We all know that diversity is important, but without inclusion and belonging, your organization won’t maximize the benefits that diversity brings, including:

• Innovation and creative problem-solving.
• A focus on facts and the identification of potential problems, leading to error reduction.
• Conflict resolution.

When leaders value and support diversity, these benefits multiply, making diverse organizations more successful on several levels. A McKinsey study found that their financial returns are as much as 35% above their industry medians. They experience higher return on equity and higher income growth compared to their less diverse counterparts. And they have better employee engagement and reduced employee turnover.

It’s important to remember that diversity is not just about race and gender. It includes age, ethnicity, spirituality and religion, sexual orientation, political views, work styles, and more. In fact, millennials (who now make up around 50% of the global workforce) view diversity much more broadly than their Gen X and baby boomer colleagues, considering things like the unique viewpoints and experiences that diverse people bring to the team or organization.

Millennials also care deeply about inclusion — which is smart, because inclusion plays a vital role in bringing out the best of members of diverse groups. In fact, both inclusion and belonging are critical for the success of your organization. If your leaders prioritize them, you will gain a significant competitive advantage. Here’s why.

1. Biologically, Exclusion Causes Pain

Neuroscience researchers at Harvard, Purdue, Duke and UCLA (just to name a few) have found that exclusion lights up the same regions of the brain as physical pain. “Being excluded is painful because it threatens fundamental human needs, such as belonging and self-esteem,” says Dr. Kipling Williams of Purdue University. “Again and again research has found that strong, harmful reactions are possible even when ostracized by a stranger or for a short amount of time.”

In fact, one fMRI study showed that pain medication can reduce the impact of rejection (which is, perhaps, a contributing factor to the opioid epidemic).

2. Exclusion Harms Performance

People don’t just bounce back from exclusion, either. When they are first excluded, studies show, people tend to have one of two responses: Some try harder to be included, engaging in behaviors designed to help reintegrate them into the group, such as conforming, complying and cooperating. When people feel that there is little hope of inclusion, on the other hand, they are likely to seek it elsewhere, essentially rejecting the group that rejected them.

When exclusion or ostracism occurs over a long period of time, and people have to return every day to an environment where they feel they do not belong, they shift to resignation. The effects of long-term exclusion are devastating and include being less able to perform difficult tasks successfully, poor impulse control, poor sleep quality and immune systems that do not function as well as they should. Excluded people also experience sadness, anxiety, depression, helplessness and feelings of unworthiness. Some self-medicate with substance abuse to relieve the immediate pain; however, this short-term relief tends to lead to a downward spiral of guilt, shame and further rejection. Some sufferers become increasingly angry.

Any form of exclusion is painful and damaging to individuals, their teams and their organizations. Long-term rejection can fuel disengagement, apathy, aggression and even violence, whereas inclusion only brings benefits. In her research, Dr. Christine Cox of New York University’s Langone School of Medicine has identified six areas that are enhanced by inclusion and worsened by exclusion: intelligent thought and reasoning, self-care and self-improvement, prosocial behavior, self-regulation, a sense of purpose, and well-being. Each of these items represents real financial gains or losses for teams and organizations.

3. Belonging Is the Goal

Belonging is the feeling of being part of something and mattering to others. We create it through inclusion, which consists of intentional acts. Employees don’t need to be popular or liked by everyone, but they do need to have a sense of belonging somewhere and with someone.

Employee engagement is not just a measure of work pride and productivity; it’s also a valuable indicator of inclusion or exclusion. As a result, it’s important that measures of engagement include questions like, “Someone at work cares about me as a person” or, “I have a friend at work.” It’s also why orientation or onboarding efforts are more effective when companies go beyond the basics of employment and help people integrate socially into their new community through programs like pairing new employees with a mentor or buddy. In fact, a study by the Aberdeen Group found that high-performing organizations are over twice as likely than lower-performing ones to assign a mentor or buddy during onboarding. The ability to find your tribe, even if it’s just a tribe of one, can make all the difference.

It’s worth noting again that belonging is not about being universally liked. In fact, we each have our own perception of how big our tribe needs to be. But research shows that, at work, what matters most to people is feeling they can make a meaningful contribution and that others value their work. From a tribal perspective, this feeling means that they’re needed and, therefore, less likely to be ousted. Neurologically, that sense of security is enough to settle the amygdala and enable people to reach higher-order thinking skills like logical analysis and innovation. As we gain more confidence of our position in the group, we perform better. And, as we perform better, we gain more confidence.

4. Invest in Training to Shift Your Culture

Some of us find true, deep belonging at work, but not everyone will. At minimum, however, we all need psychological safety: the ability to make a valuable contribution without fear of being ridiculed or rejected. We also need our colleagues to be more aware of the subtle, and often unintentional, ways they create exclusion through their words and actions. If you want to create inclusion and belonging, you must also address unconscious bias, microaggressions and privilege, all of which impact our daily interactions with colleagues and either contribute to or harm their sense of inclusion and psychological safety.

Recognizing the importance of inclusion and psychological safety, more and more companies are investing in diversity and inclusion training programs that help people have these difficult but important conversations and shift their focus to actions they can take to create inclusion. Companies like Amazon, Johnson & Johnson, AT&T, Kaiser Permanente, Ernst & Young, and eBay are all creating more inclusive workplaces through efforts like employee resource groups (ERGs), networks, learning experiences, conferences and leadership development programs. Importantly, they are making inclusion a performance marker for managers, who have clear diversity and inclusion goals that they are accountable for achieving.

Diversity, inclusion, psychological safety and belonging are not just trendy training topics. They are the bedrock of an organizational culture that positively impacts all the metrics that matter. If you want to drive better engagement, retention, productivity and innovation, then make this investment your biggest priority in 2020.

Parts of this article were excerpted with permission from “Wired to Connect: The Brain Science of Teams and a New Model for Creating Collaboration and Inclusion.”