Washington, April 18 (IANS) It has happened to most of us - sometimes we are so engrossed in talking on the phone while driving that we fail to see the lights turning red, or watching our favourite movie star so intently that we miss what the other actors are doing in the scene.

Researchers call this "inattention blindness".

People who fail to see something right in front of them while they are focusing on something else have lower "working memory capacity".

It is a measure of "attentional control", or the ability to focus attention when and where needed and on more than one thing at a time, reports The Journal of Experimental Psychology: Learning, Memory and Cognition.

"Because people are different in how well they can focus their attention, this may influence whether you'll see something you're not expecting," says study co-author, Janelle Seegmiller, psychology doctoral student at the University of Utah in the US.

Seegmiller conducted the research with two psychology faculty members - Jason Watson, an assistant professor, and David Strayer, a professor and leader of several studies about cell phone use and distracted driving, according to an Utah statement.

The new study used a video made famous by earlier "inattention blindness" research featured in the 2010 book "The Invisible Gorilla" by psychologists Christopher Chabris and Daniel Simons.

The video depicts six actors passing a basketball. Viewers are asked to count the number of passes. Many people are so intent on counting that they fail to spot a person in a gorilla suit stroll across the scene, thump his chest, and walk off.

Seegmiller, Watson and Strayer did a new version of the older experiments, designed to determine the reason some people see the gorilla and others miss it.

"We found that people who notice the gorilla are better able to focus attention," says Watson, also an assistant investigator with the university's Brain Institute.

"You can imagine that if you're driving and road conditions aren't very good, unexpected things can happen, and individuals with better control over attention would be more likely to notice those unexpected events," Seegmiller says.

Strayer has shown that inattention blindness explains why motorists fail to see something right in front of them, like a stop light turning green, because they are distracted by the conversation, and how motorists using cell phones impede traffic and increase their risk of accidents.