I have a rather difficult quandary. I'm a first-year student, and I joined my lab group to work on a clinical psychiatry/neuroscience grant. I've been making slow progress towards familiarizing myself with the grant. However, my advisor (actually, one of my two-advisors... they both run the lab together) has been having me work on a separate project of his, completely unrelated to my work. From what I can tell, this project would take a few months to work out, and the result would be my co-authoring on a small paper with another graduate student in the lab.
My worry is, I receive a stipend from the university every month, and that stipend is paid for my the psych/neurosci grant. By working on the second project, I have the feeling that I'm "stealing" from the first grant. I was told by my advisor that this sort of time-sharing between grants is normal within the research world. My question is, is that true? If it is a problem, how should I deal with this?