Center for Consciousness Center . Tucson . Arizona

Synaesthesia

Noam Sagiv

The study of individuals with various cognitive deficits has taught us a great deal about consciousness and cognition, however, there is much to be learnt from positive phenomena such as synaesthesia, hallucinations, and phantoms. Narrowly defined, synaesthesia is a condition in which stimulation in one sensory modality leads to additional experiences in a different modality. Nevertheless, inducers of synaesthesia may be more abstract or internally generated and the evoked experiences may span a wide range of qualities. Consequently, synaesthesia has implications for every major aspect of cognition: perception, attention, language, memory, emotion, and consciousness. In turn, in order to understand synaesthesia, one has to consider these aspects as well as their development and neural basis. In this workshop, I will provide an overview of what is known about the synaesthesia and what it tells us about conscious perception. I will consider phenomenological, cognitive, and neurobiological data.

I. An Introduction
I will begin by reviewing the varieties of synaesthetic experience and consider some foundational issues, such as a definition and criteria for synaesthesia as well as different views of synaesthesia (is it an abnormality or a normal mode of cognition rarely made explicit?). I will discuss the prevalence and aetiologies and compare the developmental and acquired forms of synaesthesia (including those seen in altered states of consciousness). Some of the challenges in synaesthesia research will be discussed and a brief historic review of synaesthesia research will follow.

II. Cognitive and Developmental Approaches
I will review the basic paradigms used in synaesthesia research and how they were applied in order to demonstrate the perceptual reality of synaesthesia, the role of attention and context, as well as synaesthesia without awareness. I will discuss synaesthesia and language and present the case of gustatory-lexical synaesthesia. This will be followed by discussion of synaesthesia and metaphoricity, common trends among and individual differences between synaesthetes. This section will conclude with the debate on neonatal synaesthesia.

III. Synaesthesia and the Brain
Next, we will examine models of synaesthesia. What and where is the link in synaesthesia? I will present frameworks for understanding synaesthesia, the cross-activation hypothesis, and the evidence for shared mechanisms for synaesthetic and ordinary experience. I will present the latest electrophysiological, neuroimaging, transcranial magnetic stimulation, and skin conductance data and discuss how these constrain models of synaesthesia. I will then attempt to offer preliminary answers to the following questions: Is cross-wiring plausible? Is there a synaesthesia module? Does synaesthesia come at the expense of something else?

IV. Synaesthesia and the Problem of Qualia
In this section we will discuss the implications of synaesthesia to the problem of qualia and the nature of mental representations: How does synaesthesia constrain the way we (should) think about our subjective experiences? Gray’s assertion on the inadequacy of functionalism and the limitations of his arguments. The extra qualia problem. Synaesthesia and non-sensory experiences: Some challenges to the present narrow definition of the phenomenon. Finally, I will discuss projected experiences, personification, animism, intersubjectivity and anomalous experience.

V. Future Directions
In this last section, I will briefly review what is known about the genetics of synaesthesia and the implications for understanding individual differences in perceptual experience. A discussion on synaesthesia art and creativity will follow (Is there a link? Synaesthesia as a tool for artistic experimentation. Synaesthetic experience as a source for art – some challenges to the way we think about art). The workshop will conclude with an open discussion. Some of the open questions in synaesthesia research will likely be addressed: Are we all synaesthetes? Should our definition of synaesthesia be more inclusive? What is so special about colour (that it is rated as the most common synaesthetic experience)?