Peripersonal Space

Peripersonal space (PPS) is defined as a force field that can be thought of as a virtual envelope around the skin’s surface that expands the body’s boundaries.1 It is PPS that provides a margin of error that enables us to consistently avoid walking into people as we pass by. This PPS actually extends to machinery and technology we use and is a factor in reducing collisions between motor vehicles. When we say that a person has become one with her cell phone or iPod, we mean that it has become one with her PPS. In baseball, the bat becomes part of the batter’s PPS (as does the glove when on defense). When we are eating, our PPS extends to our eating utensils.

The PPS of blind people includes the cane such as the space around the tip of the cane is as sensitive to touch as the space surrounding the hand. Neurons that detect both sound and touch also operate such that the blind person reacts as quickly to a sound originating from the tip of the cane as he would if it occurred close to the hand. An experiment by Italian scientists had sighted subjects use these canes to find objects placed on the floor of a darkened room. In this short ten minute experiment the PPSs of the sighted subjects came to resemble the PPS of the blind who regularly use the cane. The sighted subjects became as sensitive to touch and sound events originating at the tip of their canes as to similar events occurring near their hands. Unfortunately, this extended PPS did not last long after the experiment ended.

One of the most effective means of enhancing PPS is through the Chinese exercise, tai chi. Tai chi is an exercise in which slow choreographed movements are performed. These slow motions are performed as the practitioner is simultaneously focusing attention on specific body areas, especially the hands and the fingers. Experienced tai chi practitioners develop a tactile acuity in the fingers similar to that of certain musicians and blind braille readers. Tai chi may create a plasticity in the brain similar to musicians who play keyboard and string instruments, read Braille, or perform other activities that require finely toned fingertip sensitivity. “There is a strong connection between tactile spatial acuity at the fingertips and measures of brain function,”2

It should be noted that the benefits of tai chi extend beyond PPS. There are also benefits to psychological and physical health. You can learn tai chi by purchasing DVD videos, or by visiting a tai chi center in your local area. These can be readily found via Google searches.

1Restak, R. (2009). Think Smart: A Neuroscientist’s Prescription for Improving Your Brain’s Performance. New York: Riverhead Books.

2 Kerr, C.E. et al.(2007). Tactile Acuity in Tai Chi Practioners. Society for Neuroscience, presentation 74.1.

© Douglas Griffith and, 2012. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.


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