Multiple intelligences

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.”



  1. According to Colin Smith

    A researcher from Imperial College London and his colleagues have developed for the first time a map of a typical bird brain, showing how different regions are connected together to process information. By comparing it to brain diagrams for different mammals such as humans, the team discovered that areas important for high-level cognition such as long-term memory and problem solving are wired up to other regions of the brain in a similar way. This is despite the fact that both mammal and bird brains have been evolving down separate paths over hundreds of millions of years.

    The team suggest that evolution has discovered a common blueprint for high-level cognition in brain development.


  2. According to this

    As part of ongoing research to understand how miniaturization affects brain size and behavior, researchers measured the central nervous systems of nine species of spiders, from rainforest giants to spiders smaller than the head of a pin. As the spiders get smaller, their brains get proportionally bigger, filling up more and more of their body cavities.

    “The smaller the animal, the more it has to invest in its brain, which means even very tiny spiders are able to weave a web and perform other fairly complex behaviors,” said William Wcislo, staff scientist at the Smithsonian Tropical Research Institute in Panama. “We discovered that the central nervous systems of the smallest spiders fill up almost 80 percent of their total body cavity, including about 25 percent of their legs.”


    “We suspected that the spiderlings might be mostly brain because there is a general rule for all animals, called Haller’s rule, that says that as body size goes down, the proportion of the body taken up by the brain increases,” said Wcislo. “Human brains only represent about 2-3 percent of our body mass. Some of the tiniest ant brains that we’ve measured represent about 15 percent of their biomass, and some of these spiders are much smaller.”

    Brain cells use a lot of energy, so these small spiders also probably convert much of the food they consume into brain power.


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