1. The Problem What are reports and
4.The solution in practice: Sperling paradigm
5. A taxonomy of conflicting hypotheses
behaviours operationalisations of? Which better
reflect the contents of consciousness? Debates
arise when reports and behaviours indicate
conflicting contents, e.g. change blindness,
Sperling paradigm.
Subjects report seeing ‘all the letters’
but can only report 3-4 letters from a
cued row.
The contents of hypotheses differ over time,
action, function and level of generality.
So, how and what do we operationalise?
2. Some answers (and standard objections)
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
Rich view. Content is rich
(reports). Difficult to locate this
content (iconic memory, local
recurrent processing don’t
work). (Block)
Sparse view. Content limited
items in global workspace
(behaviour). Leads to ‘grand
illusion’ about the contents of
consciousness. (Mack & Rock)
Sensori-motor view. Content
is rich, delivered over time via
interaction with the world
(behaviours over time). How
can we experience ‘potential’
content now? (O’Regan & Nöe)
Hybrid views. Attended
content is rich, non-attended
content is generic. Does this
produce shifts in
phenomenology? (Tye)
3. A different solution: Predictive coding
Conflicts between reports and behaviours
are conflicts in the accuracy, rather than the
content, of parallel streams of hypothesis
generation, none of which provide the ‘real’
contents of consciousness.
De Gardelle et al. (2009): Subjects
report seeing letters even when
pseudo-letters are in non-cued rows.
AM F D
I X RW
1. Perception as inference:
Input and expectations vary
along a processing
hierarchy. Differences are
minimised via feedforward
and feedback connections.
1. Differences between hypotheses up a processing hierarchy .
These differences are reduced over time via feedforward and
feedback connections between layers.
PU ∆ E
Explanation: Subjects form accurate item-identity
hypotheses about letters in cued rows (behaviour),
but inaccurate gist hypotheses about the display
(reports).
Gist hypotheses use low-frequency input, are formed
quickly (~100 ms), are heavily dependent on neural
‘expectations’. Operationalised via report above.
H1
Hn
Hierarchy in one
processing stream
2. Different hypotheses may be generated over different viewing times (due
to greater input with which to test hypotheses), or with differe nt actions
(giving different input). Longer stimulus durations typically r esult in more
accurate hypothesis generation.
HA
t1
Item-specific hypotheses use high-frequency input, take
longer to form (~250ms). Operationalised via letter
identification task above.
Operationalising what?
Liz Irvine, University of Edinburgh,
elizabethirv@gmail.com
HB
t2
3. Differences between hypotheses in layers of a hierarchy.
Resolved either by winner -takes -all or use of a threshold.
Possibility that different probes may utilise different
thresholds?
H1
H2
6. So what are we operationalising?
Hierarchy in one
processing stream
McCauley & Bechtel (2001) Heuristic Identity Theory: Interlevel identity claims require revision of concepts at both levels.
4. Hypotheses may be available at different times in different processing
streams.
Behaviours and reports are operationalisations of the contents
of hypotheses fulfilling different functions and probe-able in
different ways (similar to Dennett’s (1991) Multiple Drafts
Theory).
Processing hierarchy for gist,
completed ~ 200 ms.
No (set of) hypotheses provide the contents of consciousness,
though some may be more context-relevant.
Further, the content of a hypothesis is determined by a whole
processing hierarchy so cannot be easily localised.
Structure of cortical processing is inconsistent with the
concept of ‘the contents of consciousness’.
We are operationalising the contents of multiple hypotheses,
not the ‘contents of consciousness’.
The concept ‘the contents of consciousness’ needs radical
revision/elimination and cannot feature in identity claims.
2. Different input
conditions, viewing times
and actions result in
different hypotheses
(change blindness
decreases with longer
viewing times).
Processing hierarchy for item -specific processing
(e.g. letter identity), completed ~ 220 -300 ms.
5. Differences in hypotheses between processing hierarchies. These
hypotheses may exist at different levels of generality.
HA=>B
Processing hierarchy for gist
HÂB
3. Competing hypotheses
can co-exist within a
processing layer and switch
over time/input (e.g.
binocular rivalry).
4. Hypotheses differ across
processing streams,
depending on function,
processing time and input
information. Accuracy
varies between streams
(gist likely to be inaccurate
about ‘unexpected’ items,
e.g. variant Sperling exp.).
5. Hypotheses differ across
generality. Gist hypotheses
not dependent on itemspecific information and
can conflict.
Processing hierarchy for item -specific processing
(e.g. letter identity)
Bibliography
Block, N. (2007). Consciousness, accessibility, and the mesh between psychology and neuroscience. Behavioral and Brain Sciences, 30, 481-548 (inc. responses).
Dennett, D.C. (1991). Consciousness Explained. London: Penguin.
Friston, K. (2005). A theory of cortical responses. Philosophical Transactions of the Royal Society B, 360, 815-836.
de Gardelle, V., Sackur, J., & Kouider, S. (2009). Perceptual illusions in brief visual presentations. Consciousness and Cognition, 18, 569-577.
McCauley, R.N. & Bechtel, W. (2001). Explanatory pluralism and heuristic identity theory. Theory and Psychology, 11, 736-760.
Mack, A., & Rock, I. (1998). Inattention blindness. Cambridge, MA: MIT Press.
O’Regan, J. K., & Noë, A. (2001). A sensorimotor account of vision and visual consciousness. Behavioral and Brain Sciences, 24, 939-1031.
Sperling, G., (1960). The information available in brief visual presentations. Psychological Monographs: General and Applied, 74, 1–29.
Tye, M. (2009). Consciousness revisited: Materialism without phenomenal concepts. Cambridge, MA: MIT Press.
Thanks to the British Society for Philosophy of Science for a PhD scholarship!