Table 2.

Sensitivity to graded consciousness^a

Type	Measure	Primary theoretical affiliation	Sensitivity to graded conscious level	Sensitivity to graded conscious content
Behavioural
Objective	Discrimination behaviour	WDT	None (either an organism is sufficiently conscious to show choice behaviour, or it is not)	The d′ value in SDT might index graded consciousness, though typically any d′ > zero is taken to imply full consciousness [1]
Objective	Strategic control	Integration theory	None (see above)	None so far. Various equations developed assume that a content is either clearly conscious or unconscious (e.g. Ref. [9])
Subjective	Introspective report	HOT	Poor and indirect; poor verbal coherence might indicate low conscious level	Introspective reports are explicitly highly sensitive to conscious content and can indicate close mismatches between observed and reported states
Subjective	Confidence ratings	HOT	Poor and indirect; confidence might diminish with conscious level	Confidence can indicate degrees of higher-order belief
Subjective	PDW	HOT	Poor and indirect though various continuous measures can be used	Gambling measures can indicate degrees of higher order belief (see Box 2)
Objective and subjective	Glasgow coma scale	None	High	None
Neuropyhsiological
EEG	Bispectral index	None	High	None
EEG/MEG	Early ERP (‘awareness negativity’ [77])	Localized integration [14,39]	Most ERPs are attenuated by sleep and low arousal, but yet not directly tested for awareness negativity	Some. Early ERPs are delayed for low-contrast stimuli [77]
EEG/MEG	Late ERP (P300)	Global Integration [40]	P300 can be elicited during sleep though with different profile [78]	Low. P300 dichotomously characterizes ‘seen’ versus ‘not seen’ trials [40]
General neuroimaging	Widespread activation	Integration	Imaging of consciousness-impaired patients can distinguish different conscious levels [45]	Low. Access to global workspace is usually considered all-or-none [10]
Synchrony	Induced γ activity	Integration (local and/or global)	Synchrony is present even in non-REM sleep [53]	Not tested (to our knowledge)
Synchrony	SSVEP (frequency ‘tag’)	Global integration	Auditory frequency tag is modulated by arousal level [79]	Not tested (to our knowledge)
Complexity	Neural complexity	Integration	High (in principle but not yet shown)	Low
Complexity	Information integration (Φ)	Integration	High (in principle but not yet shown)	Some (in principle Φ can gauge conscious contents)
Complexity	Causal density	Integration	High (in principle; shown only in our own unpublished work)	Possibly revealed by causal interaction patterns but not yet shown

^aConscious level can be graded on a scale from coma to full wakefulness, and conscious contents can also be graded (e.g. fringe consciousness and Ganzfeld experiences). This table indicates how different measures are able to track graded consciousness, as well as their primary theoretical affiliation.