Many research labs have both PhD students and postdocs. For principal investigators, what does a postdoc in your lab mean to you? What is your expectation of those postdocs?
Unfortunately, many do not see the reality. For at least some PIs, the Postdocs and PhD students are just cheap workers to be burnt - with the potential of becoming future competitors, if experimentall successful at all. Therefore, some PIs are focusing and managing in not supporting an experimental successful person. I have seen it sometimes that the most important person who made a lab successfull with many years of swimming against the stream finally was not supported at all to avoid her continuing the success story anywhere else.... Without using names, one of such persons was a first author in Cell... Then there are PIs who direct the results of students to the sons of a famous Professor, so that they support the "right" persons carreer. So, it looks to me that pursuing a scientific carreer selects for those opportunistic enough and with the right parents...
Of course, there are also quite a number of ideal examples... the reason why some of us continue in the game of science.
Unfortunately, many do not see the reality. For at least some PIs, the Postdocs and PhD students are just cheap workers to be burnt - with the potential of becoming future competitors, if experimentall successful at all. Therefore, some PIs are focusing and managing in not supporting an experimental successful person. I have seen it sometimes that the most important person who made a lab successfull with many years of swimming against the stream finally was not supported at all to avoid her continuing the success story anywhere else.... Without using names, one of such persons was a first author in Cell... Then there are PIs who direct the results of students to the sons of a famous Professor, so that they support the "right" persons carreer. So, it looks to me that pursuing a scientific carreer selects for those opportunistic enough and with the right parents...
Of course, there are also quite a number of ideal examples... the reason why some of us continue in the game of science.
i strongly support what Wang comments. Post docs are at the interface of being faculties or young investigators. So, they need to be enriched with scientific acumen and versatility.
Postdocs are godsend for the PI. Unfortunately the PI is so occupied with interfacing to the outside world, he/she will not have sufficient time to interact and support the graduate students. The postdoc will help in interfacing with the graduate students, help in their day-to-day activities, provide necessary laboratory help with instruments and equipment, write and check reports, generate new ideas for projects, etc. Practically they are used all aspects of research in the lab in the name of PI. As Robert said they are cheap workers like interns.
Just looking at the answer of Dr. Ting Wang you imediatelly can see that for PI THE POST DOCS are everything except what they are supposed to be: TREINEES WHO TRUST IN THEIR PI AND TO CREATE A CAREER PLAN CAREER. again looking at Ting Wang answer we are just skilled technician that do all the job allowing PI stay in their office and push their career forward. Looks an example of parasitic simbiosis isn't it?