According to a new study published in the journal Current Biology fruit flies (drosophila) show emotions similarly to the way humans do. This suggests that other insects such as ants and spiders could be emotional creatures as well. In addition the study indicates that the flies could experience other emotions too.
In an attempt to build blocks of emotions in humans, researchers wanted to find out whether the reflex of flying away which a fruit fly has when it encounter the wave of our hand is triggered by a stimulus which we are not aware of or simply because the fly is afraid. A stimulus could for example be a person which chases the fly with a swatter or a shadow which indicates that danger is near.
The study was conducted by researchers at Caltech. William Gibson, the lead author of the study, together with his team used shadows to observe how flies would react to something which induces fear.
The flies were enclosed in an area where they were repeatedly exposed to an overhead shadow. The buzzing insects looked scared and when they were flying they increased their speed. At times they even froze in one place. This is a defensive behavior also present in rodents’ fear response.
Although mice are closer to humans when it comes to the evolutionary family tree, insects have a simpler neurological system which makes it easier for scientists to study their brain in order to deconstruct emotions.
The researcher wanted to test a set of behaviors known as “emotion primitives”. “Persistence” is such a type of emotion which means that even after an individual is scared the negative feeling lasts. When the fear is powerful enough “context generalization” occurs, another form of primitive emotion which prevents the individual from doing other activities. That’s what the researchers wanted to observe on flies.
The flies were hungry and they were enclosed in a chamber where they also had food. The researchers used an automated fan blade to cast temporary shadows over the flies. Even after the final shadow has passed the flies were still too distracted to eat the food. In addition the more often the shadow appeared the more scared the insects were and the faster they flew away. This proves that flies display a scalable fear response and also the emotion primitives of persistence and context generalization.
Gibson said that this could help researchers discover new molecular players involved in emotion states controlling. This could enable scientists develop improved treatments for people who suffer from depression and nervous disorders.
Image Source: Emory