Synaesthesia is a hereditary, neurological condition in which common stimuli trigger unexpected secondary sensations. For example, reading letters may result in the visualisation of colour, a variant known as grapheme-colour synaesthesia. While synaesthesia is thought to confer a range of benefits such as improved memory, empathy, visual search and creativity to the synaesthete, there is a small, yet growing, body of evidence that suggests synaesthesia may also be associated with more clinical conditions. This thesis investigates potential associations between synaesthesia and a range of clinical conditions, identifying a set of cormorbidities, and exploring the possible genetic roots of these associations. First, I identified an increased prevalence of multiple sclerosis (MS) and its clinical precursor, radiologically isolated syndrome (RIS) in synaesthetes self-referring for participation in scientific studies. Furthermore, I identified an increased occurrence of anxiety disorder in randomly sampled synaesthetes. In addition, I show that synaesthetes with anxiety disorder experience reduced luminance in their synaesthetic colours. I also conducted an association study into the genetic origins of synaesthesia and propose the immune hypothesis of synaesthesia, which provides a theoretical basis for comorbidities (linked to the altered cortical connectivity thought to underlie the development of synaesthesia). Finally, in phenotyping synaesthesia in individuals, I also validated the most widely used online test for synaesthesia, and use this test to provide a reliable prevalence of grapheme-colour synaesthesia in the general population. Such baselines are important for establishing whether other (e.g., clinical) populations are showing rates of synaesthesia higher than otherwise expected. I also demonstrate there is no significant difference in grapheme-colour synaesthesia prevalence between the sexes and discuss its implications for genetic theories of synaesthesia.

Synaesthesia is a neurological condition in which a sensory or cognitive stimulus consistently co-activates another sensory/cognitive quality, in addition to its usual qualities. For example, synaesthetes might see colours when they read words. This additional quality can be from a different modality (e.g., tactile stimuli triggering colour in addition to touch sensations) or from different aspects within the same modality (e.g. visually perceived shape stimuli triggering colour in addition to shape sensations). Coloured language is one of the most common, and most studied types of synaesthesia. The processes that govern such systematic associations of colours and language have been linked to the mechanisms underlying the processing of language. This thesis provides the first psycholinguistic exploration of synaesthesia in Chinese, in particular about how synaesthetic colouring is triggered from Chinese characters and their phonetic spellings in relation to psycholinguistic processes of character recognition. This thesis presents six empirical studies to provide evidence for the following facts: (a) that synaesthetic colouring of Chinese characters is a genuine phenomenon in the Chinese population and may affect as many as 1 in 100 Chinese people, with a (non-significant) female-to-male ratio of about 2:1; (b) that synaesthetic colours are influenced by the characters' constituent radicals (i.e., morphemic units), and (c) also by their associated phonetic spellings (in the spelling systems known as Pinyin and Bopomo); and (d) that even non-synaesthete Chinese speakers colour characters in predictable ways. These findings are discussed in relation to native (L1) versus non-native (L2) Chinese synaesthetes, and to the Chinese versus English systems. Hence, a further issue of this thesis considers how synaesthetic colouring in one's first language may affect their colouring in later-acquired languages. Synaesthetic transfer is discussed in relation to how, and how fast, the transfer can be established to a new language. Taken together, this thesis provides the most detailed information so far available about mechanisms that trigger synaesthetic colours in the Chinese language.

Synaesthesia is a variation of normal human perception. A grapheme synaesthete, for example, can experience extra sensations, such as colours when seeing letters and/or numbers. Synaesthetic ability is commonly developed at an early age, and is linked to a genetic pre-disposition; however, there is a learnt component, as one must also learn to read and write to develop grapheme synaesthesia. To explore the extent to which synaesthesia can be learnt, a training method was employed, which was first used by Colizoli, Murre and Rouw (2012). In order to learn their own coloured letters a group of non-synaesthetic individuals read colour books, which are free eBooks reproduced to have four letters consistently appear in colour. Before and after reading, the participants completed a modified Stroop-design based on Mills (1999), which was used to measure if they had learnt the two key characteristics of synaesthesia, namely an involuntary and automatic reaction to letters. Both the colour reading (n=15) and control (n=6) groups did not have a significant involuntary reaction to letters. However, it was found that the participants had significantly more automatic reactions to letters. This included the control group, who did not read in colour, which suggests that merely completing the modified Stroop test is enough to learn the automatic characteristic of grapheme synaesthesia. / Psychology / M.A. (Psychology)

Designers are often concerned with communication through the visual; we focus on the printed object, images on screens, furniture, spaces, and other visual experiences. We should also be cognizant of audio and its communicative properties, especially when contextualized with visual content. Pairing visuals and audio can make a greater impact upon a viewer/listener than each media might make alone. My research focuses on a practice of working within strict sets of rules and boundaries to create visual-audio work. This visual-audio work not only communicates a concept or idea, but also lives as a research artifact of my design processes.

This thesis presents the current knowledge about synesthesia as a specific mode of perception where a sensation (i.e. an inducer) induces another sensation which is not actually present (i.e. a concurrent). Special attention is paid to lexical-gustatory synaesthesia, a special type of synesthesia in which taste is the concurrent (word > taste). The empirical part of the thesis is devoted to practical research of lexical-gustatory synaesthesia among Czech native speakers. It describes the methodology of data collection including a questionnaire survey and the selection of respondents. The core and main benefit of the thesis lies in the detailed descriptions of four selected lexical-gustatory synaesthetes with whom we conducted a one-hour interview questioning the nature of their experiences. The information obtained from this research together with realted related the findings from the literature are summarized in the conclusion of this thesis.

Synaesthesia is a fascinating condition whereby individuals report extraordinary experiences when presented with ordinary stimuli. In this thesis, we examine an individual (L) who experiences time units (i.e., months and hours) and numbers as occupying specific spatial locations (e.g., January is 30º to the left). This type of spatial-form synaesthesia has been recently investigated by Smilek et al. (2007), demonstrating that synaesthetic time-space associations are highly consistent, occur regardless of intention, and can direct spatial attention. We extended this work in Chapter 2 by showing that for L, her time-space vantage point changed depending on whether the time units were seen or heard. For example, when L saw the word JANUARY, she reported experiencing January on her left side, however when she heard the word "January" she experienced the month on her right side. In this thesis, we validated L’s subjective reports using a spatial cueing task. The names of months were centrally presented followed by targets on the left or right. L was faster at detecting targets in validly cued locations relative to invalidly cued locations both for visually presented cues (January orients attention to the left) and for aurally presented cues (January orients attention to the right). We replicated these vantage-point dependent cueing effects also using hours of day. In Chapter 3, we further explored whether synaesthetic number forms could bias spatial attention using a spatial cueing and SNARC-type task. Two synaesthetes (L and B) both described experiencing the numbers 1 through 10 running vertically from bottom to top. Both experiments confirmed their synaesthetic number forms, such that when making odd-even judgments for the numbers 1, 2, 8, and 9, they showed SNARC-compatibility effects for up-down movements (aligned with their number form), but not left-right (misaligned) movements. Likewise in the spatial cueing task, both synaesthetes showed significantly faster response times to detect targets on the bottom of the display if preceded by a low number (1,2) and the top of the display if preceded by a high number (8,9), whereas they showed no cueing effects when targets appeared on the left or right (misaligned with their number forms). Both synaesthetes were, however, reliably faster to detect left targets following the presentation of numbers 10, and 11, and right targets following numbers 19 and 20 (running from left to right). Hence, we demonstrated that cueing and SNARC tasks could be used to empirically verify synaesthetic number forms. Moreover, we showed that numbers could direct spatial attention to idiosyncratic locations similar to time-units, replicating and extending our findings from Chapter 2. Lastly, Chapter 4 was aimed to explore the automaticity and involuntary nature of L’s number-forms. We continued to use the spatial cueing task and sought to eliminate any influence of strategy on L’s performance by: (1) shortening the interval between the cue and target onset to only 150 ms and (2) having the targets only fall in synaesthetically cued locations on 14.2% of trials. As a result, these manipulations should eliminate any cuing effects if L’s performance was attributable to intentionally using the cue to predict target location. However, our findings still showed an attentional bias consistent with L’s synaesthesia. We attributed L’s resilient cueing effects to the automaticity of her number-forms, thus demonstrating one of the hallmark attributes of synaesthesia. Overall, this series of studies convincingly demonstrated the reality of time-space and number-form synaesthesia and Chapter 5 concludes by discussing how this work has significantly contributed to the synaesthesia literature and to the study of perception overall.

Synaesthesia is a fascinating condition whereby individuals report extraordinary experiences when presented with ordinary stimuli. In this thesis, we examine an individual (L) who experiences time units (i.e., months and hours) and numbers as occupying specific spatial locations (e.g., January is 30º to the left). This type of spatial-form synaesthesia has been recently investigated by Smilek et al. (2007), demonstrating that synaesthetic time-space associations are highly consistent, occur regardless of intention, and can direct spatial attention. We extended this work in Chapter 2 by showing that for L, her time-space vantage point changed depending on whether the time units were seen or heard. For example, when L saw the word JANUARY, she reported experiencing January on her left side, however when she heard the word "January" she experienced the month on her right side. In this thesis, we validated L’s subjective reports using a spatial cueing task. The names of months were centrally presented followed by targets on the left or right. L was faster at detecting targets in validly cued locations relative to invalidly cued locations both for visually presented cues (January orients attention to the left) and for aurally presented cues (January orients attention to the right). We replicated these vantage-point dependent cueing effects also using hours of day. In Chapter 3, we further explored whether synaesthetic number forms could bias spatial attention using a spatial cueing and SNARC-type task. Two synaesthetes (L and B) both described experiencing the numbers 1 through 10 running vertically from bottom to top. Both experiments confirmed their synaesthetic number forms, such that when making odd-even judgments for the numbers 1, 2, 8, and 9, they showed SNARC-compatibility effects for up-down movements (aligned with their number form), but not left-right (misaligned) movements. Likewise in the spatial cueing task, both synaesthetes showed significantly faster response times to detect targets on the bottom of the display if preceded by a low number (1,2) and the top of the display if preceded by a high number (8,9), whereas they showed no cueing effects when targets appeared on the left or right (misaligned with their number forms). Both synaesthetes were, however, reliably faster to detect left targets following the presentation of numbers 10, and 11, and right targets following numbers 19 and 20 (running from left to right). Hence, we demonstrated that cueing and SNARC tasks could be used to empirically verify synaesthetic number forms. Moreover, we showed that numbers could direct spatial attention to idiosyncratic locations similar to time-units, replicating and extending our findings from Chapter 2. Lastly, Chapter 4 was aimed to explore the automaticity and involuntary nature of L’s number-forms. We continued to use the spatial cueing task and sought to eliminate any influence of strategy on L’s performance by: (1) shortening the interval between the cue and target onset to only 150 ms and (2) having the targets only fall in synaesthetically cued locations on 14.2% of trials. As a result, these manipulations should eliminate any cuing effects if L’s performance was attributable to intentionally using the cue to predict target location. However, our findings still showed an attentional bias consistent with L’s synaesthesia. We attributed L’s resilient cueing effects to the automaticity of her number-forms, thus demonstrating one of the hallmark attributes of synaesthesia. Overall, this series of studies convincingly demonstrated the reality of time-space and number-form synaesthesia and Chapter 5 concludes by discussing how this work has significantly contributed to the synaesthesia literature and to the study of perception overall.

Synaesthesia is a variation of normal human perception. A grapheme synaesthete, for example, can experience extra sensations, such as colours when seeing letters and/or numbers. Synaesthetic ability is commonly developed at an early age, and is linked to a genetic pre-disposition; however, there is a learnt component, as one must also learn to read and write to develop grapheme synaesthesia. To explore the extent to which synaesthesia can be learnt, a training method was employed, which was first used by Colizoli, Murre and Rouw (2012). In order to learn their own coloured letters a group of non-synaesthetic individuals read colour books, which are free eBooks reproduced to have four letters consistently appear in colour. Before and after reading, the participants completed a modified Stroop-design based on Mills (1999), which was used to measure if they had learnt the two key characteristics of synaesthesia, namely an involuntary and automatic reaction to letters. Both the colour reading (n=15) and control (n=6) groups did not have a significant involuntary reaction to letters. However, it was found that the participants had significantly more automatic reactions to letters. This included the control group, who did not read in colour, which suggests that merely completing the modified Stroop test is enough to learn the automatic characteristic of grapheme synaesthesia. / Psychology / M.A. (Psychology)

We are sometimes led to a different picture of things when something unexpected occurs which needs explaining. The aim of this thesis is to examine a series of related issues in the philosophy of mind in the light of the unusual condition known to psychologists as ‘synaesthesia’. Although the emphasis will be on the philosophical issues a view of synaesthesia itself will also emerge. Synaesthesia is a distinct type of cross-modal association: stimulation of one sensory modality automatically triggers an additional phenomenal character of experience associated with a second sensory modality in the absence of any direct stimulation of the second modality. Chapter 1 introduces synaesthesia to a philosophical audience by outlining the early history of synaesthesia studies, by summarising contemporary research and by indicating areas of philosophical interest to be considered in the rest of the thesis. Chapter 2 uses synaesthesia to examine one important philosophical model of the mind, Fodor’s modularity hypothesis, and, in turn, investigates the nature of synaesthesia in the light of that model. Fodor claims that cognitive modules can be thought of as belonging to a psychological natural kind in virtue of their possession of most or all of nine specified properties. The most common form of synaesthesia possesses Fodor’s nine specified properties of modularity, and hence it should be understood in terms of an extra cognitive module, and thus as belonging to the abovementioned psychological natural kind. Many psychologists believe that synaesthesia involves a breakdown in modularity. A breakdown in modularity would also explain the apparent presence of the nine specified properties in synaesthesia. I discuss the two concepts of function which underlie the respective theories, defending the breakdown thesis, arguing, in any case, that properties deriving from evolutionary history should also be used to decide between the two theses and thus ultimately membership of a psychological natural kind such as Fodor suggests. The argument is then used to respond to two challenges to the notion of a psychological natural kind. Chapter 3 focuses on the phenomenal character of synaesthetic experience. Externalists about the phenomenal character of experience tend to argue that the character of perceptual experience is to be explained either by the properties objects present to percipients, or by the properties objects are represented by percipients as having. Some internalists argue that there is a need to postulate hrther properties of the individual - in other words, qualia - to account for the individuation of the character of perceptual experience. The existence of additional phenomenal characters of experience in synaesthesia, which cannot directly be explained by reference to features of objects, suggests the existence of extra qualia and thus the presence of qualia in normal perception. The aim of this chapter is to meet the challenge presented by synaesthesia and the extra quaZia argument, and contrariwise, use synaesthesia as a way of fbrther clarifjmg the merits of the respective externalist positions. In the previous chapters the locution of ‘coloured hearing’ will have been adopted. Occasionally the process underlying synaesthesia is described as one of ‘hearing colours’. Chapter 4 rejects the latter usage. In so doing it focuses on the place of synaesthesia vis-a-vis normal perceptual processes. Considerations from previous chapters are further developed in order to shed light both on the metaphysical individuation of perceptual modalities and on how we know the distinctive perceptual modalities. Given the actual content of our concepts of perceptual modalities, it is argued that the actual world is one in which even synaesthetes are unable to hear colours. Consideration is given as to whether there is a possible world in which people could hear colours. The justification of the usage of ‘coloured-hearing’ then leads to a discussion of the relative importance of the individuating conditions of modes of perception. The thesis focuses largely on coloured hearing. What merits the preceding considerations have might be supported if they can be generalised. Chapter 5 goes a small way in that direction.

In synaesthetic personification, personality traits and other human characteristics are attributed to linguistic sequences and objects. Such non-perceptual concurrents are different from those found in most frequently studied types of synaesthesia, in which the eliciting stimuli induce sensory experiences. Here, subjective reports from synaesthetes were analysed and the cognitive and neural mechanisms underlying personification were investigated. Specifically, the neural bases of personification were examined using functional MRI in order to establish whether brain regions implicated in social cognition are involved in implementing personification. Additional behavioural tests were used to determine whether personification of inanimate objects is automatic in synaesthesia. Subjective reports describing general characteristics of synaesthetic personification were collected using a semi-structured questionnaire. A Stroop-like paradigm was developed in order to examine the automaticity of object personification, similarly to the previous investigations. Synaesthetes were significantly slower in responding to incongruent than to congruent stimuli. This difference was not found in the control group. The functional neuroimaging investigations demonstrated that brain regions involved in synaesthetic personification of graphemes and objects partially overlap with brain areas activated in normal social cognition, including the temporo-parietal junction, precuneus and posterior cingulate cortex. Activations were observed in areas known to be correlated with mentalising, reflecting the social and affective character of concurrents described in subjective reports. Psychological factors linked with personification in previous studies were also assessed in personifiers, using empathy, mentalising and loneliness scales. Neither heightened empathy nor mentalising were found to be necessary for personification, but personifying synaesthetes in the study felt lonelier than the general population, and this was more pronounced in those who personified more. These results demonstrate that personification shares many defining characteristics with classical forms of synaesthesia. Ascribing humanlike characteristics to graphemes and objects is a spontaneous and automatic process, inducer-concurrent pairings are consistent over time and the phenomenological character of concurrents is reflected in functional neuroanatomy. Furthermore, the neuroimaging findings are consistent with the suggestions that synaesthetes have a lower threshold for activation brain regions implicated in self-projection and mentalising, which may facilitate the personification processes in synaesthesia.