2021/12/01 Articles

Dilution Effect: Focus on Quality, Not Quantity

December 1, 2021

When pleading a case, you decide to present an argument when you know it is weaker than the others. You think that by having more arguments you increase your chances of convincing the judge, but is this really the case? Is this in the client’s best interest?

According to Niro Sivanathan, professor and researcher at the London Business School, the answer to these questions is no! More specifically, in a TED Talk entitled The counterintuitive way to be more persuasive, Sivanathan warns of a judgment bias called the dilution effect.

In this article, we will define the dilution effect and discuss its implications for the practice of law. We will also explore some ideas for taking advantage of the dilution effect and improving our practice.

What is the Dilution Effect?

The dilution effect occurs when a person has to weigh several pieces of information, some of which are relevant to the judgment to be made while others are not. In such a case, the presence of irrelevant information dilutes or weakens the importance given to relevant information.

Furthermore, it seems that the ability to distinguish between the two types of information (relevant versus irrelevant) cannot prevent the occurrence of the dilution effect. Thus, even if the person knows that some of the information they have is not relevant to the judgment to be made, this information still influences their reasoning.

The most robust psychological explanation for this bias is the averaging effect. More specifically, when you gather information to make a decision or judgment, your brain assigns a weighted score to each piece of information. It then averages these scores. Contrary to what you might think, the brain does not add up the scores assigned to each piece of information. Applied to the law, this explanation means that when you introduce weak points into a pleading or negotiation, these points decrease the overall weight that a judge or the other side will give to your argument.

For example, in their study involving 3,059 Americans, Sivanathan and his doctoral student, Hemant Kakkar, found a dilution effect in drug advertising. Through various experiments, they presented the same drug to two groups of participants. The first group was given a list describing all of the drug’s side effects (major and minor), while the second group was given a list in which only the major side effects were described. The researchers found that participants who received the list containing all side effects (major and minor) rated the overall severity of these effects significantly lower than their counterparts who received the list containing only the major side effects. Moreover, those who received the list of all side effects (major and minor) were more inclined to take the drug and were willing to pay more for it. And yet the major side effects were the same in both lists. From the foregoing, it is clear that the minor side effects diluted the major side effects and therefore affected the assessment of the severity of these side effects.

A second example of the dilution effect was observed in the financial sector. More specifically, studies of financial audits found that auditors were affected by this judgment bias when assessing the risk that an audited company’s records contained misstatements. The studies showed that auditors’ judgment was influenced by irrelevant information, such as the company’s field of activity. This irrelevant information reduced the weight given to relevant information, such as past errors in the company’s audited records.

Implications for the Practice of Law

When applied to the practice of law, these examples suggest that lawyers are not immune to the dilution effect, particularly when assessing the chances of success of their cases. The dilution effect could affect the accuracy of lawyers’ assessments and, consequently, the quality of the advice given to their clients.

In addition, the dilution effect has important implications for the ability of lawyers to influence judges or the opposing party. In fact, the premise of Sivanathan’s TED Talk is that you do not improve the quality of an argument simply by increasing the number of points you raise.

Some Ways to Improve Your Practice

In light of the foregoing, here are three tips for taking advantage of the dilution effect in your practice:

  1. When starting a case, be sure to gather all the relevant facts and evidence and examine them with the same rigour. In this regard, the use of an outline setting out the specific theory of the case can assist you in gathering information and help you sort out what is relevant from what is not. In this way, you will be more accurate when assessing a case’s chances of success;
  2. When preparing for a trial or negotiation, focus on the two or three most relevant arguments. Your pleading or negotiation strategy should be based on these arguments. Lawyers who identify arguments that are truly relevant to their case are more likely to satisfy the needs of their clients than lawyers who engage in legal sagas and raise all sorts of arguments without achieving satisfactory objectives. Such legal sagas can waste the time and money of clients, who are bound to be unhappy. If a client insists that an argument be presented even though you have expressed the opinion that the argument is weak, put that opinion in writing and send a copy to your client;
  3. Finally, if you believe that all your arguments are powerful or if you have doubts about the relevance of an element for assessing the chances of success of a case, take a step back and consult a colleague. Tell them what you plan to argue, your negotiation strategy or your opinion on the chances of success of the case. This will provide you with the opportunity to get an objective opinion about the strengths and weaknesses of the case.

In closing, the dilution effect teaches us that quality must trump quantity. Focus on strong arguments in your cases. By doing so, you’ll be able to offer your clients a better service!



Australian National University, “Bias: Dilution Effect”, Integration & Implementation Sciences, February 2021, online:

Sivanathan, N. and Kakkar, H. “The unintended consequences of argument dilution in direct-to-consumer drug advertisements”. Nat Hum Behav 1, 797-802 (2017).

Sivanathan, N. “The counterintuitive way to be more persuasive”, TED Talk, TEDxLondonBusinessSchool, January 2021, online: The counterintuitive way to be more persuasive

“Dilution Effect Definition”. Psychology Research and Reference. Online:

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