Kveggma

When I am evaluating a research group leader, one of the most important things I examine is where their former students work. If their former undergraduates have moved to PhD programs at excellent universities, that makes the group leader look like an excellent mentor who teaches their students well. This improves the group leader's reputation and helps them recruit new students.

A savvy letter writer also knows that a letter which literally says "This student has excellent achievements x, y and z." implicitly says "I am a good supervisor for helping the student achieve x, y, and z."

Professionalism.

There’s also some measure of self-interest in that a good student moving elsewhere will enhance the reputation of the original group with other researchers and with other students. In particular I note that students talk and if it were broadly known that a PI “torpedoes” good students then the likelihood of recruiting good students would nosedive dramatically.

Yes.

Not doing so is extremely selfish. I don't own the student, and he should be free to pursue his own career goals. If those goals involve studying elsewhere, that's disappointing, but it's still not mine to sabotage (as not writing a strong recommendation letter would be) the student.

The PI should write a reference truly reflecting the skills of the student.

The reference should not be "dumbed down" or "over egged", both practices are incorrect both ethically and professionally.

If this means the student moves on, then so be it. There will always be other students.

It may also mean that the student comes back in the future or they end up collaborating in the future.

First of all, people who choose working in science tend to be decent non-selfish people. Those who are selfish or not decent prefer other occupations. Professors will submit good recommendation letters just because it is the right thing to do.

Second, a professor's salary does not depend on whether his student leaves his lab or not. Professors usually have a permanent position and a fixed salary. There is no direct selfish interest for a professor to keep his student in the lab.

Third, connections and collaborations matter a lot in science. It is often to a professor's advantage to let his student go abroad. The professor can, for instance, indicate his former student as a suggested referee for papers submitted from the lab and can also reach other people via his former student. The more talented the former student is, the more beneficial the connection will be.

Fourth, undergraduate students are generally less valuable than they think. Professors generally encourage and praise them, but the reality is that undergraduate students know almost nothing, cannot write good articles, consume a lot of time and energy of their supervisors, make mistakes in research calculations, etc. Many professors see working with undergraduate students as a duty rather than something beneficial.

For the above reasons, almost any professor is highly unlikely to submit a weak recommendation letter if he is able to write a strong one.

If you are worried that this might nevertheless happen, you can make the following steps to reduce the risk:

1. Prepare a draft of the recommendation letter and say something like, "I have prepared a draft, and you can modify it in any way you wish." Professors are generally very busy and have neither time nor energy to carefully write strong recommendation letters, but, given a draft, will usually just make stylistic corrections and sign/send.

2. Carefully choose people whom you ask to write a recommendation letter. If you work in a lab, you may have a few people to choose from. Choose decent people who have neither envy nor strong interest to keep you in the lab. The usual situation is that you have a head of the lab and a mentor, who is subordinate to the head of the lab. Make a wise choice between the two. Consider their human qualities, possible selfish interest, etc. If you make a few different applications, ask different people to write recommendation letters for different applications so that no one will be able to spoil all applications of yours.

3. Promise to collaborate in the future. Tell them that you plan to build a great career and will always be helpful and thankful. Tell them that after you move abroad, they can indicate you as a suggested referee for papers submitted by them. Promise to be a very friendly reviewer. Say and do everything to ensure that people see your departure positively.

4. If the recommendation letter has to be sent by email, consider asking to include you in BCC. Just say that you want to be sure that the letter is sent. It will be hard to refuse such a request, and if it is refused, consider asking another person to write a recommendation letter. Analogously, if the recommendation letter has to or can be sent by ordinary mail, consider asking to give you the signed letter. You can then just put it in an envelope, write the professor's address as the sender's address, and send the letter by mail. If the letter can be sent by fax, just get a signed letter and send it by fax. The idea is that if the professor knows you will see the letter, he is unlikely to deliberately weaken it.

You are describing one of the many conflicts of interests which can occur in academia.

While in reality, most of the people might be selfish and not professional at this stage, the majority will still be and won't sabotage your future. Worse case they usually don't help you like in the other post you have outlined. I have outlined the possible reasons I have observed why a PI would support you independently of the conflict of interest:

Why? Because it shows that you are a good mentor who can not only support his/her own interests but also of the people around you. It is a sign of both personal and professional growth.

Depending in which country and at which stage of you career as a PI, some people will be interested to know if you have achieved this step personally. One way to show this is that you push these people to continue to work in the academic system and that your mentoring help these people to achieve even greater results.

Alternatively, there is another explanation which occurs in people who are already reached tremendous success. It also personally rewarding in terms of your ego when you see all the people you have mentored working in supporting all the ideas and work you have invested your life in to be carry on in the future. It shows that this topic or area of research is interesting and important. It increases your own importance and relevance for posterity.

Your peers will read them

The audience for your letters of recommendation are your peers who are leading other labs in your field. If the letters they get from you indicate that you're sabotaging your students (and they'll know, they're as experienced as you or more and they know all of the nuances of this process), well, then you'll gain a reputation in your field for sabotaging your students.