[from Gary Cziko 2006.08.01 17:01 GMT]
This looks great, Gary. Thanks. But it’s a little hard to tell what
they did based only on the abstract. If you (or anyone else) have
access to the whole article, could you give me a few more details on
their methods. What confuses me is the last part of the abstract where
they say that travel distance is overestimated by animals walking on
stilts and underestimated by animals walking on stumps. How do they
determine what the animals distance estimates are? I would imagine that
they would have an animal walk to a goal under normal conditions and
then walk to it on stilts or stumps. So I think what they mean is that,
when walking on stilts they walk past the goal (since N steps takes
them farther on stilts than on legs) and when walking on stumps they
don’t make it to the goal (since N steps doesn’t take them as far on
stumps as on legs). Is that what they did?
That is my understanding.
So they really don’t really
over or under “estimate” distance; they just end up going too far or
not far enough when on stilts ot stumps, respectively.
Right.
This is a version of “the test” where the stilts or stumps represent a
disturbance to a possible controlled variable (distance measurement).
But it seems to me that they haven’t quite isolated the controlled
variable. The conclusion of the article is that “step count” is a
controlled variable. But couldn’t it also be integrated joint angle,
assuming that each step (whether on legs, stilts or stumps) moves
through approximately the same angle.
To test this, they would have to restrict the range of motion of each leg and see if they compensate (or not) by taking more steps. This sounds a lot harder to do than shortening or lengthening their legs.
Also of interest is that fact that the altered ants eventually learn to adjust their steps to get back home. So the higher-level controlled variable is getting home. And when the usual number of steps (or integrated joint angles) doesn’t deliver the goods, they reorganize and learn to change their steps.
Hey, this PCT stuff can be pretty useful for understanding ants!
–Gary
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On 8/1/06, Rick Marken marken@mindreadings.com wrote: