What should you ask an applicant's reference? When recruiting a student or post-doc to join my group, I trim down the list of applicants to a few names (3–5) by looking at CV's, research/teaching statements, existing publications, etc. Then, I will write to the mentors/professors/teachers/PhD advisors they listed in their list of references. I will also write to people who would be obvious choice as a reference, but aren't listed (fresh PhD who doesn't list his advisor, e.g.).

But what do I ask these people? My “standard” email would be something like:


  A former PhD student in your research group, Dr XXX, is applying for a position in my group. I wonder if you can give me a frank and confidential appraisal of his abilities and working style. How efficient is he, how quickly does he get things done? Is he able to communicate clearly, both in writing and orally, at a level you would expect from an good researcher? Does he interact well with other scientists, and work in a team?


At least one senior professor whom I sent such an email replied with a rather negative tone, saying “Dr. XXX is a good scientist. I don't want to comment on your other questions.” So, I am wondering: am I asking something I shouldn't? Or not in the right manner? What should you ask of applicants' references?
This may well depend on the country. In the US, being the litigious society that it is, there have been some people going after (legally and non-legally) people who give negative references. The candidate can have a stronger case if you are contacting someone they didn't approve. Now, there is freedom of speech and many, many other issues but simply put, some people in the US are scared to give candid assessments unless the assessment is positive.

So, I would tend to take the response you received as an implied negative but I would also have to keep an open mind that the referee simply did not want to answer and it might not reflect at all on the candidate.

As for the questions you ask, they seem quite standard and I don't believe anyone would be taken by surprise by them. However, they might not answer out of fear.

On a side note, when it comes to reference checking, you need to be sure you are getting are response from the proper person. Emails get hacked, fake accounts get created. I personally prefer doing my reference checking over the phone. This may also come across as a casual conversation without written evidence, making the referee more comfortable in being candid.