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DISSERTATION - MEMORY QUALIA
Optimized decision-making requires us to track the origins of
our mental experiences as accurately as possible. While humans are quite
reliable at distinguishing, say, memories from imaginings, we are also
susceptible to false memories and psychogenic amnesias. People can be
manipulated into believing false childhood memories that were implanted by an
experimenter, or suggested by a person in authority. In these circumstances
subjects not only find fictions familiar and have strong beliefs about their veracity,
but they also claim to re-experience vividly the details of their prior
occurrence. Conversely, psychogenic amnesias have been reported in patients
with multiple personality disorder, dissociative fugue or post-traumatic stress
disorder subjects—e.g. rape victims. Individuals in these situations respond to
stimuli connected to an instigating event without
any familiarity or sense of connection to this past. In light of the evidence
that subjective judgment is a poor guide to the true origin of our thoughts, one
might wonder whether consciousness has any functional use in cognition at all.
Perhaps consciousness is epiphenomenal? This is the predominant view in
cognitive science.
In my dissertation I argue that consciousness is not
epiphenomenal. I elucidate how the subjective experience of memory (mnemic
qualia) contributes to cognition, knowledge, planning and decision-making. I
begin by examining the subjective experience itself via the contributions of
Aristotle, Hume, James and Russell. Hume noted that unlike imaginings, memories
seem more vivid or convincing. People often justify assertions by examining the
quality of the mental experience, such as the level of detail in their mental
images, the degree of emotional salience or even a sense of ‘being there’. People
offer factual details of events they purport to remember. Thus, memories are
distinguished from imaginings partially by the way they feel and partially
because of background beliefs. Inspired by the American pragmatists, I outline
how the experiential and representational can be reconciled within a
representational theory of mind.
I go on to integrate my philosophical defense of qualia with the
source-monitoring literature from psychology. Successful source monitoring is
an inferential process that requires people to examine and categorize their
mental state based on qualitative features of the experience itself and
coherence with other beliefs. The inferential contribution is evident in cases
of ‘déjà vu’, where we experience the feeling of memory but rationalize that we
are not remembering.
The coherence view in the source monitoring literature in
psychology is supported by a Bayesian account of belief. This view is that the
congruence between independently generated beliefs can raise the probability of
what is remembered to the level of practical certainty in a way analogous to
that in which agreement of independently given testimonies can eventually convince
us that what is being testified is true. The theory works on the basis that there
is initial credibility (i.e. a non-zero prior probability) for the memory in
question. Coherence increases the posterior probability that x occurred with
the number of consistent beliefs. However, the coherence of independent items
of evidence has no impact on the probability of a conclusion unless each item has
some credibility of its own; for example, a person with poor vision would be
unwise to treat mental images from an event as seriously as their auditory
memories.
The Bayesian account explains how normal memories are
successfully segregated from other mental phenomena. But, perhaps more impressively,
it sheds light on circumstances when source-monitoring fails. Because we must
already begin with a degree of belief in a particular memory, Bayesianism explains
why psychogenic amnesia patients have no capacity to revise beliefs. It also
shows how individuals who are unusually gifted at creating cross-modal
phenomenology are particularly prone to false memories. Individuals who are
fantasy-prone, or hypnotically suggestible are wise to remain skeptical of
their qualia, because coherent subjective experiences are too easily
constructed by their imaginations.
I conclude that regardless of the functional underpinnings of
our cognitive architecture, consciousness impacts our reasoning and this is
rationally explained by combining the empirically informed source-monitoring
literature and a Bayesian probability calculus.
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