- [Narrator] Welcome to the information elevator.
This is Holly Frey from the History Stuff podcast.
Right now, her head is full of computations
for the next sewing project she'll be working on,
as well as stray bits of thoughts on the Tsavo lions.
Thoughts that one day could lead to unified theory
of man eating behavior in mammals.
She knows that she's in this metal box
hurtling through space and time.
But how does she really know?
If she were to close her eyes and touch her nose,
she would be using a kind of sense.
Something called proprioception.
The ability to orient yourself to your environment.
Clues from receptors located in
the skin, muscles, and joints
build the internal sense of Holly's body.
All culminating with the sense of effort
that it takes to, say,
cross her hands protectively around her body.
But is proprioception reliable?
Consider diabolical researchers at the Karolinska Institute
who created an experiment where subjects
had a realistic looking rubber arm
placed right next to their arm.
Both arms were stroked with a paintbrush,
creating the illusion that the subject had a third arm.
Then, the researchers produced a knife
and made threatening gestures toward the fake arm.
Participants not only flinched
as though the arm belonged to them,
but the sensors they wore
measuring their galvanic skin response
indicated an uptick in sweat production.
One of the split second hallmarks of fear.
This extension of the borders of ourselves
to something outside of ourselves
is called proprioceptive drift.
And, if Holly were a jet fighter,
she might experience an extreme example of this
in the form of an out-of-body experience or astral trip,
which has been reported during
gravity-induced loss of consciousness.
This is when some pilots claim
to have been outside of their bodies.
In these instances, the pilots' minds
are so disassociated from their bodies
that they can't map themselves in space and time.
And, in this absence, a story of the body
is created by the mind.
Astral trips have been reported in several other scenarios.
Near-death experiences, sensory deprivation,
trauma to the brain,
and transcranial magnetic stimulation of the brain.
There's even the idea that some people
may be more susceptible to
out-of-body experiences than others.
You are here, Holly.
You are here with me.