Category: Conferences

Although I’m greatly interested in machine learning, I think it must be admitted that there is a large amount of low quality logic being used in reviews. The problem is bad enough that sometimes I wonder if the Byzantine generals limit has been exceeded. For example, I’ve seen recent reviews where the given reasons for rejecting are:

1. [NIPS] Theorem A is uninteresting because Theorem B is uninteresting.
2. [UAI] When you learn by memorization, the problem addressed is trivial.
3. [NIPS] The proof is in the appendix.
4. [NIPS] This has been done before. (… but not giving any relevant citations)

Just for the record I want to point out what’s wrong with these reviews. A future world in which such reasons never come up again would be great, but I’m sure these errors will be committed many times more in the future.

1. This is nonsense. A theorem should be evaluated based on it’s merits, rather than the merits of another theorem.
2. Learning by memorization requires an exponentially larger sample complexity than many other common approaches that often work well. Consequently, what is possible under memorization does not have any substantial bearing on common practice or what might be useful in the future.
3. Huh? Other people, thank you for putting the proof in the appendix, so the paper reads better. It seems absurd to base a decision on the placement of the content rather than the content.
4. This is a red flag for a bogus review. Every time I’ve seen a review (as an author or a fellow reviewer) where such claims are made without a concrete citation, they are false. Often they are false even when concrete citations are given.

A softer version of (4) is when someone is cranky because their own paper wasn’t cited. This is understandable, but a more appropriate response seems to be pointing things out, and reviewing anyways. This avoids creating the extra work (for authors and reviewers) of yet another paper resubmission, and reasonable authors do take such suggestions into account.

NIPS figures fairly prominently here. While these are all instances in the last year, my experience after interacting with NIPS for almost a decade is that the average quality of reviews is particularly low there—in many instances reviewers clearly don’t read the papers before writing the review. Furthermore, such low quality reviews are often the deciding factor for the paper decision. Blaming the reviewer seems to be the easy solution for a bad review, but a bit more thought suggests other possibilities:

1. Area Chair In some conferences an “area chair” or “senior PC” makes or effectively makes the decision on a paper. In general, I’m not a fan of activist area chairs, but when a reviewer isn’t thinking well, I think it is appropriate to step in. This rarely happens, because the easy choice is to simply accept the negative review. In my experience, many Area Chairs are eager to avoid any substantial controversy, and there is a general tendency to believe that something must be wrong with a paper that has a negative review, even if it isn’t what was actually pointed out.
2. Program Chair In smaller conferences, Program Chairs play the same role as the area chair, so all of the above applies, except now you know the persons name explicitly making them easier to blame. This is a little bit too tempting, I think. For example, I know David McAllester understands that learning by memorization is a bogus reference point, and probably he was just too busy to really digest the reviews. However, a Program Chair is responsible for finding appropriate reviewers for papers, and doing so (or not) has a huge impact on whether a paper is accepted. Not surprisingly, if a paper about the sample complexity of learning is routed to people who have never seen a proof involving sample complexity before, the reviews tend to be spuriously negative (and the paper unread).
3. Author A reviewer might blame an author, if it turns out later that the reasons given in the review for rejection were bogus. This isn’t absurd—writing a paper well is hard and it’s easy for small mistakes to be drastically misleading in technical content.
4. Culture A conference has a culture associated with it that is driven by the people who keep coming back. If in this culture it is considered ok to do all the reviews on the last day, it’s unsurprising to see reviews lacking critical thought that could be written without reading the paper. Similarly, it’s unsurprising to see little critical thought at the area chair level, or in the routing of papers to reviewers. This answer is pretty convincing: it explains why low quality reviews keep happening year after year at a conference.

If you believe the Culture reason, then what’s needed is a change in the culture. The good news is that this is both possible and effective. There are other conferences where reviewers expect to spend several hours reviewing a paper. In my experience this year, it was true of COLT and for my corner of SODA. Effecting the change is simply a matter of community standards, and that is just a matter of leaders in the community leading.

One way that many conferences in machine learning assign reviewers to papers is via bidding, which has steps something like:

1. Invite people to review
2. Accept papers
3. Reviewers look at title and abstract and state the papers they are interested in reviewing.
4. Some massaging happens, but reviewers often get approximately the papers they bid for.

At the ICML business meeting, Andrew McCallum suggested getting rid of bidding for papers. A couple reasons were given:

1. Privacy The title and abstract of the entire set of papers is visible to every participating reviewer. Some authors might be uncomfortable about this for submitted papers. I’m not sympathetic to this reason: the point of submitting a paper to review is to publish it, so the value (if any) of not publishing a part of it a little bit earlier seems limited.
2. Cliques A bidding system is gameable. If you have 3 buddies and you inform each other of your submissions, you can each bid for your friend’s papers and express a disinterest in others. There are reasonable odds that at least two of your friends (out of 3 reviewers) will get your papers, and with 2 adamantly positive reviews, your paper has good odds of acceptance.

The clique issue is real, but it doesn’t seem like a showstopper to me. If a group of friends succeeds at this game for awhile, but their work is not fundamentally that interesting, then there will be no long term success. The net effect is an unfocused displacement of other perhaps-better papers and ideas.

It’s important to recall that there are good aspects of a bidding system. If reviewers are nonstrategic (like I am), they simply pick the papers that seem the most interesting. Having reviewers review the papers that most interest them isn’t terrible—it means they pay close attention and generally write better reviews than a disinterested reviewer might. In many situations, simply finding reviewers who are willing to do an attentive thorough review is challenging.

However, since ICML I’ve come to believe there is a more serious flaw than any of the above: torpedo reviewing. If a research direction is controversial in the sense that just 2-or-3 out of hundreds of reviewers object to it, those 2 or 3 people can bid for the paper, give it terrible reviews, and prevent publication. Repeated indefinitely, this gives the power to kill off new lines of research to the 2 or 3 most close-minded members of a community, potentially substantially retarding progress for the community as a whole.

A basic question is: “Does torpedo reviewing actually happen?” The evidence I have is only anecdotal, but perhaps the answer is “yes”. As an author, I’ve seen several reviews poor enough that a torpedo reviewer is a plausible explanation. In talking to other people, I know that some folks do a lesser form: they intentionally bid for papers that they want to reject on the theory that rejections are less work than possible acceptances. Even without more substantial evidence (it is hard to gather, after all), it’s clear that the potential for torpedo reviewing is real in a bidding system, and if done well by the reviewers, perhaps even undectectable.

The fundamental issue is: “How do you chose who reviews a paper?” We’ve discussed bidding above, but other approaches have their own advantages and drawbacks. The simplest approach I have right now is “choose diversely”: perhaps a reviewer from bidding, a reviewer from assignment by a PC/SPC/area chair, and another reviewer from assignment by a different PC/SPC/area chair.