When the babies saw a snake or a spider (second row) instead of a flower or a fish (first row) of the same size and colour, their pupils enlarged significantly (red versus green curve). And this already at the age of six months, when they are still very immobile and have had little opportunity to learn that these animals can be dangerous. Scientists at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) in Leipzig and the Uppsala University, Sweden, recently made a crucial observation: Even in infants a stress reaction is evoked when they see a spider or a snake. Such studies with children only tested whether they spot spiders and snakes faster than harmless animals or objects, not whether they show a direct physiological fear reaction. The drawback of most previous studies on this topic was that they were conducted with adults or older children-making it hard to distinguish which behaviour was learnt and which was inborn. While some scientists assume that we learn this fear from our surroundings when we are a child, others suppose that it is innate. Until now, it was not clear where this widespread aversion or anxiety stems from. In developed countries one to five per cent of the population are affected by a real phobia of these creatures. Such people are always on edge and cannot enter a room before it is declared “spider free” or cannot venture out into nature for sheer fear that they may encounter a snake. This fear can even develop into anxiety which limits a person’s daily life. Nevertheless, there are few people that would not shiver at the thought of a spider crawling up their arm, however harmless it may be.
Likewise for snakes there are just two species that are indeed poisonous but they are so rare that you hardly ever encounter them. Here in this country there are no spiders that pose a threat to humans. Presumably, in Germany most people have never come across a poisonous spider or snake in the wild. This fear of spiders is of evolutionary origin. There are few people that would not shiver at the thought of a spider crawling up their arm, however harmless it may be.
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