The other day, while trawling the web, I came across an article from the online COSMOS magazine dated 25 September 2006 titled "Scientists discover 'shadow person.'
The story reported on a 22 year old female, under evaluation for epilepsy. When her left temoroparietal junction of her brain was electrically stimulated she told of seeing a 'shadow person' which mimicked her own bodily movements.
She had a sense that there was another person present, which she described as young, of indeterminate gender, who did not speak or move.
The researchers involved, including one Olaf Blanke from University Hospital, Geneva, Switzerland, believed that the woman was experiencing a perception of her own body.
"The temporoparietal junction is known to be involved in creating the concept of 'self' and the distinction between 'self' and 'other.'
I recall reading of similar observations from abductees, where they would report feeling an invisible 'sense of the presence of someone or something else' watching them.
The research reported in the COSMOS article may be the start of an understanding that there may not be a 'real' alien presence there. It might well be the creation of a "Shadow person' within the mind of the abductee.