Brain represents tools as temporary body parts, study confirms

June 22, 2009 |

Researchers have what they say is the first direct proof of a very old idea: that when we use a tool — even for just a few minutes — it changes the way our brain represents the size of our body. In other words, the tool becomes a part of what is known in psychology as our body schema, according to a report published in the June 23rd issue of Current Biology, a Cell Press publication.

“Since the origin of the concept of body schema, the idea of its functional plasticity has always been taken for granted, even if no direct evidence has been provided until now,” said Alessandro Farnè of INSERM and the Université Claude Bernard Lyon. “Our series of experiments provides the first, definitive demonstration that this century-old intuition is true.”

In the new study, Farnè, Lucilla Cardinali, and their colleagues reasoned that if one incorporates a used tool into the body schema, his or her subsequent bodily movements should differ when compared to those performed before the tool was used.

Indeed, that is exactly what they saw. After using a mechanical grabber that extended their reach, people behaved as though their arm really was longer, they found. What’s more, study participants perceived touches delivered on the elbow and middle fingertip of their arm as if they were farther apart after their use of the grabbing tool.

People still went on using their arm successfully following after tool use, but they managed tasks differently. That is, they grasped or pointed to object correctly, but they did not move their hand as quickly and overall took longer to complete the tasks.

It’s a phenomenon each of us unconsciously experiences every day, the researchers said. The reason you were able to brush your teeth this morning without necessarily looking at your mouth or arm is because your toothbrush was integrated into your brain’s representation of your arm.

The findings help to explain how it is that humans use tools so well.

“We believe this ability of our body representation to functionally adapt to incorporate tools is the fundamental basis of skillful tool use,” Cardinali said. “Once the tool is incorporated in the body schema, it can be maneuvered and controlled as if it were a body part itself.”


The authors include Lucilla Cardinali, INSERM, UMR-S 864, Bron, France, Université Claude Bernard Lyon, Lyon, France, Hospices Civils de Lyon, Hôpital Neurologique, Lyon, France, Francesca Frassinetti, Università di Bologna, Bologna, Italy; Claudio Brozzoli, INSERM, UMR-S 864, Bron, France, Université Claude Bernard Lyon, Lyon, France, Hospices Civils de Lyon, Hôpital Neurologique, Lyon, France, Christian Urquizar, INSERM, UMR-S 864, Bron, France, Université Claude Bernard Lyon, Lyon, France, Hospices Civils de Lyon, Hôpital Neurologique, Lyon, France, Alice C. Roy, Université Claude Bernard Lyon, Lyon, France, CNRS, Institut des Sciences Cognitives, L2C2, UMR 5230, Bron, France; Alessandro Farnè, INSERM, UMR-S 864, Bron, France, Université Claude Bernard Lyon, Lyon, France, Hospices Civils de Lyon, Hôpital Neurologique, Lyon, France.


8 Responses to Brain represents tools as temporary body parts, study confirms

  1. Anonymous June 23, 2009 at 1:44 pm #

    Video games — even abstract ones, but ones with a recognizable physical model — do neat things to my body schema.

  2. Anonymous June 23, 2009 at 8:35 am #

    It would be interesting to see the results of a similar study done on archers. When the archer “becomes one with the bow” it really is as if he can simply reach out and touch the target. BTDT. After a time with the bow, not having it leaves a distinct emptyness.

    As a blacksmithing teacher, I spend my time trying to get students to ‘speak’ the language of blacksmithing through the hammer. This article has made explicit that one of the things they need to do is assimilate the hammer into their body image. Thankyou.

    – Carl West

  3. Anonymous June 22, 2009 at 9:46 pm #

    The article does a lackluster job of explaining this, but the body schema is very different. Body schema is not about making adaptations to an environment, such as the experience of “sea legs.” The body schema is essentially the concept of the body, and what it encompasses. Essentially, it defines “where and what is my body?” The answer to these questions — and therefore, defining a body schema — is not as straightforward as it seems. That debate can happen elsewhere. However, one part of the answer to the “where is my body” question is partially answered by proprioception, which is arguably part of the body schema. Proprioception is the mostly unconscious awareness of where your body is in space. It is what allows you to walk without looking at your legs, or touch your nose with your eyes closed. This leads to the point the study attempts to make.

    The important part of the study, here, is that proprioceptive drift is experienced after people use tools. Again, the article doesn’t explain this very clearly, but the point is that after a person has used tools, the locations or points at which the person’s body ends and the tool begins become blurred and the tool becomes “a part of the body”. As a result, after using the tool, even when it is not present, a person’s proprioception, or “awareness of the body’s physical location in space” will be slightly “off”, as it had come to include the tool. This is not muscle memory, etc., or experiencing “sea legs”, which are adaptations to an environment. This is, instead, the incorporation of a specific, and foreign, object into the body’s proprioception. However, whether or not this constitutes actually becoming a “temporary body part” is debatable, I think.

  4. Anonymous June 22, 2009 at 7:41 pm #

    … needs editing.

  5. Anonymous June 22, 2009 at 11:09 am #


  6. Anonymous June 22, 2009 at 7:11 pm #

    How is body schema different from the neuromuscular training and previsualization that elite athletes have been doing for decades? Is the Cardinali study regressive and the athlete training programme progressive? Without being able to read the study… it does NOT look like any new ground was plowed here – of course, anybody who has had ‘sea legs’ would have said the same thing.

  7. Anonymous June 22, 2009 at 6:34 pm #

    Tools are cool dude!


  8. Anonymous June 22, 2009 at 6:07 pm #

    Staring at a rectangle 95% of your waking hours (citation: TheOnion), we often forget that we have other body parts than eyes, brain, and perhaps hands. That’s one reason people forget to take decent care of their body.

Leave a Reply

* Copy This Password *

* Type Or Paste Password Here *