The risk of carrying a cup of coffee

June 15, 2012 By Angela Herring, Northeastern University
Professor Dagmar Sternad and postdoctoral researcher C.J. Hasson show that we subconsciously adjust our "safety margin" when we move a dynamic object like a cup of coffee based on the amount of variability in the situation. Credit: John Guillemin

Object manip­u­la­tion or tool use is almost a uniquely human trait, said Dagmar Sternad, director of Northeastern’s Action Lab, a research group inter­ested in move­ment coor­di­na­tion. “Not only does it require cer­tain cog­ni­tive abil­i­ties but also dis­tinct motor abilities.”

Simply moving one’s own body, for instance by directing a hand toward a coffee cup, requires the orga­ni­za­tion of var­ious phys­i­o­log­ical sys­tems including the cen­tral and periph­eral ner­vous sys­tems and the mus­cu­loskeletal system.

Once the hand grasps and picks up the cup, the ques­tions become even more com­pli­cated. What if the cup is filled with liquid? At this point, the com­plexity of the con­trol problem bal­loons — the pres­ence of the liquid intro­duces non­linear fluid dynamics with the risk of a spill because of the inherent vari­ability in one’s movement.

Sternad, a pro­fessor of , biology, elec­trical and com­puter engi­neering and physics and post­doc­toral researcher C.J. Hasson are inter­ested in how we adapt our move­ment strate­gies when inter­acting with dynamic objects in the environment.

In a recent paper pub­lished in the Journal of Neu­ro­phys­i­ology, Hasson and Sternad explored the ques­tion by looking at the everyday task of manip­u­lating a cup of coffee. They show that how we adapt our move­ment strate­gies is directly related to the amount of vari­ability and reli­a­bility in our sur­round­ings and ourselves.

“Because we’re humans and not machines, we’re noisy and vari­able,” said Hasson. “We can’t expect that a move­ment will unfold exactly as we planned it.”

For the study, 18 healthy par­tic­i­pants vis­ited the Action Lab to play a video game, wherein they attempted to move a vir­tual cup filled with vir­tual liquid across a large video screen. Instead of a normal video-​​game con­troller, sub­jects moved the vir­tual cup by grasping a manip­u­landum — a large robotic arm. Sim­ilar to the real-​​life sce­nario, the robot sim­u­lated the forces one would feel from the weight of the object and the sloshing of the liquid in the cup.

They asked par­tic­i­pants to move the cup across the screen within a com­fort­able time of two sec­onds, a task for which there is an infi­nite number of pos­si­bil­i­ties. You could move fast for one second and slow for one second, slow for a half second and then fast for one and a half sec­onds. The team hypoth­e­sized that par­tic­i­pants would nat­u­rally adapt a safe move­ment strategy with prac­tice — and they did.

But the most intriguing result, said Hasson, was that the size of each participant’s safety margin —or how close they let the liquid get to the edge of the cup — could be pre­dicted by how vari­able they were in their move­ments. Those with more vari­ability tended to adapt a “safer” strategy with a larger safety margin.

“If you have a large safety margin and I move with a small margin, the ques­tion is, ‘Why am I more risky than you?’” Hasson said. “Well, you may find that I am much more con­sis­tent in my move­ments, so I don’t need a big safety margin. If you’re more vari­able, you need a larger safety margin.”

The results have impli­ca­tions in assessing elderly patients and patients of motor dis­or­ders such as cere­bral palsy. “If vari­ability deter­mines the move­ments that you do, maybe that’s an inter­ven­tion point,” said Sternad.

Explore further: Coactivator stokes continuing fire of endometriosis

Related Stories

Coactivator stokes continuing fire of endometriosis

June 4, 2012
(Medical Xpress) -- Endometriosis, which can cause severe pain and even infertility in the estimated 8.5 million U.S. women it affects, is driven by one of the cell's master regulators ­ steroid receptor coactivator ...

Teenage pregnancy is not a racial issue

February 7, 2012
While researchers have long set to determine if there is a tie between race and teenage pregnancy, according to a new study, equating black teenagers with the problem of teenage pregnancy is a misrepresentation of today's ...

Recommended for you

Your brain responses to music reveal if you're a musician or not

January 23, 2018
How your brain responds to music listening can reveal whether you have received musical training, according to new Nordic research conducted in Finland (University of Jyväskylä and AMI Center) and Denmark (Aarhus University).

New neuron-like cells allow investigation into synthesis of vital cellular components

January 22, 2018
Neuron-like cells created from a readily available cell line have allowed researchers to investigate how the human brain makes a metabolic building block essential for the survival of all living organisms. A team led by researchers ...

Finding unravels nature of cognitive inflexibility in fragile X syndrome

January 22, 2018
Mice with the genetic defect that causes fragile X syndrome (FXS) learn and remember normally, but show an inability to learn new information that contradicts what they initially learned, shows a new study by a team of neuroscientists. ...

Epilepsy linked to brain volume and thickness differences

January 22, 2018
Epilepsy is associated with thickness and volume differences in the grey matter of several brain regions, according to new research led by UCL and the Keck School of Medicine of USC.

Research reveals atomic-level changes in ALS-linked protein

January 18, 2018
For the first time, researchers have described atom-by-atom changes in a family of proteins linked to amyotrophic lateral sclerosis (ALS), a group of brain disorders known as frontotemporal dementia and degenerative diseases ...

Fragile X finding shows normal neurons that interact poorly

January 18, 2018
Neurons in mice afflicted with the genetic defect that causes Fragile X syndrome (FXS) appear similar to those in healthy mice, but these neurons fail to interact normally, resulting in the long-known cognitive impairments, ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

PPihkala
not rated yet Jun 16, 2012
I recollect another article about driving: The faster one drives, the more inclined we are 'cutting corners', keeping at the middle of the road, to increase the margin to the edge of road. Also older persons have this tendency to drive at the middle, to compensate for their slower reaction times.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.