For over 30 years, scientists had been observing Japanese monkeys (Macaca fuscata) in the wild. In 1952, they began an experiment—dropping sweet potatoes in the sand for the monkeys to find. The monkeys loved the taste but hated the gritty sand that clung to them.

Then one day, an 18-month-old monkey named Imo made a discovery. She could solve the problem by taking her potato to the water’s edge to wash before eating it. She taught this trick to her mother, then her playmates learned it and taught their mothers too.

For six years, the older monkeys stubbornly clung to the old way. But eventually, almost overnight, a critical mass adopted this new behavior—what researchers called the “Hundredth Monkey Effect.” The practice spread rapidly across the entire tribe, and washing potatoes became the new norm.

While claims that the behavior suddenly leaped to other tribes across the island lack evidence, what’s undisputed is this: a single monkey’s change in behavior sparked a cultural shift that spread throughout her community.

The importance of this story is its principle:

Individual behaviors can create a ripple effect that changes collective norms and reshapes the whole.

What social scientists call “social contagion”—the well-documented phenomenon where behaviors, attitudes, and norms spread through populations once they reach a critical threshold.

As research consistently shows, when enough individuals within a group adopt new behaviors, change accelerates exponentially until it becomes the new standard. Whether we’re talking about safety practices in organizations, cultural shifts in communities, or social movements, the pattern holds: individual choices have a ripple effect, spreading outward spreading out to shape new norms.

Right now, as political polarization reaches dangerous new heights, we’re witnessing the darkest ripples take hold. Political violence has claimed lives. Assassination attempts have become part of our political discourse. Too many people now view those who disagree with them not as fellow citizens with different perspectives, but as enemies to be defeated—or worse, eliminated.

Fear breeds more fear. Hatred fuels more hatred. What was once unthinkable—celebrating violence against political opponents or business leaders—is becoming normalized in some circles. Dehumanization hasn’t just crept into our culture; it’s taken root.

Yet just as negative ripples spread, so too can positive ones.

So too can civility, courage, and compassion.

So too can the choice to see the humanity and inherent goodness in those with whom we don’t see eye to eye, and to speak in ways that respect the dignity of our fellow humans, regardless of whether we agree with them.

As I wrote in The Courage Gap:

Change happens in circles, not rows.

It doesn’t take everyone to change everything. But if we each take responsibility for our personal agency, we can contribute to collective change. Whether it is one hundred monkeys or one million, each of us can do our part. Here are four ways you could start this week:

1. Practice the pause. Before responding to something that triggers you—whether it’s a social media post, a comment at work, or a heated dinner conversation—take a breath. Ask yourself: “Will my response add to the division or help bridge it?” Choose your words accordingly.

2. Lead with curiosity, not judgment. When someone shares a view that differs from yours, try saying: “Help me understand your perspective” or “What led you to that conclusion?” Genuine curiosity disarms defensiveness and opens dialogue.

3. Call out the good. When you see someone choosing civility over contempt or respect over ridicule—acknowledge it. A simple “I appreciate how you handled that” reinforces positive behavior and encourages others to follow suit.

4. Choose one relationship to repair. Think of someone you’ve written off or distanced yourself from due to differing views. Reach out with genuine intent to reconnect as humans first, not opposing sides. It might be uncomfortable, but discomfort generally precedes breakthrough.

Change happens in circles, not rows. What ripple will you choose to spread?