Imagine an attorney going over her notes before oral argument. She already has a solid set of reasons lined up and then decides to add one more argument that has been a little controversial within the team: some like it, but most think it is weak. Flash forward to the judge’s hearing on the argument, and it turns out the majority were right: The judge did not buy that reason at all. So when the attorney opted to include it, did it actually just fail to help, or did it actively hurt the case? You might think, “Well, the strong arguments are still there with or without the weak one, so while it might not help to add a weak argument, it won’t hurt either.” Logically, you might be correct, but psychologically, you would be wrong. The effect of arguments isn’t just additive, it is “averaged” in our perception, meaning that the addition of a weak argument will bring down the average perceived strength of the case.
The social science bears this out. According to a study reported in the journal Nature (Obermaier & Koch, 2024), looking at the joint presentation of both strong and weak arguments in a variety of contexts, strong arguments help, and even moderate arguments help as well, but weak arguments actually hurt. “In a series of four consecutive experiments covering interdisciplinary political and health-related topics,” they note, “our findings consistently demonstrate that the inclusion of clearly weak arguments diminishes the persuasive impact of a strong argument.” This suggests that, even as advocates want to use everything possible that might advance their case, they need to practice discipline when it comes to argument selection and should simply set aside an argument that just isn’t likely to work.
It comes down to selectivity and emphasis: what you pick and what you leave on the cutting room floor will be critical to both written and verbal legal persuasion.
Avoid the ‘Let’s Give It a Shot’ Approach to Argument
The study authors call it the “more the better” heuristic, reflecting the common assumption that more reasons are going to be more convincing than fewer reasons, along with the assumption that less effective arguments may not help as much, but “can’t hurt” either. Legal advocates tend to be sophisticated arguers, so they are likely to put a huge emphasis on argument quality and not just quantity. At the same time, I think the legal setting can also make it a challenge to leave something on the table when there’s even a chance that it might help.
Select Carefully, With the Goal of Presenting the Strongest Overall Case
Rather than approaching arguments additively, seeing each as a potential lottery ticket that could win it all, it is better to think of your arguments as a proportional way of spending your audience’s finite attention and motivation: You want to spend the time on the good stuff. As the study authors note, “If you have strong arguments, you should certainly mention all of them. If you can think of arguments of moderate strength, go ahead and include them to make your argument even more convincing.” But when it comes to the weak reasons, they note it “would be better to keep them to yourself and avoid weakening your argumentation,” adding, “in this case, it is actually true that less is more.”
Raise Your Standard: Is It More Likely Than Not a Help?
An advocate who wants to leave no stone unturned in zealously advocating for their client will be understandably wary to leave out an argument that might have a greater than zero chance of helping. When dealing with human perception and attention span, however, this can be an unreliable impulse. In civil trials, we expect our jurors to apply a preponderance standard — more likely than not — to the question of whether a claim has been proven. This seems like the right test to apply to an argument’s strength as well: The question should not be whether an argument has a chance of helping, it should be whether we have a reason to believe an argument is more likely than not to be helpful. Use your colleagues as sounding boards on this, and when you can, use focus groups and mock trials as well.
So, if we go back to that attorney preparing her outline on the eve of oral arguments, she already has the feedback she needs. Because the judge will be reacting to overall argument strength, adding the weaker argument is more likely to hurt rather than help.
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Other Posts on Argument Strength:
- With Eggs and Arguments, Keep the Sunny Side Up, But Cook Both Sides
- When It Comes to Your Greatest Case Weakness, Steer Into the Skid
- Case Assessment: Check Your “Myside Bias”
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Obermaier, M., & Koch, T. (2024). The paradox of argument strength: how weak arguments undermine the persuasive effects of strong arguments. Scientific Reports, 14(1), 22244.