According to Greg Miller
Although the octopus brain rivals the size and complexity of many vertebrate brains, its architecture differs dramatically. “Short of martians showing up and offering themselves up to science, cephalopods are the only example outside of vertebrates of how to build a complex, clever brain,” says neuroscientist Cliff Ragsdale of the University of Chicago in Illinois. For that reason, Ragsdale says, these creatures have much to teach us about brain evolution.
But computer scientists might learn a lot from a very different invertebrate cousin of ours, the jumping spider (genus Portia). A human brain has 100 billion neurons. The tiny jumping spider only has 600,000. If there were two jumping spiders on every seat in the Rose Bowl, the total number of neurons in all those little spider brains wouldn’t be much more than in a single human brain.
Yet, as you can read here, some researchers argue that they “do an image search of their prey based on mental templates. They make intelligent decisions and choices, not just living by instinctive behaviour.”
According to John McCrone
Portia is a jumping spider that makes a living by eating other spiders […] Portia, no bigger than a thumbnail, is perched on a branch with its beady eyes trained on a Scytodes pallida, another spider that specialises in eating other spiders. Scytodes is a spitting spider. It can squirt zig-zag jets of poison-coated silk from its mouth glands that would snare Portia in the blink of an eye. […]
Fortunately for Portia, Scytodes doesn’t know it is being watched. Spitting spiders have weak eyes […] Portia, on the other hand, has excellent eyesight, with spatial acuity better than a cat or a pigeon. From a safe distance about half a metre away, Portia sits scanning Scytodes.
First it needs to know whether Scytodes is carrying a sac in its fangs. This is how Scytodes protects its eggs. And to do any spitting, it has to drop them first. If the spider had eggs, Portia would mount a frontal assault. […]
On this occasion there is no egg sac. Worse, there is no way Portia can […] jump Scytodes from behind. So perched on its branch, Portia begins to plot. For a good quarter of an hour it scans the undergrowth, its tiny brain working out possible pathways across boulders and branches. The retinas of its two principal eyes have only a few thousand photoreceptors, compared to the 200 million or so in a human eye. But Portia can swivel these tiny eyes across the scene in a systematic fashion, patiently building up an image. Eventually Portia makes up its mind and disappears from sight. A couple of hours later, the silent assassin is back, dropping down onto Scytodes on a silk dragline attached to a rocky overhang, like something out of Mission: Impossible.
According to Emily Sohn
According to a growing number of studies, some insects can count, categorize objects, even recognize human faces — all with brains the size of pinheads.
Because we are intelligent animals with big brains, people have long assumed that big brains are smarter brains. Yet, scientists have found scant evidence to support that view, Chittka said.
In fact, scientists have calculated that a few hundred neurons should be enough to enable counting. A few thousand neurons could support consciousness.
“It’s wonderful to see that insects are finally being compared equally with vertebrate animals,” she added. “They have smaller brains, but they still have complex enough brains to do these things.”