Health In Focus


  • Fear and disgust for snakes and spiders are evolutionary and innate in humans.
  • Babies as young as six months old feel stressed when they see these creatures
  • The fear may be associated with the co-existence of human ancestors and these groups of animals which could be potentially dangerous.

For a long time, research has been trying to identify if the instinctive fear humans have for spiders and snakes is innate or learnt through life. A new study by Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) in Leipzig and the Uppsala University has discovered that it is innate and hereditary.

The Fear

Even in developed countries, where humans do not come in contact with spiders or snakes, are frightened by these creatures that they have hardly seen. While the debate has continued over the years to determine if this fear is acquired or is it in-born. A new study by research teams at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) in Leipzig and the Uppsala University have shown that the response of fear and aversion is in-born and hereditary.
Fear of Spiders and Snakes Evolutionary, Shows Study

In some people, the fear is so profound that they develop into anxiety and phobias. Such people find it difficult enter a room with a spider and cannot go out into the wild due to the fear that they may encounter a snake.

Overview of the Study

Most previous studies on this topic were conducted with adults or older children, which made it hard to distinguish between learnt and in-born fear. Also, these studies only tested whether children were able to spot spiders and snakes faster compared to other harmless animals. The studies did not necessarily focus on establishing a direct physiological fear reaction.

The new study has adopted a research design that overcomes the limitations of previous studies by testing the fear response in children as young as six months. The findings of the study are crucial in understanding the origin of this fear. Even in infants a stress reaction was evoked when they saw a spider or a snake. Moreover, this was at the age of six months, where they are still very immobile and have had little or no opportunity to learn that these animals can be dangerous.

When the babies saw a snake or a spider, instead of a flower or a fish of the same size and color, their pupils enlarged significantly. This change in the size of the pupils is an indication that the noradrenergic system in the brain is activated, a region responsible for stress reactions. This indicates that the babies felt stressed looking at these animals.

Interestingly, other studies have shown that babies do not associate pictures of rhinos, bears or other theoretically dangerous animals with fear.

The Evolutionary Link

While the study has proved that the fear of spiders and snakes is hereditary and something that humans are born with, even before the exposure to such creatures, the reason for this is unclear.

The study suggests that this may in fact be a protective evolutionary measure embedded into our genes due to the co-existence of these potentially dangerous animals with humans and their ancestors for more than 40 to 60 million years.

This may the reason why pictures of animals we consider dangerous today, like a lion or a rhino do not invoke a fear response in babies. These animals haven't been in co-existence with human ancestors and are relatively new in terms of evolutionary distance compared to snakes and spiders.

Source: Medindia

Most Popular on Medindia

More News on: