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.