Carnegie Mellon University
June 24, 2020

The Rabbit Goes Around the Tree

New research at CMU maps how the brain represents a particular sequence of actions when tying a knot

By Stacy Kish

Sitting on my grandmother’s stoop, I distinctly remember my aunt lovingly teaching me to tie my shoes. Others had tried and given up on me, but my aunt persisted. Even today, every time I bend down to tie my shoe laces, I think of her.

Robert Mason and Marcel Just’s new research at Carnegie Mellon University has found that the very steps intoned by my aunt are ingrained not only in my loving memory, but also in a unique pattern that fires in my brain every time I bring the laces together.

Just, the D.O. Hebb University Professor of Psychology, and Mason, a senior research associate, have decoded the step-by-step processing that takes place in the brain when various knots are tied.  Their work was published online in the May issue of the journal Psychological Science.

“Tying a knot is an ancient and frequently performed human action that is the epitome of everyday procedural knowledge,” said Just, senior author on the paper. “Understanding how the brain learns and represents procedural tasks is an important part of the science of learning.” 

The researchers recruited seven subjects and taught them to tie seven distinct knots. Each participant was scanned in an fMRI machine while they imagined tying a knot or physically performed the task. Just and Mason developed a machine learning algorithm to process the fMRI images to identify the association between each knot and their respective neural signatures.

The researchers found that each knot produced a distinctive set of neural signatures that produced a unique pattern during the tying process. Each participant produced a similar pattern for each unique knot. In addition, each neural signature was so distinct that the researchers could identify the knot the participant was thinking when reviewing the scans.

“Once we identified the neural representations of the procedures of how to tie each specific knot, we were able to predict which knot they were about to tie before they started tying it,” said Mason. “That was possible because we have a plan for tying each knot, a plan that becomes activated just before the actual procedure is executed.”

This work differentiates from past studies because it focuses on the ‘knowing’ component of a task. The researchers honed in on the particular sequence of actions captured as neural snapshots in the fMRI scans that illustrate the pattern of ‘knowing’ that fire in the brain, even when the act of tying a knot is imagined.     

According to Just, the ability to identify the neural representation of a procedure may be useful in developing instructional techniques that teach procedures with high efficiency and in developing brain–computer interfaces that translate a mental procedure into a robotic performance.

The researchers’ paper is titled, “Neural Representations of Procedural Knowledge.” The Office of Naval Research sponsored the research.