What Is That "Crawling" Sensation?
The shiver down your spine when you see a lotus seedpod. The uneasy feeling in your chest when you look at the dense holes of a shower head. Why do we react this way to clusters?
Evolutionary Psychology: A Leftover Danger-Detection System
The leading hypothesis is that trypophobia is "a byproduct of a danger-detection system our ancestors evolved to survive."
Three danger patterns worth avoiding
- Venomous creatures: poison dart frogs, octopus suckers, toxic mushrooms — organisms that advertise danger with dense patterns
- Signs of infection: skin abnormalities from smallpox, measles, or parasitic disease
- Parasite egg clusters: eggs of botflies and other flies, human botfly larvae
The ability to instantly judge these as "dangerous" and avoid them would have greatly improved our ancestors' survival rate.
The cost of "over-detection"
The catch is that the human danger-detection system evolved in the direction of "better to overreact than to miss a threat." This is known as the Smoke Detector Principle, and as a result we:
- React to lotus seedpods, which pose no real danger
- Stay wary of geometric patterns like honeycombs
- Even feel disgust toward foods (salmon roe, pomegranates)
Neuroscience: Where It Happens in the Brain
A 2017 University of Kent study measured brain activity with fMRI while subjects viewed aggregate images, and found activation in:
- Amygdala: governs fear and aversion
- Insular cortex: processes disgust and visceral sensations
- Visual cortex: pattern recognition
Notably, these responses resemble the pattern of "disgust" (typical of disease-avoidance systems) rather than "fear" (typical of phobias). This supports an evolutionary origin in infection avoidance.
The Visual Characteristics Hypothesis
Aggregate images contain a distinctive spatial frequency profile (high contrast × mid-range frequency) that places a heavy load on the brain's visual processing. This can:
- Produce "visual discomfort"
- Create unease from being unable to fully resolve the pattern
In other words, even purely as "images that tire the eyes," they may contribute to the aversion.