Andrew Peterson and Tim Bayneunreflective behavior that characterizes much of our daily life, such as picking up a slice of pizza
or braking in response to a traffic light turning red. We view such unreflective actions as inten-
tional, despite the fact that they are not guided by endogenous intentions.
Thirdly, skepticism about the degree to which covert command-following is a marker of con-
sciousness threatens to spawn a broader skepticism about the degree to which overt command-
following is a marker of consciousness. If one is unwilling to ascribe consciousness on the basis
of covert evidence of command-following, why should one be willing to ascribe it on the basis
of overt evidence of command-following?
Fourthly, it is possible to defend the use of command-following studies to ascribe con-
sciousness to patients without appealing to the connection between intentional agency and
consciousness. Instead, one might appeal to the content of the command in question. Highly
automated responses to familiar stimuli (e.g., braking in response to a red traffic light) may not
require consciousness, but appropriate responses to unfamiliar and complex stimuli probably do. In
our view, the instruction to imagine oneself playing tennis or navigating around one’s home is
both unfamiliar and complex. To comply with these commands one must understand them, and
it is doubtful that comprehension of the relevant sentences could occur unconsciously.
5 From the Bedside to the Scanner: Passive ParadigmsMethods that require patients to covertly follow commands are cognitively demanding, and it is
therefore conceivable that certain patients could be conscious but be unable to pass command-
following tests. To identify such patients, methods have been developed that assess consciousness
without requiring the patient to perform a task. These methods are called “passive” paradigms.
One such paradigm probes the capacity of patients to respond to stimuli with narrative
structure, such as films. In the first demonstration of this method, Naci et al. (2014) presented an
engaging, eight-minute Alfred Hitchcock film entitled “Bang! You’re Dead” to a group of healthy
participants and post-comatose patients while recording their brain activity with fMRI. The
film’s plot involves a young boy who mistakes his uncle’s loaded revolver for a toy. In several
scenes of the film, the boy spins a single bullet in the revolver (as in a game of Russian roulette)
and, taking aim at other characters, pulls the trigger.
Naci et al. (2014) found that neural activity associated with executive processing (such as in
the fronto-parietal network) was synchronized across healthy participants while they viewed the
film, particularly during suspenseful scenes. This activity was then compared against the brain
activity of two VS patients as they viewed the film. One of these patients produced brain activ-
ity that was highly synchronized with that of the healthy participants, suggesting that the film
had elicited experiences in him akin to those enjoyed by the healthy participants. Astonishingly,
this patient had been behaviorally non-responsive for 16 years. In a subsequent study, Naci et
al. (2017) found evidence of neural synchronization in similar patients using an engaging sound
clip from the film Taken.
Another passive paradigm that has been developed for detecting covert consciousness involves
the use of EEG to identify neural responses to two kinds of auditory irregularities: local irregulari-
ties and global irregularities. Local irregularities occur when a deviant tone follows a repeating
standard tone (e.g., four low tones followed by a high tone), whereas global irregularities occur
when a deviant sequence of tones follows a repeating standard sequence (e.g., a sequence of five
low tones following three iterations of a sequence in which four low tones are followed by a high
tone). Evidence from studies involving priming and anesthesia suggests that although local irregu-
larities can be detected unconsciously, consciousness is required for the detection of global irregu-
larities. Crucially, global irregularities are associated with a distinctive brain-response—known