Prisons are about as devoid of nature as a place can get. The concrete and steel only adds to the misery and rage felt by those confined inside.

The intensive management unit's IMU-E cellblock at the Snake River Correctional Institution in Oregon is no more lush than any other prison: It has poured concrete walls, metal furniture and maximum security cells containing a single bed, toilet and thick metal door. The 48 men in the isolation unit for inmates convicted of heinous crimes and troublemakers removed from the general population were unsurprisingly prone to fights and other shows of aggression, not to mention lots of verbal conflict with prison staff.

Then one day, the prison staff decided to put aside batons and brute force and try another behavior modification technique: nature videos with scenes of pretty blue oceans, evergreen forests, majestic mountains and fluffy white footage shot from airplanes flying through clouds.

The results, according to a study presented at a conference Friday, were dramatic.

"We found that inmates who watched nature videos committed 26 percent fewer violent infractions," study author and clinical psychotherapist Patricia H. Hasbach said in a statement. It was "a substantial reduction in real world conditions, since nearly all such events result in injuries to inmates or officers," Hasbach said. She presented the results at the American Psychological Association’s 124th Annual Convention in Denver.

Hasbach said the program demonstrates the curative power of nature and its images. "We need nature for our physical and psychological well-being,” she said. “Although direct contact with real nature is most effective, studies have shown that even indirect nature exposure can provide temporary relief from psychological stress in daily life.”

In written surveys, inmates said they liked videos with beaches, jungle and forest. In spoken interviews, they went on about the animals, colors and, not surprisingly, open spaces, Hasbach said in an interview, “places like where you’d go hiking and scenes of animals and places to dream about.”

The study had its flaws. No one knows how honest the inmate responses were. The presence of the researchers -- most of them women --  could arguably have lifted the spirits of a group of men who rarely see the opposite sex. Finally, as the year-long study wore on, researchers noticed a 10- to 20-percent decline in viewing, possibly because the inmates exhausted the limited amount of available material and the images were getting old.

The experiment started on a lark. A sergeant at Snake River saw a TED talk by Nalini Nadkarni, a University of Utah professor who guided the Sustainability in Prisons Project for the state of Washington's corrections facilities. The sergeant shared the idea with his superiors, who reached out to Nadkarni, who assembled the team behind the latest study.

Together they created a pilot program, the Nature Imagery in Prisons Project, in 2013. The researchers found 38 videos, and the staff placed them in an indoor fitness room that inmates visit four to five times a week for about an hour as part of an exercise allotment. They could workout or watch videos or do both. The room was painted light blue to improve viewing of the videos.

When Hasbach and others returned with the surveys, they were surprised by the reaction. The inmates said the videos helped ease tension, gave them something to talk about when their families came to visit, and made them better communicators in sessions with prison staff. More surprising, she said, is that the staff said pretty much the same. The staff had taken the additional step of allowing inmates time in what became known as "The Blue Room" to watch nature videos when inmates appeared agitated or on edge, rocking back and forth in their cells, for example.

"It was very interesting to hear on both sides that it improved the communication," Hasbach told The Washington Post. Only a few months after the videos were offered, staff began to offer them to inmates regardless of whether they had gym time after noticing how the images soothed them.

Hasbach said using nature videos to calm a prison's most hardened population is a first. Prisons in Washington state had used gardening and other techniques to soften attitudes in the general prison population for years, and the idea spread to other parts of the country.

But such touchy-feely nature techniques were not extended to the baddest of the bad. There are about 100,000 inmates in so-called intensive management units in 44 states. At Snake River, the staff noticed a change almost immediately.

One staffer stated in the research survey that “the response was amazing because sometimes all it took was 15-20 minutes in the nature imagery area to calm them down and get them back on task.”

More than 90 percent of inmates surveyed agreed "that they felt calmer when they watched the nature videos." Eighty percent said the calm was sustained for hours, and nearly 80 percent agreed that when they felt agitated, they thought of the videos to calm themselves. A majority also said it improved their relationships with their jailers and a wide majority said it made serving time easier.

Hasbach believes the experiment could be a model for correctional institutions nationwide to help limit stress, mental fatigue, violence and other negative behaviors. An analysis of video selection at Snake River showed that inmates preferred footage featuring "a diversity of landscapes from different countries, high quality video and cinematography...a mix of animal life, no human presence, scenes of blue skies...and wide-open landscapes." Nature sounds and silence were more preferred than music.

One inmate who watched a mountain video said, according to the study, that it's where he would go "if I were out of here." His family visited, and "I tell my kids, 'We’re going camping when I get out of here.' It makes me think about my stuff.”

For more science news, sign up for our weekly newsletter here.