Learning to un-fear snakes

In February I wrote a post about an encounter with a snake and an explanation for my reaction to said snake. Well, I’ve been thinking about this a lot and I think it warrants more attention. In that previous post I mentioned Seligman’s Preparedness Theory as an explanation for my reaction. The theory goes that humans are prepared or more inclined to fear evolutionary relevant things such as snakes and heights in comparison to modern  dangers such as cars and power outlets. Consequently the part of my brain that is evolved to initiate a reaction to snakes sprang into action as I perceived a harmless tree snake in my peripheral vision and made me jump in the air before I even realised that there was a snake beneath my feet.

Preparedness theory was initially tested to death by Arne Öhman and associates from the University of Uppsala Sweden. There they created a conditioning paradigm in which research subjects were shown pictures of snakes, spiders, flowers and mushrooms, while at the same time given electric shocks for particular pictures. The electric shocks were thus the unconditioned stimuli, or the stimuli that would require no conditioning for people to fear them. The pictures were the conditioned stimuli; the idea being that an electric shock administered with a particular picture would condition the subject to fear that picture. The measure of a person’s fear in this case was skin conductance. If skin conductance was higher then that indicated a fear response. Sweaty palms are a pretty good indicator of fear.

Interestingly the researchers found that where people were given a shock they readily acquired a fear – recorded as an increase in skin conductance – in association with the photograph type with which the shock was associated. So in that sense, preparedness theory was not supported because it predicts a difference between pictures of snakes and spiders as compared to pictures of flowers and mushrooms with regard to how easily people acquire a fear of them. But the theory was not a write off just because of that finding. After conditioning the subjects to fear particular types of photographs, the researchers switched off the electrodes so that the subjects no longer received shocks in association with any types of photographs. They were interested in how quickly the conditioned fear was extinguished when an unconditioned stimulus was no longer associated with the conditioned stimulus.

As for the flower and mushroom photographs, once people no longer received a shock in association with such photos, the subjects’ conditioned fears were quickly extinguished. But surprise surprise, where subjects were conditioned to fear images of snakes and spiders, their fear responses took longer to extinguish. Even though they knew they were no longer going to receive an electric shock in association with a picture of a snake or spider, they still gave a higher skin conductance reading for longer. What’s more the reseachers found this effect not only in cases where pictures of snakes and spiders were compared with pictures of flowers and mushrooms, but where they were compared with pictures of modern fear-relevant dangers such as guns, knives, and power outlets. So Seligman’s theory was not disproven. But this is not the end of the story. In the next installment I’ll describe the visual search test that took the theory further.

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