Snakes and spiders evoke fear in many people and now we know why – it’s hereditary. But when does it turn into a phobia?
There are few people who would not shiver at the thought of a spider crawling up their arm, however harmless it may be.
Presumably, in industrialised countries, most people have never come across a poisonous spider or snake in the wild, as humans usually destroy them and their habitats. Nevertheless, one to five per cent of the population are affected by a real phobia of these creatures.
Until now, it was not clear where this widespread aversion or anxiety stems from – whether it’s leant or innate.
Scientists recently made a crucial observation: Even six-month-old babies show a stress reaction when they see a spider or a snake.
Even six-month-old babies show a stress reaction when they see a spider or a snake
“When we showed pictures of a snake or a spider to the babies, instead of a flower or a fish of the same size and colour, they reacted with significantly bigger pupils,” says Stefanie Hoehl, lead investigator of the underlying study and neuroscientist at Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) and the University of Vienna.
“In constant light conditions this change in size of the pupils is an important signal for the activation of the noradrenergic system in the brain, which is responsible for stress reactions. Accordingly, even the youngest babies seem to be stressed by these groups of animals.”
When does it turn into a phobia?
“We conclude that fear of snakes and spiders is of evolutionary origin. Similar to primates, mechanisms in our brains enable us to identify objects as ‘spider’ or ‘snake’ and to react to them very fast. This obviously inherited stress reaction in turn predisposes us to learn [to perceive] these animals as dangerous or disgusting. When this accompanies further factors it can develop into a real fear or even phobia,” says Hoehl.
“A strong panicky aversion exhibited by the parents or a genetic predisposition for a hyperactive amygdala, which is important for estimating hazards, can mean that increased attention towards these creatures becomes an anxiety disorder.”