Humans Detect Snakes More Accurately than other Animals | Science Research

Scientists from Nagoya University in Japan experimentally confirmed the theory that human cognitive abilities are better equipped for recognizing dangerous animals.

In a noisy image or setting we can more easily distinguish a poisonous snake than a harmless rabbit or butterfly. Their study is published in the journal PLOS One.



Experiment card with 20 images of a snake with varying degrees of random noise.

The design of the experiment was very simple; 20 students aged 18 to 26 watched pictures that depicted fish, birds, cats or snakes. 

All images were processed using the random image structure evolution algorithm (RISE). This algorithm parses the original image through the Fourier transform (FT) and reassembles it with a step-by-step reduction in noise percentage. This technique creates a unique image in terms of content, but uniform in terms of style distortion.

Using this algorithm, the authors made 20 series of 20 images of each type of animal; in each of the serial images of the series, the noise dropped by 5% - from 95% noise to a clear image. 

Each volunteer was shown 4 randomly selected series of images of fish, 4 cats, 4 birds and 4 snakes. As soon as the participant in the experiment found out what was drawn in the picture, he pressed one of the 4 buttons with the symbol of the corresponding animal.

The participants recognized the snake as soon as the noise dropped to 60-70%. 
Cats, birds and fish were detected only after reducing noise below 50%. 

The authors of the study believe that such differences in animal detection are not coincidental but might be an evolutionary trait - a reaction to an evolutionarily fear-relevant stimuli, such as snakes or spiders. 

The possibility that prior experience with snakes may play a role in enhanced human sensitivity to noisy images of snakes, was previously dismissed

In visual detection tasks, young children with relatively little prior exposure to snakes or their representations also identify snakes faster than other animals.

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