Science asks: Why are these people shaking boxes?

Observers can accurately tell, just by watching someone shake a box, what the shaker is trying to learn about its contents.

Publishing in PNAS, researchers from Johns Hopkins University asked hundreds of ‘observers’ to watch ‘players’ shaking boxes in 5 fun experiments. 

Researcher and lead author Sholei Croom says the experiments were designed to dig into how much information people can infer just by watching another person interact with an object.

In each experiment, players were filmed participating in a physics game: they were asked to guess either the shape, or number of items inside an opaque box by simply shaking it. In the shape round, the box contained either a sphere or a cube. While in the number round the box contained between 5 and 15 coins.

Then, a separate and larger group of observers were asked to watch the videos (which contained no audio or visible faces) and try to guess what type of information the player was trying to find out.

The researchers varied elements across the 5 experiments – player accuracy, box contents, and the detail of instructions provided to observers. Yet each time the majority of observers correctly inferred what the player was trying to learn, by watching their actions.

Observers were able to accurately and intuitively tell whether the player shaking the box was seeking information about shape or number based on their strategy.

“People tend to shake up and down for number,” Croom says. “Whereas for shape, people tend to shake side to side because it’s a lot easier to figure out if it’s a cube, or if it’s a sphere, depending on whether it’s slides or rolls.”

Observer success was independent of whether the player actually got the answer right. And even when the instructions were stripped back to the bare minimum – ‘Why do you think these people were shaking the boxes?’ – observers were still able to infer that people were seeking information about the objects inside the box.

People move their bodies for all sorts of different reasons: to accomplish a physical task, to seek information, to communicate socially and for creative expression. The study focuses on seeing and understanding ‘epistemic actions’, or movements designed to find out information about the world. 

Shaking a box is a relatable epistemic action – handling a Christmas present, or shaking an unopened parcel to guess what’s inside.

Assistant professor and the paper’s senior author Chaz Firestone says other examples of epistemic actions include someone pushing on a door to see whether it is locked, or dipping their toe in the pool to find out the temperature. 

Croom says we interpret meaning in other people’s actions all the time. “If we see someone sort of wandering around in a city – looking at their phone, and then looking back up – we can kind of just immediately assume that they’re probably lost.”

The results of the 5 box shaking experiments show that when a person uses their body to learn about the world, other – observers – can readily recognise the kind of information they are trying to find out.

Croom says, unlike many psychology experiments, observers and players both had fun. “The excitement of ‘something’s in the box! What’s in there?’ just taps into this kind of childlike sense of wonder and fun.”

Firestone says “a lot of questions we investigate in cognitive science, involve things that are very easy to do, rather than that are hard to do. A lot of the substance of our field, is trying to understand how a person does all the things that kind of come naturally to them.”

He says it’s a domain of inquiry that has gone relatively unexplored.

Croom says, “these inferences seem so common sense and easy and really intuitive. But there’s a lot of really complex cognition under the hood.”

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