New scientific studies show that pep talks work. From the baseball field to the workplace, great leaders energize teams with their words.

The Houston Astros provide the latest example. On November 1st, the Astros beat the Dodgers in game 7 to win the 2017 World Series, the team’s first championship in franchise history. Anyone who’s seen Moneyball knows that data drives success on the baseball field. Astros General Manager Jeff Luhnow began a data-driven rebuilding process in 2012. According to an article in The Wall Street Journal, he hired economists, physicists and engineers to create one of the game’s best research departments. But the team was missing one ingredient, a “disconnect,” according to one player who was interviewed for the article. “Every player was a number instead of a person.”

The data had helped the Astros put the right players in the right positions, but they still needed to focus on connection, chemistry and culture. In the off-season, the team hired three veteran players at a cost of nearly $70 million. Here’s the key. “The Astros hoped all three players would contribute on the field, of course. But just as important, they were targeted to serve as leaders and mentors for the homegrown stars.”

The ‘heartbeat’ of a successful team

The veterans were called “the heartbeat” of the Astros team. And they used what academics call ‘verbal persuasion’ to pump energy into their teammates. For example, the Astros almost didn’t make it to the World Series. They had lost three in a row against the New York Yankees in the American League Championship series and were one game away from elimination. After the third loss, one of the veterans, Carlos Beltran, stood up and delivered “an impassioned speech” that reminded the players of their ability and reenergized their motivation. One player said, “I knew we were going to come back and do special things.”

The story of the 2017 Houston Astros would come as no surprise to Tiffanye Vargas, an associate professor of sport psychology at Cal State University, Long Beach. I recently spoke to Vargas about her extensive research into the psychology of pre-game speeches, or pep talks. Vargas focuses on the power of speech to raise a person’s “self-efficacy.” Simply put, self-efficacy is believing in yourself. Stanford psychologist Albert Bandura pioneered the study of self-efficacy. He found that if a person believes that they can accomplish a task—believe it with every ounce of their being—they are more likely to accomplish it.

Vargas is studying how the content of speeches—verbal persuasion—can raise self-efficacy. While her studies are focused on sports teams, they have implications for every team and their leaders. Vargas has found that the content of a leaders’ speeches does make a difference, raising “perceived self-efficacy,” which means players feel more energetic, determined, charged and confident.

In one study published in the Journal of Applied Social Psychology, Vargas and her colleagues studied 31 male and female soccer players who were told to imagine themselves playing in a championship game. Each player was exposed to audio recordings of a real coach giving one of three types of speeches. While other studies were conducted in real locker rooms in game-time situations, this study gave Vargas control over the exact content the players would hear:

1. Informational/Instruction. In this speech, the athletes were told which uniform to wear, how to walk onto the field when introduced, how to stay hydrated during the game, etc.

2. Strategy. In this speech, the athletes were given information about the other teams’ strengths and how to capitalize on their weaknesses.

3. Emotional. The third type of speech was emotionally charged. The athletes heard that their opponents discounted their skill. In one example, they heard that an opposing coach didn’t believe they posed a threat and that he might play his second or third string players. They were inspired to play with passion, pride and to show no fear.

The conclusion was clear. Emotionally charged speeches were the best way to elevate an athlete’s perception of their game performance. “The results showed that athletes who were exposed to the emotionally charged pre-game speech prior to the imagined championship game had the highest efficacy scores compared to those who were exposed to the other speeches.”

Pregame speeches stick in our psyche

As it turns out, people really do want to “Win one for the Gipper.” It’s one of the reasons why pre-game speeches in movies stick in our collective psyche. I can still recall Coach Dale tell his basketball team in Hoosiers that he didn’t care about what the scoreboard said. In his book, they were winners: “Forget about the crowds, the size of the school, their fancy uniforms, and remember what got you here…” In Remember the Titans, I can still recall Denzel Washington as Coach Boone dragging his football players out of bed to visit the Gettysburg battle field. Racial strife was tearing them apart. Boone reminded his players: “Take a lesson from the dead. If we don’t come together, right now, on this hallowed ground, we too will be destroyed—just like they were.”

Pregame speeches don’t always make headlines, but one did in October of 2012. San Francisco Giants outfielder Hunter Pence gave an inspirational speech to motivate his team, which was down 2-0 in the National League Divisional Series. The Giants swept the next three games to win the series and went on to win the World Series that year. Baseball writers say Pence’s speech was the motivating trigger his teammates needed to hear. Pence said, “Get in here, everyone get in here…look into each other eyes…now! Look into each others eyes, I want one more day with you, it’s the most fun, the best team I have ever been on. And no matter what happens we must not give in, we owe it to each other, to play for each other…” One veteran third-base coach said that no speech had ever moved him as much.

Emotional speeches impact performance. Data can help sports and business teams fill critical positions but, ultimately, winning teams need leaders who understand that humans aren’t numbers. Emotion plays an essential role in bringing teams together and inspiring individuals to perform their best.

Here you can create the content that will be used within the module.

Read article on Forbes.com