The research found that students with a green view outside a classroom window performed better on tests requiring focused attention and recovered better from stress. It is the first study to establish a causal relationship between exposure to a green view and students' performance, said William Sullivan, head of the landscape architecture department. The findings are being published in the April 2016 issue of the journal Landscape and Urban Planning. The article is available now online.

"It's a significant finding, that if you have a green view outside your window, you'll do better on tests," said Dongying Li, a doctoral student who conducted the research with Sullivan. Students' capacity to pay attention increased 13 percent if they had a green view outside their classroom window, the study found.

Li said she and Sullivan hope the results of their research will lead to policy changes. Changes in school design and in policies regarding recess, for example, "would be a much better investment than any of the things we spend money on in secondary education today," Sullivan said.

The research involved 94 students at five central Illinois high schools. Students were randomly assigned to one of three types of classrooms - windowless, with a window looking out onto built space (such as another building façade or a parking lot), or with a window looking out onto green space. Each type of classroom had a similar size, layout and furniture.

The students participated in one-on-one experiments in which they did 30 minutes of activities that included a proofreading exercise, a speech and a mental math exercise. Following the activities, the students were given an attention test, then a 10-minute break in the classroom and another attention test following the break. These tests asked students to repeat a series of numbers in the same and reverse order in which they heard the numbers.

During the entire experiment, sensors took physiological measures of their stress levels by measuring their heart rate, skin temperature and skin moisture. The students were also asked to rate their mental fatigue and stress by filling out a questionnaire at different points during the experiment.

The findings: Students did better on the attention tests given after the break if they were in a classroom with a green view, Li said. Those students showed a 13 percent increase in performance following the break. There was no statistical difference in performance for the students in the windowless room or the room with a view onto a built space.

Similarly, the students in the room with the green view showed a greater physiological recovery from stress after the break than the other students.