Archive for March, 2011

Random robot gripping improvements tab dump

March 25, 2011

At some point we’re going to turn around and this kind of stuff will actually be useful, especially with improvements in vision so that machines can see the orientation of the things they’ve picked up.

DARPA fashions miracle robotic attachment from balloon, coffee • The Register

The manipulator works by pressing the soft balloon full of loose coffee grounds down on the object to be gripped. Then the air is sucked out of the balloon, causing the coffee granules to press together and lock into a rigid shape – just as they do when vacuum-packed. The object is now securely grasped by the manipulator, and can be released as desired by ending the suction on the granule-filled bulb.

Grip-Happy Compliant Electroadhesion Sneaking Into Everyday Usage

Today, they’ve moved onto bigger and better things, like gripping a banana using the same technique. Meet “compliant electroadhesion.”

As was the case back in 2008, electroadhesion still requires very little power to function. According to SRI, 11 square feet of electroadhesive material will support about 440-lbs. using 40mW.


This is why you test your new formulas first

March 24, 2011

The First Law of Development Stats: Whatever our Bizarre Methodology, We make Africa look Worse

The biggest change in method was that the new HDI is a geometric average rather than a normal (additive) average. Geometric average means you multiply the separate indices (each ranging between 0 and 1) for income, life expectancy, and education together and then take the cube root (I know your pulse starts to race here…)

Now, students, please notice the following: if one of these indices is zero, then the new HDI will be zero, regardless of how great the other indices are. The same mostly applies if one of the indices is close to zero. The new HDI has a “you’re only as strong as your weakest link” property, and in practice the weakest link turns out to be very low income (and guess which region has very low income).

You can see why the geometric average might have been attractive: by multiplying and then taking a root, it avoids the Bill-Gates-Walks-Into-A-Bar problem that besets arithmetic averages. But instead it makes errors in scaling or in linearity much worse. You gains on the swings, but you loses on the roundabouts.

And ultimately it’s always going to be about the scaling. $2 may make you twice as happy as $1, but $2 million is unlikely to make you twice as happy as $1 million, much less a million times as happy as $2.

It’s much, much easier, both mathematically and politically (because you get to avoid claims of subjectivity) to measure utility or development in linear terms of clear quantities like dollars or years of life or bushels of food. Too bad all you learn is ever more precisely where the house keys aren’t.

Pretty useless science story, reasonably reported

March 24, 2011

BBC News – Sexual preference chemical found in mice

As the story points out, going from this to human brains requires a whole bunch of speculative leaps (including the obvious one) that a serotonin-free brain is functioning normally at all. Without checking the rats on a wide range of other cognitive tasks, you’re pretty much picking the one bit of weird behavior in their brains that might make headlines.

(On the other hand, there’s lots of evidence of SSRIs leading to sexual dysfunction and messing with libido, so at least this result is in the same solar system.)

Technological genres and market illogic

March 19, 2011

Ages ago, when his name was still one to conjure with, I took a long walk with John Seely Brown to discuss the applicability of literary criticism to the success of inventions. My recent ex at the time had gotten a thesis and several books out of the  idea (going back to kierkegaard at least) that it was in many ways impossible for people schooled in 19th-century traditions to read modern writers, so I was primed for the discussion. What Brown’s researchers had found was that new gadgets were usable — at least at first — only insofar as they could be understood as a better/faster/smaller X, where X was a genre of technology that people already thought they understood.

That meant innovators had to think about how the things they were creating fit into existing ideas about the world (most obvious case: the desktop metaphor) and/or tell stories about the world that shifted people’s perceptions in ways that made new gizmos more comprehensible and acceptable — just as modernist writers have so often had side gigs as book reviewers and manifesto-promoters. And people who bought and tried to use the new tools had to learn — and sometimes privately revise– the stories they were told, until they had something that made sense.

The history of recent tech is littered with innovations that have stories, from blogs to “community” to android phones and e-book readers.  Some of the stories make sense, some of them don’t, or at least not yet.

So now let’s apply this to financial innovations. All the fancy mortgage instruments, for example, were billed as cheaper/more flexible/more accessible/longer/lower/wider/faster versions of existing mortgages, even when they were only barely related to same. (Really: the last time people were issuing loans with no verification of income stream and options to add the first few years’ payments to the loan balance was during the savings&loan scandal, and most of them ended up in jail.) But the story made for good sales.

And the fancy instruments the big boys played had their own set of stories as well. They were just well-analyzed aggregations of existing securities, or adaptations of well-understood methods of laying off risk (never mind that the last time the insurance industry had a crisis they found out that no one had a clue of who had laid off how much risk to whom, or how much had come right back to its original roost). And in a sort of bitch-slap version of the usual genre issues, if you thought that they were too complex and opaque for people to be trading safely, then you clearly didn’t have the analytical chops and were better off playing in the low-risk kiddie pool.

That last bit is important because of the way it intersects with Keynes’s dictum that the market can stay irrational longer than you can stay solvent. In this particular case, the irrationality consisted in believing the stories being told about all these opaque financial instruments. If you decided to trade in them (with the exception of a few very-deep-pocketed pessimists who took the short sides of transactions) you pretty much had to accept the models that everyone else was using, or else your valuations would be way off from everyone else’s, and you’d get clobbered in the day-to-day shifts. Playing that particular game involved accepting the shared consensual hallucination — buying into the MBS/CDO genre — so that your conversations, as expressed in bids and asks, would be mutually intelligible.

And once everyone was speaking the same language, they were all lost.