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Cheating: Sign-Stealing in MLB

The Houston Astros’ sign-stealing scheme rocked the baseball world, leading to a game-changing MLB investigation and fallout.

In baseball, catchers signal to pitchers which type of pitch to throw. Usually, catchers do this by holding down a certain number of fingers on their non-gloved hand between their legs as they crouch behind the plate.  It is typically not as simple as just one finger for a fastball and two for a curve, but not a lot more complicated than that.

In September 2016, an intern for the Houston Astros major league baseball (MLB) team named Derek Vigoa showed Astros’ general manager Jeff Luhnow a PowerPoint presentation. It featured an Excel-based application programmed with an algorithm that could decode the pitching signs that opposing teams’ catchers flashed to their pitchers. The Astros called it “Codebreaker.”  One organization employee referred to the sign-stealing system that evolved as the “dark arts.”

MLB rules allowed a runner standing on second base to do what he could to steal signs and relay them to the batter. But MLB rules strictly forbade using electronic means to decipher and signal signs.  The Astros “Codebreaker” violated these rules.

According to Wall Street Journal writer Jared Diamond:

The way Codebreaker worked was simple:  Somebody would watch an in-game live feed and log the catcher’s signals into the spreadsheet, as well as the type of pitch that was actually thrown.  With that information, Codebreaker determined how the signs corresponded with different pitches.  Once decided, that information would be communicated through intermediaries to a baserunner, who would relay them to the hitter.

Starting around June 2017, the system was embellished by Astros players.  They started watching a live game feed on a monitor near the dugout and then would bang on a trash can to communicate the coming pitch to the batter.  The “banging scheme” lasted through the 2017 World Series, which the Astros won over the Los Angeles Dodgers.

Late in the 2017 season, MLB caught the Boston Red Sox relaying signs from their video room to an Apple watch worn by a trainer sitting in the dugout. Commissioner Rob Manfred fined the Red Sox and issued a strong warning to all teams against illegal electronic sign-stealing. It was suspected (accurately, as it turns out) that the New York Yankees had also been using technology to steal signs in 2015 and 2016. Despite these incidences, and the MLB warning, the Astros continue with “Codebreaker.”

The Astros’ scheme lasted into the 2018 season, in road games as well as home games, even though other teams were very suspicious that the Astros were stealing signs. Other teams often changed their own signs several times a game in an attempt to thwart the suspected sign stealing by the Astros.  An executive for an opposing team was quoted as saying “The whole industry knows they’ve been cheating their asses off for three or four years.  Everybody knew it.” (Svrluga & Sheinin).  Indeed, many teams had complained to MLB’s executives about the Astros’ cheating. Some suspect the cheating continued through the 2019 season, though others think not.

For the uninitiated, sign-stealing might not seem like it would give a big advantage.  After all, even if a batter knows that a certain pitch is coming, he still has to hit it.  It can’t be easy hitting a 100-mph fastball or a major league-caliber slider, even if you know it’s coming.  Nonetheless, the advantage is substantial.  According to the Washington Nationals’ pitching coach Paul Menhart, “It’s the worst feeling in the world stepping on that mound and having an idea that the hitter knows what’s coming.  It’s one of the most unnerving feelings.  You feel helpless.  You just get ticked off to the point where you lose total focus and confidence.” (Svrluga & Sheinin).

There is no question that many of the Astros players were actively involved in the scheme.  The Astros manager, AJ Hinch, clearly knew about it.  There is substantial, though perhaps not airtight evidence, that General Manager Rob Luhnhow also knew.  Carlos Beltran, a Hall-of-Fame caliber player near the end of his 20-year playing career, was a leader in the scheme. Bench coach Alex Cora was a primary instigator.  Owner Jim Crane appears not to have known of the dark arts being practiced by his club.

The scandal became public on November 12, 2019, when former Astros’ pitcher Mike Fiers blew the whistle in an interview published in “The Athletic” (Rosenthal & Drellich).  MLB then launched an investigation that granted the Astros players immunity in return for their fessing up. Commissioner Rob Manfred soon issued a nine-page report that found that most of the Astros players knew of the scheme and many participated in it. The report also found that manager Hinch knew of the scheme and that GM Luhnow should have prevented it.  Manfred suspended both Hinch and Luhnow, who were quickly fired by Astros’ owner Crane.  MLB fined the Astros $5 million and stripped the club of its first- and second-round draft picks in both 2020 and 2021. Cora and Beltran lost managing jobs they had acquired.

The damage done by the Astros is significant. As veteran catcher Stephen Vogt said, “The integrity of our game is what we have, and now that’s been broken.” Former major-leaguer Doug Glanville concluded that MLB now faces an “existential crisis” saying that the Astros’ “selfish act makes everyone question the validity of the future and the truth of the past.”

Discussion Questions

  1. How might the fact that two of MLB’s best teams had been caught illegally sign stealing (Red Sox) or suspected of it (Yankees) affected the Astros? Is “if everyone is doing it, it must be okay” a rationalization that is consistent with the conformity bias? Explain.
  2. Former Astro J.D. Davis later explained: “I was a rookie, and I was going up and down the system, and I was fighting for my life. … As a 24-year-old at the time, I was pretty star-struck at the time being around some of the veteran guys and being around the big-league clubhouse and everything. I had never been part of a major-league clubhouse.  Maybe what they did was the norm, I have no idea.  I had never been in another big-league clubhouse.”  Does this sound like the conformity bias in action, or just another rationalization? What do you think and why?
  3. If J.D. Davis in the previous question had been a seasoned veteran, would it have been easier for him to “just say no” to the scheme? Explain.
    1. Would it have been easy? Why or why not?
  1. Although some MLB players lauded Mike Fiers for coming forward about the scandal, others criticized him for allegedly violating baseball’s “code of silence” (also called the “clubhouse code.”) Is that code common in professions or organizations other than MLB (and the Mafia)?
    1. Is it part of the problem? Why or why not?
    2. Is it a manifestation of the conformity bias? If so, how?
    3. How might this code be reformed or even ended?There were clearly Astros players who were uncomfortable with the cheating. Why didn’t they speak out?  What about the Astros players, other than Fiers, who left the club knowing of the scheme, but never reported it?  Why didn’t they speak out?
  1. There were clearly Astros players who were uncomfortable with the cheating. Why didn’t they speak out?  What about the Astros players, other than Fiers, who left the club knowing of the scheme, but never reported it?  Why didn’t they speak out?
  2. It has been widely reported that former President Trump is a notorious cheater when he plays golf. As reported in Rick Reilly’s book:

“I played with him once,’ says Bryan Marsal, longtime Wingfoot member and chair of the coming 2020 Men’s U.S. Open. ‘It was a Saturday morning game. We go to the first tee and he couldn’t have been nicer. But then he said: ‘You see those two guys? They cheat. See me? I cheat. And I expect you to cheat because we’re going to beat those two guys today.’ So, yes, it’s true, he’s going to cheat you. But I think Donald, in his heart of hearts, believes that you’re gonna cheat him, too. So if it’s the same, if everybody’s cheating, he doesn’t see it as really cheating.

    1. Does this sound like the conformity bias in action? Explain.
    2. Does it sound like the collective illusion concept, which describes how people in a group go along with an idea that they don’t agree with simply because they believe (incorrectly) that most people in the group agree with that idea? Explain.
  1. As the Obedience to Authority video in this series explains, people’s tendency to want to please people in a position of authority also played a role in the Astros’ sign-stealing behavior. Describe how.
  2. What other behavioral concepts studied in this series might also have played a role? For example, did the self-serving bias play a role? Explain. How about framing? Explain.
Conformity Bias: Sports Edition

Conformity Bias: Sports Edition

We have a tendency to conform our behavior to the actions of those around us. In sports, “everybody’s doing it” is a remarkably common justification for unethical behavior.



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Erik Boland, “Yankees Won’t Be Returning to the Scene of Astros’ Crime,” Newsday, May 14, 2020, at

Boston Herald Staff, “Calling Foul over MLB Report on Sox Sign-stealing Scandal,” Boston Herald, April 26, 2020, at

Thomas Boswell, Cheating Ruins Everything About Sports. The Astros Got What They Deserved, Washington Post, Jan. 13, 2020,

Howard Bryant, “Why the Houston Astros’ Cheating Scandal Could Be Worse for MLB than the Steroid Era,” ESPN, Mar. 8, 2020, at

James Dator, The Astros Sign-stealing and Cheating Scandal, Explained, SB Nation, Jan. 13, 2020,

Jared Diamond, ‘Dark Arts’ and ‘Codebreaker’: The Origins of the Houston Astros Cheating Scheme, Wall Street Journal, Feb. 7, 2020, at

Mike Downey, In Astros Cheating Scandal, the Bad Guys Won, CNN, Jan. 15, 2020,

Tyler Kepner, The Rise and Sudden Fall of the Houston Astros, New York Times, Jan. 18, 2020, at

Doug Glanville, Baseball’s Existential Crisis, New York Times, Jan. 21, 2020, at

Gene Laques, Injured Parties, Defiant Execs and a Tainted Title: Houston Astros’ Sign-stealing Scandal Checks All the Boxes, USA Today, Jan. 15, 2020, at

Bob Nightengale, Former Astros Outfielders J.D. Davis, Jake Marisnick Apologize for Their Roles in the Sign-stealing Scandal, USA Today, Feb. 14, 2020, at

Mike Oz, New Details in Astros Cheating Scandal Put Carlos Beltran’s Legacy in Jeopardy,, Yahoo Sports, Feb. 11, 2020, at

Mike Oz, “Worth It? Does MLB’s Reaction to Astros, Red Sox Tainted Titles Mean Cheaters Can Prosper?, Yahoo Sports, Apr. 22, 2020, at

Scott Polacek, Athletics Filed Complaint on Astros’ Cheating to MLB Before Mike Fiers’ Comments, The Bleacherreport, Feb. 12, 2020, at

Michael Powell, Astros Fire Two, but That Won’t Clean Out Baseball’s Den of Thieves, New York Times, Jan. 15, 2020,

Pat Ragazzo, “What We Learned about Release of ‘Yankee Letter,’” Sports Illustrated, April 28, 2022, at

Rick Reilly, Commander in Cheat: How Golf Explains Trump (2019).

Ken Rosenthal & Evan Drellich, The Astros Stole Signs Electronically in 2017—Part of a Much Broader Issue for Major League Baseball, The Athletic, Nov. 12, 2019, at

Barry Svrluga & Dave Sheinin, The World Just Learned of the Astros’ Cheating. Inside Baseball, It was an Open Secret, Washington Post, Feb. 11, 2020, at