Most of his work has been in two broad areas-healthcare facility design research, and human interactions with nature. He has researched, for instance, the effects of hospital window views on recovery from surgery, the influences of visual stimulation on patients in intensive care units and psychiatric wards, and has performed several studies comparing the effects of different types of visual surroundings on stress and physiological well-being. His research is perhaps the first to scientifically document the health-related benefits for hospital patients of viewing nature. He has also developed a Theory of Supportive Design that has become influential as a scientifically-grounded yet "designer friendly" guide for creating successful healthcare facilities.