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What Birds Know About Fractal Geometry

Posted by samzenpus on from the looking-good dept.

sciencehabit writes "In a new study, researchers find that a single number that describes the complexity of feather patterns on bird chests, a parameter called the fractal dimension, is linked to whether a bird has a strong immune system or is malnourished. When scientists restricted the food of red-legged partridges, the patterns on their chests had a lower fractal dimension than those sported by their well-fed colleagues. The food-restricted birds, on average, weighed 13% less than their well-fed colleagues and had weaker immune systems, which makes fractal dimension an easily recognizable sign of a potential mate's health and vitality, the researchers contend."

15 of 74 comments (clear)

  1. Call it what you will by CuteSteveJobs · · Score: 5, Insightful

    'Fractal dimension' seems like a cool buzzword which will make it easier to get research noticed, so call it what you will, but a the color of birds feathers except for blues are determined by their diet. Blue is determined structurally. The pattern is determined by proteins following genetically-laid out patterns, same as like stripes or spots on other animals. There is some logic that birds with good diets would have 'better' patterns as determined by their prospective mates.

    http://www.smithsonianmag.com/science-nature/Why-Are-Some-Feathers-Blue.html
    http://www.birds.cornell.edu/AllAboutBirds/studying/feathers/color/document_view

    1. Re:Call it what you will by Anonymous Coward · · Score: 5, Informative

      You are absolutely correct, it just so happens that the patterns formed are also fractal in nature. All fractals are described statistically with fractal dimension, a relative measure of complexity, in order to differentiate between scaling properties in different fractal patterns. Really, all this research is saying is healthier birds have more complex patterned feathers, but with a mathematical definition of what that complexity is.

    2. Re:Call it what you will by craigminah · · Score: 4, Insightful

      The title is misleading...the birds like the pattern and know nothing about fractals. Reminds me of the story of a mathematician's dog who "knew calculus" because of the way it waited for a ball to bounce off a wall. It didn't know calculus, it just learned what happens when a ball is tossed against a wall. To know calculus or fractal geometry would mean you'd do some form of calculations and be aware of the interrelationships of the variables within...neither the birds nor the dogs did any such thing.

      People at nightclubs simply like or dislike the way someone acts/looks to determine if they want to "mate" with them...no math there but a story will come out saying men and women at nightclubs perform complex trig to find mates.

    3. Re:Call it what you will by fuzzyfuzzyfungus · · Score: 4, Insightful

      What? The world has come to this? Instead of how intelligent, strong, or attractive we are, the primary factor is socio-economic status?

      Wow, I bet that realisation causes more than a few suicides.

      At the level described in TFA(malnutrition leading to visible differences in development persisting into maturity) or similar(doesn't sound like they tested it; but parasite load and certain sorts of environmental pressures probably have the same effect) there really isn't a terribly strong separation of physical factors and socio-economic status(to the degree that birds have that). At the knife-edge-of-subsistence level, the fact that intelligence, strength, and attractiveness are paid for in calories and nutrient distributions really tightens the connection between personal virtues and economic status.

    4. Re:Call it what you will by Viol8 · · Score: 5, Funny

      "a story will come out saying men and women at nightclubs perform complex trig to find mates."

      Hey , you've obviously never tried to look cool in front of some babes at a club while carrying a load of beers and having to carefully avoid all the drunks and druggies swaying about by calculating the optimal path across the dancefloor cross referenced in the time domain against the beat of the music!

    5. Re:Call it what you will by cupantae · · Score: 4, Informative

      'Fractal dimension' seems like a cool buzzword which will make it easier to get research noticed

      Well, maybe it is, but you can't actually fault them for using it. The term "fractal dimension" is as old as the study of fractals, and is taught in university mathematics courses. It is a useful concept, as you'll see if you read the wikipedia page. It's also consistent with the traditional geometric idea of dimension.

      I've only skimmed through the paper so far, but they've directly calculated the FD from its definition. The data looks pretty good. From what I've seen in the paper, I would say it's all legit.

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    6. Re:Call it what you will by Abstrackt · · Score: 2

      It went fairly well until I pulled out the slide rule.

      --
      They say a little knowledge is a dangerous thing, but it's not one half so bad as a lot of ignorance. - Terry Pratchett
    7. Re:Call it what you will by museumpeace · · Score: 3

      Did you see the movie "a beautiful mind" about John Nash...who took game theory as it existed in early '40s to a whole new level when he realized how it applied to the efforts his buddies at the bar were making to score with some girls who had shown up there? He was a genius then, and crazy, but his math was right.

      --
      SLASHDOT: news for people who can't concentrate on work or have no life at all and got tired of yelling back at the TV.
  2. Now seriously! by docilespelunker · · Score: 4, Interesting

    The notion of birds calculating the fractal dimension of a prospective mate's feathers seems about as farfetched as baseball fielders calculating the exact mathematical damped parabolic path of the ball to work out where to put their hand. It also indicates that if true, birds are much nerdier than my physicist friends and should in theory have less chance of getting a date. As such, this theory is debunked by birds not being extinct through lack of mating! I do buy the notion that birds could see the effect without doing the maths though.

    1. Re:Now seriously! by docilespelunker · · Score: 2

      Excelent point well made. No chips for me this lunch then!

  3. More Slashdot Pundit FAIL by Required+Snark · · Score: 5, Insightful
    Fractal dimension is not a set of buzzwords, but a useful concept in both mathematics and technology. http://en.wikipedia.org/wiki/Fractal

    Fractals have many uses http://en.wikipedia.org/wiki/Fractal#Applications_in_technology It is a perfectly reasonable hypothesis that birds recognize the fractal dimension of plumage in their own species. Conflating this with "being able to compute a fractal" is ignorant. Some birds are known to get information about magnetic fields through their visual channel. This does not mean they are solving Maxwell's equations.

    It is possible to extract fractal dimension information from images. Typing in "fractal dimension image detection" into Google Scholar results in over 25000 references. If academics have figured out how to do this then evolution may also embody these concepts.

    Posting on Slashdot is an opportunity to share knowledge and learn things. Unfortunately far to many people who post here show that they are ignorant and arrogant. I call them the Slashdot Pundits.

    Just because you know one thing does not mean that things you haven't heard of are wrong. With Google and the like, it's easy to fact check. On this topic so far all we have seen is woefully uninformed people criticizing academics and making fools of themselves. I would think that shear embarrassment would tend to eliminate this kind of drivel, but I guess if you are stupid enough to make such uninformed statements, you are also incapable of understanding how bad it makes you look.

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    Why is Snark Required?
    1. Re:More Slashdot Pundit FAIL by fuzzyfuzzyfungus · · Score: 5, Insightful

      There is, arguably, a meaningful distinction between 'knowing' something(in the sense of being able to use that something in conscious cogitation) and 'knowing' something in the sense of 'exhibiting behavior that could not be accomplished without possessing some similarly capable mechanism; but not necessarily possessing any conscious knowledge, or even consciousness at all'.

      It's an open question(that the paper isn't really interested in attacking) whether birds 'know' anything about fractal dimension in the first sense, or what if anything they know at all in that sense; but there is a much stronger case to be made that they do exhibit behavior that could only be accomplished with access to the results of such a computation, even if the processing is a total black-box. Much the same is true of humans: you don't need to take physics to play catch(and, indeed, even those who have generally don't start using conscious calculation to catch falling objects); but our ability to catch objects is pretty hard to explain without positing that we have some mechanism that gives us access(and rather fast access, no less) to good approximations of answers to certain classes of physics problems.

  4. Misleading title by henryteighth · · Score: 3, Informative

    The title seems to be trying to suggest (to me at least, and based on the other comments here also to plenty of other readers) that birds can perceive fractal dimensions (FDs). However, if you read the journal article, it's all about a study of how the fractal dimension of the plumage correlates to different measures of the bird's health. They then also investigate some causative effects, by changing the bird's food intake and measuring the effect this has on FD. Nowhere in the article do they make any claim that birds can necessarily perceive or calculate a fractal dimension: the paper ends by saying "We therefore suggest that considering FD should shed new light onto the evolution and maintenance of complex animal patterns. " So they suggest (entirely reasonably IMHO) that it would be interesting to study that latter aspect, which is quite an important difference from what the Slashdot title is trying to imply.

  5. why animal testing has a bad rap by decora · · Score: 2

    if you are studying some awful disease, like smallpox, most people do not have a problem with purposely starving a mouse.

    if you are just doing it to measure fractals, a lot of people do have a problem with it... even meat eaters.

    "oh but we need basic research and that justifies it because it might save someone some day" -- yeah no it doesnt, unless you have some examples. because i can give you thousands and thousands of examples of where 'science' committed horrifying atrocities against human beings in the name of 'basic research' and used that same argument to justify it. thats the whole point - its not about 'save the animals', its about basic morality.

  6. Yet another stupid title by jklovanc · · Score: 2

    Birds know nothing about fractal geometry. One does not need to know the fractal geometry of a feather pattern to deem the pattern desirable.

    Another point is that they didn't prove the link between fractal dimension and desirability. It is quite possible that the prospective mate does not notice the change in plumage but looks at the overall health of the bird. Now if someone took identically healthy birds and modified some bird's plumage to change the FD and that changed the selection probability then that would be proof.