Working in two research lab at the same time – unethical? Is it unethical to work for two professors (two seperate research lab in two non-related fields) at the same time? I am an undergrad student currently working for professor A in a full-time research assistant co-op job. On the other hand, I volunteer using my spare time working for another research lab in an almost unrelated field. Professor A doesn’t know about this. 

So my question is, is it unehtical for me to do this?

I ask because my friends warned me not to do this. On the other hand, I don’t think it is too much of issue since I am not stealling data or anything from anyone and, more importantly, they are in two different unrelated fields. 

Similiar question is asked here, but I am asking from an ethical perspective.
So my question is, is it unehtical for me to do this?


Unethical - no. Smart? Probably also no.

Firstly, as Corvus correctly states, it seems very unlikely that you can perform well in both roles and do your undergrad studies in parallel (and I am not even talking about going outside and doing people stuff occasionally, which you should also not forget about).

Secondly, you should not forget that professors are human. Even though you are not doing anything "wrong" by any stretch of imagination, it is not difficult to imagine scenarios where either of the professors (or both!) don't take it well, and I am assuming you want letters from these guys down the road. The professor that you work for, for instance, may assume that you find his research very unfulfilling if you feel you need to invest your spare free time into a completely unrelated area instead of hanging out with friends etc. (S)he may assume you are really doing it only for the money / letter. The other professor may be disappointed at some point when an important deadline should be met that you can't commit more time to her/his project, because of your other duties.

Finally: 


  Professor A doesn’t know about this.


That's never great, and you should change this ASAP. Even if the professor basically does not care about the issue at hand, (s)he may get mad simply because you didn't tell (I certainly would). And I think you are aware that the chance of you keeping this a secret forever are slim to non-existent?