Carrying Coffee is a Complex Task

The simple act of moving a cup of coffee involves a rather complex co-ordination between the brain and hand.

According to researchers, such movements require not just "cer­tain cog­ni­tive abil­i­ties but also dis­tinct motor abilities."

Like if you had to grasp a cup of coffee, your brain needs to tell the hand to hold the cup in a certain way. It then need to determine how much liquid (coffee) is present in the cup and tell the hand to move accordingly. Any miscalculation and you would spill the coffee.

All these calculations of get-the-cup-without-spilling-the-coffee happen in real time and after taking in to account any fluctuations that occur in the environment.

“Because we’re humans and not machines, we’re noisy and vari­able. We can’t expect that a move­ment will unfold exactly as we planned it," CJ Hasson, co-author and post doctoral researcher at Northeastern University said.

For the study, researchers asked 18 volunteers were asked to move a virtual cup filled with virtual liquid across a large display screen, using a robotic hand. The robotic hand simulated the forces that one would feel while holding a cup filled with coffee.

The participants were given 2 seconds to move the cup. All the participants followed a minimum risk pattern while moving the cup. There are plenty of ways that a person can move a cup without spilling the contents in 2 seconds but all participants used almost the same strategy while moving the cup.

How close the participants let the liquid get to the edge of the cup – the safety margin- could predict the variability in their movements. A larger safety margin shows that the person is more variable in movements and is likely to stick with the safest plan.

“If you have a large safety margin and I move with a small margin, the ques­tion is, ‘Why am I more risky than you?’” “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.”

This study may help assessing people with motor disability, researchers say.

“If vari­ability deter­mines the move­ments that you do, maybe that’s an inter­ven­tion point,” said Dagmar Sternad, pro­fessor of biology, electrical and computer engineering and physics at Northeastern University and co-author of the study.