Several notable outcomes emerged from the present study in which we evaluated the effects of visual exposure to natural versus built stimuli on impulsivity and time perception. These results (I) validate previous research showing that exposure to natural environments results in less impulsivity (i.e., greater self-control), (II) show novel evidence that exposure to natural environments can lengthen perception of time, and (III) show evidence for the relationship between time perception and impulsivity. Below, we explore each of these in turn, while discussing similarities and differences between this study and previous research.

These results are particularly important given the potentially sweeping implications of nature’s effect on impulsivity. Reducing impulsivity in one realm has been shown to influence impulsivity in other realms [ 30 ], suggesting similar underlying processes at work. Thus, the present results have implications for global reductions in impulsive decision-making that may apply not only to disorders associated with impulse control, but also to our everyday decision-making–including those in the environmental realm (e.g., the choice to take public transportation with an increased delay but reduced emissions, rather than driving a private car with a reduced delay but more emissions, [ 2 , 11 , 57 ]).

Consistent with previous findings [ 2 , 35 ] exposure to natural environments resulted in greater self-control relative to exposure to built environments. Given that this has been demonstrated using different natural and built stimuli as well as real world natural and built exposure across various impulsivity tasks [ 2 , 35 ], this effect appears to be robust. This line of research adds to the growing body of evidence highlighting the beneficial aspects of natural environments for humans. Exposure to natural environments reduces stress, increases happiness, improves mood and restores attention [ 44 , 53 – 56 ]. The present study confirms that apart from cognitive and mood influences, exposure to natural environments may also improve human decision-making.

This effect was strongest (and statistically significant) for the more objective measurement of the passage of long intervals of time (the estimate involving minutes passed and not scale ratings of perceived time speed). This makes sense in that the scale long measure was not anchored with the actual time passed, and thus it is less clear what a low or high score might mean in relation to actual time. In contrast, the numerical estimate long task in minutes can be directly compared to the actual amount of time, and thus is a more precisely anchored measurement, in this context, of the “lengthening” of time.

Time perception is malleable–it psychologically speeds up and slows down based on various cues [ 58 – 60 ]. The present study provides evidence that part of this variability in time perception is due to the presence or absence of natural environments. Merely viewing natural environments can lengthen time perception: people who viewed natural environments reported longer time estimates than those who viewed built environments.

Natural Environments, Time Perception, and Impulsivity

Viewing natural scenes influenced both time perception and impulsivity, although this was manifested in different ways across the two separate long interval time perception measures. First, the ‘scale long task’ measurement, while showing a weaker relation to the experimental manipulation than the ‘numerical estimate long task’ measurement, showed a stronger (and significant) relationship to impulsivity. It is possible that impulsivity is more related to long interval scale measurements of time perception because those scale measurements are more subjective in nature. The 'scale long task' measurement is a measurement of what time “feels” like, unanchored by actual time, and it could be that that feeling is more tied to impulsivity than a more objective measurement such as the ‘numerical estimate long task’.

Taken in total, then, we have (a) a time-impulsivity effect for a scale measurement of time perception (scale long task), and (b) a time-condition effect for the minutes passed estimate measurement of time perception (numerical estimate long task). Further, there was no effect of short interval time perception (measured by temporal bisection) in relation to impulsivity or condition. Baumann and Odum [13] showed that although some measures of time (an interval bisection task) were weakly correlated with impulsivity in a delay discounting task, others were not (Zimbardo Time Perspective Inventory), and thus the present results are not necessarily surprising. Although we did not show that time perception as measured by an interval bisection task was correlated with impulsivity in the present experiment, we used shorter stimulus durations than those used previously [13] making direct comparisons difficult. It is possible that longer as opposed to shorter stimulus durations in an interval bisection task correlate more closely to the relatively longer time considerations presented in delay discounting tasks (i.e., days to years). It should also be noted that because the numerical estimate long task (estimate in minutes) by necessity followed the delay discounting task, differences in time perception may be influenced by the natural-built manipulation and choices of larger versus smaller rewards, rather than an intrinsic relation between timing and impulsivity. More research on this topic is warranted.

Some evidence from other timing studies shows that those who perceive time to pass more slowly tend to be more impulsive ([13], see [40] for a review on time perception and impulsivity). These studies, however, have largely been conducted with timing discrimination tasks at very short intervals, measuring fine temporal perception within the milliseconds to seconds range [40]. Recall that in the present study, we found no differences in time perception across natural and built conditions at very short timing intervals (i.e., milliseconds to seconds). It is possible that lengthened time perception of longer intervals (i.e., minutes or longer) with exposure to natural environments, may have different effects on impulsive decision-making and may represent something akin to an expanded perception of time in which waiting for delayed consequences is less aversive. Another interpretation is that lengthened time perception of longer intervals enables individuals to bridge the gap between the present behavior and future consequences, or possibly represents greater future foresight [38]. These results converge with other evidence suggesting that the focus on temporal domains alters delay discounting [37], although the direct relation between millisecond to second time perception and longer durations is still unclear. More evidence is needed to draw firm conclusions on the relation between exposure to natural environments, time perception, and impulsivity, and the relations between short and long interval timing mechanisms.

Considering the consistent pattern of previous research on the relationship between time perception and impulsivity, along with the present results, we suspect that there is a connection between time perception and impulsivity, but that the mechanism driving differences in impulsivity across environmental conditions is more complex than simply time perception. For example, as attention is restored by visual exposure to natural relative to built environments [44] and increased attention is also related to decreased impulsivity [61], it is possible that attention and/or arousal—which we did not measure in the present study—combined with temporal perception, also influences differences in impulsivity observed across natural and built scenes. More research is necessary before drawing a firm conclusion about the underlying mechanisms driving differences in impulsivity with exposure to natural versus built environments, but the present study adds important evidence to this discussion.