Do two doctors make twice a researcher?

Despite pandemic-related university cuts and rising inflation in many countries, the PhD application program is still not operational. In 2020, more than 55,000 people earned doctorates in the United States, producing more doctorates than any other country. Approximately 1.1% of the population in the 38 countries in the Organization for Economic Co-operation and Development (generally democracies that support free market economies) received a doctorate in 2021. And the percentage of doctorates awarded in science, technology, mathematics and engineering (STEM) has steadily increased over the past decade. In 2020, 12,561 life sciences doctorates were awarded in the United States—23% of all doctorates awarded in the country that year and nearly double the number awarded in 1990.

However, China is projected to overtake the United States by 2025. At current enrollment levels, Chinese universities will produce more than 77,000 STEM doctoral students annually by then, according to a 2021 report by the Center for Security and Emerging Technologies at Georgetown University in Washington (see go.nature.com/3uwj9).

Earning one PhD is hard enough – but there are rare people who choose to swim extra laps in the pool of stress to secure a second. Some do so to carve out a distinct research niche for themselves, others to access resources not available in their home countries. Some may simply have superior results. Nature spoke to three ‘dual doctors’ to ask what they’ve won – and if it’s worth it.

VICTOR DYKE: Resources elsewhere can elevate your science

Climate scientist at the Beijing Institute of Atmospheric Physics.

As a requirement of my first PhD program, which was in atmospheric physics at Imo State University in Owerri, Nigeria, I spent three months at the International Center for Climate and Environmental Science in Beijing. The center had computing power that was not available in Nigeria. I realized that I would need more technical skills in meteorology to excel in climate research. During my initial visit, I was always in the lab from 8am to 11pm—I wanted to get all the experience I could during my time in China.

I didn’t plan on earning two doctorates. Before I returned to Nigeria, I learned about a program of the Chinese Academy of Sciences that awards scholarships to international students. In 2014, I applied, received funding and started my second PhD, which was in meteorology at the Institute of Atmospheric Physics at the Chinese Academy of Sciences in Beijing. Using climate models, I designed and implemented experiments to simulate how oceanic conditions drive extreme rainfall over West Africa and throughout the tropical climate region.

I don’t want anyone to think that my first PhD in Nigeria was not ‘good enough’. I had amazing mentors who empowered me to find the resources to take my research to the next level. I had planned to return to Nigeria, but China had the supercomputers I needed to run complex weather models – so I, like many scientists, moved to continue advancing my field. Access to modern equipment is a problem that will not be solved without more efforts. After earning my second PhD, I began a postdoctoral position in the same lab where I continued to study extreme weather events on shorter, seasonal time scales.

I am the only African in my 34-story apartment building, but there are more than 500 Nigerian students, mostly in science and engineering, in Beijing. We have social organizations and a group on the messaging app WeChat that we use to discuss science, with subgroups for people in the same fields. I spend a lot of time mentoring other Africans.

I learned a little Mandarin, but my labmates prefer to use English so they can practice it. I completed my postdoc but remain at the same institute with funding from the National Natural Science Foundation of China. My expertise is in predicting severe weather events such as extreme seasonal rainfall in different parts of the world to help authorities reduce disaster risk.

I wouldn’t do anything different. I have been in China for almost eight years. Although I would like to return to Nigeria to help train the next generation of scientists, the security situation related to the recent terrorist activity is making me reconsider this. Even now I am looking for opportunities all over the world to continue my work. I want to contribute to science without risking my personal safety.

RAF AERTS: Put a human face on ecology

Ecologist and epidemiologist at the Catholic University of Leuven and Sciensano, the national public health institute of Belgium, in Brussels.

I have long been fascinated by tropical ecology. After spending two years as a reforestation project coordinator in northern Ethiopia, I applied for a Flemish Interuniversity Council program in 2003 that offered funding to conduct research in developing partner countries. The money supported my doctoral work, conducting international reforestation research in Ethiopian sites I knew well.

After my first PhD, which I earned at the Catholic University of Leuven in Belgium in 2006, I did a postdoctoral project on how agricultural intensification affects Arabica coffee (Arabica coffee), a plant native to the Ethiopian forests. In total, I spent ten years as a postdoc. I also studied the ecosystem impacts of invasive species, such as the American black cherry (prunus serotina), in Germany, France and Belgium.

Then, in 2016, one of my colleagues received a grant to study the impact of biodiversity on human health. Working with what was then called the Belgian Scientific Institute of Public Health, I was offered a four-year postdoctoral contract to study human exposure to biodiversity, pollen and air pollution and how this affects people’s allergy symptoms.

At the time, the institute did not have a full-time ecologist, but there were several projects looking at the public health benefits of green spaces that aimed to inform policymakers. There was a need for someone who could manage the research projects to produce high-level international publications to inform policy.

I decided to earn a second PhD in environmental epidemiology at Hasselt University in Belgium so that I could “speak the language” of epidemiologists. For example, statistics used in epidemiology, such as survival statistics, differ from those used in ecology. I found an advisor who wanted to support my research on residential green spaces and human health. I will officially graduate in September 2022.

I have carved my own niche in research—I am now well-positioned to compete for funding in One Health, a transdisciplinary area of ​​research encompassing all interactions between plants, animals, the environment, and human health.

First-time PhD students often ask me why I would do this twice, given the stress of being a graduate student. To be honest, the second time was much easier. Field experiments are prone to failure. In the first PhD program, some of my seedlings were trampled by animals or taken by farmers. This is not the case when you work in epidemiology, although we work with human participants who come with their own challenges. For my second PhD, I worked largely with existing data, such as pollution maps and socio-economic variables, which were available from the national census, drug sales or government reports. The data is there and I just analyze it.

I have noticed that the human health aspects offer a new way to convince policy makers to protect biodiversity both inside and outside of urban habitats. Now that I’m also an epidemiologist, I think my case might be stronger.

UMA KARMARKAR: Create a unique research niche

Neuroeconomist at the University of California, San Diego.

I have always struggled to “stay in my academic lane”. As a student, I was interested in neuroscience in the broadest sense of the word. I was curious about how we process information in the world. In 2004, I completed my first PhD in neuroscience in an interdisciplinary program at the University of California, Los Angeles. I specialized in how our brains encode time. At the end of my term paper, I broke a bottle of champagne because I assumed I would never take an exam again.

Later, in 2004, I took a postdoctoral position at the University of California, Berkeley. I studied learning and memory at the cellular level. But I began to feel that I had gone too far in biology and wasn’t doing enough to explore my interests in psychology. I couldn’t connect my love of the field with my day-to-day science, which is critical to success. It was extremely disorienting. I had funding, a supportive advisor and an interesting project – but I wasn’t satisfied. I decided to find a way to reconnect with psychological research.

Through family connections, I learned that business schools were expanding their long-standing interest in consumer decision-making into brain research for insights. At Stanford University in California, I started talking to people who were pioneers in a field called the neuroscience of decision making, or neuroeconomics. The study of consumer behavior at the level of neural systems was just beginning to happen in business schools, which gave me the opportunity to study brain mechanisms while relating them to everyday human behavior. It was a difficult transition. Business schools rarely offered postdoc positions in 2005, so it became clear that I would have to do a second PhD in consumer behavior at Stanford. I had to learn the new academic culture and pursue the neuroimaging experiments I wanted to do. It was a culture clash, coming and going—for example, business schools don’t have labs you can join—but I graduated in 2011.

I wanted to ask questions about how we process information from both a psychological and a practical perspective. I needed the models and methods that come from brain science. In 2017, I applied for an interdisciplinary position at UC San Diego that required applicants to be assigned to two schools. During the interviews, I showed exactly how I would combine neuroscience and business. I presented behavioral research and brain imaging data to show that risk “confidence” has financial value for consumers—and is something companies need to know to communicate effectively with customers.

Throughout my career, I was fortunate enough to land enviable positions at fine institutions, but my career path felt muddled. It seemed riskier at the time, but in retrospect I see value in the journey I took. I don’t necessarily recommend earning two PhDs, especially if you can integrate those interests into one project – and avoid some messes. Different institutions vary in how comfortable they are with this level of flexibility, but getting a second PhD is possible if you can find a place that is receptive to the research you want to do.