What Birds Know About Fractal Geometry

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."

Re:Call it what you will

[Anonymous Coward]

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.

Re:Call it what you will

[cupantae]

'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 [wikipedia.org]" 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.

Misleading title

[henryteighth]

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.