all, the two often go together: Focusing on a tart, crunchy bite of a Granny
Smith makes the experience more tangible, enhancing your awareness of it.
And when attention is diverted, obvious
things escape detection — a slip called
inattentional blindness. The most famous
example comes from a study in which
observers are asked to count the number
of times a basketball is passed between
people. Engrossed in the ball-watching,
many viewers are oblivious to a man in a
gorilla suit who ambles into the middle of
the scene, beats his chest and ambles out.
But just because consciousness and
attention are often linked doesn’t mean
that they are the same thing. A gripping
demonstration comes from a recent
experiment’s subliminal spiders. Participants who were terrified of spiders
watched a screen as pictures of a spider or
an outdoor scene flashed for 20 milliseconds — a split second that many scientists think is too fast to detect. None of the
subjects could report what was flashed,
indicating that the people who saw the
spiders were not conscious of them.
Later, the participants were asked
to walk into a room and touch a real
tarantula. People who were exposed to
the spider pictures got closer to the real
spider than those who saw the natural
scenes. The subliminal spiders desen-
sitized people and reduced their fear,
even though the participants were
oblivious, psychologist Joel Weinberger
of Adelphi University in Garden City,
N.Y., and colleagues reported last year
in Consciousness and Cognition. Though
the pictures flashed too quickly to break
into consciousness, the mind took note.
Now you see it Carefully designed experiments (one outlined below) allow scientists to
separate the confounding effects of attention from awareness. Such studies have revealed that
visual inputs don’t reach consciousness as soon as they hit the primary visual cortex, as many
researchers had thought. SOURCE: M. WATANABE E T AL/SCIENCE 2011
Left eye Right eye
Left eye Right eye
1. By showing study participants
a grating in either the same
eye as a circle or a different eye,
researchers can manipulate
awareness of the grating.
2. By adding a demanding task,
in this case the command to
focus on a letter, researchers
can draw attention away from
the grating in some cases.
This setup offers a way to study
people who have awareness
without attention, attention with-
out awareness, both or neither. c
their attention distracted by a counting
job. At the same time, the team manipulated the participants’ awareness of the
afterimage-inducing circle by showing it
to only one eye while flashing a checkerboard pattern to the other eye. When the
mind toggles to this dazzling pattern, the
circle remains outside of consciousness.
In this way, participants could attend
to something they didn’t see (attention
without consciousness) and see something they didn’t attend to (
consciousness without attention).
At the end of the experiment, once all
the signals on the screen were turned off,
the volunteers indicated how long the
aftereffect lasted. Surprisingly, attention
and awareness had different effects, the
team reported in 2010 in the Proceedings
of the National Academy of Sciences: The
more attention a person deployed, the
shorter the afterimage lasted. The more
conscious a person was of the stimulus,
the longer the afterimage lasted.
Though some scientists are still skeptical, these results and others like them
appear to separate attention and consciousness, meaning each may have its
own role in the brain. “The attentional
spotlight picks out aspects of the environment and highlights them,” says
van Boxtel. In contrast, consciousness
may be a synthesizer that merges bits of
information into a broader picture.
Recent studies designed specifically to
clarify V1’s job show that when attention
is removed from the equation, V1 behavior is no longer tied to consciousness.
In an fMRI study reported in the
Nov. 11 Science, participants were either
made aware of a striped pattern on a
screen or not. Then, they either focused
attention to the pattern or away from it.
Like the study on aftereffects, this setup
allowed scientists to separate awareness
from attention. The fMRI signal in V1
didn’t change as the stripes became visible or invisible if attention held steady.
But when attention shifted, so did V1
activity, Watanabe’s team reported.
More evidence comes from a recent
monkey study, presented by neuroscientist Alexander Maier of Vanderbilt
University in Nashville, Tenn., and col-
ADAPTED BY B. RAKOUSKAS