Diversity has become an important issue for companies and organizations. Whether for ideological or performance reasons, for their image or under legal constraints, many organizations openly seek diversity among their employees.
But diversity is a complex thing. We cannot except positive outcomes (concerning inclusion, performance, …) just by adding some diversity in a team or a whole organization.
Yet, Milliken and Martins  concluded in 1996 that diversity is a “double-edged sword”, that it has advantages and disadvantages. Let’s look at diversity to understand why it has both positive and negative effects, and how these two sides interact with each other.
The bright side of diversity
Numerous studies show that diversity has multiple benefits for the organizational world.
Among other things, diversity:
- Stimulates productivity 
- Fosters innovation 
- Increases financial performance 
- Improves social performance (CSR) 
To explain these positive effects, it is generally considered that diversity brings a variety of ideas, knowledge, perspectives, etc. This variety of available information stimulates the work and allows a better success.
The dark side of diversity
Unfortunately, diversity also comes with a certain amount of challenge. Some studies mitigate the results presented above.
Among other things, diversity:
- Increases misunderstandings 
- Decreases job satisfaction 
- Reduces team attachment 
These effects are generally explained by social-categorization, a concept well known to sociopsychologists. When we see diversity in our team, our brains tend to create categories of “us” and “them”. Under certain conditions, this categorization can lead to prejudices, stereotypes and discrimination. Of course, these hinder the quality of work.
Diversity or diversities?
In short, diversity shows both positive and negative effects. To address this ambiguity, it was suggested that there was not one, but several diversities. These could be classified into two types, one corresponding to positive effects and the other to negative ones.
The first type is “deep-level diversity”. It corresponds to diversities that are not directly visible, such as diversity of education, values, personality, etc. Deep-level diversity would be beneficial, as it provides a variety of information and perspectives. But it remains invisible enough to prevent categorization.
The second is “surface-level diversity”. It corresponds to more explicit diversities, such as cultural, gender, age, … diversities. These diversities would have more deleterious effects, because they are often linked to strong stereotypes.
This dichotomy has been (and still is) very successful. However, several meta-analyses* (some of them are almost 20 years old! ), encourage us to abandon this conception. For example, van Dijk, van Engen and van Knippenberg, a Dutch research team , show that this approach does not explain the observed effects of diversity. But, let’s go further.
* A meta-analysis is a scientific method for jointly analysing the results of many previous studies.
The two sides of diversity
This surface/deep level dichotomy has the merit of highlighting two aspects of diversity. Overall, it seems that all types of diversity have both a surface-level side and a deep-level side: they are the two sides of the same coin.
For example, cultural diversity has on its surface a variety of accents, names, clothing styles, faces, etc. But at deep-level, it also involves differences in values, representations, knowledge, etc.
It is possible to do this work for each type of diversity. Each of them has a part of surface and a part of deep, more or less important.
But how does that help us? How does this help us to understand why diversity sometimes has positive and sometimes negative effects?
Van Knippenberg, De Dreu and Homan  proposed (and subsequently demonstrated) that the two sides of diversity interact together. According to this conception, diversity brings benefits for the performance of work teams. But, at the same time, it can create relational difficulties, under certain conditions. These difficulties will limit the positive impact of diversity on team performance.
The overall effect of diversity is then a question of balance between these two side. If the strength of the “surface-level” part is greater than that of the “deep-level” part, then diversity will have a negative impact. Otherwise, it will have a positive effect on teamwork.
The model predicts that the strength of the “surface-level” part depends on context. For example, a diversity-friendly work environment will limit its negative impact and unleash its full positive potential.
Of course, this model is presented here in a simplified way. Our aim is to go beyond the surface/deep level dichotomy and to present a more realistic and up-to-date approach to diversity.
Diversity remains a complex phenomenon. It must be understood globally and with taking the context into account. Indeed, the work environment plays an essential role in determining the consequences (positive or negative) of diversity. It is also an important tool for the success of diversity and inclusion policies in companies and organisations.
1. Milliken, F. J., & Martins, L. L. (1996). Searching for common threads: Understanding the multiple effects of diversity in organizational groups. Academy of Management Review, 21(2), 402–433. https://doi.org/10.5465/AMR.1996.9605060217
2. Saxena, A. (2014). ScienceDirect Workforce Diversity: A Key to Improve Productivity. Procedia Economics and Finance, 11(14), 76–85. https://doi.org/10.1016/S2212-5671(14)00178-6
3. Parrotta, P., Pozzoli, D., & Pytlikova, M. (2014). The Nexus between Labor Diversity and Firm ’ s Innovation. Journal of Population Economics, 27(6972), 303–364. https://doi.org/10.1007/s00148-013-0491-7
4. Salloum, C., Jabbour, G., & Mercier-Suissa, C. (2019). Democracy across Gender Diversity and Ethnicity of Middle Eastern SMEs: How Does Performance Differ? Journal of Small Business Management, 57(1), 255–267. https://doi.org/10.1111/jsbm.12336
5. Dodd, O., Frijns, B., & Garel, A. (2019). Cultural diversity in the boardroom and corporate social performance. SSRN 3389707, 1–42. Retrieved from https://www.nzfc.ac.nz/papers/updated/49.pdf
6. Vacherand-Revel, J. (2017). Le travail coopératif d’équipes de projet d’ingénierie à l’épreuve de l’activité en réunion médiatisée et multi-localisée. Psychologie Du Travail et Des Organisations, 23(2), 89–116. Retrieved from https://www.sciencedirect.com/science/article/pii/S1420253017300109
7. McKay, P. F., Avery, D. R., Tonidandel, S., Morris, M. A., Hernandez, M., & Hebl, M. R. (2007). Racial differences in employee retention: Are diversity climate perceptions the key? Personnel Psychology, 60(1), 35–62. https://doi.org/10.1111/j.1744-6570.2007.00064.x
8. Luijters, K., Van der Zee, K. I., & Otten, S. (2008). Cultural diversity in organizations: Enhancing identification by valuing differences. International Journal of Intercultural Relations, 32(2), 154–163. Retrieved from https://www.sciencedirect.com/science/article/pii/S0147176707000740
9. Webber, S. S., & Donahue, L. M. (2001). Impact of highly and less job-related diversity on work group cohesion and performance: a meta-analysis. Journal of Management, 27(2), 141–162. https://doi.org/10.1016/S0149-2063(00)00093-3
10. van Dijk, H., van Engen, M. L., & van Knippenberg, D. (2012). Defying conventional wisdom: A meta-analytical examination of the differences between demographic and job-related diversity relationships with performance. Organizational Behavior and Human Decision Processes, 119(1), 38–53. https://doi.org/10.1016/j.obhdp.2012.06.003
11. van Knippenberg, D., De Dreu, C. K. W., & Homan, A. C. (2004). Work Group Diversity and Group Performance : An Integrative Model and Research Agenda Work Group Diversity and Group Performance : An Integrative Model and Research Agenda. Journal of Applied Psychology, 89(November 2015), 1008–1022. https://doi.org/10.1037/0021-9010.89.6.1008