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Study Reveals the Strategy Human Use to Catch a Moving Target

BlindfoldedA new study published in Psychonomic Bulletin and Review has found that people who are blindfolded adopt the same strategy as people who can see to intercept a running ball carrier, suggesting that chasing down a moving object is not only a matter of sound or sight, but of mind.

No matter whether they can see or not, the participant in the study appeared to aim ahead of the ball carrier’s trajectory and then run to the point where they predicted the target to be in the near future. This strategy is called a “constant target-heading angle” strategy by the researchers and it is similar to dogs’ strategies for catching Frisbees and baseball players’ strategies for catching fly balls.

Dennis Shaffer at the Ohio State University at Mansfield says that if you want to chase an object that is trying to evade capture, this is the best way. “If your speed and the target’s speed are constant, and both of you are moving in a straight line, then the constant-angle strategy guarantees geometrically that you will reach the target. It will also give you leeway to adjust when the target changes direction abruptly to evade your capture,” Shaffer said.

Regardless of whether they could see or not, people run after their targets at a constant angle. This fact suggests that there are brain mechanisms in place that we can call “polymodal” – brain areas that serve more than one form of sensory modality. Although sight and hearing might be different senses, within the brain the results of sensory input for this task might be the same.

Nine people took part in the research – mainly students at Arizona State University and Ohio State University, where the study took place. Some of them had experience playing football, either at high school or collegiate intramural level, while other students had limited or no such experience. The nine participants wore motion-capture equipment and took turns in pairs: one ran a football across a 20-meter (nearly 22 yards) field, and the other one chased him. The researchers randomly assigned the participants to sighted and blindfolded conditions. At the blindfolded condition, the participants donned a sleep mask and the runner carried a foam football containing a beeping device, so the chaser had an opportunity to locate the runner by sound. The runners moved in the general direction of the chasers at various angles, and sometimes they would cut left or right halfway through the run.

The experiment was designed in this way so that the chaser would not have time to think consciously about how to catch the target. “We were only focused on trying to touch the runner as soon as we can and before they escaped the field,” said Shaffer. “The idea was to have the strategy emerge by human instinct.”

For the chasers, about 97 percent of the time, they employed the constant-angle strategy – even when they were blindfolded and only able to hear the sound from the beeping football. These results were surprising, even to Shaffer. “I knew this seemed to be a universal strategy for different species, but I expected that the chasing people would vary their strategy more when blindfolded, because we are not used to running around blindfolded. What I did not expect was that the blindfolded strategies would match the sighted ones so closely.”

There exists another strategy when catching moving objects, which is called the pursuit or aiming strategy, since it involves speeding directly at the target’s current location. This strategy is used by apex predators like sharks. Shaffer said: “As long as you are much faster than the prey, you are good to use the pursuit strategy. You just need to overtake them.” However, if the competition is more equal, the constant-angle strategy works better—the chaser does not have to be much faster than the runner, and if the runner changes direction, the chaser has time to adjust.

This research builds on Shaffer’s previous study with how collegiate-level football players chase ball carriers.  He has also done research on how people catch baseballs and dog catch Frisbees. He found that the pursuers always used strategies similar to the constant target-heading angle strategy, suggesting that a common neural mechanism could be at work.

Source: The Ohio State University, Study Shows the Strategy Humans Use to Chase Objects
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