I ragni sembrano assegnare i compiti cognitivi alle loro ragnatele, rendendoli una delle numerose specie con una mente che non è completamente confinata alla loro testa.
Spiders appear to offload cognitive tasks to their webs, making them one of a number of species with a mind that isn’t fully confined within the head.
Nome comune: Ragno dalla gobba
Nome scientifico: Cyclosa conica (Pallas, 1772)
Global distribution (WSC 2021): North America, Europe, Turkey, Caucasus, Russia (Europe to Far East), Iran, Central Asia, China
Caratteristiche anatomiche: Ragno di piccole dimensioni, con maschi dal corpo di 4/4,5 mm e femmine leggermente più grandi. La peculiarità, che da nome al ragno, è la forma dell’ opistosoma, munito di una protuberanza conica all’estremità posteriore.
Comportamento: Questo ragno, come molti altri Araneidi, costruisce ragnatele orbicolari, ma oltre il numero elevato di raggi (40) la tela della C.conica (e delle altre Cyclose) viene dotata dal ragno di una serie di pacchetti, al cui interno si possono trovare sia prede che detriti di vario genere, disposti sulla linea centrale verticale della ragnatela e al cui centro il ragno sosta attendendo le sue prede. Questo comportamento probabilmente serve a rendere difficile l’individuazione del ragno da parte di un potenziale predatore, o magari a rendere la sua ragnatela visibile ad un grosso insetto, che colpendola potrebbe danneggiarla più che restare intrappolato.
Anatomical features: a small spider, with males measuring 4/4.5 mm in body size and females slightly larger. The peculiarity, which gives the spider its name, is the shape of its opisthosoma, which has a conical protuberance at the rear end.
Behaviour: This spider, like many other Araneids, builds orbicular webs, but in addition to the large number of rays (40) the web of the C.conica (and other Cycloses) is equipped by the spider with a series of packets, inside which can be found both prey and debris of various kinds, arranged on the vertical centre line of the web and at the centre of which the spider stops to wait for its prey. This behaviour probably serves to make it difficult for a potential predator to detect the spider, or perhaps to make its web visible to a large insect that might damage it rather than trap it.
[Hilton] Japyassú and Kevin Laland … argued in a review paper, published in the journal Animal Cognition, that a spider’s web is at least an adjustable part of its sensory apparatus, and at most an extension of the spider’s cognitive system.
This would make the web a model example of extended cognition, an idea first proposed by the philosophers Andy Clark and David Chalmers in 1998 to apply to human thought. In accounts of extended cognition, processes like checking a grocery list or rearranging Scrabble tiles in a tray are close enough to memory-retrieval or problem-solving tasks that happen entirely inside the brain that proponents argue they are actually part of a single, larger, “extended” mind.
Just as octopuses appear to outsource information-processing tasks to their tentacles, or crickets to their tracheal tubes, perhaps spiders outsource information processing to objects outside of their bodies — their webs.
To test whether this is truly happening, Japyassú uses a framework suggested by the cognitive scientist David Kaplan. If spider and web are working together as a larger cognitive system, the two should be able to affect each other. Changes in the spider’s cognitive state will alter the web, and changes in the web will likewise ripple into the spider’s cognitive state.
Consider a spider at the center of its web, waiting. Many web-builders are near blind, and they interact with the world almost solely through vibrations. Sitting at the hub of their webs, spiders can pull on radial threads that lead to various outer sections, thereby adjusting how sensitive they are to prey that land in those particular areas.
As is true for a tin can telephone, a tighter string is better at passing along vibrations. Tensed regions, then, may show where the spider is paying attention. When insects land in tensed areas of the webs of the orb spider Cyclosa octotuberculata, a 2010 study found, the spider is more likely to notice and capture them. And when the experimenters in the same study tightened the threads artificially, it seemed to put the spiders on high alert — they rushed toward prey more quickly.
The same sort of effect works in the opposite direction, too. Let the orb spider Octonoba sybotides go hungry, changing its internal state, and it will tighten its radial threads so it can tune in to even small prey hitting the web. “She tenses the threads of the web so that she can filter information that is coming to her brain,” Japyassú said. “This is almost the same thing as if she was filtering things in her own brain.”
Joshua Sokol, “Thoughts of a Spiderweb,” Quanta