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YOUR DAILY DOSE OF SCIENCE 17

OUR BRAIN SHOWS US 15 SECONDS

‘IN THE PAST’ TO SEE A STABLE WORLD

Our eyes gather millions of visual
information to our brain. However

defining and reorganizing them is not
that easy for our brain.

On the one hand, the visual nism that, among others, Looking at the video below, ing. It’s too much work to every day, but it can also
world alters continuously can explain this illusory the face on the left side constantly deal with every risk life-or-death conse-
because of changes in stability. slowly ages for 30 seconds, single snapshot it receives, quences when absolute
light, viewpoint, and other and yet, it is very difficult to so the brain sticks to the precision is needed.
factors. On the other, our The brain automatically notice the full extent of the past because the past is
visual input constantly smoothes our visual input change in age. In fact, ob- a good predictor of the For example, radiologists
changes due to blinking over time. Instead of ana- servers perceive the face present. examine hundreds of
and the fact that our eyes, lyzing every single visual as aging more slowly than images in batches, seeing
head, and body are fre- snapshot, we perceive in a it actually is. Basically, we recycle several related images
quently in motion. given moment an aver- information from the past one after the other. When
age of what we saw in the To test this illusion we because it’s more efficient, looking at an X-ray, clini-
To get an idea of the “nois- past 15 seconds. So, by recruited hundreds of faster, and less work. cians are typically asked to
iness” of this visual input, pulling together objects participants and asked identify any abnormalities
place a phone in front of to appear more similar to them to view close-ups of This idea – which is also and then classify them.
your eyes and record a live each other, our brain tricks faces morphing chronolog- supported by other results
video while you are walking us into perceiving a stable ically in age in 30-second – of mechanisms within During this visual search
around and looking at environment. timelapse videos. the brain that continuously and recognition task,
different things. bias our visual perception researchers have found
When asked to tell the age towards our past visual
Living “in the past” can ex- that radiologists’ decisions
The jittery, messy result plain why we do not notice of the face at the very end experience is known as were based not only on the
is exactly what your brain subtle changes that occur of the video, the partici- continuity fields. present image, but also on
deals with in every moment over time. pants almost consistently images they had previously
of your visual experience. reported the age of the Our visual system some- seen, which could have
face that was presented 15 times sacrifices accuracy
In other words, the brain is grave consequences for
Yet, seeing never feels like seconds before. for the sake of a smooth
work for us. Rather than like a time machine which visual experience of the patients.
perceiving the fluctuations keeps sending us back in When we watch video, we world around us. This can
and visual noise that a time. It’s like an app that are continuously biased explain why, for exam- Our visual system’s slug-
video might record, we per- consolidates our visual towards the past and so ple, when watching a film gishness to update can
ceive a consistently stable input every 15 seconds into the brain constantly sends we don’t notice subtle make us blind to immediate
environment. one impression so that we us back to the previous ten changes that occur over changes because it grabs
can handle everyday life. to 15 seconds. time, such as the difference on to our first impression
So how does our brain cre- between actors and their and pulls us toward the
ate this illusion of stability? If our brains were always Instead of seeing the latest stunt doubles. past.
This process has fascinat- updating in real time, the image in real time, humans
ed scientists for centuries world would feel like a actually see earlier ver- REPERCUSSIONS Ultimately, though, continu-
and it is one of the funda- chaotic place with con- sions because our brain’s ity fields promote our ex-
mental questions in vision stant fluctuations in light, refresh time is about 15 There are positive and perience of a stable world.
science. shadow, and movement. seconds. So this illusion negative implications to At the same time, it’s im-
We would feel like we were demonstrates that visual our brain operating with portant to remember that
THE TIME MACHINE hallucinating all the time. smoothing over time can this slight lag when pro- the judgments we make
BRAIN help stabilize perception. cessing our visual world. every day are not totally
We created an illusion to The delay is great for based on the present, but
In latest research, scientists illustrate how this stabiliza- What the brain is essen- preventing us from feeling strongly depend on what
discovered a new mecha- tion mechanism works. tially doing is procrastinat- bombarded by visual input we have seen in the past.