Parafoveal Vision - The Unsung and Under-researched Hero
In my fairly uninformed opinion, the first half of the Gordon Research Conference was pretty fixated on finer details of saccade mechanics (unintended but non-retractable pun). The second half has been considerably more interesting to me, as I'm pulling out bits to apply to various applications.
This entry will be about the trend I see, about how the research and discussion seems to be skipping over what I call extrafoveal vision, which to me seems to be the answer to some of the "we don't know why this is happening" responses.
First, a quick anatomy review: the fovea and extrafoveal areas are on the retina, the proverbial "projection screen" that is on the back side of your eye. The pupil contracts or dilates to allow light to fall on this surface, like an aperture on a camera. A contracted pupil will never block light. The fovea contains cones, color detectors, if you will, and these receptors are also best
about detecting the most detail in a given scene. This is about a five-degree radius from your point of central focus. (See the brown fox picture above for an example)
Moving out from the fovea, each region has fewer and fewer cones, until they are dominated by rods, receptors that mostly pick up light and dark. Accordingly, these regions are not so great with detail, but they are great for detecting movement, and this region does best in dark conditions.
If you think of it, this arrangement makes perfect sense. You can't really see objects that are standing stock-still out of the corner of your eye, but you can certainly catch the impression of something that darts around, just out of the corner of your eye. All of this makes a tremendous amount of sense, from an evolutionary perspective, if you want to be sure not to be eaten by tigers, it's best to see them well before they are standing right in front of you.
Most visual research uses some form of eye tracker, which tracks the movement of the fovea, the center ring of the eye, if you will. I don't know if there's a tracker that considers the extrafoveal areas, but to me, it's kind of obvious why certain behaviors were observed in the experiments reported within the conference, specifically:
When scanning human faces, the trend in the initial fixation point (fovea) was just down and to the right of the left eye.
When engaged in visual tracking tasks involving prediction, the eye (fovea) stops short of obediently following a bouncing object around a room.
When scanning a scene for an outstanding object, the eye (fovea) may not actually fixate exactly on the object.
Why is this? Uninformed hypotheses of mine: In the face task, the person is fixating on the most efficient point for collecting data (for later recall). The fixation point also depends upon the task at hand, and so the person is optimizing their initial starting point for detailed data collection accordingly. I asked the researcher about this later and confirmed that this was the case. He hadn't been aware that he skipped over saying parafoveal vision.
When engaged in a pursuit and prediction task, it makes TOTAL sense that the user would stop short of playing total follow the leader as the object moves through its path, because the person wants to utilize the more talented motion detecting cells in their more peripheral vision.
When scanning a scene for an outstanding object, though, this is more interesting, and to me, this lends itself to maybe there is a fuzzier pattern recognition system in our brain than we've given it credit for. Perhaps like paramecium who detect light and dark, perhaps these rod-systems of our eye also have their own light and dark pattern recognition systems?
I'd also postulate there's something else going on, and that is a Gestalt principle. When we have reason to draw our our toward an object, via grouping or a long bar, connecting A to B, like a tree branch, we may be compelled to direct our foveal attention that way, and we will go in so far, much like time/effort budgeting in the pursuit and prediction task, but we won't go all the way. There's no reason to do so, in order to get performance out of ourselves, and if time is of the essence, there's no need for the utmost visual confirmation. So to me, this lends itself to therapy, eye trackers, military applications - or any application in which there is a need for absolutely true, yes, you really saw it with your fovea confirmation. I can think of a few applications for this... maybe you can, too,
Tracking lags
