Science & Technology

Researchers discover fear of snakes and spiders is hereditary

A study conducted by scientists at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany and the Uppsala University in Sweden revealed that a fear of spiders and snakes is passed down hereditarily.

While there have been studies conducted about these fears in the past, this research looked primarily at adults and older children. This made it difficult for previous experimenters to pinpoint whether the aversion to snakes and spiders was linked to genetics, the environment or learned behavior. Additionally, previous studies only aimed to find whether people detected the image of a snake or spider faster than they detected other objects, which could be attributed to other factors that are not related to a psychologically fearful or stressful response.

To rectify the mistakes of past studies, the new one was aimed specifically at infants as young as six months old, and looked at the dilation of their pupils, which has been connected to the neuroadrenal stress response. The use of infants this small for the study allowed for the elimination of the idea that the response is solely based on learned behavior, as infants cannot be made to comprehend the cultural aversion to snakes and spiders.

The study conducted was done in two parts. The first part had infants look at pictures of spiders and flowers, the spider-flower experiment, and pictures of snakes and fish, the snake-fish experiment. In these two experiments, the two things being compared were of the same size and color. This limits the idea that the colors of spiders or snakes are what causes the stress response. It was found that the pupils of the infants dilated more in response to seeing a spider or snake than a flower or fish of the same size and color. In prior studies, the dilation of pupils had been connected to stress levels.

The second part of the study included pupillometric data, the data gathered by measuring the dilation of pupils, from two groups. One group solely viewed pictures of snakes while the other group solely viewed pictures of flowers. The same kind of results were seen in response to this part of the study as well, with pupils dilating significantly more in the infants who witnessed snakes than in those who witnessed flowers.

The scientists behind this study suggest that, due to the increased agitation of the infants that witnessed spiders and snakes as determined by pupillometric data, these specific stimuli represent an ancestral threat to humans that has been passed down through genes. The question then arises as to why other dangerous animals, such as rhinos or elephants, do not induce the same stress.

The scientists claim that the reason behind this is that spiders and snakes have coexisted with humans for 40 billion to 60 billion years. Thus, these animals specifically had more of an impact on the innate aversions of humans than mammals or other more evolutionarily recent creatures may have.

This information is not surprising to Baruch College students. When Masha Fomitchova, a freshman and prospective marketing major, was posed with the question of whether she was surprised by this data, she recalled reading a study that showed that “humans are genetically predisposed to easily spot snakes and spiders, even in low-contrast, so we have an evolutionary predisposition to a fear of these things, which just needs to be over-triggered to turn into a phobia.”

She also mentioned that “a lot of learning is based on association and identification so (…) if a child observes his parents reacting really fearfully toward spiders and snakes, they’ll identify them as a threat and associate them with a really severe fear response.”

The same question was also asked to Baruch College freshman Nia Laureano, who intends to major in computer information systems. She was unfazed by the idea that arachnophobia and ophidiophobia might be genetic.

“Thinking in terms of survival,”  Nia says, “it makes perfect sense that humans have evolved to be terrified of spiders; they were a much greater threat to us back thousands of years ago than they are today. It’s a very human thing to be afraid of spiders — I don’t know anyone who isn’t. (…) Considering spiders have been an ever-present throughout the history of mankind, I wouldn’t doubt we have the inherited tendency to recoil and panic at their presence.”

The researchers offered proof that infants at six months of age react with increased arousal to spiders and snakes compared with their reactions to flowers and fish. The study’s results revealed the existence of a developed mechanism that prepares humans to obtain phobias of ancestral dangers.

November 13, 2017

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