There is no such thing as a “quick” scientific project. All projects take careful planning and follow a stereotyped process. Understanding the life cycle of a project is critical for ensuring feasibility, avoiding suprises, and maximizing fun. Given how long any project takes (approx ~1y minimum) it is essential that every project be carefully thought-out to justify the investment. As ever, the most important question is “What is the question?”
Each project in the lab has a well-defined infrastructure. See relevant pages including
b) Project setup on PMACS (coming soon)
The ultimate impact of any project is largely determined by the question being asked. Spending two years chasing down the answer to question that is not very interesting is a recipe for disappointment. Start broad (“forest”) and try to identify questions at a conceptual (rather than methodological) that are likely to be of broad interest to the field. It is good to write this down at this stage, even if it is muddy and needs refinement. Strongly consider pre-registration and prospectively identify potential replication datasets.
This step is skipped at one’s peril. Nothing is worse than sitting down to write a paper and then realizing only at that late stage that the question was largely answered by a study you were not aware of. A literature review also is critically important in sharpening hypotheses in order to maximize the potential impact of the question being asked. As the first author, it is important to internalize that you need to rapidly become the expert on the topic of the project—do not trust your faculty mentor to be aware of all relevant literature. Often the whole reason for a new project is that it is a new area that the faculty member is not an expert in. Try to be comprehensive at this stage, and use a reference manager to stay organized. Reading abstracts and examining figures is a way to rapidly get the sense of a new field. This broad overview is usually followed by an extremely detailed examination of the most relevant half-dozen articles. All literature reviews should be conducted using a reference management system. Many in the lab prefer Zotero.
As noted above, the “what is the question?” is always the most important question. At this stage, the over-arching hypothesis should be able to be concisely stated. It is a good idea to literally write this down, as it will appear in the last paragraph of your introduction. Next, one needs to operationalize how this hypothesis will be tested according to specific predictions that are linked to a defined analytic plan. It is useful to imagine that everything in the study “works” and you get your dreamt-of results. What tests do you need to do to generate these results?
Authorship on papers is a frequent source of conflict in other labs. The best way to avoid conflict, enhance transparency, and accelerate collaborations is to identify collaborators who will be co-authors on the final paper prospectively. An important q is: Who do you need involved to get this project done? Explicitly inviting someone to collaborate rather than just peppering them with questions will often help things go smoother. While the number of collaborators may grow (a bit) as the project develops, most of the time most collaborators are fairly obvious from the beginning. Do not be afraid to discuss author order on large collaborative projects with the faculty lead (if they do not bring it up prospectively– which they should).
The lab standard is now to release all analysis code. To ensure reproducibility, all results should be replicated by an independent member of the lab at multiple stages (see below). The replication buddy should be involved in the project from the beginning, and often is the second author on the paper. This is a lot of work and should not be taken on lightly; also think ahead for a long project and ensure that the buddy will be present in the lab for the anticipated duration of the project. See the Project Reproducibility Guide for more information.
Before one spends too much time on a project, one should ensure that the necessary data is available. This step arguably should come earlier. Much of the impact of a paper is determined by the sample size; small samples reduce statistical power and preclude many methods being used. In particular, pay attention to key subject level variables such as demographics, symptom scores, diagnoses. If the imaging data has already been processed and QA’d, it is a good to check how big your sample will be after QA (see also “inclusion criteria and sample construction” below). Finally, note that all projects should receive explicit written approval from the study PI who collected the data prior to beginning. For the PNC, this includes approval of the data access committee, which meets once per month; please account for this process with regards to timeline / deadlines.
If data has not already been processed, this is an important and sometimes time-consuming step. We prefer a highly-structured process for image processing to ensure reproducibility using XCP-based modules whenever possible. See XCP documentation for further information (this is a bit of a work in progress at the moment). Note that a sub-sample (usually n~10) of subject level data should replicated, and the main subject-level derivatives produced by the pipeline should be placed in a read-only data freeze for the dataset. For most projects, analyses should only use replicated data that is pulled directly from this data freeze folder. See the Project Reproducibility Guide for more information.
It cannot be over-emphasized how critical this step is, as changes in the inclusion criteria will inevitably require re-doing all analyses as the sample changes. Similarly, the reproducibility of results depends on the reproducibility of the sample selection procedure. Thus, this step should use code to pull in data from the data freeze folder, and arrive at the final sample by filtering the data using clear QA codes. It is a good idea to explicitly go over this step—and the code—with both your replication buddy and the faculty mentor.
This stage is usually the longest, and varies considerably by project. One general point is that organization pays off: keeping code clean and updating your project repo daily guards against both lost work or the risk of nasty code excavation job at the replication stage (next).
As detailed in the Project Reproducibility Guide, once a “main result” that will be the organizing hook for a paper is revealed, it is a good idea to call your replication buddy. Cleaning your code and having them provide both a “true” replication (taking input data and running a model with their own code) and a “technical” replication (i.e., stepping through your code) is advised to make sure errors are caught before a paper is written. (Often, around this stage, a project is presented at a conference—see the conference wiki for more information).
The scientific narrative of a paper should be readily apparent from the abstract and figures. Before deciding that analyses are “done” it is good to write the abstract and make an outline (in text) of what the figures will show. Often times this step reveals that something is missing, and one or two more analyses need to be done.
It is often good to create draft figure panels for the entire paper before polishing them to high gloss for publication. These figures should be made reproducibly so they can be replicated (in the next step). Making beautiful final figures before replication often is not efficient.
14) Final reproducibility check: Clean code, make GitHub repo, companion wiki, and replicate final results
At this step, one has all the code and results in hand. Before writing (or as it begins), it is important to make a clean GitHub repo that will be submitted with the paper, along with a companion wiki that patiently steps interested readers through this code and allows them to reproduce your work. Once this is complete, send the wiki and repo to your replication buddy, who will check your work (see Project Reproducibility Guide). Note that it is imperative to repeat this process if results change in the writing process below; analyses added at a late stage when one is trying to get the paper out the door tend to be more likely to be problematic.
It is strongly suggest reading this article by Konrad Cording prior to starting your paper: http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1005619.
In general, it tends to make sense to write the methods, results, and figure legends prior to writing the introduction and discussion.
Experience suggests that the number of draft iterations is one of the dominant factors in how good the final text of a paper is. Expect 3-5 rounds of revision of the text with your faculty mentor prior to sending the paper to co-authors. Tracking changes and careful version control at this phase is of course key. Saving paper versions with a date suffix (in format YYYYMMDD) tends to help. Although Latex is often desirable, most journals require manuscripts to be submitted in Word, so it is usually just easier to use that from the beginning. One alternative option is to write using a google doc to allow all authors to use the same version , and then export to word prior to submission. This saves a LOT of time when integrating comments from papers with many co-authors (see next)
We usually allow ~1-2 weeks for co-authors to provide feedback on a paper. For those who do not reply in the specified window, usually the faculty lead will send a reminder email. For papers with many authors, consider distributing the paper as a google doc; this will make the process of integrating co-author changes much less painful. When sending co-authors the paper as a google doc, just be explicit that they are to track changes using the “suggesting” mode (screenshots are helpful to include).
After months-years of work, you are now ready to submit the paper. One reminder is that the final built PDF should be proof-read many times. Egregious formatting errors or typos are caught at this stage. Furthermore, pay careful attention to the quality of the figures in the built PDF. Note that if figures are large, the journal will downsample these considerably when making the PDF. Note that many reviewers will not click on the “high resolution figure” link available to them—they will just use what is in the built PDF. It is a bummer when we work hard to make gorgeous figures, and then what the reviewers see are poorly rendered due to downsampling. While this depends in part on the figure type that the journal accepts, one way around this is to submit figures as compressed PDFs—there is free software available for this. Once the paper is submitted to the journal, it is a good idea to put it on a preprint server as well (arxiv, biorxiv, etc; NB: biorxiv does NOT allow you to remove preprints—only update them). Use of preprints will help generate enthusiasm for the work even while it is stuck in peer review, prevent others from “scooping” you (esp w/ public datasets like the PNC), and also increases transparency. Feel free to tweet the link when it is up.
As noted above, it is the lab standard to submit all analysis code (in the form of a GitHub repo) along with the paper. Please make sure the repo submitted with the paper is cleaned, and does not include old code for parts of the project that did not pan out / were not included in the final manuscript. Including old code is a good way to confuse reviewers and others interested in reproducing your work. One way to do this is to make a new public repo that only uses a subset of code from the original working repo.
Please advertise new preprints on Twitter, and post them on the main pennlinc.io publications page.
Peer review is a slog: there is no way to spin it otherwise. To use a football analogy, the first submission is like being on the 20-yard line—certainly not the 1-yard line. Dogged persistence and a thick skin is critical for navigating peer review. In general, it is almost always better to “show them with data” and perform any additional analyses requested. Even if rejected, it is generally useful to try to address the reviewers’ comments in the subsequent (new) submission, as it is quite possible you will get the same reviewer at the next journal. This stage is often the part of the project that requires the most intense work in order to meet revision deadlines. Quick turn-around for revision and resubmissions is very important to prevent the project from stalling.
Congrats! Your paper was accepted. Next, make sure it reaches as many eyes as possible, through mechanisms including Twitter, Penn/SOM PR, a post on our website blog, etc. Make sure the final version of the paper is posted on the pennlinc.io “publications” page.