Consciousness Flashcards
The Hard Problem of Consciousness
The alleged metaphysical mystery of the existence of consciousness (subjective experience, qualia, what-it-is-like-ness) in an otherwise unconscious physical universe.
[Linked to: explanatory gap]
The Explanatory Gap
The alleged epistemological mystery of how one could ever provide a satisfying account of consciousness in physical terms.
[Linked to: hard problem of consciousness]
Mary’s Room (aka the Knowledge Argument)
Thought experiment by philosopher Frank Jackson to provoke the intuition that the hard problem of consciousness / the explanatory gap really exists.
Summarised by this Bertrand Russell quote (don’t memorise): “It is obvious that a man who can see, knows things that a blind man cannot know [i.e. what red looks like]; but a blind man [i.e. Mary] can know the whole of physics.”
Locke’s Inverted Spectrum
Thought experiment by John Locke, again pointing to the intuition that third-person physical science can’t fully explain conscious experience.
(“Woah, like, the colours that I see bro, might not be the same ones you see!”)
Hemispatial Neglect
A clinical disorder of consciousness, where the person is unaware of left side of their normal field of consciousness.
(Will draw half a clock)
Subliminal Messaging
Subliminal stimuli have a very weak or nonexistent effect on us
Completely fabricated experiment: inserting frames of Coke images into cinema reel
Key Lesson from Unconscious Processing
There is more information encoded in our brains than we have conscious access to
Binocular Rivalry
Different visual stimuli are presented to each eye
The person consciously perceives one at a time, switching between the two
It’s a way of decoupling information processed in the retina from information in conscious perception -> useful for experiments
Subjective Threshold
Lower limit of conscious processing, according to self-reporting of information extraction
[As opposed to: objective threshold]
Objective Threshold
Lower limit of conscious processing, according to third-person measures of information extraction (e.g. above chance performance)
[As opposed to: subjective threshold]
Problem with investigating ‘unconscious processing’
If you choose to use a subjective threshold, then by definition any response to a stimulus that a person cannot report but that affects behaviour is unconscious processing
If you choose to use an objective threshold, then by definition you have ruled out unconscious processing (because if it was processed, it would affect behaviour; it didn’t, so it wasn’t)
So: it seems that whether or not you find evidence for the existence of unconscious processing will likely depend on what threshold you stipulate
Conservative Response Bias
Experimental confound whereby people tend to not report a conscious perception, even if they think they might have noticed something
(Suspiciously, JDH always gave the example that this is in case they perceive something sexual and don’t want to appear dirty-minded)
[Linked to: subjective threshold]
Blindsight
Above chance performance in guessing about stimuli in a supposedly ‘blind’ visual region
(i.e. processing below subjective threshold but above objective threshold)
Pathway: LGN -> extrastriate cortex, skipping V1
Unperceived flicker
Flickering above 50Hz appears continuous to us
(Old TVs were below 50Hz, so we saw them flicker)
But retinal and V1 activity still reflects the flickering
Two dimensions of consciousness
Physiological Arousal (aka wakefulness)
Level of Awareness (of self or environment)
1) Microconsciousness theory
Small ‘units’ of consciousness exist in separable brain areas whenever they are activated. No added ingredients required
e.g. as long as there is activity in the fusiform face area, you will experience a face
Supported by evidence from binocular rivalry:
face vs house images -> face area vs place area activation corresponds with conscious experience
2) Level of activity theory
Microconsciousness + Threshold
You need a certain minimum level of activity for consciousness
Supported by masking experiments:
target stimuli presented followed by a patterned mask -> likelihood of conscious experience correlates with duration of exposure to target stimuli
3) Higher stages of visual processing theory
It’s not about just having (certain levels of) activity: it needs to be in the right areas, especially higher visual processing areas e.g. inferior temporal cortex
Early parts of processing are not relevant for consciousness
Supported by binocular rivalry studies with monkeys:
20% of cells in visual cortex dependent on whether they experience the left or right input
Up to 90% in higher cortical areas
4) Ventral vs dorsal pathways theory
There are two streams of visual processing from V1:
Ventral = what pathway. Conscious?
Dorsal = where/how pathway. Unconscious (action direction)?
Supported by patient DF: could post a letter into a rotating slot (‘where/how’), but not describe the orientation (‘what’)
5) Recurrent processing theory
Recurrent visual processing (i.e. from everywhere to everywhere) is necessary for conscious experience, not just feedforward pathways
Feedback loops and horizontal processing: high-level and low-level visual areas must interact, enabling widespread exchange of information between areas processing different properties of visual scene
Supported by experiments with monkeys making saccades: shows early-stage processing, but also late-stage recurrent activity only when stimulus is consciously seen
6) Synchronization theory
Cells that encode different properties of the same object synchronise their spikes
Builds up a signal that stands out from the background noise -> conscious perception
Offers a potential solution to the ‘binding problem’ (how come different aspects of our perception appear integrated?)
Supported by: synchronised firing rates for different objects when looking at duck-rabbit-type illusions
7) Global workspace theory
Neural network model, where stimuli representations compete to be made accessible for conscious representation
So, information can either be kept encapsulated and unconscious in specialised areas (e.g. visual cortex), or propagated into the ‘global workspace’ (certain high-level cortical areas that propagate stimulus information across long-range connections)
Key features:
1) competition between stimuli
2) ‘all-or-nothing’ conscious awareness (winner takes all), as opposed to graded levels of consciousness
Supported by: all-or-nothing patterns of brain network activity, plus the intuition that only when we are conscious of something can it then be used in many different ways
