According to Professor Olaf Blanke (a man whose name seems to indicate that he'll soon declare war on the Fantastic Four), "Our experiment induced the sensation of a foreign presence in the laboratory for the first time. It shows that it can arise under normal conditions, simply through conflicting sensory-motor signals. This confirms that it is caused by an altered perception of their own bodies in the brain." Another way to put it is they scared the s**t out of some coeds by hooking stuff up to their bodies until they thought the lab was haunted.
Incredibly, the point of all this was not to come up with a fun and exciting new way to induce a heart attack. Rather, it was to identify the parts of the brain that cause us to see spirits and provide a rational explanation for many claims of the supernatural on record. So the next time someone runs out of their house shrieking about poltergeists, you can calm them down by saying, "Actually, it was science! The ghosts are in your skull."