David Barrett(the one with the horse back end). Clearly, then, something like visual object recognition is
taking place. And we already know that process goes straight through intermediate levels to the
high level representations.
Hence, we have examples of subjects who process stimuli in totally normal ways, but who
are quite blind to those stimuli. They are the perfect implementation of our strategy; we need
only consider the differences between them and us to have evidence on which to build a theory
of consciousness. What, then, does the right inferior parietal cortex do? It is most associated
with the control and allocation of attention. Unilateral neglect is understood to be an attentional
deficit—as opposed to a strictly visual deficit. We have, then, an extra piece in the puzzle about
consciousness: perhaps conscious states are those IRs that are attended to.
Before running with that theory, it would be best to consider extra evidence from people
with intact brains. Considered alone, the neurological damage in patients with unilateral neglect
is not the most convincing. It could easily be that the damage to the parietal cortex dam-
ages attention and some other functional capacity (or capacities). This other functional capacity
might make a difference to what makes IRs conscious, or it might not. But the unilateral neglect
patients will not be able to tell us. So, it is premature to conclude that consciousness is attended
IRs purely on the basis of their evidence.
Luckily, there is much known about attention and awareness in people without brain dam-
age. Two conditions are noteworthy: attentional blink and inattentional blindness. In the first case,
when two stimuli are presented in close enough succession (the second stimulus occurring
before ~450 milliseconds after the first), the first captures attention while the second stimulus
is not noticed. Though Prinz does not mention it, there is evidence that the attentional blink
occurs in the auditory and tactile modalities and can even occur cross-modally—that is, a visual
target can cause such a ‘blink’ for an auditory stimulus presented quickly enough after the
visual target, or vice versa (see Soto-Faraco et al. 2002). Inattentional blindness occurs when
attention is paid to a particular stimulus, rendering other stimuli in (say) the visual field invis-
ible. The classic example is of a person in a gorilla costume walking through a group of people
passing around a basketball (see Simons and Chabris 1999). Subjects are tasked with counting
the number of passes, attention to which makes some subjects (though not all, unsurprisingly)
unaware of the gorilla. Since they are aware of the number of passes, and since the person in
the gorilla suit walks straight through the middle of the other people passing the ball, it is clear
that the subjects could be conscious of the gorilla. It is as if they have a neglect for anything but
the passes of the ball. Since these attention-related phenomena occur in all people, it provides
stronger evidence for our working hypothesis that attention is the mechanism that makes our
IRs conscious.
It is worth pointing out that these bits of evidence give us suggestive reason to think atten-
tion is important for consciousness, but they are somewhat limited. They show that attention
is necessary for consciousness—in particular, that a lack of attention means a lack of conscious-
ness—but they do not show that attention is sufficient for consciousness. If we can find evi-
dence that attention paid to stimuli renders those stimuli conscious, we would have a strongly
supported theory. Prinz is quick to point out that such evidence exists. A phenomenon called
‘pop out’ is suggestive. When we look at a set of objects that are almost entirely uniform, save
for one object that stands out as different, we become quickly conscious of the dissonant object.
It is thought, Prinz reports, that attention is grabbed by that object. If so, it is a case of attention
paid to an object bringing that object into consciousness. Posner (1980) is also famous for first
deploying an experimental method, which is named for him (the so-called ‘Posner cuing para-
digm’). In these experiments, accuracy in judgments about, and speed of detection for, objects
is enhanced by a cue that precedes the target object. In those cases where the cue appears in a