UC Davis

Over the course of human evolution, the successful detection of drinking water in arid environments mitigated the physiological stress of dehydration and acted as a strong source of natural selection for recognizing the optical cues for water and perhaps physiological indices of relief. The current research consisted of two studiesinvestigating whether viewing water in outdoor settings affected autonomic tone and subjective ratings of relaxation. The first study examined blood pressure and heart rate of 32 participants who focused their attention on water in a swimming pool, a tree in a parking lot, and a small sign over a busy street. The results of this studyshowed that viewing water for 1 min 40 s reduced blood pressure reliably compared with viewing the tree and sign. Heart rate was also lower reliably while viewing water than the sign. The second study extended this research to a university arboretum, recording blood pressure, heart rate, and subjective ratings of relaxation of 73 participants successively at six sites along a 1.62 km path next to a creek, two small lakes, and the adjacent ground with open grassy areas and trees. At each site, participants alternated randomly in viewing the water or the ground first. Averaged for the six sites, analyses showed that the systolic/diastolic ratio for blood pressureand heart rate were reliably lower when viewing the water compared with the adjacent ground, an effect associated with the subjective rating of relaxation. Together, these findings indicate that viewing water can affect autonomic tone in a way that might account for the subjective rating of relaxation.