October 08, 2004

Friday Cat Blogging (It Always Pays to Read the Annals of Improbable Research Carefully Issue of Science Geek Edition)

I am saved this week from dredging up vaguely-amusing cat-related papers by the Annals of Improbable Research, whose current issue is specially devoted to cats. The following article is particularly recommended:

Tenzing A. Jones, "Cat Research Review: Research about, for, and/or by cats", Annals of Improbable Research 10:5 (2004): 18--19 [PDF]
This covers investigations into hairballs, tomcatting, the effects of catnip on human toddlers and on mice, the effects of khat on cats, and how to brush your cat's teeth. Also, it has pictures of many cute cats.

I am therefore freed up to talk about one particular paper which I learned of by reading Jones:

Belinda Y. Betsch, Wolfgang Einhäuser, Konrad P. Körding and Peter König, "The world from a cat's perspective: Statistics of natural videos", Biological Cybernetics 90 (2004): 41--50 [Journal link; PDF via Dr. Einhäuser]
Abstract: The mammalian visual system is one of the most intensively investigated sensory systems. However, our knowledge of the typical input it is operating on is surprisingly limited. To address this issue, we seek to learn about the natural visual environment and the world as seen by a cat. With a CCD camera attached to their head, cats explore several outdoor environments and videos of natural stimuli are recorded from the animals' perspective. The statistical analysis of these videos reveals several remarkable properties. First, we find an anisotropy of oriented contours with an enhanced occurrence of horizontal orientations, earlier described in the "oblique effect" as a predominance of the two cardinal orientations. Second, contrast is not elevated in the center of the images, suggesting different mechanisms of fixation point selection as compared to humans. Third, analyzing a sequence of images we find that the precise position of contours varies faster than their orientation. Finally, collinear contours prevail over parallel shifted contours, matching recent physiological and anatomical results. These findings demonstrate the rich structure of natural visual stimuli and its direct relation to extensively studied anatomical and physiological issues.

One should expect, on general evolutionary and information-theoretic grounds, that animals' sensory systems will be more or less adapted to the statistical properties of their environments. (See, e.g., Spikes.) Accordingly, there's been a lot of attention paid to the statistics of natural images. (I am fond of the idea that these resemble the statistics of turbulence.) But what counts as the relevant statistical properties of the environment will in turn be influenced by the sensory apparatus, and even more by the behavior and ecological niche, of the organism. (This is an old familiar song, with two classical versions and some catchy modern renditions.) Given that, before around 1945, most animals spent essentially no time sitting still looking at successions of static images on cathode-ray tubes, which is what most of this has examined, it would be more interesting to know the statistics of movies obtained under typical conditions for that species. This is exactly what's the group in Zürich has done in this paper, in a very clever way. (I call the reader's attention to Figure 1a.) The analysis of the resulting statistics is nicely done, and even better makes sense biologically. This is, IMHO, very cool.

It's also intimately connected to the saga of Esther the Cold War Kitty, but you'll have to read AIR for that.

Biology; Minds, Brains, and Neurons; Enigmas of Chance; Friday Cat Blogging; Learned Folly

Posted at October 08, 2004 10:16 | permanent link

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