Only Draymond Green will ever know the truth about what happened when he took that shot in Game 3 of Golden State's Western Conference series in May. Green's leg flew up and collided with Steven Adams's groin. The Oklahoma City player collapsed on the floor in obvious agony.

After the game, Green said the kick was unintentional. "I followed through on a shot," he said. "I'm not trying to kick somebody in the men's section. I'm sure he wants to have kids one day. I'm not trying to end that on the basketball court. That don't make sense." The NBA fined Green but let him play the next game.

Commentators and basketball fans around the country have had plenty of opportunities to debate whether the league made the right call. Yet the fact that they were able to see the kick in slow motion might have introduced a subtle bias into how they viewed Green's actions, new research suggests.

The research, published last week in the Proceedings of the National Academy of Sciences, shows that people are more likely to view an action as intentional if they see the incident in slow motion.

It is easy to laugh at Adams's bad luck, but the new study could have far more serious implications. Juries in criminal cases often must decide whether the defendant acted intentionally, a determination that affects the sentence the court will impose.

The researchers write about the case of John Lewis, who shot and killed a Philadelphia police officer during a robbery in 2007. During the trial, a jury reviewed surveillance footage of the incident to determine whether the murder was premeditated. The jury also saw the tape in slow motion.

If the jury decided the murder was not premeditated, Lewis's punishment would be life in prison. If they decided it was not, Lewis could be executed by lethal injection.

The jury concluded that Lewis's actions were premeditated. His lawyers appealed to the Pennsylvania Supreme Court, arguing the slow-motion footage had biased the jurors. The court rejected that argument, and Lewis is now on death row.

What the study found

The researchers -- Eugene Caruso of the University of Chicago, Zachary Burns of the University of San Francisco and Benjamin Converse of the University of Virginia -- conducted a series of experiments in which they showed several groups of subjects footage of one of two violent incidents -- another shooting captured by a surveillance camera and an illegal helmet-to-helmet tackle in an NFL game.

Footage of the shooting is below.

Some of the participants in the experiment saw the videos in slow motion, and others saw them at full speed. Afterward, those who saw the videos in slow motion were more likely to say they believed the action was intentional.

About 77 percent of those who saw the shooting in slow motion believed it was intentional compared to 71 percent of those who watched in real time. Here is the shooting again, in slow motion.

Among those who viewed the shooting at both speeds -- first in real time and then in slow motion -- 72 percent said the shooting was intentional, but they felt that way more strongly than those who only saw it in real time. Those who decided it was accidental were more ambivalent than their counterparts who saw it only in real time.

In criminal trials, jurors are able to watch any surveillance footage at both speeds, and must make a binary choice: did the defendant act purposefully, or not? So these results suggest that more research is necessary to understand how this bias might affect jurors in practice.

How the illusion works

Time is easy to lose track of. It can go by in a rush. Now and then, however, it seems that as though decades elapse between the salads and dessert.

Accurately judging how much time has passed is particularly difficult when watching a video in slow motion.

The researchers believe that slow motion makes it appear that a person has more time to think, plan and then act than they really do. Thus, slow-motion video could create the illusion that a person is acting intentionally when he or she is not.

"Seeing something in slow motion gives you the false impression that the actor had more time to act, so it feels more premeditated," Caruso said. "When you see it in slow motion it just has this, like, air of inevitability."


(Bryan Terry/The Oklahoman via AP)

Slow motion can help observers form more accurate judgments about events that happen quickly. Slow motion can clearly show who won a 100-meter sprint, or whether a football player scored a touchdown before being tackled.

At the same time, slow motion can mislead when it comes to the thoughts and intentions of others. Footage of a person in slow motion does not necessarily reveal any additional clues about what is happening inside that person's head.

"It is a version of reality, and some could argue it’s a better version of reality," Caruso said. "What I think that overlooks is how hard it is to adjust for the fact that what they’re seeing isn’t how actions unfolded in real time."

Caruso pointed out other ways that time can distort these judgments. Sloths can appear not to move with purpose, because they shift their limbs so slowly, and that a time-lapse of a vine reaching toward a source of light can make the plant appear to have a mind of its own.

Other researchers have found that people are more likely to attribute mental process to animals, robots and formless blobs that appear to move at a speed similar to that of ordinary human movement. The same researchers found that people moving with extreme slowness can appear more like statues or sculptures than humans, an uncanny effect that makes a viewer doubt whether they have any thoughts, feelings or intentions whatsoever.

How we perceive intentions and other mental processes in those around us depends on our perceptions of time. Those perceptions are easily manipulated.

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