Science » Technologies and discoveries

Shadows as body's extensions

A human brain views our own shadows as the body's natural physical extension.

According to the latest research conducted by English, Italian and German neurobiologists, human shadows are instinctively viewed as extensions of peoples’ own bodies.

Volunteers Francesco Pavani from London’s University Royal Holloway along with Umberto Castiello from Italian University Trento (Universita degli Studi di Trento) were reacting to their hand shadow “stimulation” as though nothing was happening to the actual hand.

The results simply proved a commonly known phenomenon. Intuitively, people always tend to feel commonness with their shadows. This used to be the basis for various superstitions, rituals as well as religious views. A human shadow was also a quite popular literary topic.   
 
 
“Similar to children, we sometimes become scared for our own shadow. We want to protect it from being stepped on by someone,” states Margaret Livingstone from Harvard’s Medical School, MA. “I have a post-graduate student who is still sensitive towards such ‘incidents’”. 
There have been several known experiments with people trying to establish mental connection with a nonexistent “third” hand. Scientists for instance, stroke a person’s hand while he was presented with a fake. Whereas such reaction with a fake hand can be understood, scientists are still rather perplexed at what causes a strange connection with people’s own shadows.  


Pavani and Castiello placed simulators on participants’ thumbs and index fingers. Each one of the ten volunteers was later asked to react to a slight touch to either one of the fingers by means of special controls attached to their feet.
Previously conducted research has indicated that in case a person is being touched, his reaction speeds up in case of a simultaneous flash on the side. This happens because a human organism interprets both of the signals simultaneously. The same experiment was conducted with flash sparking right in front of hands. As a result, the volunteers reacted 72 milliseconds later (a bit slower than during the initial experiment). However, there appeared no significant differences between the experiments. Therefore, it allows researchers to hypothesize that a human brain identifies a body’s shadow as its natural extension rather than a mere outline.


What this means is that a person’s brain uses visual hints received not only from limbs but also from its own shadow.
“A shadow is capable of providing additional information about body’s location with respect to surrounding objects,” state the researchers in the Nature Neuroscience.

Source: 

Shadows are hardwired into the brain - New Scientist
"Shadows implanted in Brains"– translated material at InoPressa.ru