Welcome to the Jungle: The Effects of Ultrasoundscape Exposure on Cognitive Performance and Perceived Restoration
Abstract
Engaging with natural environments has been shown to reduce stress and improve cognitive performance. This beneficial effect is attributed to natural stimuli refreshing our ability to focus by providing a respite from constant demands on our attention. In addition to this effect, natural stimuli may also restore emotional and physiological well-being, mitigating the negative effects of stress. The effectiveness of this restoration has been demonstrated by comparing the effects of exposure to recordings of natural soundscapes versus urban soundscapes. Natural environments often include frequencies that are beyond the range of human hearing (ultrasound). Stimuli with ultrasound appear to increase alpha activity in the brain more than stimuli without ultrasound, which is significant because increased alpha wave activity is associated with a state of relaxed alertness. This relaxed alertness could, in principle, assist with tasks that require focused attention, thereby improving cognitive performance. Moreover, elevated alpha wave activity is typically linked to decreased stress levels, suggesting that exposure to natural soundscapes with ultrasound may offer enhanced restorative benefits. It is presently unknown whether incorporating the ultrasound range into recordings of natural soundscapes can enhance their cognitive and perceived restorative properties. To investigate this, we conducted a randomized controlled trial comparing the effects of different types of soundscapes (nature or urban) with different bandwidths (audible-only or audible plus ultrasound) to quantify their effects on cognitive performance and perceived restoration. We used a backward digit span task and an n-back task to both deplete and assess attention. Participants completed the Positive and Negative Affect Schedule (PANAS), Perceived Restoration Scale as well as cognitive fatigue, and aesthetic assessments to measure perceived restoration. Both the task blocks and assessments were completed before and after the soundscape intervention. The results revealed no significant effect of ultrasound on cognitive performance. However, ultrasound exposure was found to increase cognitive fatigue. Additionally, there was no effect of ultrasound on affective or restorative outcomes. Notably, the environment, mediated by aesthetic preference, most accurately predicted the subjective outcomes of soundscapes, showing significant effects on emotional regulation, perceived restoration and cognitive fatigue.