Abstract A forest environment can promote the mental state of people and the effect can result within short frames (e.g., minutes of visit). Most studies to date have used questionnaire investigation or medical examination to study how forest affect people. However, these methods were not rapid enough to assess real-time emotion of visitors who were immersed in a forest experience. In this study, twenty-four university students (21 years old, 11 females and 13 males) were recruited to visit four urban forest-park locations or to walk along an urban street in two early-summer days. Participants were asked to take selfies every 30 min between the hours of 09:00 am and 14:00 pm by posing with their natural facial expressions and real-time emotion. Environmental factors were monitored simultaneously at every photographing phase. Photographs were analyzed using the FireFACE™ software to obtain scores for happy, sad, and neutral expressions, which were also used to calculate the positive response index (PRI) which is an expression of happy minus sad facial expressions. The forest experience evoked higher happy and PRI scores, but lower neutral scores compared to that in urban environment. Analysis of variance using a mixed model indicated a higher green-light spectrum-ratio in the sunlight spectrum, higher relative humidity (RH), lower temperatures, and lower noise in forests especially at noon and all were significant explanations of facial expression. Stepwise regression indicated that the green-light spectrum-ratio had a positive relationship with happy scores and the combination of lower noise and higher humidity contributed to a higher PRI in the forest. In conclusion, the forest experience can result in more positive emotional expressions on visitors’ faces, and the understory conditions of green colored light, less noisy peaceful atmosphere, and moist air measured through RH likely led to this experience.

中文翻译：

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城市森林体验中环境因素与游客面部表情的关系

摘要 森林环境可以促进人们的精神状态，其效果可以在很短的框架内（例如，访问分钟）产生。迄今为止，大多数研究都使用问卷调查或医学检查来研究森林如何影响人们。然而，这些方法不足以评估沉浸在森林体验中的游客的实时情绪。在这项研究中，招募了 24 名大学生（21 岁，11 名女性和 13 名男性）在两个初夏的日子里参观了四个城市森林公园地点或沿着城市街道散步。参与者被要求在上午 09:00 至下午 14:00 之间每 30 分钟自拍一次，摆出自然的面部表情和实时情绪。在每个拍摄阶段同时监测环境因素。使用 FireFACE™ 软件分析照片以获得快乐、悲伤和中性表情的分数，这些分数也用于计算积极响应指数 (PRI)，即快乐减去悲伤的面部表情。与城市环境相比，森林体验唤起了更高的快乐和 PRI 得分，但中性得分较低。使用混合模型的方差分析表明，阳光光谱中更高的绿光光谱比、更高的相对湿度 (RH)、更低的温度和更低的森林噪音，尤其是在中午，所有这些都是面部表情的重要解释。逐步回归表明，绿光光谱比与快乐分数呈正相关，较低的噪音和较高的湿度相结合有助于森林中较高的 PRI。综上所述，