The big idea

A singular material, nickel oxide demonstrates the ability to learn things about its environment in a way that emulates probably the most basic learning abilities of animals, as my colleagues and I describe in a brand new paper.

For over half a century, neuroscientists have studied sea slugs to know basic animal learning. Two fundamental concepts of learning are habituation and sensitization. Habituation occurs when an organism’s response to a repeated stimulus repeatedly decreases. When researchers first touch a sea slug, its gills retract. But the more they touch the slug, the less it retracts its gills. Sensitization is an organism’s extreme response to a harmful or unexpected stimulus. If researchers then shock a sea slug, it’s going to retract its gills far more dramatically than when it was merely touched. This is sensitization.

When nickel oxide is alternately bathed in hydrogen gas and air, its behavior changes.
Purdue University/Kayla Wiles, CC BY-ND

Nickel oxide has features which can be strikingly much like this learning behavior. Instead of gills retracting, we measured the change in electrical conductivity of the fabric. The stimulus, as an alternative of a finger poke, was repeatedly alternating the environment of the nickel oxide between normal air and hydrogen gas.

Nickel oxide is interesting because while you expose it to hydrogen gas, its crystalline structure subtly changes and more electrons develop into available to generate an electrical current. In our experiment, we kept switching between the hydrogen-only and regular air environments. You would expect the electrical conductivity to oscillate up and down directly in relation to the exposure to hydrogen or air. But just as with the ocean slugs, the change in conductivity of the nickel oxide slowly went down the more we stimulated it. It got habituated to the hydrogen.

When we exposed the fabric to vibrant light or ozone, though, it rapidly modified its conductivity – the identical way a slug will all the time respond dramatically to a small shock.

A small piece of material underneath a large piece of scientific equipment.
The conductivity of nickel oxide stores information similarly to the best way slugs learn.
Purdue University/Kayla Wiles, CC BY-ND

Why it matters

The ability to learn, remember or forget information as needed is a robust skill for any animal or machine. So far, the overwhelming majority of research in the sphere of artificial intelligence has focused on software-based approaches to machine learning, with far less effort dedicated to studying the educational abilities of materials.

At the middle of those two related areas of research lies the sphere of brain-inspired computers. For intelligence to be encoded into hardware, scientists need semiconductors that may learn from past experience and adapt to dynamic environments in a physical way much like that of neurons in animal brains. Our latest research showing how nickel oxide demonstrates features of learning hints at how this or similar materials could function constructing blocks for computers of the long run.

What still isn’t known

Before such materials may be incorporated into computer chips there are some knowledge gaps that must be addressed. For instance, it isn’t yet clear at what time scales a cloth must learn for it to be useful in electrical systems. How quickly does something must learn or forget to be useful? Another unknown is how or whether it is feasible to alter the structure of nickel oxide to provide different learning behaviors.

A small square of gray material with stripes.
It is unclear whether nickel oxide itself may be used for computing, however the concepts at play could encourage further innovation.
Purdue University/Erin Easterling, CC BY-ND

What’s next

In addition to further experiments on the fabric itself, there are theoretical lessons to explore. Observations of collective behavior of animals in nature – equivalent to bird flocks and schools of fish – have inspired researchers to develop fields of AI like swarm intelligence. In an identical fashion, the interesting collective motion of atoms and electrons in materials could encourage AI and hardware design in the long run.

As latest materials that may accommodate mobile atoms are discovered, I’m optimistic we are going to see further breakthroughs that may bring researchers one step closer to designing computers that emulate animal brains.

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