Judging knot strength throws people for a loop: Experiment reveals new blind spot in our physical reasoning

[erronis]

https://phys.org/news/2024-12-strength-people-loop-reveals-physical.html
(Original article in MIT Press Express: https://direct.mit.edu/opmi/article/doi/10.1162/opmi_a_00159/124792/Tangled-Physics-Knots-Strain-Intuitive-Physical)



For something that has been practiced for eons, this is amazing. Maybe it's because we're in the era of velcro, zip ties, and rubber bands.

We tie our shoes, we put on neckties, we wrestle with power cords. Yet despite deep familiarity with knots, most people cannot tell a weak knot from a strong one by looking at them, new Johns Hopkins University research finds.

Researchers showed people pictures of two knots and asked them to point to the strongest one. They couldn't.

They showed people videos of each knot, where the knots spin slowly so they could get a good long look. They still failed.

People couldn't even manage it when researchers showed them each knot next to a diagram of the knots' construction.

"People are terrible at this," said co-author Chaz Firestone, who studies perception. "Humanity has been using knots for thousands of years. They're not that complicated—they're just some string tangled up. Yet you can show people real pictures of knots and ask them for any judgment about how the knot will behave and they have no clue."

The work, newly published in the journal Open Mind, reveals a new blind spot in our physical reasoning.

[MomInTheCrowd]

1. Thx for posting. Super cool

[usonian]

2. I think that's expecting too much from people.

Knot strength is complex ( who understands topology? ) and results are in practice determined empirically, as in "The boat has broken free of the moorings!" or "knot"

https://news.mit.edu/2015/untangling-mechanics-knots-0908

Simple and intiitive? Not really.

The configuration, or “topology,” of a knot determines its stiffness. For example, a granny knot is much easier to undo, as its configuration of twists creates weaker forces within the knot, compared with a reef knot. For centuries, sailors have observed such distinctions, choosing certain knots over others to secure vessels — largely by intuition and tradition.

Now researchers at MIT and Pierre et Marie Curie University in Paris have analyzed the mechanical forces underpinning simple knots, and come up with a theory that describes how a knot’s topology determines its mechanical forces.

The researchers carried out experiments to test how much force is required to tighten knots with an increasing number of twists. They then compared their observations with their theoretical predictions, and found that the theory accurately predicted the force needed to close a knot, given its topology and the diameter and stiffness of the underlying strand.

“This is the first time, to the best of our knowledge, that precision model experiments and theory have been tied together to untangle the influence of topology on the mechanics of knots,” the researchers write in a paper appearing in the journal Physical Review

Can't go wrong with a bowline. Recommended.

[CuriousSavage]

3. Trick question??

Am I blind or are both A&D reef AKA square knots and thus, the stronger knots?
B & C appear to be "granny" knots. After more than a decade of being a Scout leader, I should know by now...

[2naSalit]

4. Are devolving?

Oh NO, it's DEVO!!

[Think. Again.]

5. A and D look like the same knot to me...

...are they knot?

[usonian]

6. A and D are subtly diffrent in that the bitter ends are on the same or opposite sides.

Now, if this isn't obvious (it isn't) that's why there was a scientific study referenced in my post. It's complex. That's why I say that the test was a stretch.

Expecting people to understand the topology of A and B is a bit much. I can't tell you why and I got a bluejacket's manual the hard way and a long stint with fly fishing knots. And a degree in physics for crying out loud.

Oh well. Use a bowline (60 %). whenever it's right, and when I finally master the short cut (50 years out of the service) I'll post it here.

Until then, it's
Over under
Over under
Over under
Pull tight

Or some thing very close to that.