Lab PI vs an Outside Research Mentor: What’s the Difference?

By Dr. Harman Brah, MD · Judge, California Science & Engineering Fair

A lab PI (principal investigator) owns the science and the lab: the larger research program, the equipment, the data and the decisions about what experiments run. An outside research mentor owns none of that, and instead coaches the student on their own question, their writing and how they defend the work to judges.

The two roles fit together. Neither one writes the project for the student. The student does the work and owns the question, the data and the writing.

What the PI does

The PI runs the lab and sets its direction. A high school student in a university lab works inside that larger project, usually alongside postdocs.

The lab gives the student data and a bench. In our view, it rarely gives them time on the application, because the PI and postdocs are running their own science.

That is not a criticism. It is simply what the job is.

The PI also has a formal place in competitions. For Regeneron STS, research done alongside adult researchers at a research institution is permitted, and the mentor’s permission is needed to submit. For an ISEF-affiliated fair, work done at a university needs the Regulated Research Institutional/Industrial Setting Form (2C), displayed at the booth.

What an outside mentor does

An outside mentor works on the parts of the project that belong to the student, not the lab.

The question. The hard part is separating the student’s own question and contribution from the lab’s larger project, and saying it plainly. A mentor helps the student find that one sentence and test whether it holds up.

The writing. A lab report or the lab’s manuscript is not an STS paper. The student has to write their own paper, up to 20 pages, for a reader outside the field. A mentor reads drafts, asks where a reader gets lost and sends it back. The student does the rewriting.

The defense. Judges probe whether the student can explain why each choice was made and what they would do next, without a script. A mentor runs practice questions until the student can answer in their own words.

What an outside mentor never does

An outside mentor never writes the paper, the abstract or the answers. A project that looks parent- or mentor-built is seen through quickly, and judges assess whether the work is substantially the student’s own.

An outside mentor also works with the lab, not against it. That means no new experiments without the PI, no changes to the lab’s data, and the help disclosed.

Disclosure is part of the deal

Regeneron STS requires disclosure of all support received with the research project and the application. Entrants and mentors must also disclose participation in paid programs.

So outside help is allowed, as long as it is named. A student who can say exactly what the PI provided, what the mentor coached and what they did themselves is in a strong position.

What if there is no PI?

Many students never join a university lab, and that is fine. Under ISEF rules, home, school and field are standard work sites, and one of our mentees ran his STS project at BioCurious, a community lab in Santa Clara.

In that case the outside mentor guides the whole arc, from scoping the question to the board interview. The student still does the work.

Which one does your child need?

If your child is already in a lab, they have a PI. What they may lack is someone whose job is their question, their paper and their defense.

If your child is not in a lab, an outside mentor can help them build an independent project from the start.

Judges reward a student who can explain why each choice was made, not the most advanced technique. Both roles exist to get the student there.

Learn how we guide students at https://admissioninsight.org/science-fair-research-mentorship/, and if your child is a senior, read https://admissioninsight.org/regeneron-sts-2027-final-weeks/.

FAQ

My child already works with a professor. Why would they need an outside mentor?

The professor runs the lab and its science, and rarely has time for the application itself. An outside mentor helps your child name their own contribution, write their own paper and practice defending it, while working with the lab rather than around it.

Is it allowed to have an outside mentor for Regeneron STS?

Yes. STS requires disclosure of all support received with the research project and the application, and entrants and mentors must disclose participation in paid programs. Help is fine when it is named.

Will the outside mentor write the paper or abstract?

No. The student writes everything. A mentor reads drafts and asks questions, and judges assess whether the work is substantially the student’s own.

Can my child use the lab’s paper as their STS paper?

No. The lab’s manuscript is not an STS paper. Your child needs to write their own original paper, up to 20 pages, for a reader outside the field.

Does an outside mentor change anything in the lab’s experiments?

No. An outside mentor runs no new experiments without the PI and makes no changes to the lab’s data.