Parts of your brain are wired to ‘get’ physics

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The coloured patches show where the brain’s ‘physics engine’ resides. It revs up when presented with a physics problem.
Credit: Jason Fischer / JHU

When your grandmother’s glass vase is teetering on the edge of a coffee table, and the potential for a shattering outcome flashes through your mind, it isn’t the vision part of your brain that’s giving you a warning sign.

Rather, there’s a separate specific centre in your brain that intuitively understands physics and can guess at possible outcomes as a result.

This neural “physics engine” in the brain has been identified through a new study by US researchers in the Proceedings of the National Academy of Sciences.

“We run physics simulations all the time to prepare us for when we need to act in the world,” explains lead author Jason Fischer, a psychologist at Johns Hopkins University

“It is among the most important aspects of cognition for survival. But there has been almost no work done to identify and study the brain regions involved in this capability.”

Fischer and his team set about discovering how humans instinctively understand the way objects interact with one another and within the world.

They set up three experiments involving physical interactions between objects and participants’ brain activity was recorded with magnetic resonance imaging.

In the first experiment, 12 participants were asked to watch videos such as the clip below depicting towers of coloured blocks as they toppled.

They were asked to first predict how the blocks would fall when toppled – the physical interaction of objects – and also to describe the colour of the blocks they could see. 

The researchers saw a specific region of the brain is engaged when we predict physical outcomes. This network, in the frontal and parietal cortices, overlaps with the parts of our brain responsible for action planning and tool use.

While questions about colours engaged brain regions based on sight, the physics-related question lit up this particular section of the brain, which the research team calls the “physics engine”.

In a second experiment, participants watched a video of dots bouncing together on a screen and were asked to predict the next movements. Sure enough, the physics engine was engaged while participants sought to solve the question, and the action planning areas of the premotor cortex and supplementary motor area also lit up.

Finally, brain activity was recorded as participants watched movie clips – some of which contained physics content. The physics engine was sparked at the appropriate times, even though participants were just passively watching physical activity.

“The brain activity reflected the amount of physical content in a movie, even if people weren’t consciously paying attention to it,” Fischer explains.

“This suggests that we are making physical inferences all the time, even when we’re not even thinking about it.”

The researchers acknowledge that other levels of awareness – such as the flow of liquids, the behaviour of springs and the movement of bendable objects like rope and string – will probably result in different outcomes, once studied.  

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