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How Group Dynamics Brought Athens and Sparta to War


By Joe Byerly

I originally published this post over at The Zen Pundit as part of The Thucydides Round Table, an eight week deep dive into an exceptional work of history. If you haven’t read Landmark Thucydides yet, I encourage you to pick up a copy, read along, and join in on the discussion here

In Book 1 of The Landmark Thucydides the council of citizens in Sparta gather to hear the Corinthians, the Athenians, King Archidamus, and one of the ephors debate whether or not Sparta should go to war with Athens. It is within this scene that we witness a psychological phenomenon called “Group Think”; ultimately ending in a declaration of war.

After several of the sides had spoken their piece, the ephor, Sthenelaidas rose to address the group. He quickly dismissed the logical arguments of Archidamus, who thought that the decision to go to war should be deliberate and made only after the Spartans were better prepared to face the Athenians. Instead, Sthenelaidis appealed to the assembly’s emotions, calling for them to “Vote therefore, Spartans for war, as the honor of Sparta demands, and neither allow for further aggrandizement of Athens, nor betray our allies to ruin, but with the gods let us advance against the aggressors.”

To understand the significance of what happened next, we must first understand how the Spartans traditionally voted. In J.E. Lendon’s Song of Wrath: The Peloponnesian War Begins the author writes:

“For decisions on matters such as war and peace, Lycurgus had given the Spartan also an assembly of citizens, which voted not by show of hands as at Athens, but by shouting, and the presiding ephor decided which shout was louder.”

Instead of allowing the vote to take place in accordance with Spartan tradition, the ephor asked the crowd to divide. He pointed to a place in the assembly hall and asked all Spartans in favor of war to move to that spot. He then pointed out another location in the assembly hall, and asked those in favor of peace to move to that spot. Here is where the group gains power over the individual and in this instance drove the Spartans to war.

Research has shown that groups can impact individual decision-making when anonymity is reduced; which is what happened when the method of voting switched from yelling within a crowd to having the voters physically divide themselves. Thucydides believed that Sthenelaidas understood this because he writes that he switched the method of voting because, “he wished to make them declare their opinion openly and thus to increase their ardor for war.”

How could Spartans have potentially avoided the pitfalls of group think? In a 2014 Harvard Business Review article, authors Sunstein and Hastie recommend the Delphi Method:

“This approach, developed at the RAND Corporation during the cold war, mixes the virtues of individual decision making with social learning. Individuals offer first-round estimates (or votes) in complete anonymity. Then a cycle of re-estimations (or repeated voting) occurs, with a requirement that second-round estimates have to fall within the middle quartiles (25%–75%) of the first round. This process is repeated—often interspersed with group discussion—until the participants converge on an estimate. A simple (and more easily administered) alternative is a system in which ultimate judgments or votes are given anonymously but only after deliberation. Anonymity insulates group members from reputational pressures and thus reduces the problem of self-silencing.”

One is left to wonder what might have happened if the ephor did not manipulate the voting method to push the Spartans toward war. Could the Peloponnesian War have been avoided? Or could the Spartans have bought more time and better prepared for the conflict with Athens? This vignette from Book 1 serves as a warning for leaders who attempt to make critical decisions based on the consensus of groups. Understanding these dynamics is the best way for leaders to safe guard against the pitfalls of group think.