Sunday, 17 May 2015

Sense of presence - another perspective

Sound graphSome people occasionally report feeling a sense of presence. It is a strong feeling that there is a person present nearby but invisible. It can clearly give rise to ghost reports. I've only ever experienced it myself a few times. On two occasions I felt it was triggered by sounds. My best bet, at the time, was that ambient sounds happened to resemble a person moving around, so generating the sense of presence (see here). This could be the explanation but it may be more subtle than that.

I was prompted to consider another explanation by an article in last week's New Scientist about how some blind people click their fingers to echolocate objects around them. They can even use ambient sounds, rather than producing their own, sometimes. I was struck by the description one person gave of being able hear nearby trees. It got me wondering. Could there be sighted people who unconsciously develop this same echolocation ability without even realizing it. They might unintentionally develop the skill through their lifestyle or work. They wouldn't normally notice it because their visual and sonic pictures of their surroundings would generally coincide. But what would happen if they conflicted? Could it produce a sense of presence?

Last year I mentioned an experiment where scientists had induced a sense of presence in the laboratory using conflicting sensory information (see here). A disagreement between someone's unconscious sonic picture of a scene and their conscious visual version might well constitute just such a sensory conflict. The difference might simply arise because the sonic version, produced by ambient sound and echolocation, was not as accurate as the visual version. The sonic version of a scene could, of course, only appear when there was a suitable sound, required for echolocation to work. So the feeling of presence would only appear when an unexpected sound occurred. The sound would not have to resemble anything an actual person might produce.

I have also come across a sense of presence produced by a visual stimulus (see here). It appears to me that a sense of presence can, like an apparition, be generated by any one of several different mechanisms.

Generally, science goes for the simplest explanations. But if strange phenomena had simple explanations they would probably have all been discovered long ago. So, just because the echolocation theory appears complicated, it doesn't necessarily mean it isn't true.

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