Unless evolutionary biology decides to get a little freaky, we’re unlikely to literally have “eyes in the back of our heads” anytime soon – but a new study has hinted that we can, in a manner of speaking, perceive the visual world behind us.
The research, published in Scientific Reports, doesn’t claim that we can in any way directly see in real time what’s happening outside of our field of vision. Rather, it makes a distinction between visual field and visual processing, in that the latter helps us to unconsciously “learn” about our surroundings in order to build up a 360° picture of what’s happening around us at all times.
“In other words, our brain constructs a 360-degree world even though visually we are usually only aware of the area in front of us,” Tohoku University explains in an accompanying press release.
Prior research has indicated that using visual (and non-visual, eg sound) information, our brains have the ability to construct a 3D reconstruction of our surroundings even when we can’t see much of them. Sometimes we recall how areas looked from certain viewpoints; at other occasions, we use rapid eye movements known as saccades, where our point of view changes very rapidly in order to build up an integrated picture of the environment.
As the team note early on, this ability to predict or otherwise visualize what’s going on around us is incredibly important.
In a cramped environment, this ability stops us knocking things over and moving more smoothly. Anyone who has ever played a first-person shooter videogame, or has been paintballing, will know that visualizing what your opponent may be doing behind you is vital for your survival.
What the team wanted to know was just how precise our visual processing capabilities are – crucially, those that don’t involve any conscious effort.
In order to find this out, a series of six screens surrounded a volunteer. Letters appeared on these screens all at the same time, with one of them being the “target” the volunteer had to identify.
Over time, as letters appeared on various screens, it appeared that the volunteer was able to locate the target object more quickly and successfully, even if it appeared behind them, outside of their visual field.
Variations of this experiment – involving repeated and randomized letter appearance patterns, and more – seemed to demonstrate that this effect appears to be real, not one born of chance or individual ability, and not one based on the conscious recognition of any repeated pattern learning. It’s entirely implicit and automated within our noggins.
This describes what is known as a contextual cueing effect, which describes how repeated exposure to a (visual) environment seems to quickly improve our ability to search for things in it.
The team’s paper – apparently the first to specifically and directly investigate this phenomenon – adds more evidence to this concept, which has been colloquially attached to the “eyes in the back of your head” idea. As ever, though, plenty more work needs to be done before the concept can be more concretely validated.
It’s also unclear as to what part of the brain is responsible for this apparent ability, although the team point fingers at the medial temporal lobe, something normally linked to explicit (conscious thought) memory, but one that may play a more implicit role too.