Information Cascade as seen in jury duty– 12 Angry Men
https://www.abajournal.com/books/article/podcast-episode-158
Twelve Angry Men, the powerful 1957 film on a jury’s deadlock in a murder trial has stood the test of time through its unpacking of how fallacious judgements come to be, unvarnished showcase of various individual response to group dynamics, and a deft handling of tension in the admission of reasonable doubt amid the path to unanimity.
The plot line is driven by rounds of voting by the twelve jurors. As they sway and revert for reasons purely logical or not, we see ourselves in them. While we can relate to the same underlying impulses and emotions guiding the jurors, the Networks lecture on Information Cascades pinpoints exactly what forces are at play. The jurors face a binary decision of Guilty (G) or Not Guilty (NG). The first round of voting, where all but one juror is convinced by witness accounts of the murder, takes place publicly and sequentially. Jurors 1 and 2 claim G and are succeeded by the same signal until Juror 8 claims NG, who is unable to overturn the cascade as Juror 9 goes on to claim G, as do Jurors 10 11 and 12, leaving Juror 8 as the sole outlier much to everyone’s chagrin. Indeed it was seen in class, that cascades arise easily, based on very little information with a lot of people involved, and that cascades can very well turn out wrong. Juror 8 doesn’t necessarily have access to better or more information in this scenario, he has simply decided to give more weight to his private signal. Interestingly, in the follow-up round of his proposed secret vote (himself abstaining), one person among the original 11 who had voted G switched to NG. This aptly captures the illusion of crowd wisdom when guesses are not made anonymous— others’ votes are taken in as signals in the determination of your own.
The movie transitions into a gradual persuasion for the rest of the jurors to fall in line, and we might question why Juror 8 ended up successfully overturning the cascade when for a long time, the net difference between G and NG votes was way over 2. This ties in another part of the course: voting, where the requirement of unanimity serves a unique function in our legal system’s determination of guilt. Had it been a majority rule, common in elections and referendums, the first round of votes would have ended the movie. That the jury can not deliver a guilty verdict until unanimous can be viewed as them only able to reveal, but not act on their signal, until all are identical. This delay is where information cascades in juries depart from that of product advertisement for example, where signals are buying decisions that can’t be undone. This perhaps speaks to the cautious attitude of our legal system towards sentencing people.
Twelve Angry Men poses a warning tale on human judgement that has woven its way into our social fabric, and hopefully with an understanding of cascades we can recognize the capricious nature of consensus-building rested on order and anonymity of votes.