It is conversation I frequently have when sending jurors off to deliberate as part of a mock trial.

"Can we ask the attorneys questions about the case?"

"No, just do your best with what you remember."

"But what if there are things we forget?"

"Don't worry, as a group you're going to remember more than you would as individuals."

That seems like it would be true, right? A group should have a stronger collective memory, operating as a sum of the individual recollections within the group. That is part of the reason why the legal system in this case opts for group rather than individual decision-making. But what if it turns out that this isn't true?

And it turns out, this isn't true. According to a recent meta-analysis of 64 studies on the recollection results of collaborating groups (Marion & Thorley, 2016), groups are less effective in recall than the individuals in those groups would be. Based on a process the researchers call "collaborative inhibition," the group actually remembers less effectively than the individuals would have remembered if they were working alone. This strikes me as a finding that goes to the heart of what it is that we think works about the jury system, and carries some implications for how we address group recollection. So in this post, I will take a look at this unexpected finding and share some thoughts on what it says about making your case stick with a jury.

Importantly, there is some nuance to the finding. Groups still outperform a single individual at a memory task. However, when you compare the group's performance to the potential performance by that group by looking at the pooled recollection of the individual members of that group, the group does worse than the individuals would have done on their own.

So that prompts a few questions.

Why Would Groups Do Worse at Recollection?

There are actually a few common reasons. One is what the researchers call "social loafing," as group members reduce efforts due to a diffusion of responsibility. In other words, "Since it isn't all on me, I'm going to relax a bit, confident that the others in the group will make up for it." Another reason why the group would do worse is "evaluation apprehension," which causes you as a group member to not share as much out of fear that another group member will tell you that you're wrong.

But the main explanation for reduced group performance is one that carries an important lesson on human cognition. The explanation is called "retrieval strategy disruption," and the study authors explain what it means: "Collaborative group members each attempt to recollect information in an order consistent with their own optimal retrieval strategies. As each member's strategy differs, they disrupt each other and the group's recollection is impaired."

So, for example, let's say that one group member recalls information in a timeline order, while another recalls it based on their own idiosyncratic order of importance. As they each contribute information, they each end up disrupting the other's preferred strategy and they end up doing worse as a team than they would as individuals.

And what applies to recollection is also going to apply to other cognitive activities. Jurors are not just going to recall the case in different ways, they're going to process and evaluate it in different ways as well. That disruption effect perhaps explains why one of the first reactions to seeing a mock jury deliberate in real time is, "This is so messy."

What Do You Do About It?

The authors note that the effect seems to be inherent in group process, and observe that the disruption effect is stronger in larger groups: So your 12-person jury is likely to do worse in collective understanding than a 6-person jury would be. The researchers also observe that the effect is stronger in groups of strangers than in groups of close acquaintances, so a jury is going to be particularly susceptible to collaborative inhibition.

The solution is to think continuously, not just about what you are putting into evidence, but about what the jury is likely to be getting. Build your case, not out of the sum-total of evidence, but around the points that you expect to serve as the peaks of attention, and around the few messages that are likely to stick from each witness.

Importantly, the study authors found that the group-recollection deficit is less of a problem when the information is presented as a narrative, finding "smaller effects occurring for story-like materials than uncategorized materials." So following the common advice to "Tell a story" makes your case not only more persuasive but also more likely to stick in the group's recollection.

An Argument for Interim Deliberations?

There is one final and interesting result of the research that might suggest that the problems in group recollection are not an argument for less deliberation, but rather an argument for more deliberation. The researchers also tested the question of how well individuals do at recall after working with other group members. And the answer is that they do better. "Despite the disruptive effect of collaboration on group remembering," they write, "the good news is that later individual memory generally benefits from prior collaborative retrieval." So, in other words, if groups were allowed to engage in interim deliberation, and were able to discuss the evidence with each other on a daily basis as the evidence is coming in, there is reason to believe that their recollection of that evidence is going to be better.