Monday, November 23, 2015

How Does Disgust Affect Memory?

Emotional experiences clearly affect memory.  At the 50th anniversary of the assassination of John F. Kennedy many people shared their memories of where they were when they heard the news that he had been shot.  This event was shocking, and many people reported having vivid memories of that day, even a half-century later.  People who lived through the explosion of the space shuttle Challenger and the events of September 11, 2001 also have significant emotional memories from these dates.  Although these memories may not be 100% accurate, it is clear that people are influenced by the emotional experience at the time.
It is hard to disentangle all of the factors that influence memory in these stressful situations.  They events are surprising.  They are arousing emotional experiences.  They are negative.  They involve a combination of anger, fear, and sadness. 
Because emotional experiences have an influence on memory, controlled laboratory studies have begun to tease apart the elements of emotion that affect what you remember later.
A fascinating set of studies in the November, 2013 issue of the Journal of Experimental Psychology: General by Hanah Chapman, Kristen Johannes, Jordan Poppenk, Morris Moscovitch, and Adam Anderson looked at the way fear and disgust affect memory. 
In one study, the researchers gathered a series of pictures that were disgusting, scary, or neutral.  Disgusting pictures showed things like a cockroach or a picture of a gruesome disease.  Scary pictures showed things like threatening animals or riots.  The neutral pictures were items like coat hangers or coffee makers.  Ratings obtained before the study found that the scary pictures were slightly more arousing overall than the disgusting pictures. 
Each picture was shown for 2 seconds.  When the picture was presented, a line appeared above it or below it.  Participants had to indicate where the line was relative to the picture by pressing a button.  Then, after a delay of either 10 minutes or 45 minutes, participants were asked to recall as many of the pictures as they could.  This memory test was a surprise.  They had not been told that they had to remember the pictures.
Overall, people remembered more of the arousing pictures (both scary and disgusting) than the neutral pictures.  So, pictures that created a negative emotion were more memorable than those that did not.  The disgusting pictures were better remembered than the scary ones.  This difference was particularly strong after a 45-minute delay.  Finally, participants took longer to respond to the location of the line when the pictures were disgusting than when they were scary or neutral.  This finding suggests that people’s attention was more strongly drawn to disgusting pictures than to scary or neutral ones.
Another study in this series found that this effect was also strong even when there was a one-week delay between the initial exposure to the pictures and the test.
Why does this happen? 
Memory for specific items and specific situations is often not important.  When you encounter a coat hanger, you need to know what it is for, so you need to recognize that it is a hanger.  However, it probably does not matter which hanger it is or when you may have seen that particular hanger before.  As a result, we do not really differentiate our experiences of common objects that do not engage our emotions.
When you experience a frightening situation, though, you probably do want to remember it, because you want to be able to avoid that situation in the future.  With disgusting items, there is even more reason to want to remember them. The things we find disgusting are often items that could make us sick.  So, if we encounter them again, we want to know to avoid them.  In this way, memory acts to help keep us safe.