Dissertation Statement
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.
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.
