Curious publicity

Our conscious image of what we are seeing usually appears complete; it is the whole visual field. This is an illusion. The image is built up from many narrower views of parts of the scene that we attend to in rapid succession. Our visual system also establishes a knowledge of the general balance of the whole scene, such as what are the dominant colours of the scene and this seems to help produce the illusion that we see all simultaneously. Ordinarily we notice changes and they attract our attention. However there is ‘change blindness’. A change can occur during a blink, an eye movement, an abrupt blanking of vision. The actual moment of change is missed and the change will not be noticed unless the part that has changed was being attended to at the time. The study of change blindness has given rise to the ‘coherence theory’ that predicts that “whenever a change is detected the observer will always know what has changed since the observer will necessarily have a representation of the corresponding portion of the original image.” Howe and Webb in a recent paper (citation below) set out to test this prediction. “…there are good reasons to believe that observers should be able to detect changes by monitoring the statistics of the scene, but that monitoring the scene statistics may not provide enough information to identify which object in the scene was changed. However, the behavioural evidence that this actually happens in practice with natural scenes is mixed.” Their experiments appear to confirm change detection without the identification of the change and that the detection is probably mediated by reaction of changes to the statistics of the overall scene. It is nicely done but not very surprising.



However, for some reason this paper was billed as “Debunking the sixth sense - New research has helped debunk the common belief that a sixth sense, also known as extrasensory perception, exists.” by ScienceDaily (here). Even though there is no mention of ESP in the actual paper. ScienceDaily quotes Howe, “There is a common belief that observers can experience changes directly with their mind, without needing to rely on the traditional physical senses such as vision, hearing, taste, smell and touch to identify it. This alleged ability is sometimes referred to as a sixth sense or ESP. We were able to show that while observers could reliably sense changes that they could not visually identify, this ability was not due to extrasensory perception or a sixth sense.



Who are these people who are interested in neuroscience but still believe in ESP? It’s a curious treatment of some experiments that were not published with this slant!



Here is the article’s abstract: “Does becoming aware of a change to a purely visual stimulus necessarily cause the observer to be able to identify or localise the change or can change detection occur in the absence of identification or localisation? Several theories of visual awareness stress that we are aware of more than just the few objects to which we attend. In particular, it is clear that to some extent we are also aware of the global properties of the scene, such as the mean luminance or the distribution of spatial frequencies. It follows that we may be able to detect a change to a visual scene by detecting a change to one or more of these global properties. However, detecting a change to global property may not supply us with enough information to accurately identify or localise which object in the scene has been changed. Thus, it may be possible to reliably detect the occurrence of changes without being able to identify or localise what has changed. Previous attempts to show that this can occur with natural images have produced mixed results. Here we use a novel analysis technique to provide additional evidence that changes can be detected in natural images without also being identified or localised. It is likely that this occurs by the observers monitoring the global properties of the scene.”

Howe, P., & Webb, M. (2014). Detecting Unidentified Changes PLoS ONE, 9 (1) DOI: 10.1371/journal.pone.0084490

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