We lace up our shoes, wear neckties, and untangle power cords. However, despite being very familiar with knots, a recent study from Johns Hopkins University reveals that most people struggle to distinguish between weak and strong knots just by looking at them.
In their research, scientists presented individuals with images of two knots and asked them to identify the stronger one. They were unable to do so.
They then showed videos of each knot, spinning slowly for better observation, yet the participants still could not succeed.
Even when researchers displayed each knot alongside a diagram illustrating how each was tied, people still couldn’t make a correct judgement.
“People are really not good at this,” stated Chaz Firestone, co-author and perception researcher. “Humans have been using knots for thousands of years. They’re not overly complex; it’s just string twisted around itself. Yet, when you show people actual photos of knots and ask them to evaluate their performance, they struggle to make any predictions.”
This study, published in the cognitive science journal Open Mind, uncovers a surprising gap in our understanding of physical reasoning.
The idea for the experiment came from Sholei Croom, a PhD student in Firestone’s lab who enjoys embroidery. While working on a project, she examined a complicated mess of embroidery thread and found herself confused – despite it being her own handiwork. As someone who studies intuitive physics, which is how people perceive their surroundings just by observing, Croom suspected that knots might be a unique challenge.
“People regularly make predictions regarding physical interactions, yet knots seemed to challenge my intuition,” Croom noted. “You can tell how stable a stack of books is without touching it. You can guess how many bowling pins a ball will knock over without lifting it. However, knots seem to disrupt our judgment in unexpected ways.”
The experiment was straightforward: Researchers showed participants four knots that were physically alike but varied in strength. Participants looked at the knots, two at a time, and were asked to identify the strongest one.
Consistently, participants made incorrect choices. When they did correctly identify a sturdy knot, they often based their decision on unrelated features.
The knots included the reef knot, one of the strongest known, and the grief knot, which is so weak that it can come undone with a light tug. Even when shown side by side, participants struggled to select the strong one.
“We tried to give people the best opportunity in the experiment by including videos of the knots in motion, but it didn’t help at all. In fact, participants’ responses were even more erratic,” Croom explained. “The human psychological approach fails to derive any meaningful physical insights from how the knot looks.”
According to Croom, softer materials like string may be more challenging for people to analyze compared to rigid objects. Even with vast experience in tying laces and unwinding cords, most people cannot overcome this challenge. However, Croom suggests that professionals like sailors or survival experts who depend on knot strength might perform better than the non-specialists in the study.
“We simply cannot discern a knot’s internal structure from visual inspection,” Croom concluded. “This serves as an intriguing example of the many unanswered questions we have about our ability to understand our environment.”
