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.
In 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 (Psychological Science, vol 15, p 27).
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 can't say what was altered or where the alteration occurred. "I think this effect explains a lot of the belief in a sixth sense." He has no idea what physical processes generate mindsight, but says it may be possible to confirm it exists using brain scanners.
Mindsight is not simply a precursor to normal visual perception, he argues, because there seems to be no correlation between how long it takes someone to feel the change, and the time taken to identify what it is. The two sometimes happened almost simultaneously, while at other times the subjects did not report seeing any difference until seconds after they were aware of it.
Vision researcher Dan Simons of the University of Illinois in Urbana-Champaign says Rensink's finding "suggests the
Contact: Claire Bowles