Department of Psychology, University of Michigan at Ann Arbor
Rotman School of Management, University of Toronto
Department of Psychology, Stanford University
Department of Psychology, Columbia University
Published in 'Psychological Science', 16 (9), 724-731, 2005
The object of this paper was to test the hypothesis that the effects of weather on mood and cognition are moderated by the degree of direct exposure to the weather and by season. The researchers collected data from a total of 604 participants as a result of two correlational studies and a controlled experiment. The National Climatic Data Center provided the necessary temperature information and barometric pressure details were given as a reliable substitute for sunlight, measurements of which were unavailable. According to the authors, high pressure is typically associated with clear, sunny weather whereas low pressure is associated with cloudy, wet and stormy weather.
Study 1: Relationships of weather, mood, and cognition in the Spring
54 females and 43 males, aged between 18 and 29 years, took part in the study between April and June 2001. All participants were students at the University of Michigan and they were required to complete a set of questionnaires measuring their current mood, the amount of time they spent outside, their activity levels that day, and various demographic information. They were then asked to complete two cognitive tasks, one assessing memory and the other assessing participants' openness to new information in order to measure how weather affects 'cognitive broadening'. This refers to a style of thinking where the individual becomes more creative and this cognitive shift results in more exploratory and flexible patterns of behaviour. The results of the study indicated that higher temperature and pressure were both associated with more positive moods among people who spent 30 minutes or more outside. Pressure (but not temperature) was also positively related to the two cognitive tasks as the length of time spent outside increased. The authors suggested that being outdoors on clearer days may help to improve memory as well as mood, and may also encourage more flexible thinking styles depending on the length of time people are exposed to the weather conditions.
Study 2: Random assignment of time spent outside in the Spring
The researchers manipulated the length of time participants spent outside between April and the end of July 2003 in order to determine whether or not people in better mood or broader mindsets are more willing or able to go outside in pleasant weather. Data was collected from 121 participants, who were aged between 18 and 32, and were recruited through a local newspaper article seeking people who relieved stress by 'walking outside, dancing, or meditating'. Participants were randomly assigned to walk outdoors or dance indoors, walk outdoors or walk indoors on a treadmill, and meditate indoors or outdoors. As in Study 1, participants' moods increased for those who were outside on warm, high pressure (clear) days. In contrast, moods decreased among those who had to be inside on such days. Unlike Study 1 however, temperature (but not pressure) was positively related to better memory for digit spans.
Study 3: Relationships of weather, mood, and cognition across locations & seasons
As the previous two studies involved data collected in a Northern climate during the spring and early summer, the researchers collected further data over a period of one year using participants from various geographical locations. This was to determine whether or not the weather-mood relationship differed across seasons and locations, as warm and sunny weather in spring and summer may be considered as an uplifting novelty for people living in a more Northerly region. Information was gathered from January to December 2002 via the Internet using a website dedicated to online psychological research. 387 participants, who were aged between 18 and 56, voluntarily took part in the study. 201 lived in the northern US and Canada, 174 lived in the southern US, and 12 lived in Europe. The strongest results related to the spring (April-June) and were consistent with the findings of the previous studies however there were no statistically significant interactions during the winter (January-March) or during the autumn (October-December). Warmer temperatures in the summer were associated with decreased mood as the length of time outdoors increased. Interestingly though, temperature changes toward cooler weather in the autumn did not predict higher mood. And yet the evidence appears to suggest that warm days in the spring uniquely enhance positive moods.
In summary, the evidence in this paper suggested that spending time outdoors increases the relationships of weather with mood, memory and openness to new information. Being outdoors also appeared to be a causal factor in changing these relationships. Moreover, the season mediated the relationship between weather and mood, as exposure to higher temperatures predicted elevated moods during the spring but demonstrated the opposite effect during the summer months, particularly among participants living in southern locations where hot weather is more unpleasant.
The effects of the weather on people who spent most of their time indoors was nearly as strong and in the opposite direction to those spending more time outdoors. The researchers provide a possible explanation for this by suggesting that people may resent having to stay indoors when the weather in spring is pleasant, particularly after the cold and dark months of winter. They propose that, in order to boost psychological well-being in the spring time, people should make sure that they spend plenty of time outdoors.