Back when the Dukes class action was before the Supreme Court, journalists and academics wrote a number of pieces—some longer, some shorter—about whether a class action could be too large. (After the fact, University of Chicago professor William Hubbard published an illuminating article on the same topic.) For the most part, the conclusions tended to be the same: it was not the size of the class action that mattered, but the cohesiveness.

Now Rotterdam PhD candidate Alexandre Biard has weighed in on the topic from a new perspective: behavioral psychology, and the conclusions he reaches are both fascinating and practical. The name of the paper is Iudex non calculat?: Judges & the Magnitude of Mass Litigation from a Behavioural Perspective, and while Biard performs no independent studies himself, his review of the literature offers up some interesting ideas, some of which confirm and some of which contradict my own intuitions about the subject.

According to Biard, the key concept to understand is “entitativity,” which could be roughly defined as cohesiveness, or the degree to which a collection of individuals can be perceived as an entity. Generally speaking, the more a group looks like an entity, the more likely it is that the judge will treat it like one.

Among the qualities that can confer “entitativity” are the number of intimate connections within a group (families, for example, are good examples of entities), and the degree to which the group shares tasks and goals (like sports teams do). As one might expect, these findings have some interesting implications for class certification briefing. Among others, it really is worthwhile to fight over the commonality requirement, because, rhetorically at least, that is where the real heavy lifting is getting done. If the plaintiffs can paint a picture of a class bound by common goals and common connections, then they have a better shot at getting a class certified. Similarly, if the defendant can show that the proposed class is really just a loose connection of people who happened to stumble into similar circumstances, it can defeat certification.

(As a side note, this view of “entativity” may also explain why securities and antitrust classes are often considered easier to certify: it’s easier to see how stock investors or direct purchasers in an industry might be bound by common goals. It is harder to see how used-car purchasers or competitors for work promotions are.)

Biard also finds that the outlier effect tends to affect these groups. The outlier effect describes how individuals will impute characteristics to a group based on what they perceive in its most extreme (or most memorable) members. This suggests a psychological reason for the typicality and adequacy requirements: if the class representative is too far off from the group in one aspect or another (she faces unique defenses for example, or she has an unusually compelling story, then she will skew perception of the merits for the entire group. That’s not good in either direction: either the defendant is being treated unfairly, or the putative class is.

But most importantly, Biard argues that, when confronted with an extremely large group like a prospective class, judges (like any human beings) tend to rely more on emotional reactions than on pure logic. The reason for this is that it is easier to process judgments about large groups of people by using the cognitive shortcuts our emotions afford us. Unfortunately, this also means that judges will rely on stereotypes and intuitive judgments about right and wrong, rather than strict logic or legal text.

So what are the practical implications of this work? It suggests a number of rhetorical focuses for the defendant:

• Keep focused on the diversity within the proposed class. To the degree one can show a proposed class is not a single entity with common objectives, it will be easier to defeat certification. To that end,

• Keep focused on the named plaintiffs. Most named plaintiffs are outliers, if only because they have taken the unusual step of heading up a class action. As a result, keeping the litigation focused on their stories is likely to show how the proposed class is not a cohesive whole.

• Emphasize law and facts. Particularly in class actions, the more a defendant can stick to the existing law and facts as opposed to naked emotional appeals, the more likely it is that it can circumvent any bias that may result from the judge’s employment of the affect heuristic.

[NOTE – This post has been edited to include a previously missing link.]