Asked by: Lisa Price, Tewkesbury
Both. Overall rates of arachnophobia are around 5 per cent (although a milder fear of spiders is reported in up to a third of the population), with more women than men fearing them, even in countries that have no poisonous spiders. Arachnophobes may scream or have panic attacks on seeing a spider, and judge spiders as bigger and closer than they are, so increasing their fear.
There are good reasons why arachnophobia might be inherited. We evolved over millions of years in Africa where many spiders are poisonous and avoiding them could be useful but this does not prove the case, and excessive fear might even be counter-productive. Children tend to fear spiders if their parents do but this need not be genetic. Like many mammals, we learn preferences and fears from our parents at a young age. Watching a parent react with terror to a spider in the bath could instil fear in the child. So this makes it hard to know how much is learnt or inherited.