New York, July 27 (IANS): If the movies by filmmaker Alfred Hitchcock, nicknamed "The Master of Suspense," made your palms sweat and pulse race, there is a scientific reason for this.

Researchers from the Georgia Institute of Technology have discovered how his movies affect audiences' brains.

They measured brain activity while people watched clips from Hitchcock and other suspenseful films. During high suspense moments, the brain narrows what people see and focuses their attention on the story.

During less suspenseful moments of the film clips, viewers devote more attention to their surroundings.

"Many people have a feeling that we get lost in the story while watching a good movie and that the theatre disappears around us," said Matt Bezdek, post-doctoral psychology researcher who led the study.

"Now we have brain evidence to support the idea that people are figuratively transported into the narrative," he added.

In the study, participants watched scenes from 10 suspenseful movies, including Hitchcock's "North by Northwest" and "The Man Who Knew Too Much," as well as "Alien" and "Misery."

As the movies played in the centre of the screen, a flashing checker board pattern appeared around the edges. The researchers discovered an ebb and flow of activity in a brain area that receives and processes most visual information.

When the suspense grew, brain activity in the peripheral visual processing areas decreased and activity in the central processing areas increased.

Essentially, when suspense is the greatest, our brains shift activity to increase processing of critical information and ignore the visual content that does not matter.

"It is a neural signature of tunnel vision," said Eric Schumacher, associate professor in the school of psychology.

During the most suspenseful moments, participants focused on the movie and subconsciously ignored the checker boards.

The brain narrowed the participants' attention, steering them to the centre of the screen and into the story, the authors said.

The study is forthcoming in the journal Neuroscience.