Mind Hacks™: Tips & Tools for Using Your Brain (20 page)

Sudden movement or light can grab your attention, thanks to a second region for visual
processing.

Stand so that you’re facing a crowded scene. Watching a crowded theater settle
down is ideal. A busy street corner is a good choice, too. A TV screen or video game will
do as well, as long as there’s a lot going on in the frame.

Don’t try to direct your attention; just let it wander and feast your eyes on the full
field of view.

Notice that when a person waves, or stands up, your attention is grabbed and snaps to
focus on the person’s position. It’s not so much that you notice the waving or standing up
itself; the event simply captures your attention and you properly focus on that place a
fraction of a second afterward.

Since you’re relaxed, your attention soon drifts away, until someone else moves and
captures it again. Your attention scintillates across your whole field of view, darting
from point to point.

After visual information leaves the eye, it doesn’t just go to one place for
processing; the signal divides. Our conscious appreciation of visual information is
provided by processing done in the visual cortex. It sits at the back of the brain in the
area called the
occipital lobe
and performs what we typically
associate with the job of vision: figuring out exactly what shape the thing you’re looking
at is, what color, if it’s moving, then in what direction and how fast, what it means, and
so on — providing the raw information needed to put names to faces and avoid stepping in
front of a car while crossing a road.

Attention capture, on the other hand, relies on processing done by a region of the
brain called the
superior colliculus
. It gets a copy of the same
visual information the visual cortex does from the retina, but processes it in a different
way. This region is evolutionarily ancient, which means the basic structure was
established and refined in brains far simpler than our own, through many species of
animals. (Rather than relegating it to second place, fish and amphibians do most of their
visual processing with their equivalent of the superior colliculus, called the
optic lobe
.) So as one might expect, it’s not particularly
sophisticated, compared to the visual cortex. And it doesn’t use much of the information
it receives; the superior colliculus looks at a black-and-white world through frosted
glass. Then again, it doesn’t need much. This processing is for rapid response, when it
appears something potentially dangerous is happening and urgent action is needed quicker
than the complex visual cortex can respond. It’s just useful enough to guide reflex
movements, tell the head and body to orient in a particular direction, and force attention
to snap to important-seeming events.

That’s what’s going on when attention is captured. There’s a sudden movement and the
rapid response bit of your brain says, “Hey, I don’t know what that was, but pay it some
attention and figure out what to do in case it attacks us.” Looking at the crowd, your
attention darts around automatically because this bit of your brain feels startled enough
to interrupt consciousness every time somebody waves suddenly.

When you’re sitting in a darkened theater, absorbed in the dialog on stage, think
about what happens when a door opens at the side of the room. The sudden appearance of
light grabs your attention. If it happens again, despite the fact that you know you’re not
interested, it still grabs your attention and demands a response. It’s distracting. That’s
the automatic nature of attention capture coming into play.

On the upside, that bright light flashing in the corner of your eye could well be a
ray of sunlight being revealed as a large dangerous
something
lumbering out of the shadows toward you. The automatic capture of attention serves to
orient conscious perception in important directions.

Events that capture attention include the two already mentioned: sudden light
(actually, a sudden change in contrast) and sudden movement. In keeping with the purpose
of facilitating rapid response, it’s only new movement that captures attention. Ongoing
motion, like a moving car or a walking person, doesn’t trigger the automatic shift in
attention.

Two other triggers provide hints as to what else our brains regard as so critical to
survival that they deserve a rapid response. One is an object appearing abruptly. In
general, our brains give special treatment to objects — as opposed to backgrounds and
shadows, which are given less attention. This makes sense, as objects such as other
people, animals or food usually require a response of some kind. There are even dedicated
routines to object tracking
[
Feel the Presence and Loss of Attention
]
. An extra person,
rock, or car in the scene — especially if it appears suddenly — is likely to be a big deal, so
attentional capture is triggered.
¹

John Eastwood and his colleagues also suggest another trigger that is worth
mentioning as it shows just how deep our social nature goes. The trigger here is facial expression.
²
Eastwood’s team made simple line-drawing faces, happy and sad ones, and
asked people to count certain of the lines that made up the drawings. When the drawings
were upside-down, so they were unrecognizable as faces, people did the counting exercise
easily. But when the drawings were the right way up, counting took longer for drawings of
faces that displayed negative emotions rather than for drawings of positive expressions.
Why? The team’s conclusion is that negative expressions — sad or angry faces — distract you,
in just the same way as light through a theater door grabs your attention away from the
main action.

Your visual attention contains a basic function that puts the dampers on second
glances.

Like negative priming
[
The Brain Punishes Features that Cry Wolf
]
, which is how contextual
features are suppressed from attention, inhibition of return is such a low-level effect
that it’s hard to show without precision timing equipment. Again, just like those other
effects, it turns up in all kinds of cases because attention is so widely employed.

Imagine you’re taking part in an experiment in which an icon flashes up on a screen
and you have to touch that position. It’ll take you longer to move and touch the icon if
some other icon had previously, and recently, been in that position.

Inhibition doesn’t kick in immediately. Let’s say you’re playing Whack-A-Mole, in
which moles emerge from holes and you have to hit them with a hammer. A hole could light
up momentarily before the mole appears. This would be a prime candidate for the
inhibition-of-return effect. If the brightening occurs very shortly before the mole
appears, only a fifth of a second or so, it serves to draw your attention to that place
and you’ll actually respond to the mole faster.

If, on the other hand, the brightening occurs and then there’s a longer pause — more
than a fifth of a second and up to 3 or 4 seconds — that’s enough time for your attention to
be dragged to the brightness change then shift away again. Inhibition of return kicks in,
and when the mole appears in that same spot, you have to overcome the inhibition. It’ll
take longer for you to react to the mole (although it’s not likely you’ll miss it.
Reaction time increases only on the order of a twentieth of a second or so — enough to make
a difference in some circumstances, but hard to spot.) One caveat: if the brightening
happens before the mole pops up every single time, you’re going to learn that pattern and
end up being better at whacking the mole every time instead.

The big question is why this happens. One possibility is that it’s because we prefer
novelty and want to suppress distracting stimuli. An attention-grabbing event is good if
it’s useful, but if it’s not the event we’re looking for, then we’re better off focusing
our attention elsewhere in the future and ignoring that distracting location.

Raymond Klein, in his review paper “Inhibition of Return,”
¹
gives the example of efficient foraging for food. He suggests that
potential locations that have been found bare should be remembered as places to be
avoided, and this acts as a mechanism to orient toward novel locations. This could be used
just standing in one place and looking ahead to find edible plants on the ground. For a
task like visually searching straight ahead, it would be extremely useful to have a
mechanism that allows you to briefly look harder (for a fifth of a second) and helps you
to look for novel locations (for a few seconds after).

Current research indicates there may be two ways in which inhibition of return is
produced. One is at a very low level, subcortically in the
superior
colliculus
, which does rapid visual processing (but isn’t responsible for our
conscious visual processing
[
Understand Visual Processing
]
, which takes longer) and helps
orient the pupils and body. Indeed, damage to this part of the brain stops inhibition of
return from taking place
²
, at least for stopping the eyes moving back to locations they’ve previously
been.

Inhibition of return could also be triggered by higher-level operations in the
allocation of attention. The fact that the inhibition remains in place even when the
objects are moving around supports this — it can no longer rely on just eye position. Think
of counting a crowd of people when they’re all moving around: you’re able to do this
because you can
deselect
people who have already been counted. This
is the inhibition of return in play.

In fact, that this mechanism crops up in more than one place in the brain points to it
being a good, generic solution to tricky search problems, rather than a workaround for
some problem specific to a particular function like feature processing. I can see the same
strategy coming into play when I’m looking for something I’ve lost in my house. I’ll
search one location pretty thoroughly, then move on to the next, and the next, and the
next. If someone suggests I return to my first location and look there again, I’m pretty
reluctant. After all, I would have found it first time around, right?

If this is a common strategy in search, there are some pointers for interface design.
Don’t attract people’s attention to a place briefly if you really want to grab their
attention there shortly after. So if a news ticker on a web site, for example, appears
with a flash but then has a 2-second pause before the news appears on it, people aren’t
going to notice the news coming up. The initial flash will have inhibited their attention
returning there for the subsequent few seconds. If something is going to happen, make it
happen immediately, not after a brief pause. When people are skimming over stuff, they
don’t want to have their attention squandered — inhibition of return makes second glances
less likely.