I guess I never got far enough with my failed degree in electronics to discover that there’s a fundamental component missing from the metaphorical toolbox.

But apparently there is… or there was. Now, though, the memristor is more than just a concept, and realising it may provide a key to building artificial intelligences… with a little help from slime molds:

Four interconnected things, mathematics says, can be related in six ways. Charge and current, and magnetic flux and voltage, are connected through their definitions. That’s two. Three more associations correspond to the three traditional circuit elements. A resistor is any device that, when you pass current through it, creates a voltage. For a given voltage a capacitor will store a certain amount of charge. Pass a current through an inductor, and you create a magnetic flux. That makes five. Something missing?

Indeed. Where was the device that connected charge and magnetic flux? The short answer was there wasn’t one. But there should have been.

It’s a fairly lengthy article that covers a lot of ground, so it’s hard to summarize with a quote or two. Go read the whole thing; not only is the science itself quite intriguing, it’s also an example of the better sort of journalism that New Scientist puts out.