- Individuals who contributed experimentally (i.e. conducted experiments or analyzed data)
- Individuals who made significant intellectual contributions to the project (i.e. conceived the project or conducted critical preliminary studies)
- And, of course, PIs of the labs involved
While I'm on authorship questions: How useful is co-first authorship? I've received "second billing" co-first authorship on a couple of papers, but I realize it's important to have sole first author papers as well. When people read that co-first author paper, they may or may not read that footnote "These authors contributed equally to this work", and co-first authorship doesn't show up on PubMed--you're just another name. One PI/journal editor from my graduate program feels that co-first authorship is total crap--either your did the majority of the work or you didn't. Is co-first authorship really valid? How many ways can you split authorship before it becomes ridiculous?