Weatherford Democrat

September 15, 2013

Cycle, car wrecks a matter of perception?

Vehicle, motorcycle wrecks could be linked to one’s brain miscalculating time of impact of smaller objects, study shows


Weatherford Democrat

— Lone Star News Group

Incidences of cars pulling out in front of motorcyclists run regularly in headlines – there could be a scientific reason.

Recent research by a Texas Tech University psychologist suggests the regularity of this problem isn’t necessarily a case of poor driving or carelessness, but may be related to a basic human judgment error.

Pat DeLucia, the coordinator of the Human Factors Psychology Program, said her results show that small, near objects can appear farther away than larger, farther objects. The study is published in the peer-reviewed scientific psychology journal “Current Directions in Psychological Science.”

An interest in softball as an undergraduate prompted DeLucia, also a professor at Texas Tech’s Department of Psychology, to study how the human brain perceives objects, their size and motion and an object’s time to impact.

Her finding – that an object’s size affects distance perception – may be the basis explaining why car drivers miscalculate motorcyclists’ distance and speed.

DeLucia explains that the brain uses two visual information cues for judging time to impact. In the first, a moving object is reflected on the eye’s retina. It expands as it approaches the eye, providing the brain accurate information about when the object will hit. This is called an “optical invariant.”

However, the brain also uses “rules of thumb” as well, such as various “artist” depth cues as a shortcut, she said.

Many times, the brain interprets objects with a larger retinal image as closer. Since motorcycles are smaller than cars, DeLucia said the brain may use this shortcut to judge a smaller motorcycle farther away than it actually is.

“With computer simulations, we had a big, far object and small, near object approaching the viewer, where the small object would hit first,” she said. “We wondered if people would choose the big one, based on the artist depth cue of relative size, or choose the smaller one, based on the more accurate optical invariant. Unexpectedly, people picked the bigger object again and again. We found people relied on rules of thumb.”

This effect of size on collision perception violates theories of perception that believe people evolved to rely on the most accurate information, such as optical invariants. Instead, DeLucia’s findings suggest that perception is based on multiple information sources.

This size-arrival effect can lead drivers to misjudge when a vehicle would arrive at an intersection and could be considered a contributing factor in motorcycle/vehicle accidents.

DeLucia hopes to find funding from the Texas Department of Transportation to create an educational program to inform drivers of her findings and reduce the incidents of these types of accidents.