Measuring
consciousnes
s
From last time…
Operationism: Science depends on
working (operational) definitions of phenomena
Hunger is not identical with the last time you ate something, or how vigourously you search for food
Operationism
Crucial: Operational definitions are
tied to experimental paradigms and measures
Consciousness science: Need to specify
Why are measures of
consciousness important?
Boundaries of conscious and unconscious
perception
Interpreting/understanding pathologies
and ‘weird’ phenomena
What are the distinct properties/functions
of consciousness?
Developing theories of what
Today:
What are possible measures of
consciousness?
An old debate: subjective/objective
measures
New work: new methods, new measures
What hope is there for convergence on a
So….
What experiments and measures would
An old (and important) debate
How reliable are reports? Subjective vs. objective measures of
consciousness
Various cycles of popularity in
psychology
Currently a mess in consciousness
A bit more history…
(Perceptual defense demo) Psychophysics originally used ‘free’
subjective reports to test the limits of conscious perception
Lots of findings of unconscious
perception
Signal detection theory
Noise plus signal
distribution Noise
distribution
Distance between
Implications
Older findings of unconscious perception are
‘criterion effects’
‘Free’ subjective reports are transformations of
objective ability to respond to stimuli through a context-sensitive criterion.
“…there is no such thing as an unmediated
Implications
Studies of unconscious perception now
use objective measures (d’=0)
BUT performance when d’>0 does NOT
imply that subjects are conscious of stimuli
So, still lack a measure for the presence
Alternative methods?
Jacoby process dissociation (1991) Visser & Merikle qualitative differences
(1999)
Look for differences in task performance
E.g. ability to inhibit primed responses in word stem completion tasks
Alternative methods?
BUT SDT shows many of these areactually criterion effects
There are a number of qualitative
differences in task performance
Which one maps onto the
Lau: Performance
matching
“One may respond…that the effectiveness of
information processing is the same thing as
consciousness…The argument would be that…if one is conscious of the stimuli, one can perform well [on a task]. If one is unconscious of the
Performance matching
Lau: Performance is not the same thing as consciousness.
Blindsight: (forced choice) task performance can
overestimate consciousness
Sperling: task performance can underestimate
consciousness
Marcel: task performance is not unified, but
consciousness is
Reports across button presses, verbal reports,
eye-blinks can differ for the same stimulus
Against objective measures
“…signal detection theory could actually
also be applied to characterizing the sensitivity of a photodiode…Therefore, according to this [measure]…what we are actually looking at is the basic
mechanism of how the brain processes information and produces useful
Against objective measures
“Is [information processing] what we are
interested in looking at? I suspect that a good number of [consciousness]
researchers are prepared to give a blunt "yes" to this question…But the reason that there is so much interest in
[consciousness science] is that we have the powerful intuition that
Subjective vs. objective
Do subjective measures also measure(complex) information processing?
Can we ever measure anything more
than ‘mere information processing’?
So far, what do you think of objective
More and more measures…
(Seth et al.)
Worldly discrimination theories: Consciousness
enables behaviours
Behavioural measure: Objective measures of task
performance (SDT)
(Global) integration theories: Consciousness enables
global integration of information
Behavioural measures: Objective measures of strategic
control, subjective measures of stimulus discrimination
Neurophysiological measures: late ERP, gamma band
More measures…
Higher order thought theory:Consciousness is a second order state (requires meta-knowledge) (roughly!)
Informational measures
Information integration: Consciousness is
the ability to (or actual) integration of information
Measures: neural complexity, information
integration Φ, causal density
These measures ascribe consciousness to
any system with non-zero values of the measure.
Theoretical measures, difficult to measure in
How to choose?
“Just as theoretical positions conflict with one another, conflicts among measures can be expected and, in
many cases, have been observed. These conflicts can guide further experiments…The most informative new studies will be those that combine multiple measures, both behavioural and brain-based…An integrative
approach combining both types of measure in a single study encourages a virtuous circularity in which putative measures and theoretical advances mutually inform,
validate and refine one another. The ultimate virtue in a measure is…its ability to build on intuitions, identify
interesting divides in nature and then correct the
Convergent approaches?
Can this help with the debate over objective
and subjective measures? Over first and second-order measures?
SQ: If the subject reports to be unconscious
of something, but a brain-based measure reveals that the information is processed in the brain, could that information be
considered as consciousness?
Is there a principled way of identifying the
Your questions!
How strongly are subjective and objective measurements
correlated in healthy subjects?
What can objective measurements of performance tell
us, when they are inconsistent with the subjective report (when forced choice paradigms lead to a very good
result, but the subjects claim they haven't perceived anything)?
What is the role of subjective and objective
Your questions!
If you are under anaesthesia, you cannot behave but you
might still be conscious about a situation, or your brain can still process information, or you might respond to
commands without being conscious, then all the methods for measuring consciousness might fail?
How plausible is the assumption of a specific conscious
(next to an unconscious) network in the brain? Do
unconscious and conscious stimulus processing have to be qualitatively different and distinct on the level of brain
Your questions!
In a framework where we don't have clear concept to
describe consciousness, how can the discussion about different levels of consciousness be addressed?
How can any method to assess the level of consciousness
through behavioral paradigms isolate the phenomena in se, and, especially in case of patients, not be vulnerable to
sensory or peripheral deficits?
If 'the ability to choose accurately under forced choice
conditions' is a marker for consciousness every fruit fly is conscious. What does that mean for the definition of
