Look out! Threats that come from the left side are scarier than those from the right, new research finds.
Whether they're hurrying to cross one-way streets or thinking about evacuating because of radioactive waste, people respond more cautiously to dangers that originate from their left sides, according to the study, which will be published in an upcoming issue of the journal Management Science.
A lot of research has focused on how people make decisions in response to risk, study researchers Arul Mishra and Himanshu Mishra, both of the University of Utah, wrote in an email to Live Science. Most of those studies presented risk information verbally, even though many risk-management decisions are actually made visually.
"When we look around in everyday life, we have to make many decisions by visually scanning the environment around us to assess the inherent risk," the Mishras wrote. "But not much research is focused on visual risk. That is what got us interested in examining what happens when the risk is presented visually. How would people behave/react?" [Understanding the 10 Most Destructive Human Behaviors]
From the left
To find out, the Mishras, along with doctoral student Oscar Moreno, also of the University of Utah, conducted a series of experiments. They first asked 166 college students to look at a map showing two cities. The students were told that an earthquake had hit one city — either the one on the left or the one on the right — and warned that aftershocks could affect the other city (their own). They were then asked to rate their likelihood of evacuating on a scale of 1 to 7, with 7 being most likely.
When the original earthquake was on the left, the participants were more likely to say they would evacuate than when it was on the right, with an average rating of 5.21 on a scale of 7 for a threat from the left and an average rating of 4.72 for a threat from the right.
The researchers tried to replicate these findings using tornadoes instead of earthquakes but were unable to do so. However, another threat did show the same left-side effect. This time, the researchers asked 89 students to look at threat maps identical to those in the first study, except that the danger was radioactive fallout from a waste facility to the left or the right. This time, however, participants who saw the threat coming from the left were told the danger was 200 miles (322 kilometers) away. Those warned of a threat coming from the right were told the danger was only 180 miles (290 km) away.
Even though the danger from the right was closer, people warned of a danger from the left were more worried. People who were told the cloud of waste was coming from the left gauged their chances of being affected at 65.6 percent, on average, while people who were told the threat was coming from the right estimated their chances of a problem at only 52.7 percent.
These effects could still be the result of people's inherent notions about wind patterns, the researchers reasoned. So they took their experiments into the real world.
First, they set up a video camera at the intersection of two one-way streets in Bucaramanga, Colombia, a city with a high risk of traffic fatalities. (In the month before the experiment, nine pedestrians had died from being hit by cars, and more than 200 had been injured.) [Top 10 Leading Causes of Death]
The camera was set up at a busy spot without a crosswalk, and the researchers filmed for two hours, measuring how long it took pedestrians to cross the street in either direction. They found that when people crossed in such a way that the traffic came from the left, they took an average of 6.05 seconds to cross the street. When people crossed against traffic coming from the right, they were slightly slower, taking 6.32 seconds, on average. These findings seemed to suggest that people felt less threatened by the traffic from the right, since they moved more slowly in those cases.
In another experiment in Colombia, the researchers set up mock street surveys, recruiting passersby to sit in one of a row of eight chairs to fill out a brief questionnaire. They paid a grungy-looking homeless man to sit at one end of the row, and then measured how far away the survey participants sat.
When the homeless man was sitting on the left, the participants sat an average of 5.06 chairs away. When he was on the right, they sat a bit closer — only 4.32 chairs away, on average.
Finally, the researchers tried the experiment with one more threat: that of disease, contagion and disgust. They created fake dog poop out of peanut butter and chocolate sauce and put it smack-dab in the middle of a busy sidewalk on a university campus. They then surreptitiously filmed 227 people walking by and measured how far they stepped away from the fake feces depending on whether they approached with the gross object to their left or their right.
Yet again, people seemed more disturbed by a threat from the left. When approaching with the fake poop to their left, people veered over an average of 1.7 inches (4.3 centimeters), compared with only 0.13 inches (0.33 cm) when the poop was on their right side. [What Really Scares People: Top 10 Phobias]
Why left is scary
The researchers are uncertain why threats from the left would be scarier than those from the right. One possibility, the Mishras said, is that people perceive their world in the same way that they read. For the Colombians and Americans in the study, that would be left to right.
"A threat approaching from the left appears in line with the flow, since it is easier to perceive that it will flow from the left (source) to the right (target)," they wrote. If so, readers of right-to-left scripts, such as Arabic, might fear right-sided threats more than left-sided ones, they said.
Alternatively, the bias toward fearing the left might have to do with handedness and specialization of the brain hemispheres, the Mishras said, in which case the leftie minority should be more nervous about threats from the right. A similar, but related, idea is that people process things on their dominate side more easily, and thus attribute negative feelings to the "tougher" stuff on their weaker side.
A fourth possibility is a phenomenon called "pseudoneglect," which is a tendency for people to overestimate the right side of things when, for example, cutting a pie in half. (Hot tip for anyone going splitsies on dessert: People usually place their center line a little too far to the left.) This, again, might be the effect of brain specialization, with the right hemisphere being used more for spatial processing. Or, it could be another side effect of reading and writing left to right.
More research will be necessary to tease out which, if any, of these explanations is correct. In the meantime, the authors suggest that public safety officials could use the findings.
"For instance, countries like India and Vietnam have thousands of unmanned, open railway crossings and busy streets with no pedestrian signals," they wrote in their paper on the findings. "Location bias would suggest that, in such situations, individuals underestimate the risk of an oncoming vehicle (train, bus or car) if it is approaching from their right side compared to their left."
Maps shown on television or online that illustrate threats might be subject to the same bias, the researchers added. But there's no reason to flip all the maps around; simply making people aware of their unconscious tendencies could solve the problem.
"Making people aware of the location bias can help them make better decisions and avoid potentially disastrous outcomes by correcting for their instinctive perception of a left-to-right flow being applicable everywhere," the researchers wrote.
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.