"Female Drosophila melanogaster Respond to Song-Amplitude Modulations"

One of my papers came out in final published form a few days ago. Here are some details. (Also see the paper's supplementary material for an interview with the first author, my former D.Phil. student Birgit Brüggemeier.)

Title: Female Drosophila melanogaster Respond to Song-Amplitude Modulations

Authors: Birgit Brüggemeier, Mason A. Porter, Jim O. Vigoreaux,and Stephen F. Goodwin

Abstract: Males in numerous animal species use mating songs to attract females and intimidate competitors. We demonstrate that modulations in song amplitude are behaviourally relevant in the fruit fly Drosophila. We show that Drosophila melanogaster females prefer amplitude modulations that are typical of melanogaster song over other modulations, which suggests that amplitude modulations are processed auditorily by D. melanogaster. Our work demonstrates that receivers can decode messages in amplitude modulations, complementing the recent finding that male flies actively control song amplitude. To describe amplitude modulations, we propose the concept of song amplitude structure (SAS) and discuss similarities and differences to amplitude modulation with distance (AMD).

A Video of My Seminar on "A Simple Generative Model of Collective Online Behavior"

On Friday 27 May, I gave a talk at the Oxford Internet Institute on "A Simple Generative Model of Collective Online Behavior". The video was posted online today. My talk, which took place at the Oxford Internet Institute, was part of an event for the Computational Social Science Initiative London.

I spoke about this paper, which I like to call our "Small Data" paper.

You may also be interested in videos of some of my other presentations.

14th-Order Differential Equations

The setup of today's SMBC takes a while, but the punchline is worth it --- and, um, way too close to the truth.

A Model of Motion Sickness

In my latest blog entry for the Improbable Research blog, I report on a model for motion sickness. (This, of course, is an example of a Rotating Hell.)

Ant Fight Club

In my latest post for the Improbable Research blog, I discuss modeling of combat in ants.

One of the reasons I chose to write about this paper is that it also allowed me to introduce modeling issues (e.g., the choice of a differential-equation model versus an agent-based model).

Next time, maybe I'll even use a Mortal Kombat reference. Finish him!

Elevator Action

The elevator problems in Oxford's new Mathematical Institute have gotten so severe that one of the building's denizens has tried to come up with a helpful mathematical model of the problem... according to rumor, while actually stuck in the elevator...

We moved into the building at the boundary of August/September 2013. Is this really that hard to solve? I wonder what Arrowsmith would say about this problem?

(Tip of the cap to Philip Maini.)

"Big Data" is a Religion

As far as I can see, "Big Data" seems more like a religion than anything else.

I like "Good Data" (which is far from the same thing) and "Good Models" (which can, e.g., include parameters fitted from data). I feel like I have a chance to actually understand things that way.

Data analysis definitely has its place and I certainly also have my moments when I do data analysis (see some of my papers), but data is far from everything. In short, I have ambiguous feelings about "Big Data".

Anyway, data analytics is an approach, and I use it sometimes, but there are also many other approaches that one should pursue to try to understand phenomena and solve problems.

By the way, I first posted the picture to which I link above in this blog entry, I ranted a bit about it in this blog entry, and I talked about a Small Data project at ECCS in 2013. (That work I described in that talk has subsequently been published in PNAS.)

Tales from the ArXiv: Herbivore Meltdown

I love the main label of the caption of Figure 5 (on page 12) of this new paper. It starts with the bold text "Meltdown of the herbivores." I love it!

Anyway, the next time you go into a forest, be very careful in case of herbivore meltdown. (I have all sorts of wonderful images in my head at the moment.)

And googling "herbivore meltdown" yields the fact that "ecological meltdown" is actually a standard term. It's certainly very image-provoking. I have to say, though, that I also find the term very humorous, even with its very serious implications.

Our Work on Modeling of Bipolar Individuals in The Guardian

The title of the entry basically already says everything, but Marc Abrahams (of Ig Nobel Prizes fame) has written an article about our work on modeling bipolar individuals in The Guardian. An excerpt of the blurb also appears in the Improbable Research blog.

The peanut gallery is skewering us. (Well, there is a mixture of coherent opinions that happen to be different from mine --- which I respect, as one could then have an intelligent discussion with such people about the merits or lack thereof of our research --- and then people who are just either trolling or being vitriolic.) I still need to learn not to read the comments section when one of my articles makes the press. Inevitably, those comments are not going to improve my mood.

In case you were wondering, if you look in the papers that have cited our paper (even though there are not many such papers), you will see that some of our ideas have helped subsequent work, that there is now more scientific evidence that the toy model that we cooked up does seem to capture some things (a similar model has now been derived mechanistically drawing from biochemical considerations), etc. The idea is that one can start with a toy model as a perspective to try to get at the simplest possible mechanisms and use such things --- in combination with clinical data to estimate parameters in such simplistic models --- to really try to get somewhere. This is a complementary way to "Big Data" approaches, and I think that trying to use simple (and even extremely simplistic) models can guide experiments, clinical studies, and so on. Our work on its own cannot do this, as we didn't use real data (which we didn't have), but modelling can inform clinical studies (and experimental studies more generally), and data from such studies can be incorporated into simple models to really try to get somewhere. Our paper is one extremely small stone in this endeavor, but I do believe that it is genuinely a stone.

Videos of Two of My Talks

In February 2013, I gave a talk on Cascades and Social Influence on Networks at Cornell University. I was giving the Center for Applied Mathematics colloquium (i.e., the colloquium in the program from which I got my PhD). This was my first visit to Cornell since I graduated in 2002. During the past few days, I gave updated versions of this talk at Simon Fraser University and University of British Columbia.

In December 2011, I gave a plenary talk on Social Structure of Facebook Networks at a conference in Henley.


Enjoy!

"This is the first serious modeling application in the field of love dynamics."

That is the first highlight listed for this paper, which is called A mathematical model of "Gone with the Wind".

(Tip of the cap to Jesús Cuevas Maraver.)

"Multi-Stage Complex Contagions"

I just blogged about my new paper on billiards, which just got published in final form today in Chaos. Well, the very next article in the journal, which was (unsurprisingly, given these statements) also published today, is my new paper on modelling social influence. Here are the details for that paper.

Title: Multi-Stage Complex Contagions

Authors: Sergey Melnik, Jonathan A. Ward, James P. Gleeson, and Mason A. Porter

Abstract: The spread of ideas across a social network can be studied using complex contagion models, in which agents are activated by contact with multiple activated neighbors. The investigation of complex contagions can provide crucial insights into social influence and behavior-adoption cascades on networks. In this paper, we introduce a model of a multi-stage complex contagion on networks. Agents at different stages --- which could, for example, represent differing levels of support for a social movement or differing levels of commitment to a certain product or idea --- exert different amounts of influence on their neighbors. We demonstrate that the presence of even one additional stage introduces novel dynamical behavior, including interplay between multiple cascades, which cannot occur in single-stage contagion models. We find that cascades—and hence collective action—can be driven not only by high-stage influencers but also by low-stage influencers.


Fun Fact: This might be the first published mathematics paper that uses the word "hipster". You should click on the link and see how we use it. :)

Tales from the ArXiv: Heavy Metal Edition

I just saw a new paper on the arXiv that looks like it will be a promising contender for an Ig Nobel Prize.

Title: Collective Motion of Moshers at Heavy Metal Concerts

Authors: Jesse L. Silverberg, Matthew Bierbaum, James P. Sethna, Itai Cohen

Abstract: Human collective behavior can vary from calm to panicked depending on social context. Using videos publicly available online, we study the highly energized collective motion of attendees at heavy metal concerts. We find these extreme social gatherings generate similarly extreme behaviors: a disordered gas-like state called a mosh pit and an ordered vortex-like state called a circle pit. Both phenomena are reproduced in flocking simulations demonstrating that human collective behavior is consistent with the predictions of simplified models.


Bonus:This paper, entitled Data Mining of the Concept "End of the World" in Twitter Microblogs (but do the authors feel fine?), also seems like it might be a legitimate contender.

Tales from the ArXiv: Statistical Physicists Conclude that Love is Universal

Here is a new paper about love.

Title: A model about love in human dynamics

Authors: Bin Zhou, Shujia Qin, Xiao-Pu Han, Bing-Hong Wang

Abstract: Human-initiated systems are the most complex systems. From now on, many people have done lots of works which are mostly centralized in time and space aspect in human dynamics, but relative to the cognizance which we have known, there must be underlying mechanisms about human society behavior that have not yet been discovered. We should research human society behavior form more other aspect to get more deeply and externally truth. In this letter, we propose a love model from a completely new angle to explain the love question between males and females in human society behavior. First, we establish the dynamics mechanism about the love model and get the exact analytical result about our love model, we compare the simulative results with the analytical predictions and find they completely coincide with each other, therefore, the analytical results can absolutely express the rule of our love model. Second, in several different conditions, we get the approximative and compact results which almost agreement with the simulative results, hence, the approximative results is dependable. Finally, we collect the experimental date by the network and compare it with the simulative results, and we can find, when the model parameter is given a specifical value, that the experimental evidence corresponds with the simulative results. This explains the love question which is universal existent between the male and female in reality and indicate the correctness and practicality of our love model in a certain extent.

Fluid Dynamics and Penguin Huddling

Recently published in the journal PLoS One is a mathematical model for penguin huddling that takes some inspiration from fluid dynamics. I know the third author (Arnold Kim), who I met when I interviewed for a faculty position at UC Merced in 2005 (and of whom I had heard before then).

(Tip of the cap to whoever does the posts for American Physical Society on Facebook.)

Applied Mathematics and Statistics are Not the Same!

Applied mathematics is not statistics. And vice versa.

Personally, I think this is an obvious statement, but at least one prominent sexy journal (Proceedings of the National Academy of Sciences) does not get it, and in my opinion this leads to a rather unfair bias against applied mathematics in this journal. Take a look at PNAS's editorial board, and in particular take a look at the three scholars listed under the category "Applied Mathematical Sciences". All three of them --- Peter Bickel, David Donoho, and Stephen Fienberg --- are card-carrying statisticians.

This is a major inequity. (I think it's also a major problem, but instead of arguing that per se, let me instead argue the lesser claim that it's a major inequity.) For example, applied mathematicians and statisticians have completely different notions of the word "model". To a typical applied mathematician, modelling constitutes the development of dynamical and/or generative models. A model might be a set of coupled differential equations that is derived using momentum balances and constitutive laws, it might be a phenomenological set of differential or difference equations that attempts to describe some qualitative features in a biological system, it might be a set of rules for generating an ensemble of random graphs, etc. Wikipedia has a long discussion of what constitutes a mathematical model, and many of these are the "dynamical models" that have long been favored by applied mathematicians. A statistical model, however, is something completely different. The phrasing in Wikipedia states that a statistical model "describes how one or more random variables are related to one or more random variables." Clearly, the Navier Stokes equations do not constitute a statistical model; but they are a mathematical model.

So why am I ranting about the inequity at PNAS? Well, if I try to get a paper in their applied mathematics section, I am going to have to get my paper through a statistician. And I have had a paper desk-rejected because the formulation contained in my paper did not constitute a statistical model. And that's true---it didn't. But I submitted an applied mathematics paper---not a statistics paper---and therefore I want to have it judged by card-carrying applied mathematicians. PNAS purports to represent applied mathematics, but it doesn't. There needs to be truth in advertising. They need to either claim that applied mathematics isn't part of their purview (which, by the way, I do not think is the right solution), or their list of editors in "Applied Mathematical Sciences" must include at least one actual applied mathematician!

Note: There is some overlap between models in applied mathematics and statistics when it comes to ensembles of random graphs, but even then applied mathematicians and statisticians tend to look at these beasts in different ways.

Order and Disorder in Pastry Displays

Perhaps strange dreams beget strange ideas, and here's my idea for the day.

I was at Green's Cafe today, and I noticed that the ordering of the pastries in their display case differs from day to day. And this makes me ask: Is it better strategically to do this (perhaps so people think there is more variety than there actually is?) or is it better to go with regularity and put everything --- when it's in stock --- in basically the same place every day. Also, it might be interesting to come up with a mathematical model of this. Do any of you have any thoughts on whether order or disorder is better in this situation? (Also, I'm guessing that the model would have a phase transition between a region in which the pastries should be ordered and one in which disorder ought to be favorable.)

Congratulations to the 08-09 mathematical modelling MSc students!

Today we finished the vivas (thesis defenses) and awarded the diplomas for the mathematical modelling and scientific computation MSc (Masters) students for 2008-2009. We also awarded 5 "distinctions" (out of 18 students). I was the advisor or co-advisor of 4 of the 18 students. Two of my students received distinction, and one of my students (Ben Franz) won the Nuclear Electric prize for best overall student in the cohort. It just goes to show how far one can get by working on a project on cow synchronization. (Naturally, my other 2 students also performed well.) When giving out the results, we didn't have any stories amusing incidents like we did last year. I couldn't find a blog entry about last year, so let me briefly recount the story here:

The students line up alphabetically to come into a room and formally be given their results one by one. There was one student (I don't remember whom) to whom we forgot to tell some germane piece of information so we had to call him back in. Then we realized we had forgotten to tell him something else, so we called him back in again. Between one or both of his appearances in the room, other students had gotten their results. Then after we had called him back in twice, we decided we should call him back in a third time a little bit later just to screw with him. That incident remains perhaps the funniest moment I've experienced at Oxford, and it's certainly one of my best memories here outside of things of the form 'quality time with good friends'.

Anyway, congratulations to all of the students who graduated today! (And that would be all 18 of the students, by the way. We didn't fail anybody this year.)

I think the best quote that might have come from this is one I heard about second-hand---namely, a rather distraught statement of "I just had to read 100 pages about hypergeometric functions!"

By the way, John Ockendon ("Ock") says I should give a shout out to our esteemed External Examiner from Limerick, who came to Oxford armed with the knowledge that I have strong opinions and tend to be very passionate about things. I'm glad I have established my reputation. Also, I was once again the strictest Examiner by far this year. So end my duties as an MSc Examiner. (Two more years as a Part C Examiner, and then all of my Examiner duties will be over for a very long time.)

On a somewhat unfortunate note, I am feeling extremely depressed at the moment, though there isn't any good reason for it. The chemicals in my body simply aren't cooperating, and I have managed to get into a depressive episode. I even saw it coming, but my efforts to avert it weren't successful.

Quote of the Day

The following comment just occurred in one of the modeling week talks: "If you ignore the bad parts, then it's a good model."

Comment: D'oh!

(To be fair, there is a reasonable version of this statement---namely, that they seemed to capture some features reasonably.)

Poland so far

I've been a bit silent for a few days, so here are some of the things going on in Wroclaw. I'll post pictures later (aside from the ones that are already in the photoblog) once I return to Oxford on Sunday.

1. I found a restaurant named "PRL", which you can already see in my photoblog.

2. Before I even arrived, I had it in mind to get some good perogis, and this trip has not disappointed. I have twice gotten beef perogis---on the first night where they unexpectedly came with bacon bits and last night at a Jewish restaurant called "Sarah" (though I was unable to find the mezuzah).

3. My hotel's restaurant was a Chinese restaurant, which I did not expect. I ate there one night when I was feeling lazy, and I was awarded with an epic fail.

4. Bicycles are big in this town, as are walking down.

5. Another thing that is huge here are the small statues of gnomes. I have been told that there are over a hundred of them, but a blog entry with an excellent description of their origin incorrectly claims that there are over 15. (Some of the students here claim to have taken pictures of over 20 of them.) You can find pictures of some of them on this website. I've taken pictures of two of them, and I will post them in my Wroclaw photo album.

6. I found a really nice hole-in-the-wall coffeehouse where I have been getting iced lattes and nice pastries, chilling out, and reading.

7. I also found a decent dessert place, which had a really nice environment right outside the shop on Sunday morning before other people showed up with their kids. I was outside with a blended coffee drink (this was before I found the other place, which I like much better for coffee) and was reading and enjoying the weather. I noticed some pigeons with a neat flocking pattern. Whenever the pigeons were disturbed, they would fly up from the ground and then they would make one or two cycles of a consistent size, and then they would return to their feast. Unfortunately, I was unable to get a good picture of this. However, I was wondering why there was usually one cycle and on occasion two (and to a lesser extent about the specific, consistent size of the cycle). When I was sitting there, it made me think of some lazy weekend mornings playing chess with Vito Dai outside of a coffee place---Vito with his tea and me with my coffee. I really felt the urge to be playing chess at that moment.

8. The 'old town' (marketplace) area is really cool---there are a lot of neat restaurants, places to sit, an awesome fountain, a plaza where live music could easily be done, etc.

9. Radiohead apparently is having a concert (or has had a concert) here during my trip. Leonard Cohen played in Vienna while I was there, and I slightly regret being lazy and not going to the concert. (I was feeling rather tired and a bit lazy at the time.)

10. Many of the churches here (unsurprisingly) have very similar architectural styles to each other.

11. Naturally, I got horribly lost while trying to find the university for the first time on Sunday. That was inevitable. Because of this and my prior explorations, I did a ton of walking on Sunday and my feet are still hurting a bit as a result of it. After lots of circling, finding my way in the wrong part of town, and going back to the hotel, I finally made it to the university and I even took a reasonable route (starting from my second time at the hotel, so ignoring/pruning the long closed-loop excursion)---although not the one that I had initially attempted. I got slightly lost again on the way back---though I quickly realized that I was on the route that I had attempted initially. It evidently got completely foiled by just one epic fail of a decision on that particular street. I knew where I was because I noticed the "W. Kruk" store (though I later found another one of those even closer to the hotel) that I had marked in my head earlier in the day because it made me think of the baseball player John Kruk. In general, the way I follow directions doesn't rely on cardinal directions because I get disoriented really easily---it takes me several days of being in a new city to do a decent job of where north is, and then if the sun is in my eyes, I go all deer-in-headlights and my internal compass just goes completely haywire---so I rely on "landmarks" that I have noted for some reason (large or interesting buildings, prominent signs, or whatever else) and also relative directions and distances a la logo. Ah well, I got back without any real delay.

12. One of the modelling week problems is how to climb (by foot) a mountain. It uses data that comie from a mountain by the name of "Wank" (yes, that is apparently the real name of the mountain). So the problem then becomes how to climb Mount "Wank". (It's not quite "Climbing the Mountain of Conflict", but it will do.) Another problem is called "Improving the Efficiency of Prick-tests", which I think could use a better name.

13. Food is extremely cheap here (though not at the level of Taiwan). My meat perogis with bacon bits + a drink + a tip cost me 35 Polish zloty, which amounts to roughly 7.5 pounds. My meat perogis + a drink last night + a tip cost me 20 zloty.

14. The first restaurant that I've now mentioned a couple of times served some food in tinfoil that was shaped like a bird. It reminded me of R.J.'s---may that restaurant rest in peace!---though in this case it wasn't for leftovers being taken home. I definitely felt the pangs of nostalgia when I saw that.

15. I had dinner with some of the students on Monday night. Among the crowd were 3 of the 4 Oxford students attending the meeting (so, along with me, we had all of us except one person) and a few students from other places. The waiter was facetiously trying to get the women among us to order vodka. One of them ordered "half a liter of water", and the waiter pretended to misinterpret: "Half a liter of vodka?"

16. I was using my digital camera to get screenshots of whiteboards to help with the note-taking.

17. My students worked really hard and did an excellent job. The problem I gave them to study was ranking American football teams, and my goal was for them to come up with a different way of doing it than I had done in my prior research. (After a couple of days, I showed them what we had done.)