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Transitioning fields between a Ph.D. and postdoc

This Advertising Feature has been commissioned, edited, and produced by the Science/AAAS Custom Publishing Office

Switching fields midstream requires thoughtful analysis, research, and due diligence. Hear advice from researchers who have made the transition.

It takes guts to pursue a career in science and even more to switch fields midstream. Executing a disciplinary change between the Ph.D. and postdoc appointment requires thoughtful analysis, research, and due diligence. You have to demonstrate to your new colleagues how your expertise can be a potential boon for their research group, and you have to gain an understanding of the new field and its culture and language. For researchers who have the fortitude to start over in a new discipline and can effectively market their abilities, changing fields can lead to a career homerun.

Amir Erez is a theoretical physicist who yearned to change the world. "People would ask what I do and I had trouble explaining what impact my condensed matter research could have on our lives," he says. As a grad student at Ben Gurion University in Israel, he had the chance to work on a collaborative project at Princeton University for a few months when he heard that a biophysics professor from his alma mater was on sabbatical at Memorial Sloan Kettering Cancer Center (MSKCC), about an hour away in Manhattan. He reached out to the scientist and the two hit it off, remained in contact, and 2 years later, Erez suggested that he work with him, under a fellowship from the Human Frontier Science Program, an international nonprofit that support postdocs who move into the life sciences from other disciplines. Now a postdoc at MSKCC, Erez uses techniques from the physics of complex systems to study the dynamics of immune response in the context of cancer. "Suddenly I could ground my research in the real world and not just keep it in the Ivory Tower," he notes.

I used to communicate using quantitative information and theoretically rigorous approaches but during my postdoc I had to deal with more qualitative information and empirical approaches.

Diego Fazi

The decision to change fields is not always about personal preference. Some professionals do so to ensure their employability. Maria Patterson had been concerned about the narrowing career opportunities for astronomers who wanted to remain in academia. "I knew it was a rough road ahead," she says, where less than 10% of astronomy postdocs land tenure-track positions in the field. So she began looking at other vocations, including data science. As a graduate student, she was accepted into a fellowship program that exposed her to big data problems, and it was during this experience that she met her future principal investigator (PI), a computational biologist, with whom she began corresponding and discussing potential collaborative projects. She ended up at the University of Chicago in the Center for Data Intensive Science, Knapp Center for Biomedical Discovery, where she currently uses her expertise in spatial analyses to mine electronic medical records for patterns of geospatial clusters of disease. She describes her move as enjoyable as she now uses her skills in novel ways. "In astronomy, as you move up, the topics become very narrow and if I had an impact it would be small and only a few people would know about it," she says. "But in medicine, the research has the potential to have a great impact on a lot of people."

Shaun McCullough


Other scientists discover and delve into new disciplines while trying to solve the classic "two-body problem," in which two academics who have a personal relationship must job search at the same time. Such was the case with Shaun McCullough, a postdoc at the Environmental Protection Agency (EPA). When his wife landed a post in Research Triangle Park (RTP), North Carolina, he became the "trailing spouse" and cast a wide net to find a job in the region. Educated in biochemistry and molecular genetics, McCullough found a home in the Clinical Research Branch of the EPA’s Environmental Public Health Division in RTP, where he conducts both clinical and in vitro cell-based research in toxicology. It wasn’t what he expected to do when he originally chose the life sciences, but he finds his research to be extremely rewarding since toxicology "is constantly evolving to emphasize a broader range of sub-specialties in molecular biology," he notes. "It needs emissaries from these different fields to work together to find novel and creative ways to answer critical and pressing questions in the field. This need has created opportunities for someone like me, to apply my skills in epigenetics and molecular biology to solving the next generation of problems facing this field."

Noting differences between fields

As you adjust to a new discipline, there are many challenges to be met. One major difference in any new field is how the experts think about problem-solving. Each field has its own research approaches, which you have to learn quickly when transitioning areas. This requires an abundance of reading papers, speaking with experts, learning techniques, and shadowing colleagues. "The first few months into my postdoc, the only thing I wanted to do was sleep, because it was so much to learn and incredibly mentally exhausting," says Elizabeth George, a postdoc at the Max Planck Institute for Extraterrestrial Physics near Munich, Germany, who migrated from cosmology with the cosmic microwave background (CMB) to infrared astronomy.

The cultural differences between disciplines can be surprising, even if the science seems to overlap.  George’s culture shock manifested as she realized the different approaches to solving scientific problems in astrophysics versus astronomy. "Infrared astronomy is much more traditional astronomy, where you look at objects and try to understand what you are seeing," she says. "But in CMB cosmology, you start with a model of the universe and only measure one thing—the cosmic microwave background radiation—and try to fit your data to the model."

In making her transition, Patterson noticed a difference in how data itself is perceived and handled in different subjects. Astronomers are very open with their results, and since astronomical data is shared often, it has a uniform format, no matter the source. But in medicine, the tables are completely turned: data is sensitive and since it is drawn from medical records, there is much more concern over who has access to what. Additionally, "people don’t want to share their data as much, because it is valuable for commercial purposes," she notes.

Ewan Cameron had to learn how to collaborate with nonscientists, such as policy makers and representatives of nongovernmental organizations and nonprofits.


Moving from a lab-based science to one that involves patients requires nimbleness and flexibility. "I had never worked with humans before," says McCullough. "As a molecular biologist, I worked with cells in a dish. They didn’t talk, and they didn’t have to be informed" about the nature and risks of the studies. But in investigating how environmental factors contribute to disease, he had to learn a new protocol and ensure that the subjects understood everything that was taking place. When Ewan Cameron, an astronomer-turned-epidemiologist, "jumped ship" (as he puts it) to become a senior computational statistician in the spatial ecology and epidemiology group in the Department of Zoology at the University of Oxford, he not only began working with human subjects but he also had to learn how to collaborate with nonscientists, such as policy makers and representatives of nongovernmental organizations and nonprofits.

With any disciplinary switch, there’s usually a new language to master. "The jargon barrier can be quite formidable," notes Erez. "I’m 8 months in to my postdoc, and I’m just beginning to know the right jargon for my neck of the woods, and what the right questions are to ask."  Diego Fazi, a theoretical physicist who migrated to renewable energy via a postdoc at Argonne National Laboratory (ANL), had to adapt to variances in the manner in which professionals share information. "I used to communicate using quantitative information and theoretically rigorous approaches," he says, but "during my postdoc I had to deal with more qualitative information and empirical approaches."

“I used to communicate using quantitative information and theoretically rigorous approaches but during my postdoc I had to deal with more qualitative information and empirical approaches.”— Diego Fazi

Day-to-day differences can also pop up, especially for those who switch from theoretical to experimental fields. Both Erez and Fazi had never done wet lab work. "Before I came here, I was a theorist with clean hands," says Erez. Adds Fazi: "I had to learn basic chemical techniques, such as making a solution and setting up an experimental apparatus."

And of course, "when you switch fields, you incur a time penalty," notes Erez. "It takes time to settle into a new field," to learn its nuances and then be able to be productive enough to publish. Adds George: "Changing disciplines feels like you are starting grad school all over again, except that you are a much better learner." It took her 6 months to "start feeling productive, and to be able to begin asking questions that pushed knowledge forward and were as useful to my colleagues as they were to me." Erez recommends giving yourself a break as you ramp up your knowledge. "Don’t expect to be as productive in your first year as you would have if you stayed in the same field," he says.

Making the switch

Whether your switch seems radically different, like physics to immunology, or something seemingly more related, like astrophysics to astronomy, it is important to be ready to market your talents and show what you can offer a new field based on your background. This is especially crucial given the fact that as you transition, you are not necessarily going to be acknowledged for your research reputation, as George discovered as she plotted her move. "In my new discipline, I am a completely unknown quantity. People haven’t read my papers," she says. To land a postdoc, she pitched her PI that her experience in building and deploying astronomical instruments, unusual for an astrophysicist, could serve as an asset for the new research group.

"Start as early as possible in your planning," says Erez. Many scientists who change fields launch their career plan in grad school. For example, Patterson took classes in Python and programming. Erez attended biophysics talks at physics conferences as well as on his campus, and engrossed himself in papers and books that focused on his newfound subject.

Your grad school mentor might be helpful too, if you can present your switch as an advantage to them to advance their own research interests. In doing so, "you might find that your advisor is inclined to send you to a conference in the field you are interested in," says Eric Brown, acting deputy division leader of the Materials Science and Technology Division at Los Alamos National Laboratory, whose doctorate is in physics. Furthermore, he recommends leveraging the resources offered by the professional association of your new field. "Many science societies issue reports on demographics, career paths, and employment statistics," he says, which can be invaluable in the career planning process.

As you transition, you have to establish a connection between your past and your desired future. "Those bridges, of taking what you learned from one area and applying it to another, need to be visible," says Jason Cooley, who switched from biology to biochemistry and then eventually found his way to the chemistry department of the University of Missouri as a solution to his own two-body problem. He equates it to telling a story with a narrative that explains the natural progression of how you got to where you are today. Without it, "people will think that if you get bored, you will jump somewhere else," he adds. In George’s case, her narrative showcased her desire to build high-quality scientific instruments, which she had demonstrated as a grad student and which she planned to do as a postdoc.

No matter your story, your publications are your "scientific currency", so "before you move, write a paper that relates, even in a tangential way, to your future field," urges Joel Cavallo, a postdoc in psychiatry with a dual appointment as a fellow in the Program of Clinical Pharmacology and Pharmacogenomics at the University of Chicago. As he completed grad school in neuroscience and psychology, Cavallo authored an article on the erasure of associative memories in a sea slug. Because maladaptive learning and associative memories can play a role in mental disorders, this work helped show his dedication to his desired discipline of psychiatry.

Getting the appointment

It’s not surprising that, despite your best intentions, it can be difficult to change fields, especially right after grad school. "It wasn’t easy to get a postdoc because most biologist PIs wanted someone with experience in biology," admits Erez. He was lucky to have found a mentor who appreciated his background in physical science and had experienced a similar transition into the field. "I needed a PI who had a good background in biophysics because otherwise it would be very difficult to communicate, since I didn’t speak the language of biology and he wouldn’t have spoken the language of physics."  But as more STEM fields become interdisciplinary, sources say that there will be growing opportunities for innovators who can understand and unite multiple universes. Brown notes that it is becoming more common for early career scientists to switch subjects between the Ph.D. and postdoc, as "it’s an opportunity to jump into something that is new and fresh and exciting," he says. And having the capacity to connect seemingly disparate fields can hold other advantages. Indeed, Fazi, who recently leveraged his postdoc into a full time position at ANL as a technology innovation strategist with a focus on green tech, says that changing course for him "gave me more perspective in science," he says. "I came out a more complete scientist with more cards to play."

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