Do frogs’ eyes follow you?

Apparently not: Oliver Sacks has a rather disappointing roundup of consciousness books in the NYRB which claims that

Whatever the mechanism, the fusing of discrete visual frames or snapshots is a prerequisite for continuity, for a flowing, mobile consciousness. Such a dynamic consciousness probably first arose in reptiles a quarter of a billion years ago. It seems probable that no such stream of consciousness exists in an amphibian, like a frog, which shows no active attention, and no visual following of events. The frog does not have a visual world or visual consciousness as we know it, only a purely automatic ability to recognize an insect-like object if this enters its visual field, and to dart out its tongue in response. It has been said that a frog’s vision is, in effect, no more than a fly-catching mechanism.

So a frog’s eye is just a motion sensor, and not a very complex one at that. Dragonflies, with much smaller brains (though proportionately much larger eyes) are able to catch prey on the wing. Intuitively it seems a more complex and admirable thing to fling your whole body after an insect than just your extensible tongue. Perhaps it isn’t very much more complicated. That would depend on the control mechanisms of dragonfly flight. If the beating of the wings, and their pitch, are sealed off into autonomous modules, then it might not require a huge amount o extra circuits to be able to say “hard astern” or “zoom right 45 degrees”.

It is not necessary, at this point, to write in pointing out that the dragonfly has no inner, Cartesian dragonfly captain issuing these commands.

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1 Response to Do frogs’ eyes follow you?

  1. Rupert says:

    I guess that all of us, dragonfly, frog or hom. sap., have a ‘There’s a thing, go get it’ trigger, and it’s up to other froggy, flyish or mannish bits to take that output and convert it into action. Even with us, it’s not always a conscious act – isn’t it the case that we can catch cricket balls far faster than our 300ms awareness lag can allow? Well, perhaps you can: my inability to do anything remotely useful with a ball was comprehensively demonstrated at school. Not that this stopped them trying to make me. Bastards. May they all be turned into frogs and attempt to eat hornets due to lack of discriminatory processing.

    As for dragonflies: I note that the latest Barbie doll, Secret Spells Barbie, has a dragonfly familiar as part of her accessories set, together with a spell book, a magic wand and a cauldron that’s shaped like a martini glass. On the same page of Fortean Times – the discovery of the world’s largest known coprolite. Size of a kitchen stove, apparently.

    R (in Edinburgh for Hogmanay, after which I’m off the evil glug for January. Bring me a cauldron…)

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