Guest post by graduate student Kia Walcott
If an animal is lucky enough to escape a predator, that animal will not only avoid the predator but it will have learned to avoid other animals that resemble it in the future. Survivors learn what can eat or hurt them and label them as harmful.
Duke neuroscientists Joseph Dunsmoor and Kevin LaBar and NIH neuroscientist Alex Martin wanted to see if we too can learn to fear and avoid related threats.
The researchers showed 26 healthy volunteers an assortment of images belonging to two categories: tools or animals. Some of the images associated with a particular category came along with an “annoying but not painful” electrical shock. They saw 20 images during four training sessions. The images included typical objects such as a dog or hammer as well as more atypical objects such as an auger (a fancy type of drill) or a leaf insect. The participants saw each image for six seconds, during which time they rated their shock expectancy. Researchers also measured the subjects’ sweat rate, which links to their emotional arousal as a result of fear.
The participants returned 24 hours after the last session for a surprise memory test which included the 80 total images (20 images over four training sessions) as well as 40 new images (20 tools and 20 animals), and were asked to rate whether each image was new or old and their level of confidence. The test was to see if participants were more likely to remember objects belonging to the shock category versus the ‘safe’ category.
By relating an object to a broader category, the participants quickly and effectively determined which group of objects was associated with the shock. A difference in sweat rate was also seen in response to objects in the shock category versus those in the non-shock category. Participants were more likely to remember items from the shock category than items from the non-shock category.
These results suggest that fear can be learned and remembered by categories. In the future, the researchers would like to use brain imaging to see how areas of the brain important for visual object recognition and conceptual knowledge interact with areas important for associating harmful and harmless things. Another important question is how learned fear and memory interact, especially in the case of traumatic experiences.
People who are unable to make connections between known threats and conceptually related things might fail to generalize fear properly, which could prove dangerous. On the other hand, people who make too many connections to a known threat could suffer too, as in posttraumatic stress disorder.
Citation: “Role of conceptual knowledge in learning and retention of conditioned fear,” Joseph Dunsmoor, Alex Martin, Kevin LaBar. Biological Psychology, Nov. 2011. doi: 10.1016/j.biopsycho.2011.11.002