It used to be almost an act of faith that a researcher should undertake a postdoctoral position abroad. In the days before cheap air travel and the Internet, this was the only way to gain international experience and exchange ideas with researchers in other countries on a daily basis. It was a once-in-a-lifetime experience. Now, it has become commonplace — and this is not necessarily a change for the better.

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We propose that mobility should no longer be about postdocs spending one to three years abroad, but rather about institutions becoming more international by recruiting undergraduates from abroad, facilitating the movement of master's and PhD students from one institution to another and recruiting early-career professors for teaching and research positions.

This is happening in Europe, where universities have made an effort to become more cosmopolitan. Nations are harmonizing programmes to ease movement — for example, by letting students with bachelor's degrees from one country do a master's in another.

PhD positions are increasingly filled by international students. In the sciences, foreign citizens received 46% of the PhDs awarded in the United States in 2007–08, and 40% in the United Kingdom and Switzerland. In Sweden, 33% of those starting a PhD in the same time period were from elsewhere. Universities are also making their undergraduate programmes more international, by setting up foreign campuses and recruiting foreign students to the home campus. Some people take a year off after high school to travel, work or study abroad.

Thus, many researchers have had exposure to foreign countries before reaching the postdoc level. There is no longer the need for international experience during the postdoc that there may once have been. Perhaps the requirement is a myth, kept alive because grant and appointment committee members travelled themselves. Young scientists thinking of going abroad must make sure that any move is in the interests not only of enriching their lives, but also, more importantly, of expanding their CVs.

The postdoc is a key period in the development of a research career. The environment must allow mutual development, so that the visitor does not simply provide technical expertise to the host lab. Postdocs must ensure that their time abroad is worth more than time spent at home. Ideally, a postdoc is done at an institution with a good reputation in the field, but this need not be in a foreign country. The urge to see the world can be satisfied in other ways.

Most would contend that those who move about in academia fare better than those who do not, but our experiences suggest otherwise. One of us (MEB) had a PhD supervisor who only ever worked at one university. His career did not suffer — he flourished, and all of his PhD students became professors. Most of them did postdocs abroad; but the one who was most successful (not MEB) never left the town, yet rose to be rector of his alma mater. Another of us (DDB) moved only 200 kilometres within the Netherlands: from Groningen to Nijmegen and finally to Leiden, where he supervised 50 PhD students and became rector of the university. The third (LHB) spent 26 years in England and the United States as a lecturer in molecular biology and epidemiology, and in drug development in the pharmaceutical industry, before returning home to work at a teaching hospital.

Once a connection has been made, worldwide collaboration can be fostered in many ways. Before crossing borders, postdocs should consider the career implications, good and bad.