Emotion-related impulsivity (ERI) refers to the tendency to react impulsively during heightened emotional states [1, 2], which measures whether people will act recklessly in a highly emotional state that they may regret later [3]. ERI can lead to many adverse consequences for individuals. On an individual level, ERI stands as a significant predisposing factor for a range of mental health issues. For instance, it elevates the likelihood of individuals experiencing heightened anxiety and depression, as well as a host of other negative emotions [3]. Moreover, it can catalyze the development of eating disorders [4] and may push individuals towards self-harming tendencies or, in severe cases, even suicidal thoughts [5–7]. On the interpersonal level, ERI can instigate numerous challenges when comparing individuals with higher levels of emotion management skills to those who with emotionally impulsive responses; the latter group typically exhibits lower social functioning and poorer healthy peer relationships [8–10]. Furthermore, emotionally impulsive individuals tend to display increased aggressive behavior [11, 12]. Therefore, it is crucial to find ways to inhibit ERI.
Previous research has predominantly focused on mitigating ERI at the individual level while overlooking the pivotal role of the external environment. For instance, some studies have highlighted the efficacy of cognitive control training [13] and mindfulness training [14] in significantly reducing individuals’ ERI. Additionally, online psychological interventions have proven effective in diminishing aggressive behavior stemming from emotional impulses [15]. Notably, physical exercise, particularly high-intensity interval training, has reduced levels of ERI [16]. However, it is worth noting that the interventions above, whether psychological or physical, demand considerable effort from the individual and can consume their finite mental and physical resources. Curiously, the prospect of merely altering the natural environment surrounding individuals' living spaces, particularly by incorporating natural elements like blue spaces, holds promise in mitigating ERI. Nevertheless, this avenue of research has largely been overlooked.
Water is an essential aspect of human life. More than a third of people live near water [17]. The World Health Organization (WHO) stresses the significance of blue spaces, which are natural or artificial outdoor environments featuring water, such as coasts, lakes, ponds, or artificial water features [18], in promoting people's physical and mental health [19]. Much research has shown that exposure to blue space could reduce stress [20], improve positive emotion [21], and restore cognitive resources [22].
Nevertheless, previous research has predominantly focused on the significance of active exposure to blue spaces while largely overlooking the impact of passive blue space exposure (PBSE). PBSE involves individuals encountering blue spaces in their daily lives and activities without intentionally immersing themselves or actively engaging with these environments [23], and its effects have remained uncertain [24]. PBSE allows individuals to simply step outside or gaze out of their windows to observe nearby blue landscapes and benefit from it [21]. Generally, people are more susceptible to the influence of their daily surroundings and more likely to encounter passive blue spaces. Regrettably, the positive impacts of PBSE on individuals have not been appreciated.
The current study proposes that PBSE could inhibit ERI. ERI is usually accompanied by intense emotional experiences, and blue spaces are closely related to high levels of emotional recovery, including relief from negative emotions such as anxiety, sadness, depression, and fatigue, as well as increased positive emotions such as calmness, tranquility, and energy [25]. For instance, participants in a study on promoting happiness in coastal areas reported feeling calmer by the seaside, and blue spaces seemed to "purify" their emotions [26]. A survey of 4255 respondents who recalled their recovery experiences after visiting different natural environments found that they felt calmer and more relaxed when visiting coastal areas compared to urban parks [27].
Following previous studies for passive nature exposure and surrounding greenness, PBSE, or surrounding/nearby blue space, can be generally evaluated by both objective index and subjective report [23, 28, 29]. Objective PBSE is primarily evaluated using the normalized difference water index (NDWI) within a range of 300 to 1000 meters surrounding individuals’ home address [30, 31], while subjective PBSE relies on the amount of blue space around the residence and the degree of visual exposure to blue space outside the home window [32].
In addition, as urbanization advances, overcrowding has become a typical feature of city life. According to the dual-systems theory of self-control, in crowded environments with information overload, individuals' self-control systems are inhibited, and the likelihood of impulsivity increases [33]. In this study, we investigated whether PBSE (including both objective and subjective PBSE) could reduce ERI via alleviating perceived crowdedness. The current study bridged a gap in the existing research by examining the impact of PBSE on ERI. It advances our understanding of how PBSE in people's daily lives shapes their social behavior.
1.1 PBSE and Perceived Crowdedness
During the rapid urbanization process, many people experience a sense of crowdedness. Perceived crowdedness arises when individuals constantly respond to excessive stimuli in their environment and consume their limited cognitive resources [34–36]. It could lead to many negative consequences, such as increased anxiety, apathy, aggression, and cognitive overload [34, 37–39]. Cognitive overload occurs when individuals’ cognitive resources are insufficient to handle the stimuli in multiple social environments [40]. Therefore, reducing an individual's cognitive load and restoring their cognitive and attention resources may effectively decrease perceived crowdedness.
The cognitive resources of humans are finite and can become depleted through usage [41]. Attention Recovery Theory (ART)[42] pointed out that depleted cognitive resources can be replenished in a restorative environment. This is because such environments can stimulate individuals' inadvertent notice and rehabilitate their ability to direct attention, ultimately restoring cognitive resources [43]. Several studies have demonstrated the restorative effects of blue spaces on cognitive resources [44–46]. For example, researchers have discovered that a 30-minute walk in a blue space can enhance cognitive function compared to a residential area [47]. Notably, the cognitive enhancement effect is not limited to active exposure to blue spaces but is also observable in individuals who are passively exposed to blue spaces. For instance, research conducted on the elderly population found a noteworthy correlation between blue space coverage within a 1000-meter buffer zone of their residence and a decrease in hospitalization rates for Parkinson's disease [48]. This correlation indirectly supports the link between PBSE and improved cognitive function. Based on this, it is reasonable to argue that PBSE may alleviate perceived crowdedness by restoring cognitive resources to individuals.
1.2 Perceived Crowdedness and ERI
Perceived crowdedness may amplify individuals’ ERI by elevating their stress levels. Crowdedness is considered an acute stressor [49], since individuals tend to rapidly deplete their limited emotional and cognitive resources under such circumstances, leading to more stress experience. According to the Conservation of Resources (COR) theory, stress arises primarily from the loss of resources, and individuals always try to preserve and construct their valuable resources [50, 51]. Numerous studies have established a link between perceived crowdedness and stress, including subjective self-reported and objective indicators, such as the level of stress-related hormones [52–54]. Stress significantly contributes to ERI [3]. Some researchers have found that pressure weakens the control function of the prefrontal cortex in the brain, leading to impulsive behaviors such as overeating, excessive consumption, etc.[55]. Furthermore, perceived crowdedness could lead to individuals’ emotional disorders [56], triggering negative emotions and negative emotional expression, making it challenging for individuals to cope with the negative effects of pressure [57].
Additionally, perceived crowdedness increases individual stress and gradually undermines the individual’s self-control system [58]. The dual-system theory of self-control highlights that self-control is often produced by the combined action of two systems: self-control and impulsivity [33, 59]. The self-control system produces different psychological activities in response to external stimuli, requiring the individual's conscious participation and attention resources. In contrast, the impulsive system generates automatic emotional responses to external stimuli without the need for conscious resource involvement. In general, individuals consciously regulate their behavior. However, when the consumption of emotional and cognitive resources intensifies, the individual's self-control system may become ineffective in guiding their behavior, resulting in the impulse system taking over [33]. As mentioned before, perceived crowdedness continuously depletes individuals limited emotional and cognitive resources, thereby reducing the effect of the self-control system and increasing the dominance of the impulse system in the process of self-control, leading to more ERI.
1.3 The present study
Based on the above argumentation, we proposed that PSBE (including objective and subjective PBSE) negatively predicts ERI by alleviating perceived crowdedness. Consequently, the current study had three main objectives:
First, we explored the effects of objective PBSE on people’s ERI. We asked participants to provide their residential address and calculated the NDWI within a 1000m buffer surrounding their residential area as the objective PBSE [60, 61]. We first proposed the following hypothesis:
Hypothesis 1
Objective PBSE is negatively associated with ERI.
Second, we explored the effects of subjective PBSE on people’s ERI. We asked participants to rate their perception of PBSE. Two indicators represented the PBSE: (1) the degree of blueness in the surrounding area and (2) the degree of blue scenery visible outside the window from the inside [2, 62]. Thus, we proposed the following hypothesis:
Hypothesis 2
Subjective PBSE is negatively associated with ERI.
Third, we investigated the mediating effect of perceived crowdedness on the predicted negative relationship between subjective PBSE and ERI. Specifically, we proposed the following hypothesis:
Hypothesis 3
More subjective PBSE reduces people’s perceived crowdedness, which in turn decreases ERI.