This chapter distinguishes between two kinds of ordinary multisensory experience that go beyond mere co-consciousness of features (e.g., the experience that results from concurrently hearing a sound in the hallway and seeing the cup on the table). In one case, a sensory experience in one modality creates a perceptual demonstrative to whose referent qualities are attributed in another sensory modality. For example, when you hear someone speak, auditory experience attributes audible qualities to a seen event, a person’s speaking motions. The (...) second kind of multisensory experience attributes features experienced in several sensory modalities to one and the same object via a process of amodal perceptual integration, i.e., integration that occurs separately from processing within the individual sensory modalities. Multisensory experiences arising from holding and seeing a tomato or from seeing the Indian curry boil and smelling it are examples of the second kind of multisensory experience. At the end of the chapter we look at synesthesia, a kind of atypical multisensory experience, and argue that one version of this phenomenon may be able to shed light on the neural mechanism underlying amodally integrated multisensory experience. (shrink)

Studies of linguistic synaesthesias in English have shown a range of fine-grained language mechanisms governing the associations between colours on the one hand, and graphemes, phonemes and words on the other. However, virtually nothing is known about how synaesthetic colouring might operate in non-alphabetic systems. The current study shows how synaesthetic speakers of Mandarin Chinese come to colour the logographic units of their language. Both native and non-native Chinese speakers experienced synaesthetic colours for characters, and for words spelled in the (...) Chinese spelling systems of Pinyin and Bopomo. We assessed the influences of lexical tone and Pinyin/Bopomo spelling and showed that synaesthetic colours are assigned to Chinese words in a non-random fashion. Our data show that Chinese-speaking synaesthetes with very different native languages can exhibit both differences and similarities in the ways in which they come to colour their Chinese words. (shrink)

In grapheme-color synesthesia, a number or letter can evoke two different and possibly conflicting color sensations at the same time. In this study, we investigate the relationship between synesthesia and executive control functions. First, no general skill differences were obtained between synesthetes and non-synesthetes in classic executive control paradigms. Furthermore, classic executive control effects did not interact with synesthetic behavioral effects. Third, we found support for our hypothesis that inhibition of a synesthetic color takes effort and time. Finally, individual differences (...) analyses showed no relationship between the two skills; performance on a ‘normal’ Stroop task does not predict performance on a synesthetic Stroop task. Across four studies, the current results consistently show no clear relationship between executive control functions and synesthetic behavioral effects. This raises the question of which mechanisms are at play in synesthetic ‘management’ during the presence of two conflicting sensations. (shrink)

Grapheme-color synesthetes experience color, not physically present, when viewing symbols. Synesthetes cannot remember learning these associations. Must synesthetic percepts be formed during a sensitive period? Can they form later and be consistent? What determines their nature? We tested grapheme-color synesthete, MC2, before, during and after she studied Hindi abroad. We investigated whether novel graphemes elicited synesthetic percepts, changed with familiarity, and/or benefited from phonemic information. MC2 reported color percepts to novel Devanagari and Hebrew graphemes. MC2 monitored these percepts over 6 (...) months in a Hindi-speaking environment. MC2 and synesthete DN, reported synesthetic percepts for Armenian graphemes, or Cyrillic graphemes + phonemes over time. Synesthetes, not controls, reported color percepts for novel graphemes that gained consistency over time. Phonemic information did not enhance consistency. Thus, synesthetes can form and consolidate percepts to novel graphemes as adults. These percepts may depend on pre-existing grapheme-color relationships but they can flexibly shift with familiarity. (shrink)

In a variety of synaesthesia, photisms result from affect-laden stimuli as emotional words, or faces of familiar people. For R, who participated in this study, the sight of a familiar person triggers a mental image of "a human silhouette filled with colour". Subjective descriptions of synaesthetic experiences induced by the visual perception of people's figures and faces show similarities with the reports of those who claim to possess the ability to see the aura. It has been proposed that the purported (...) auric perception may be easily explained by the presence of a specific subtype of cross-modal perception. We analyse the subjective reports of four synaesthetes who experience colours in response to human faces and figures. These reports are compared with descriptions of alleged auric phenomena found in the literature and with claims made by experts in esoteric spheres. The discrepancies found suggest that both phenomena are phenomenologically and behaviourally dissimilar. (shrink)

Is synaesthesia cognitively useful? Individuals with time–space synaesthesia experience time units as idiosyncratic spatial forms, and report that these forms aid them in mentally organising their time. In the present study, we hypothesised that time–space synaesthesia would facilitate performance on a time-related cognitive task. Synaesthetes were not specifically recruited for participation; instead, likelihood of time–space synaesthesia was assessed on a continuous scale based on participants’ responses during a semi-structured interview. Participants performed a month-manipulation task, which involved naming every second month (...) or every third month in reverse-chronological order, beginning and ending with a target month. Using hierarchical multiple regression, we found that time–space synaesthesia corresponded with faster performance on both versions of the task. We propose that time–space synaesthesia may expedite the cognitive manipulation of time-based information. Our results also indicate that synaesthesia is far less unusual than widely believed. (shrink)

Recent research has suggested that not all grapheme-colour synaesthetes are alike. One suggestion is that they can be divided, phenomenologically, in terms of whether the colours are experienced in external or internal space. Another suggestion is that they can be divided according to whether it is the perceptual or conceptual attributes of a stimulus that is critical. This study compares the behavioural performance of 7 projector and 7 associator synaesthetes. We demonstrate that this distinction does not map on to behavioural (...) traits expected from the higher–lower distinction. We replicate previous research showing that projectors are faster at naming their synaesthetic colours than veridical colours, and that associators show the reverse profile. Synaesthetes who project colours into external space but not on to the surface of the grapheme behave like associators on this task. In a second task, graphemes presented briefly in the periphery are more likely to elicit reports of colour in projectors than associators, but the colours only tend to be accurate when the grapheme itself is also accurately identified. We propose an alternative model of individual differences in grapheme-colour synaesthesia that emphasises the role of different spatial reference frames in synaesthetic perception. In doing so, we attempt to bring the synaesthesia literature closer to current models of non-synaesthetic perception, attention and binding. (shrink)

Cross-modal perceptual illusions occur when a stimulus to one modality impacts perceptual experience associated with another modality. Unlike synaesthesia, cross-modal illusions are intelligible as results of perceptual strategies for dealing with sensory stimulation to multiple modalities, rather than as mere quirks. I argue that understanding cross-modal illusions reveals an important flaw in a widespread conception of the senses, and of their role in perceptual experience, according to which understanding perception and perceptual experience is a matter of assembling independently viable stories (...) about vision, audition, olfaction, and the rest. (shrink)

In cases where one sense-modality is stimulated by another, we speak of synesthesia, i.e., of a subjective experience of multiple distinct sensations as being quite literally conjoined. The term “synesthesia” is derived indirectly from the Greek words “syn,” meaning “together,” and “aisthesis,” meaning “sensation.” This article focuses on the question of whether synesthesia is in fact a mental disorder or a creative gift. Both the commonsense views that have emerged in recent times, and neurological research, demonstrate that our knowledge of (...) this relatively uncommon phenomenon is slowly but constantly expanding. Proper experimental research conducted with the right sorts of synesthete, and philosophically and scientifically nuanced conceptual studies of synesthesia, can all be helpful when seeking answers to the question posed above, while also confirming general claims about the extent to which our perceptions are really subjective. Most synesthetes see themselves as gifted, and claim that this “conjoining of the senses” enriches the quality of their lives. (shrink)

The apparent dichotomy between qualitative versus quantitative dimensions in science intersects with the domain of several disciplines, as well as different research fields within one and the same discipline. The perception of qualitative as “poor quantitative,” however, is methodologically unsustainable, because there are perfectly rigorous ways to conduct qualitative research. A somehow different question is whether a science of qualities per se is possible: that is, whether a science of appearances can be devised, what its observables are, and its methodological (...) implications. The article deals with this last issue, and especially from the point of view of experimental phenomenology. The weakness of the current approach to perception is discussed, and an alternative view that goes beyond veridicalism is presented. The analysis tackles crucial issues such as color and spatial appearances, the qualitative dimension of perceived depth, and the role of visual meaningful gestalten as information tools for the survival of living beings in the environment. If developed, a science of the qualitative dimensions of appearances may contribute to revising the ecological theory of perception by making its natural semantics more explicit. (shrink)

Grapheme-colour synaesthesia is a perceptual experience where graphemes, letters or words evoke a specific colour, which are experienced either as spatially coincident with the grapheme inducer (projector sub-type) or elsewhere, perhaps without a definite spatial location (associator sub-type). Here, we address the question of whether synaesthesia can be rapidly produced using a hypnotic colour suggestion to examine the possibility of ‘hypnotic synaesthesia’, i.e. subjectively experienced colour hallucinations similar to those experienced by projector synaesthetes. We assess the efficacy of this intervention (...) using an “embedded figures” test, in which participants are required to detect a shape (e.g., a square) composed of local graphemic elements. For grapheme-colour synaesthetes, better performance on the task has been linked to a higher proportion of graphemes perceived as coloured. We found no performance benefits on this test when using a hypnotic suggestion, as compared to a no-suggestion control condition. The same result was found when participants were separated according to the degree to which they were susceptible to the suggestion (number of coloured trials perceived). However, we found a relationship between accuracy and subjective reports of colour in those participants who reported a large proportion of coloured trials: trials in which the embedded figure was accurately recognised (relative to trials in which it was not) were associated with reports of more intense colours occupying a greater spatial extent. Collectively, this implies that hypnotic colour was only perceived after shape detection rather than aiding in shape detection via colour-based perceptual grouping. The results suggest that hypnotically induced colours are not directly comparable to synaesthetic ones. (shrink)

Ineffability, the degree to which percepts or concepts resist linguistic coding, is a fairly unexplored nook of cognitive science. Although philosophical preoccupations with qualia or nonconceptual content certainly touch upon the area, there has been little systematic thought and hardly any empirical work in recent years on the subject. We argue that ineffability is an important domain for the cognitive sciences. For examining differential ineffability across the senses may be able to tell us important things about how the mind works, (...) how different modalities talk to one another, and how language does, or does not, interact with other mental faculties. (shrink)

Children often personify non-living objects, such as puppets and stars. This attribution is considered a healthy phenomenon, which can simulate social exchange and enhance children's understanding of social relationships. In this study, we considered that the tendency of children to engage in personification could potentially be observed in abstract entities, such as numbers. We hypothesized that children tend to attribute personalities to numbers, which diminishes during the course of development. By consulting the methodology to measure ordinal linguistic personification (OLP), which (...) is a type of synesthesia, we quantified the frequency with which child and adult populations engage in number personification. Questionnaires were completed by 151 non-synesthetic children (9--12 years old) and 55 non-synesthetic adults. Children showed a higher tendency than adults to engage in number personification, with respect to temporal consistency and the frequency of choosing meaningful answers. Additionally, children tended to assign unique and exclusive descriptions to each number from zero to nine. By synthesizing the series of analyses, we revealed the process in which number personification diminishes throughout development. In the discussion, we examined the possibility that number personification serves as a discrimination clue to aid children's comprehension of the relationships between numbers. (shrink)

Determinants of synesthetic color choice for the Japanese logographic script, Kanji, were studied. The study investigated how synesthetic colors for Kanji characters, which are usually acquired later in life than other types of graphemes in Japanese language , are influenced by linguistic properties such as phonology, orthography, and meaning. Of central interest was a hypothesized generalization process from synesthetic colors for graphemes, learned prior to acquisition of Kanji, to Kanji characters learned later. Results revealed that color choices for Kanji characters (...) depend on meaning and phonological information. Some results suggested that colors are generalized from Hiragana characters and Arabic digits to Kanji characters via phonology and meaning, respectively. Little influence of orthographic information was observed. The findings and approach of this study contributes to a clarification of the mechanism underlying grapheme-color synesthesia, especially in terms of its relationship to normal language processing. (shrink)

People with grapheme-color synesthesia perceive specific colors when viewing different letters or numbers. Previous studies have suggested that synesthetic color experience can be bistable when induced by an ambiguous character. However, the exact relationship between processes underlying the identity of an alphanumeric character and the experience of the induced synesthetic color has not been examined. In the present study, we explored this by focusing on the temporal relation of inducer identification and color emergence using inducers whose identity could be rendered (...) ambiguous upon rotation of the characters. Specifically, achromatic alphabetic letters and digits were presented at varying angles to 9 grapheme-color synesthetes. Results showed that grapheme identification and synesthetically perceived grapheme color covary with the orientation of the test stimulus and that synesthetes were slower naming the experienced color than identifying the character, particularly at intermediate angles where ambiguity was greatest. (shrink)

Synaesthesia is a heterogeneous phenomenon, even when considering one particular sub-type. The purpose of this study was to design a reliable and valid questionnaire for grapheme-colour synaesthesia that captures this heterogeneity. By the means of a large sample of 628 synaesthetes and a factor analysis, we created the Coloured Letters and Numbers questionnaire with 16 items loading on 4 different factors . These factors were externally validated with tests which are widely used in the field of synaesthesia research. The questionnaire (...) showed good test–retest reliability and construct validity . Our findings are discussed in the light of current theories and new ideas in synaesthesia research. More generally, the questionnaire is a useful tool which can be widely used in synaesthesia research to reveal the influence of individual differences on various performance measures and will be useful in generating new hypotheses. (shrink)

Grapheme-colour synaesthetes experience unusual colour percepts when they encounter letters and/or digits. Studies of English-speaking grapheme-colour synaesthetes have shown that synaesthetic colours are sometimes triggered by rule-based linguistic mechanisms . In contrast, little is known about synaesthesia in logographic languages such as Chinese. The current study shows the mechanisms by which synaesthetic speakers of Chinese colour their language. One hypothesis is that Chinese characters might be coloured by their constituent morphological units, known as radicals, and we tested this by eliciting (...) synaesthetic colours for characters while manipulating features of the radicals within them. We found that both the function and position of radicals influence the nature of the synaesthetic colour generated. Our data show that in Chinese, as in English, synaesthetic colours are influenced by systematic rules, rather than by random associations, and that these rules are based on existing psycholinguistic mechanisms of language processing. (shrink)

Despite some principal similarities, there is no systematic comparison between the different types of synesthesia . This comprehensive review compares the three principal types of synesthesia and focuses on their phenomenological features and their relation to different etiological models. Implications of this comparison for the validity of the different etiological models are discussed.Comparison of the three forms of synesthesia show many more differences than similarities. This is in contrast to their representation in the literature, where they are discussed in many (...) respects as being virtually similar. Noteworthy is the much broader spectrum and intensity with the typical drug-induced synesthesias compared to genuine and acquired synesthesias. A major implication of the phenomenological comparison in regard to the etiological models is that genuine and acquired synesthesias point to morphological substrates, while drug-induced synesthesia appears to be based on functional changes of brain activity. (shrink)

Recently, swimming-style colour synaesthesia was introduced as a new form of synaesthesia. A synaesthetic Stroop test was used to establish its genuineness. Since Stroop interference can occur for any type of overlearned association, in the present study we used a modified Stroop test and psychophysiological synaesthetic conditioning to further establish the genuineness of this form of synaesthesia. We compared the performance of a swimming-style colour synaesthete and a control who was trained on swimming-style colour associations. Our results showed that behavioural (...) aspects of swimming-style colour synaesthesia can be mimicked in a trained control. Importantly, however, our results showed a psychophysiological conditioning effect for the synaesthete only. We discuss the theoretical relevance of swimming-style colour synaesthesia according to different models of synaesthesia. We conclude that swimming-style colour synaesthesia is a genuine form of synaesthesia, can be mimicked behaviourally in non-synaesthetes, and is best explained by a re-entrant feedback model. (shrink)

Although the condition known as synaesthesia is currently undergoing a scientific resurgence, to date the literature has largely focused on the heterogeneous nature of synaesthesia across individuals. In order to provide a better understanding of synaesthesia, however, general characteristics need to be investigated. Synaesthetic experiences are often described as occurring ‘internally’ or in the ‘mind’s eye’, which is remarkably similar to how we would describe our experience of visual mental imagery. We assessed the role of visual imagery in synaesthesia by (...) sampling a large group of synaesthetes and found that they report experiencing more vivid mental images than controls. These findings have important implications for our general understanding of synaesthesia and, in particular, emphasize the need to control for visual imagery in behavioural and neuroimaging paradigms. (shrink)

Autonomous sensory meridian response is a complex sensory-emotional experience characterized by pleasant tingling sensations initiating at the scalp. ASMR is triggered in some people by stimuli including whispering, personal attention, and crisp sounds. Since its inception, ASMR has been likened to synesthesia, but convincing empirical data directly linking ASMR with synesthesia is lacking. In this study, we examined whether the prevalence of synesthesia is indeed significantly higher in ASMR-responders than non-responders. A sample of working adults and students were surveyed about (...) their experience with ASMR and common types of synesthesia. The proportion of synesthetes who were classified as ASMR-responders was 52%, whereas 22% of ASMR-responders were also synesthetes. These results suggest that: over half of those identifying as synesthetes also experience ASMR, and that synesthesia is up to four times as common among ASMR-responders as among non-responders. Findings also suggest a prevalence rate for ASMR of approximately 20%. Overall, the co-occurrence of ASMR and synesthesia lends empirical support to the idea that ASMR may be driven by synesthetic mechanisms, but future research would benefit from examining how ASMR and synesthesia are different, as well as similar. (shrink)

Determinants of synesthetic color choice for Japanese phonetic characters were studied in six Japanese synesthetes. The study used Hiragana and Katakana characters, which represent the same set of syllables although their visual forms are dissimilar. From a palette of 138 colors, synesthetes selected a color corresponding to each character. Results revealed that synesthetic color choices for Hiragana characters and those for their Katakana counterparts were remarkably consistent, indicating that color selection depended on character-related sounds and not visual form. This Hiragana–Katakana (...) invariance cannot be regarded as the same phenomenon as letter case invariance, usually reported for English grapheme-color synesthesia, because Hiragana and Katakana characters have different identities whereas upper and lower case letters have the same identity. This involvement of phonology suggests that cross-activation between an inducer brain region and that of the concurrent area in grapheme-color synesthesia is mediated by higher order cortical processing areas. (shrink)