are of course more compelling. So how can you bolster jurors’ motivation and ability to facilitate that central processing? Set the tone early by empowering them as arbiters who have the power to right a wrong or settle a longstanding debate between parties. Request to provide mini-summaries at appropriate points during the trial to reacquaint jurors with key evidence and testimony, particularly with lengthy trials or those interrupted by holidays. Also, make a concerted effort throughout the trial to keep things simple. Limiting jurors’ cognitive load by breaking down difficult to digest information into manageable, understandable, and relatable chunks can facilitate both their motivation and ability. Research indicates that jurors resonate with compelling stories, likely because it helps demonstrate why they should care (Pennington & Hastie (1992, 1993)). It improves their motivation, which facilitates central processing. Thus, constructing a captivating narrative around your facts can strengthen jurors’ acceptance of your arguments.

Once you’ve ensured the audience is motivated and able, the research suggests you should focus on the quality of your arguments, and the number of them you are going to present (Wood et al. (1985)). According to research by Shu & Carlson (2014), in a persuasive setting (like a courtroom), the Rule of Three stands; persuasion bolsters from one claim to two, and further from two claims to three. So what happens beyond three? In this case, making more claims is actually worse, and the old adage of “if it seems too good to be true, it probably is” kicks in. Anything beyond three attenuates the persuasive effect, and triggers skepticism. More specifically, going from three claims to four results in significantly decreased positive elaboration (positive thoughts about the claim), while also significantly increasing negative elaboration thoughts and “counterarguing” (not believing the claim and seeing it as contradictory to other claims). Interestingly, the researchers found that a “2+1” approach, i.e. presenting two claims and then adding a third one, strengthened the overall persuasive effect, as opposed to simply starting with all three claims.

So is it that simple? Are three quality arguments always optimal in persuasive settings? When it comes to refuting the opposition’s points, research reveals that presenting a larger number of counterarguments can be more effective at changing minds (Ecker, et al. (2019)). Nevertheless, whether on offense or defense, you can conflate your arguments and strive for three points, or present arguments in buckets of threes (or even better, in “2+1” fashion) to harness the persuasive power of the research presented here. In short, for your next trial, remember to motivate your jurors, bolster their ability to attend to your arguments, and leverage the persuasive power of three. These research-backed suggestions can help the jury lean in your client’s favor and ultimately contribute to a winning case.

Calder, B., Insko, C.A., & Yandell, B. (1974). The Relation of Cognitive and Memorial Processes to Persuasion in a Simulated Jury Trial. Journal of Applied Social Psychology, 4, 62-93.

Coulter, K., & Punj, G. (2004). The Effects of Cognitive Resource Requirements, Availability, and Argument Quality on Brand Attitudes: A Melding of Elaboration Likelihood and Cognitive Resource Matching Theories. Journal of Advertising, 33(4), 53-64.

Ecker, U. K. H., Lewandowsky, S., Jayawardana, K., & Mladenovic, A. (2019). Refutations of equivocal claims: No evidence for an ironic effect of counterargument number. Journal of Applied Research in Memory and Cognition, 8(1), 98-107.

Luttrell, A. “To Be Persuasive, Make Just Three Claims.” Psychology Today, Sussex Publishers, LLC, 15 Nov. 2020, www.psychologytoday.com/us/blog/difference-opinion/202011/be-persuasive-make-just-three-claims.

Pennington, N., & Hastie, R. (1992). Explaining the evidence: Tests of the story model for juror decision making. Journal of Personality and Social Psychology, 62,189-206.

Pennington, N., & Hastie, R. (1993). The story model for juror decision making. In R. Hastie (Ed.), Inside the juror: The psychology of juror decision making (pp. 192-221). New York: Cambridge University Press.

Petty, R. E., & Cacioppo, J. T. (1984). The effects of involvement on responses to argument quantity and quality: Central and peripheral routes to persuasion. Journal of Personality and Social Psychology, 46, 69-81.

Petty, R. E., & Cacioppo, J. T. (1986). Communication and persuasion: Central and peripheral routes to attitude change. New York: Springer-Verlag.

Shu, S. B., & Carlson, K. A. (2014). When three charms but four alarms: Identifying the optimal number of claims in persuasion settings. Journal of Marketing, 78(1), 127-139.

Wood, W., Kallgren, C. A., & Preisler, R. M. (1985). Access to attitude-relevant information in memory as a determinant of persuasion: The role of message attributes. Journal of Experimental Social Psychology, 21(1), 73–85.