Is your arachnophobia a load of monkey crap?

What’re worse eight-legged freaks or a scaly slimy set of fangs? Well, according to endless researchers it seems the eight-legged freaks, or spiders, are actually not even a real threat to humans or nonhuman primates but rather a fear we’ve constructed. Interestingly enough this challenges the previously believed notions that many neuroscientist and psychologist considered. The focus of this study Kawai & Koda conducted, is to test the innate fear-relevant stimuli of snakes and spiders in humans and nonhuman primates. The study is an expansion of previous studies that explored fear responses but instead of having fear-inducing stimuli with neutral stimuli that were plants or fungi the stimuli is a non-threatening animal.

The test participants were three female Japanese monkeys, aged three (“Pero” and “Ume”) and five years old (“Shiba”). All three of the subjects were born into social groups and raised until the age of three at the Primate Research Institute of Kyoto University in Japan.  The experiment was performed in an operant box with acrylic panel walls. A 15-inch touch-sensitive LCD screen was mounted on one side of the operant box while a food dispenser was placed inside to provide a food reward. 

The actual experiment had two different kinds of visual stimuli. The fir

st experiment contained gray-scale images of nine snakes and nine koalas in naturalistic situations. Whereas, in the second experiment, the images of snakes were replaced by nine images of spiders. Prior to this experiment, the three monkeys already had experience in using the visual search task which was what was utilized and performed during this experiment. The monkeys were required to touch the one deviant picture, the fear-relevant animal, on the touch-sensitive monitor from among eight pictures of a different category, for example, the fear-irrelevant animal to receive a reward. After each monkey reached the target accuracy of 95%, the data was collected for six consecutive days.

The reaction time for detecting deviant pictures of the snakes was less than those for detecting deviant pictures of the koala bears. The deviant pictures mean that the pictures were “hidden” among non-fear related stimuli. Across the two experiments, the reaction times were significantly less for snake–than for spider–for all three monkeys.

The present study clearly demonstrates that macaque monkeys detect deviant pictures of snakes among distracting koala pictures faster than vice versa. Macaque monkeys are predisposed to learn by observation to fear snakes and correlate the increased threat based on their posture because evolutionary they are most likely to stay alive. These studies suggest that monkeys are specifically sensitive to snakes, providing strong support for the Snake Detection theory while also suggesting that spiders are not evolutionarily relevant threat stimuli. The results of this experiment along with the information discovered by LoBue in 2010 shows that human’s fear of spiders is not a stimulus drive processes but rather conceptually driven processes that have been ingrained in us from social learning and could even have only evolved in humans.

Kawai, N., & Koda, H. (2016). Japanese monkeys (Macaca fuscata) quickly detect snakes but not spiders: Evolutionary origins of fear-relevant animals. Journal Of Comparative Psychology, 130(3), 299-303. doi:10.1037/com0000032