Researchers have discovered that a soft, spongy gel rich in water is not only able to play the video game Pong, but it gets better over time.
The findings come nearly two years after brain cells in a lab were taught to play the 1970s classic, a result the researchers involved said showed “something resembling intelligence.”
The team behind the latest study said that while they were inspired by that work, they did not claim their hydrogel was sensitive.
“We are saying that it has memory and that through that memory it can improve its performance by gaining experience,” said Dr Vincent Strong, first author of the research from the University of Reading.
Strong said the work could offer a simpler way to develop algorithms for neural networks (models that underpin AI systems including Chat GPT), noting that they are currently based on how biological structures work.
Released in 1972Pong was one of the first video games and has a simple premise: two paddles on a court can be moved up and down to hit a ball back and forth between them. The longer the rally, the higher the score.
Strong’s study focused on a single-player version in which a paddle is moved along a wall of a court to keep a ball bouncing.
Writing in the journal Cell Reports Physical Science, He and his colleagues describe how they placed an electroactive polymer hydrogel between two plates, each containing a 3×3 array of electrodes connected to a computer system that simulated Pong.
Six pairs of electrodes were then stimulated, in a 3×2 arrangement, to represent the movement of the ball within the playing court.
On the other three pairs of electrodes, which represent the wall along which the paddle is located, the team applied a small voltage and measured the current with sensors. The position of the paddle was defined as the point where the current was highest.
A key aspect is that the type of hydrogel used in the experiment contains charged ions, which move in response to electrical stimulation and remain where they end up.
As a result, the point along the “wall” with the highest current could shift as the ball moves, meaning the paddle could change position.
“At first, the ions are distributed evenly and randomly, so the paddle hits the ball and misses it,” Strong explained.
But as the ball moves down the court, the gel receives more and more electrical stimulation.
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“Over time, ion concentrations increase where the ball is located most, acting as a kind of muscle memory, as higher concentrations result in higher electrical current readings and the paddle can actuate more accurately,” Strong said.
In other words, the paddle can hit the ball more frequently, resulting in longer rallies.
“Our research shows that even very simple materials can exhibit complex, adaptive behaviours typically associated with living systems or sophisticated AI,” said Dr Yoshikatsu Hayashi, another author of the research at the University of Reading.
Dr. Brett Kagan, chief scientific officer at Cortical Labs, who has worked on the Pong-playing brain cells but was not involved in the latest study, said the hydrogel system demonstrates a basic form of memory similar to the way a riverbed records the memory of the river.
That, he said, could be useful for understanding how changes within a medium can help electrical signals travel better through it.
But he said much more work would be needed to show that hydrogels can “learn.”
“Performance and improvement were tied to a specific area of stimulation. When this was altered in any way, the system could not reorganize itself to continue to show performance,” Kagan said.
“This is different from our tests in neural systems, where we showed that regardless of how the information was presented, learning continued to occur.”
