When Less is More: Bad Arguments Can Weaken Good Ones

This study investigates the dilution effect in persuasion—-the hypothesis that adding weakarguments to strong ones undermines persuasiveness, rather than bolstering the overall case orleaving it unaffected. We examine this phenomenon across domains such as legal reasoning andpersuasion in AI regulation, testing whether people are less persuaded if they read a strong andweak argument rather than a strong argument one. Through experiments, we measure shifts inparticipants’ attitudes, providing empirical insights into how argument quality shapes persuasion. In Study 1, we show some promising result which shows decreased persuasiveness with anadditional weak argument, but Study 2 fails to replicate this effect. Study 3 indicates thatintroducing a weak argument opposed to people’s initial position reduces arguments’ overallpersuasiveness, providing insights into the subtleness of this effect. Our findings aim to informmore effective communication strategies in advocacy, public messaging, and beyond.