See this picture on the left? Try staring at the red circle for a moment, while paying attention to the gray ring. After a few seconds, doesn't it seem to that the circle fades away and you're left with just a red dot on a white background?You can thank Ignal Paul Vital Troxler for figuring that out: according to this Swiss philosopher, we now that that deliberately focusing on a fixed object causes other surround stationary objects to fade away.
Once you move your eyes, the gray circle should be visible again.
So what is actually going on here?
According to scientists, our eyes are always in motion and there's one type of motion we control, called saccades, such as when we deliberately scan a room, and one type we don't, microsaccades, which are just as crucial.
To understand why these microsaccades are so important in our visual perception, its also important to understand the concept of neural adaptation. Much like our nervous system adapts to the constant, unchanging stimulus of us wearing a watch or glasses, for example, the visual neurons would too adapt to constantly unchanging (static) visual stimulus. The article uses the example of a frog that cannot see a fly sitting on a wall but can see it as soon as the fly starts flying around. Our visual neurons aren't comparable to Kermit's but we also use these tiny subconscious movements, these microsaccades, to keep our visual neurons from "falling asleep" and causing stationary objects to drift away.
Research on micro-saccades is pretty niche but it isn't new — the article cites studies from the 1950's, one in particular where scientists created and fit a tiny projector over the eye in order for the visual scene to move with these micro-movements. They basically stabilised the retina, rendering the microsaccade motion useless. (If anyone reading this is a photography buff, you can think of microsaccades as the inverse of the Image Stabilizer found in some of the pricier lenses. What it does is much like what your eye does: it creates internal micro-movements within the lens to prevent image blur when shooting pictures while holding your camera, helping to combat the natural shaking of an unsteady photographer. But, if you inadvertently leave it on while shooting with a tripod, the stabilizer actually causes the blur. Our eyes want to do the opposite, they want to keep the image shaking.)
More modern research uses computer eye-tracking devices linked to a projector that moves the image you're looking at with the movement of your eyes; no more wearing scary suction cups over your eyes to participate in this type of study.
The article goes on to discuss the potential neuronal responses the micro-saccades are responsible for generating in the brain. (research with monkeys showed activation in the lateral geniculate nucleus and the primary visual cortex)
What I found particularly interesting about these micro-saccades is that researchers found that they may be useful in determining what it is we are actually paying attention in our visual field, even inadvertently. Research done at McGill University found that the direction of microsaccades was often biased in the direction where subjects were actually paying attention. Another, different, study showed that the frequency of the microsaccades affected visibility: the larger they were, the better the visibility. Or, as the article put it:
"microsaccade frequency can betray your attentional spotlight."This article seemed pretty spot on in discussing the purpose of microsaccades and sites of possible neuronal activation, but as a point of criticism, with the advent of "neuromarketing", I think its only a matter of time before labs that use EEG and eye movement tracking (usually of saccades, the bigger, intentional movements we make) will also claim to be able to track our microsaccades to tell their clients "what we're really thinking" without factouring into account that microsaccade activity correlates with other brain activity in an EEG reading (gamma band activity, to be specific).
http://www.scientificamerican.com/article.cfm?id=shifting-focus
