Thursday, August 23, 2012

Why is the belief in global warming affected by temperature?

Last week, I wrote about a strange finding.  People are more likely to believe in global warming when the weather is warmer than usual for that time of year.  In that blog entry, I summarized research by Ye Li, Eric Johnson, and Lisa Zaval that people’s ratings of their agreement that humans are causing global climate change are higher on unseasonably warm days than on unseasonably cool days.  This belief influences their willingness to perform actions like donating money to charity.
Why does this happen?
As luck would have it, a fascinating paper on this topic by Jane Risen and Clayton Critcher was published in the May, 2011 issue of the Journal of Personality and Social Psychology. 
These researchers explore two possible explanations for the relationship between belief in global warming and temperature.  One possibility is that when it is warm, that makes it easier to think about the concept of heat.  When it is easier to think about heat, then it is also easier to think about global warming, and so people’s belief in global warming goes up.
A second possibility is that when it is warm, it is easier for people to simulate what it would be like when the planet is warmer.  When it is easier to imagine a hot planet, it is easier to believe in global warming.
Now, a lot of times psychology research is criticized for demonstrating things that people already know are true.  So, before I go on and describe some of the studies, which of these possibilities do you think is correct?  (It is possible that they are both true, so don’t feel like you need to pick only one.)
Ok.  The first few studies in this paper just demonstrate the link between temperature and belief.  For example, in one study participants judged their beliefs about many political issues.  On a scale from 0 (low belief) to 10 (high belief).  The judgments were made while sitting in a room heated with a space heater to 81 degrees or in a room at a normal room temperature (73 degrees).  Participants also expressed whether their political ideology was more liberal or more conservative.  Overall, the participants who rated themselves as liberal expressed a greater belief in global warming than those who were conservative.  For both groups, though, their ratings were about a scale point higher when sitting in the hot room than when sitting in the cold room.
A few other studies in this paper explored whether making it easier to think about heat influenced judgments about global warming.  In one study, people did a version of the sentence unscrambling task developed by Bob Wyer and Thom Srull.  In this task, people are given five words like “sizzling bacon is the for” and they have to take four of the words and assemble them into sentences (“The bacon is sizzling”).  One group created sentences that were related to heat, while the control group had no sentences relating to heat.  This technique is well-known to increase how easy it is to think about the concept primed by the sentences.
To demonstrate that people in this study found it easier to think about heat, participants filled in word fragments like F _ A M E, which could be completed to form words relating to heat (like FLAME) or words unrelated to heat (like FRAME).  As expected, when primed with heat, people tended to fill in the word fragments to form heat-related words.  These participants also rated their belief in global warming.  Priming participants with the concept of heat did not affect their belief in global warming.
A third group of studies explored the prospect that heat makes it easier for people to imagine a warmer planet, which in turn influences beliefs in global warming.  In one study, participants sitting in a hot room or a room of normal temperature looked at a series of pictures.  A few of those pictures showed hot dry landscapes.  A few showed images of snow and ice.  The rest of the pictures were not related to climate.  The quality of the pictures was degraded using the transparency feature of a photo editor so that they were between 40 and 60 percent transparent.
Later in the experimental session, participants were shown clear versions of the images they had seen earlier and were allowed to adjust the transparency of the images themselves and were told to match the images to what they had seen before.  The people in the hot room adjusted the images of hot scenes to be clearer than those sitting in a room of normal temperature.  The images of cold scenes were not affected by whether the room temperature was hot or normal.  This result suggests that being hot makes it easier to imagine hot scenes. 
Finally, another group of participants rated their belief in a variety of political issues while looking at pictures relating to those issues.  For most of the issues (like charter schools), degraded quality images were shown using the transparency feature used earlier.  For global warming, one group saw degraded images, while another group saw clear images.  Thus, for the group that saw the clear pictures of hot scenes, the clarity was very salient.  The group that saw clear images rated their belief in global warming as much stronger than the group that saw degraded images.
Putting all of these studies together, it seems that when you are hot, it gets easier to imagine a world that is suffering the effects of global warming, and that increases your belief in global warming.  When it is hot, it may also become easier to think about heat conceptually, but that conceptual ease does not seem to translate into changes in beliefs about global warming.
This work also suggests that when you want to try to persuade someone about the importance of an issue whose effects won’t be felt for years to come, it is important to make the long-term consequences feel as vivid as possible.  Thus, documentaries like Al Gore’s An Inconvenient Truth may be most effective when they provide clear images of what will happen to the Earth as temperatures rise.