If you didn’t know it already, the Internet is a pretty cool thing.

Two days ago, sitting in my office, I noticed a small wolf spider moving across the window sill, and then up the window.

Wolf spiders are hunters, rather than trappers. This particular spider had a characteristic
kind of motion which I had seen before. It moved in discrete jumps, about one every 1-2 seconds. Between jumps it would stay motionless. I had observed similar motion in other animals, such as lizards and rabbits, but had never given it much thought.

I began to wonder why the spider moved with this kind of motion. The most obvious reason that occured to me was that it was trying to keep still most of the time, to avoid triggering simple motion detection mechanisms in either the critters it was hunting, or the critters that were hunting it. Presumeably this would be a kind of behavior which might have evolved over time.

Other explanations occured to me as well. Perhaps this motion might be the result of the way the spider processes information: does the spider process information in discrete bursts punctuated by action? Or perhaps this motion was particularly energy efficient.

Now, if this were 20 years ago, I might have thought idly about this for a while and forgotten it.
I might have looked up wolf spiders in the world book encylopedia my parents had bought, and probably would have learned some interesting things, but wouldn’t have learned much about the answer to this particular question. If I remembered the next time I visited the public library, I might have looked it up, but I doubt I would have found much about this particular kind of movement in spiders.

But this wasn’t 20 years ago, so I went to a popular search engine you might have heard of and typed in

"wolf spider" predator movement

…and found a number of interesting papers on wolf spiders, including this one (abstract) co-authored by Dr. Sean Walker. This particular paper says that wolf spiders are sensitive to what their potential predators (other wolf spiders) have been eating and will modify their motion in the presence of other wolf spiders that have been fed a diet of wolf spiders, as opposed to crickets. Kinda cool, huh?

Since Dr. Walker’s name was on a few of the wolf spider related papers, I dropped him a note and asked
him about what might cause the curious wolf spider motion. I’ve generally found that scientists
are often willing to share information with other curiosity seekers, unlike corporate CEOs. I suppose it helps if your interest is in something as arcane as wolf spiders.

This is what Sean wrote back:

Hi Jim,

It could be a bit of both. Wolf Spiders are their own worst enemies so
moving in a saltatorial fashion would be a bit like being camouflaged since
they are spectacular motion detectors. They also tend to do this when
hunting so it might also make them more cryptic towards prey. So, it’s not
unreasonable to hypothesize that these movement patterns are adaptive. To
be honest, I can’t think of any good experimental evidence for this
hypothesis. However, it does make logical sense.

If there is some kind of constraint in the way the animals are processing
information then this (I guess) could lead to saltatory movement. I do not
know if there is any evidence of this sort of thing in the literature.
However, this explanation does not exclude the other explanations since it
is proposing the mechanism behind the movement (so to speak) as opposed to
the adaptive value of it. It’s a really interesting idea.

Hope that helps,

Cheers,
Sean

So, no, I didn’t really find a simple answer to my question, but emphatically yes,
the Internet is great! Not only did I learn some interesting things about what is
and isn’t known about wolf spiders, from a true expert in the field, within an hour of
raising an idle question, I also learned a new word: saltatorial, Of or relating to leaping or dancing, and apparently a term biologists use to describe leaping motions. Finally I learned that the true story, as always, is more complicated than the simple
models that the mind builds when trying to understand a complex subject.

This is one of a set of four collaborative posters I am preparing for printing this month.

I made this particular image by writing a collection of Perl scripts which arrange photos from the squared circle group on flickr in a fibonacci spiral (a natural way of tiling circles, seen in sunflowers, pinecones and many other places in nature), according to color.

Posters can be ordered here:

www.krazydad.com/posters/

In my class, “Interactive Arts & Toys” I will devote considerable time to the subject of randomness in computer art. I have been using random numbers to create art since my days at CalArts. The very first computer program I wrote (in BASIC on a Timex Sinclair) computed tables of random numbers for the purposes of being used in music compositions, after the manner of John Cage.

If you take a quick peek around this website, you will see a considerable number of software toys which make heavy use of random numbers. It is perhaps worth pointing out that the use of random numbers does not agree with everyone.

John Whitney’s experimental films made use of sequences which were highly predictable. He slams John Cage a bit in his 1980 book Digital Harmony: On the Complementarity of Music and Visual Art saying that he understands Schoenberg when he said to Cage “you must have a feel for harmony.” Whitney’s movies have a high degree of apparent order to them, which would have been reduced if he had used random (or brownian) motion. He says that the movements “collect and release tension.”

In John Maeda’s book Design By Numbers, he very briefly touches on the use of randomness at the very end and then goes on to say:

…the outcome is difficult to predict, which seems to be the whole point of using random numbers. There are many better ways to become completely lost in systems of noise, and if this is the path you wish to pursue, then I hope you get lost in earnest.

Wow, harsh words! In both cases, I think these two Johns (Whitney Sr. and Maeda) are confusing one potential reason for using random numbers (i.e. giving up choice) with the use of the numbers themselves. There are many possible reasons for using random numbers – and we can choose precisely how much choice we wish to give up: a lot, a little, or none at all.

When Maeda says “the outcome is difficult to predict” he is implying “the outcome is difficult (for me) to control.” But random numbers can indeed be used in a controllable (and predictable) fashion. Just as an artist can control an airbrush to produce relatively specific results, so can a stream of random numbers be manipulated to produce very specific effects. The users of random numbers do not necessarily intend, as John Cage did, to “deny the ego” – to give up control over the outcome.

Although the first music I wrote using computer-generated random numbers was very much in the spirit of John Cage, the subsequent music was not – it was more in the style of Lejaren Hiller. I used random numbers to generate notes, but then I *sculpted* those results, by running them thru the rules of species counterpoint to create music with recognizeable western harmonies and rhythms. The rules acted as a kind of filter, just as the nozzle on an airbrush controls the flow of paint.

Random numbers generators are simply a tool – and a very powerful one at that, as anyone who has written a Renderman shader can attest!

One of the reasons that I like making kaleidoscope simulations is that the kaleidoscope is a perfect illustration of the fusion of randomness with predictability, and the interesting things that can happen when they meet.

I’ve decided to temporarily convert my homepage into a blog, in preparation for my upcoming Art Center class, “Interactive Arts & Toys,” in which I will be providing instruction on the art of the screensaver and other useless, but fun things.

My previous krazydad home page is a more static affair which basically reproduced the menu.

THE ZOOMQUILT | a collaborative art project

I live near one of the coolest public libraries in Los Angeles, Glendale’s Brand Library and Art Center.

Here are a 10 good reasons why you should go.

1. The library sits at the the top of Western Ave in a beautiful park overlooking the valley. Excellent for picnic lunches.

2. The library specializes in music and art.

3. There is not a single book about accounting, insurance, or how to pay your taxes.

4. There are no novels by Tom Clancy.

5. There are books like Peepshows: A Visual History, and the Encyclopedia of Automatic Musical Instruments that cost much more on Amazon, or are shamefully out of print.

6. The library is full of cute geeks (and cute geeky librarians) who are interested in music and art. Wink wink, nudge nudge.

7. The library is in an eccentric old Saracenic mansion, named El Miradero, that was built in 1904.

8. The mansion has its very own ghost.

9. If you go on a Saturday, you have a 2/3rds chance of running into a Glendale wedding party and seeing a 10 or 20 Armenian bridesmaids wearing poofy dresses.

10. If you meet your future geeky wife or husband at the Brand, you can get married there, and have a very romantic story to tell your geeky kids.

Since Catt created this service, I’ve geoblogged a few of my own photos. Very cool!

   

Geobloggers.

What can be better than a robot controlled by a real cockroach?

Garnet Hertz: Control and Communication in the Animal and the Machine