December 28, 2005

Peer review, human nature and scientific publication

Peer review determines what gets published and what gets funded in science and technology, at least in academia. Since most (all?) institutions evaluate their researchers based on their publication and fund raising records, the defining principle of scientific life. It is what distinguishes the respected professional from the mad scientist operating unchecked in his garage/home office.

A bulletin from the Office of Management and Budget titled "Final Information Quality Bulletin for Peer Review" ( gives the following definition:

"Peer review is one of the important procedures used to ensure that the quality of published information meets the standards of the scientific and technical community. It is a form of deliberation involving an exchange of judgments about the appropriateness of methods and the strength of the author's inferences. Peer review involves the review of a draft product for quality by specialists in the field who were not involved in producing the draft."

Criticisms of the peer review systemaboundd, not all unjustified, but nobody has been able to come up with something better so far...

Academic success is "all about how you choose your peers." Nowadays, it is not rare for researchers to log tens of "publications" per (few) year(s) on average. Journals multiply, so do peer-reviewed conferences and workshops, for which acceptance rates have become lower than journal's, while the size of their proceedings have increased so much that nobody wants to carry the printed version back home anymore. All this is further accentuated by the increase in the number of researchers.

Does the peer review system scale up? When the pool of peers grows, who selects the ones to act as reviewers? Are the best researchers likely to have a lot of time to devote to reviewing everybody else's drafts? The original purpose of peer review was to check for consistency and correctness of inference. However, peer review has become a ranking system to select the few "worthy" drafts among hundreds or thousands of submissions. Therefore the reviewers influence what will get published or funded not only on scientific merit alone, but on more subjective factors. With the increasing number of peers, the choice of the reviewers also influences the success.

Now, if reality TV has taught us one thing, it is that the best candidate to win the game according to the rules rarely wins. Successful candidates team up to eliminate underperforming individuals early, and use the high performance individuals until they become too much of a threat at which point they eliminate them. The final head-to-head confrontation involves the contestants that best understood and leveraged the human aspect of the game. Often the human (political) factors defeat the purpose of the simply stated rules. On TV it makes for (supposedly) exciting drama. In science it could make for sub-optimal progress in seemingly prosperous fields. Consider the recent scandal sparked by the revelation that Dr. Hwang Woo Suk, a leader in stem cell research, falsified some of his reported findings. The key here is not a failure of the peer review system for this specific article, but rather how he reached such a prominent position and how he got to faking data (see

While current evaluation schemes seem to favorize quantity over quality of publications, quality assessment remains a problem. Number of citations (similar to the system used by google PageRank algorithm) is a common metric, however difficult to assess and quite easily biased (search results are a good example). Publications count, weighted by some quality evaluation measure for the publishing venue, is another metric, also quite difficult to interpret and easily biased.

The reasoning behind these methods of evaluation is a bit confusing. It seems relatively safe to hypothesize, based on the core principles of scientific publication (including peer review), that (1) successful scientists publish papers, which are frequently cited:

Evaluations seem to be based on the premises that (2) scientists who publish (a lot) and are frequently cited must be successful, which cannot be inferred from (1).

(2) is often replaced with a more "efficient" variant (i.e. easier for busy committee members to work with): (2') all scientists who publish a lot must be successful.

Somewhat of a stretch. It seems that the problem is tackled backwards. In fact, this remark suggests a different approach to evaluation, using machine learning techniques. Somebody should build graphical models that capture, in each field, the dependencies between number of publications in each relevant journal, conference, workshop, etc. and scientific success. The models could be trained on a large amount of data (the level of success for each individual used for learning could be evaluated by--what else?--a peer review system).

A common over generalization of (1) is that all successful scientists publish a lot and are frequently cited, which suggests that scientists who do not publish a lot and/or a not frequently cited must be bad.

This is clearly wrong: before publishing anything, all great scientists were obviously doing good research. In fact, the peer review system favorizes continuation and discourages bold innovation and radical evolutions (see "We Are Sorry to Inform You..." in IEEE Computer volume 38, issue 12). This might be why great scientists keep praising "cross-disciplinarity." If anything new has a slight chance of being accepted by a given community, it should be coming from a different field.

Come to think of it, the fact that a researcher has been successful in the past does not guaranty success in the future. So maybe time should be taken into consideration?

In any case, human nature is such that there will always be a doubt whether a successful scientist is successful at doing great science, or is just successful at leading a scientific career. "Scientist" could be substituted for pretty much anything else, but it is especially ironic for scientists...

December 22, 2005

Synthesis, analysis and invariants

"If people do not believe that mathematics is simple, it is only
because they do not realize how complicated life is." -- J. H. Von Neumann

One can wonder why computer vision (CV) has not benefited from the increase in computational power as much as computer graphics (CG), although the two fields grew from the same seminal work (Roberts, 1965).

CG is a synthesis activity, that starts from mathematical models of some physical objects and their environment, and applies some mathematical models of light and material physics to create an image of the objects in their environments under various conditions. Better models, and computational power directly translate into more realistic images. The models are designed by humans.

Computer vision is an analysis activity, that seeks to form models of objects, environments, situations, activities, etc., from images (still pictures or video streams). Depending on their intended purpose, these models are not necessarily of the same nature as those used in graphics. The task in CV is of a very different nature from that of CG, and does not benefit directly from traditional mathematics.

Mathematics allow to manipulate invariants to study their properties and produce other invariants. Only specific branches of mathematics are concerned with extracting invariants from observations. "Machine learning" does give interesting results when applied to analytical (classification/recognition) tasks for example in speech recognition and CV.

However much remains to be done to completely formalize and understand the processes by which meaningful invariants are learned, recognized and used in cognitive activities. One principle that seems important is that an observer can never make the same observation twice: both the environment and the observer keep evolving. For example, mathematical models enforce that the same processing of the same picture will always give the same result no matter how many times it is ran. Intuitively, a human presented with the same picture several times will have a different experience each time, and maybe will notice different things in the picture. On the other hand, when presented with two pictures of the same object or person, even in totally different circumstances, a human will recognize that the object or person depicted is the same physical entity. The same goes with any perceptual/cognitive task.

To come back to the original question and the quote, it seems that a possible reason for CG's success is that mathematical tools apply directly to the problem. A possible reason for CV's apparent lag is that mathematical tools that address directly the roots of the problem are not as well developed.

Scientific freedom

"I have just one wish for you--the good luck to be somewhere where you are free to maintain the kind of integrity I have described, and where you do not feel forced by the need to maintain your position in the organization, or financial support, or so on, to lose your integrity. May you have that freedom."

Richard P. Feynman, "Cargo Cult Science," adapted from the Caltech commencement address given in 1974, published in "Surely you're joking, Mr. Feynman" (Norton, 1985).

November 17, 2005


"Don't speak unless you can improve on the silence" -- proverb, apparently spanish...

October 21, 2005

Bandwidth vs. latency

I recently attended a robotics seminar in which the speaker made an interesting point about machines outperforming humans (in some domain), but unfortunately used the word bandwidth when he really meant latency.

His point was that machines can react much faster than humans. Indeed, humans have relatively long reaction time, ranging in order from a few tens of milliseconds, to a just short of a lifetime, depending on the stimulus, the complexity of the analysis, and the complexity of the action. When it comes to latency, for simple reactive actions, current computers and robots can already outperform humans, sometimes by several orders of magnitude.

On the other hand, humans have extremely large input bandwidth. The amount of sensory data that humans can absorb and process per unit of time is still much larger than what computers can deal with, both in terms of physical bandwidth, and computing bandwidth.

In the world of digital signal processing, where bandwidth directly constrains processing time, latency and bandwidth are--artificially--tied. In the real world, including in our massively parallel brains, bandwidth and latency are not so directly coupled.

September 29, 2005

'Don't settle'

"Your work is going to fill a large part of your life, and the only way to be truly satisfied is to do what you believe is great work. And the only way to do great work is to love what you do. If you haven't found it yet, keep looking. Don't settle. As with all matters of the heart, you'll know when you find it."

"Your time is limited, so don't waste it living someone else's life. Don't be trapped by dogma--which is living with the results of other people's thinking. Don't let the noise of other's opinions drown out your own inner voice. And most important, have the courage to follow your heart and intuition."

Excerpts from Steve Jobs' graduation address at Stanford University. Full text available at:

August 31, 2005

Software design

"To a man with a hammer, everything looks like a nail. To a Computer Scientist, everything looks like a language design problem. [...] My early work clearly treated modularisation as a design issue, not a language issue. [...] We are still trying to undo the damage caused by the
early treatment of modularity as a language issue and, sadly, we still try to do it by inventing languages and tools."

David Parnas, in :
Premkumar Devanbu, Bob Balzer, Don Batory, Gregor Kiczales, John Launchbury, David Parnas, Pen Tarr, "Modularity in the New Millenium: A Panel Summary," in Proceedings of the 25th International Conference on Software Engineering, Portland, OR, 2003, pp.723-724.

August 30, 2005

What is software

"In the context of a book on software design, it should be obvious that we are concerned with designing software. It is far from clear, however, just what the word means. We can approach software from many different perspectives, each with its own implications for design. In this book, we emphasize software as a medium for the creation of virtualities--the world in which a user of the software perceives, acts and responds to experiences."

Terry Winograd, Introduction to "Bringing Design to Software."

August 25, 2005

Fear of the unknown

"You come to me for advice, but you can't cope with anything you don't recognize. Hmmm. So we'll have to tell you something you already know but make it sound like news, eh? Well, business as usual, I suppose."

Douglas Adams, "Mostly Harmless."

August 24, 2005

The right tools make all the difference

A screw is best used with a screw-driver. The screw-driver is as critical to screwing as the screw.

If all one has is a hammer, and all one studies is nailing and hammering, it will be difficult to grasp, let alone come up with, the concept of screwing. Screws handled with a hammer bear the mark of laziness and short-term reward.

But, once mastered, screwing should not be allowed to eclipse nailing: while some tasks require screwing, others clearly call for nailing. Only by understanding not only each independently, but also how they relate to each other, can one decide when to use them optimally.

Then it is time to start learning about riveting...

August 20, 2005

Academic credits

"I recently learned a disagreeable fact: there are influential scientists in the habit of putting their names to publications in whose composition they have played no part. Apparently, some senior scientists claim joint authorship of a paper when all that they have contributed is bench space, grant money and an editorial read-through of the manuscript. For all I know, entire scientific reputations may have been built on the work of students and colleagues!"

Richard Dawkins, Preface to the 1989 edition of "The Selfish Gene."

August 18, 2005

What you see is what you expect

"[...] a scientist must also be absolutely like a child. If he sees a thing, he must say that he sees it, whether it was what he thought he was going to see or not. See first, think later, then test. But always see first. Otherwise, you will only see what you were expecting."

Douglas Adams, "So Long and Thanks for all the Fish."

August 07, 2005

Welcome to

Sign of the times, this blog is now my official personal home page. It is obviously work in progress. If you are looking for professional information, follow the link to my home page at USC.