Chapter
Three
The grand illusion
Thinking about visual consciousness as a way of
acting rather than a stream of pictures exposes
some deep-seated patterns in how we think about
our experience. These theories run counter not
only to more traditional theories of vision, but also,
as we saw earlier, to our intuitive understanding
of how vision works. This might make us wonder:
how on earth could I be so mistaken about my
own consciousness? But there are good reasons
why you might be. Whatever the details of whether
and how it constructs neural models of the world,
the visual system is remarkably fit for purpose: its
complex parallel processes of texture recognition,
pop-out detection, contrast control, and all the rest
work so well together that it is easy to believe that
the parts add up to a detailed picture-like whole.
But the picture may be only the result we infer, not
in fact the mechanism we rely on. Could we learn
to see this inference emerging, and stop it in its
tracks by reminding ourselves that the picture may
be an effect rather than the cause of our ability to
see so well?
The idea of doing this may be a little scary. The
appeal of the ‘picture in the head’ model lies partly
in the stability and security it promises; how could
we function safely and reliably in the world with-
out such a picture? Don’t we need an accurate
image of the world, transmitted from eyes to brain
and then available to all the processes directing
the rest of cognition and motor action, to think
and act appropriately? The appeal is also tightly
tied to convention: it is hard if not impossible to
separate how things seem visually from the habits
for seeing that we learn from society and culture.
The invention of the camera changed how we see
the world (Berger, 1972) and our world is more
and more dominated by images designed to cap-
ture and hold our attention. Are they making the
ancient intuitions about pictures in the head ever
harder to dislodge?
We began with the idea of a stream of vision, and
the assumption that it is a stream of internal pictures
or representations. The results on filling-in, inatten-
tional blindness, and change blindness all call that
idea into question (Blackmore, 2002), raising the
possibility that vision may be a grand illusion. This is
just one aspect of the illusionist proposal (e.g. Frank-
ish, 2016a) that our ideas about all of our experience
are wrong.
one participant, Kevin, wears a head-mounted display
which shows the output from an eye tracker on a second
person, Alva. When Alva moves or looks around the room,
everything he looks at is instantly fed to ‘Kevin’. Kevin
therefore gets exactly the same visual input as Alva. Kevin
is also making eye movements, but although Alva’s eye
movements correspond to the changes of scene, Kevin’s
do not. this means that Kevin can have no mastery of
sensorimotor contingencies when moving his eyes around.
What will happen? You might like to consider your own
answer before reading on. Here are three possibilities:
1 Kevin can see perfectly well. He is receiving the same
visual input as Alva and so must see the same as Alva sees.
2 Kevin is effectively blind because although he receives
the same visual input as Alva he cannot master the
contingencies between input and eye movements.
3 Perhaps Kevin can see something but not the same
as Alva.
In her peer commentary on the 2001 paper, sue (Black-
more, 2001) suggested that the sensorimotor theory makes
the strong prediction that Kevin is effectively blind and
unable to recognise things, judge distances, grasp objects, or
avoid obstacles. Possibly he might have some other residual
vision, but if eye movements were uncorrelated with input
the mainstay of what it means to see would be gone.
In a poster (Blackmore, 2007a), she asked participants at
a vision conference, including o’Regan and noë, to giveFIGURE 3.10B • Kevin FIGURE 3.10C • Kevin option 2
option 1