Some people may be aware that a scene they are looking at has changed without being able to identify what that change is. This could be a newly discovered mode of conscious visual perception, according to the psychologist who discovered it. He has dubbed the phenomenon “mindsight”.
Ronald Rensink, based at the University of British Columbia in Canada, showed 40 people a series of photographic images flickering on a computer screen. Each image was shown for around a quarter of a second and followed by a brief blank grey screen. Sometimes the image would remain the same throughout the trial; in other trials, after a time the initial image would be alternated with a subtly different one.
n trials where the researchers manipulated the image, around a third of the people tested reported feeling that the image had changed before they could identify what the change was. In control trials, the same people were confident that no change had occurred. The response to a change in image and control trials was reliably different.
Our visual system can produce a strong gut feeling that something has changed, Rensink says, even if we cannot visualise that change in our minds and cannot say what was altered or where the alteration occurred.
Here is the full story. The bottom line? Maybe somebody really is following you, and subtly changing small items in your environment.