[robotresearcher]

It doesn't. It just likes to stick bits to its web in patterns. Feels good, (spider) man.

Something like this:

1. get bit of leaf. 2. go to center of web. 3. while standing on leaf bits, go down (with G). 4. drop bit of leaf, leaving gap to the left and right. 5. if more than 20 paces from the center. Forget it, relax. 6. goto 1.

With a bit of fiddling I have no doubt you can write a simple program to produce these shapes.

If you find this interesting, check YouTube for termite and wasp nest videos. Incredible!

[mirkules]

The process of producing decoy shapes isn't really a problem. Why these spiders made the shapes is more interesting.

I think that the spiders that didn't create these decoy structures were selected against in the evolutionary process. The production of decoys could have been genetically engrained into their instinct (via mutation), or, this species really are actually able to recognize itself and create a decoy -- both of these cases would have led to less of them being eaten by predators, hence natural selection.

I can't wait to hear the results of the study after they research it more closely!

[robotresearcher]

Which of these explanations seems more likely, in the context of a spider?

Spiders are very smart for their size (up to 80% of their body cavity is brain, and much larger than for insects), but giving them theory of mind is a stretch.

"That guy there wants to eat me. I look like this. If I make a thing that looks like me, he will think it's me and try to eat that, and I'll be safer."

vs. I just love to get bits of leaf and stick them just so!

[mirkules]

Sure, it's a stretch, I don't dispute that at all. Maybe a spider witnessed another spider being eaten, and since it was spared, decided to make another spider-looking thing so it doesn't get eaten again. It's not really a matter of self-recognition or theory of mind, but more of a pattern recognition, something spiders (I assume) are good at. "My friend was eaten, and I wasn't. I should make something that looks like my friend so I don't get eaten." But, then again, Occam's Razor and all that. :)

[Buttons840]

> "I should make something that looks like my friend."

I'm no expert, but the fact that spiders have 8 eyes suggests to me that they may, indeed, be good at recognizing visual patterns.

[takluyver]

The number of eyes isn't a particularly good guide. I'd guess most web-building spiders have quite poor detailed vision, as there's little need for it. Jumping spiders, which actively hunt prey, have good forward vision.

[bonobo]

I think that implying the spider is actually able to recognize itself is a little too far. It would require a level of awareness comparable to that of apes and dolphins. Not even dogs are able to recognize themselves when put in front of a mirror.

[sk5t]

While not a scientific article, here's an interesting read about corvids (crows, jays) presenting two sides of the argument that the birds possess theory of mind:

http://io9.com/5969515/corvids-the-birds-who-think-like-huma...