The Importance of Individual Differences in Grapheme-Color Synesthesia (original) (raw)

2005, Neuron

https://doi.org/10.1016/J.NEURON.2005.03.007

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Abstract

The subjective reports of synesthetes whom we have interviewed, however, suggest that not all grapheme-Bremmer, F., Schlack, A., Shah, N.J., Zafiris, O., Kubischik, M., Hoff-Smilek, D., and Dixon, M.J. (2002). Psyche 8 (http://psyche.cs. monash.edu.au/v8/psyche-8-01-smilek.html). Smilek, D., Dixon, M.J., Cudahy, C., and Merikle, P.M. (2001). J. Cogn. Neurosci. 13, 930-936.

The Neural Bases of Grapheme-Color Synesthesia Are Not Localized in Real Color- Sensitive Areas

The subjective experience of color by synesthetes when viewing achromatic letters and numbers supposedly relates to real color experience, as exemplified by the recruitment of the V4 color center observed in some brain imaging studies. Phenomenological reports and psychophysics tests indicate, however, that both experiences are different. Using functional magnetic resonance imaging, we tried to precise the degree of coactivation by real and synesthetic colors, by evaluating each color center individually, and applying adaptation protocols across real and synesthetic colors. We also looked for structural differences between synesthetes and nonsynesthetes. In 10 synesthetes, we found that color areas and retinotopic areas were not activated by synesthetic colors, whatever the strength of synesthetic associations measured objectively for each subject. Voxel-based morphometry revealed no white matter (WM) or gray matter difference in those regions when compared with 25 control subjects. But synesthetes had more WM in the retrosplenial cortex bilaterally. The joint coding of real and synesthetic colors, if it exists, must therefore be distributed rather than localized in the visual cortex. Alternatively, the key to synesthetic color experience might not lie in the color system.

Dynamic phenomenology of grapheme-color synesthesia

2010

Abstract. In grapheme-color synesthesia, observers perceive colors that are associated with letters and numbers. We tested the dynamic limits of this phenomenon by exposing two synesthetes to characters that rotate smoothly, that morph into other characters, that disappear abruptly, or that have colors either consistent or inconsistent with the corresponding synesthetic color. Rotating letters changed their synesthetic colors abruptly as letter identification changed or failed.

Increased structural connectivity in grapheme-color synesthesia

Nature Neuroscience, 2007

Diffusion tensor imaging allowed us to validate for the first time the hypothesis that hyperconnectivity causes the added sensations in synesthesia. Grapheme-color synesthetes (n = 18), who experience specific colors with particular letters or numbers (for example, 'R is sky blue'), showed greater anisotropic diffusion compared with matched controls. Greater anisotropic diffusion indicates more coherent white matter. Anisotropy furthermore differentiated subtypes of grapheme-color synesthesia. Greater connectivity in the inferior temporal cortex was particularly strong for synesthetes who see synesthetic color in the outside world ('projectors') as compared with synesthetes who see the color in their 'mind's eye' only ('associators'). In contrast, greater connectivity (as compared with non-synesthetes) in the superior parietal or frontal cortex did not differentiate between subtypes of synesthesia. In conclusion, we found evidence that increased structural connectivity is associated with the presence of graphemecolor synesthesia, and has a role in the subjective nature of synesthetic color experience.

Contextual Priming in Grapheme–Color Synesthetes and Yoked Controls: 400 msec in the Life of a Synesthete

Journal of Cognitive Neuroscience, 2011

■ Grapheme-color synesthesia is a heritable trait where graphemes ("2") elicit the concurrent perception of specific colors (red). Researchers have questioned whether synesthetic experiences are meaningful or simply arbitrary associations and whether these associations are perceptual or conceptual. To address these fundamental questions, ERPs were recorded as 12 synesthetes read statements such as "The Coca-Cola logo is white and 2," in which the final grapheme induced a color that was either contextually congruous (red) or incongruous ("…white and 7," for a synesthetes who experienced 7 as green). Grapheme congruity was found to modulate the amplitude of the N1, P2, N300, and N400 components in synesthetes, suggesting that synesthesia impacts perceptual as well as conceptual aspects of processing. To evaluate whether observed ERP effects required the experience of colored graphemes versus knowledge of grapheme-color pairings, we ran three separate groups of controls on a similar task. Controls trained to a synestheteʼs associations elicited N400 modulation, indicating that knowledge of grapheme-color mappings was sufficient to modulate this component. Controls trained to synesthetic associations and given explicit visualization instructions elicited both N300 and N400 modulations. Lastly, untrained controls who viewed physically colored graphemes ("2" printed in red) elicited N1 and N400 modulations. The N1 grapheme congruity effect began earlier in synesthetes than colored grapheme controls but had similar scalp topography. Data suggest that, in synesthetes, achromatic graphemes engage similar visual processing networks as colored graphemes in nonsynesthetes and are in keeping with models of synesthesia that posit early feedforward connections between form and color processing areas in extrastriate cortex. The P2 modulation was unique to the synesthetes and may reflect neural activity that underlies the conscious experience of the synesthetic induction. ■

The Long-Term Potentiation Model for Grapheme-Color Binding in Synesthesia

Sensory Integration and the Unity of Consciousness, D. Bennett and C. Hill (Eds.)

The phenomenon of synesthesia has undergone an invigoration of research interest and empirical progress over the past decade. Studies investigating the cognitive mechanisms underlying synesthesia have yielded insight into neural processes behind such cognitive operations as attention, memory, spatial phenomenology and inter-modal processes. However, the structural and functional mechanisms underlying synesthesia still remain contentious and hypothetical. The first section of the present paper reviews recent research on grapheme-color synesthesia, one of the most common forms of synesthesia, and addresses the ongoing debate concerning the role of selective attention in eliciting synesthetic experience. Drawing on conclusions of the first half, the paper’s second half examines the various models proposed to explain the cognitive mechanisms behind grapheme-color synesthesia, and discusses the explanatory virtues of a new model suggesting that grapheme-color synesthesia is grounded in memory. The last section offers an examination of some of the broader philosophical implications of synesthesia.

Colour?Grapheme Synesthesia Affects Binocular Vision

Frontiers in Psychology, 2011

In colour-grapheme synesthesia, non-coloured graphemes are perceived as being inherently coloured. In recent years, it is debated whether visual processing of synesthesiainducing achromatic graphemes is similar to that of chromatic graphemes. Here, we exploit the phenomenon of binocular rivalry in which incompatible images presented dichoptically compete for conscious expression. Importantly, the competition only arises if the two images are sufficiently different; if the difference between the images is small, the images will fuse into a single mixed percept. We show that achromatic digits that induce synesthetic colour percepts increase the incidence of binocular rivalry compared to achromatic non-digits that do not evoke such percepts. That is, compared to achromatically perceived non-digits, synesthesia-inducing digits increase the predominance of binocular rivalry over binocular fusion. This finding shows that the synesthetic colour experience can provide the conditions for promoting binocular rivalry, much like stimulus features that induce rivalry in normal vision.

Do graphemes attract spatial attention in grapheme-color synesthesia?

Neuropsychologia, 2017

Grapheme-color synesthetes perceive concurrent colors for some objectively achromatic graphemes (inducers). Using oscillatory responses in the electroencephalogram, we tested the hypothesis that inducers automatically attract spatial attention and, thus, favor a conscious experience of color. Achromatic inducers and real-colored non-inducers were presented to the left or to the right visual hemifield and orientation judgments were required for subsequently presented Gabor patches. The graphemes were irrelevant for the task so that the related brain response was purely stimulus-driven. Synesthetes (n =12), but not an equal number of controls, showed an early theta power increase for inducers presented to the right compared to the left hemifield, with sources in left fusiform gyrus. Alpha power asymmetries indicative of shifts of spatial attention were not observed. Together, synesthetes showed an increased responsiveness to inducers in grapheme processing areas. However, contrary to our hypothesis, inducers did not attract spatial attention in synesthetes.

Color Synesthesia

Encyclopedia of Color Science and Technology, 2015

Color synesthesia Definition Color synesthesia is a condition in which sensory or cognitive inducers elicit atypical binding of these inducers to concurrent color experiences. Marks of Color Synesthesia Synesthesia is a condition in which stimulation in one sensory or cognitive stream involuntarily, or automatically, leads to associated internal or external (illusory or hallucinatory) experiences in a second unstimulated sensory or cognitive system [1-9]. Although most cases of synesthesia are developmental and run in families, acquired cases have also been reported following traumatic brain injury, demyelination, ischemia, tumors, post-traumatic total ocular blindness, and neuropathology involving the optic nerve and/or chiasm [10-12]. Color synesthesia is a special kind of synesthesia that comprises cases of synesthesia in which a noncolored sensory or cognitive stimulus involuntarily leads to internal or external color experiences. The prevalence of color synesthesia is unknown. Estimates range from 1 in 200 to 1 in 250,000 [13, 14]. Some speculate that color synesthesia may be present in more than 4 % of the population [5]. One of the best-known forms of color synesthesia is grapheme-color synesthesia, in which numbers or letters are seen as colored. But lots of other forms of color synesthesia have been identified, including week-color synesthesia, sound-color synesthesia, taste-color synesthesia, fear-color synesthesia, etc. [5] For lack of space, this entry shall focus primarily on grapheme-color synesthesia. One mark of color synesthesia is that the synesthetic colors are seen either as projected out onto the world ("projector synesthesia") or in the mind's eye ("associator synesthesia") [15]. Another mark is that it exhibits test-retest reliability [1, 16]: colors identified by the subject as representative of her synesthetic experiences relative to a given stimulus in the initial testing phase are nearly identical to colors identified by the subject as representative of her synesthetic experiences relative to the same stimulus in a retesting phase at a later time (see Fig. 1). Because of the automatic nature of synesthesia and its test-retest reliability, color synesthesia is not to be confused with memory associations or stereotypical colors of objects. For example, there is no evidence that color synesthetes simply remember the colors of entities or images they were exposed to earlier in their lives or associate stimuli with their stereotypical colors [16].

Synesthesia: When colors count

Cognitive Brain Research, 2005

A tacitly held assumption in synesthesia research is the unidirectionality of digit -color associations. This notion is based on synesthetes' report that digits evoke a color percept, but colors do not elicit any numerical impression. In a random color generation task, we found evidence for an implicit co-activation of digits by colors, a finding that constrains neurological theories concerning cross-modal associations in general and synesthesia in particular. D 2005 Elsevier B.V. All rights reserved.

Effective Connectivity Determines the Nature of Subjective Experience in Grapheme-Color Synesthesia

The Journal of …, 2011

Synesthesia provides an elegant model to investigate neural mechanisms underlying individual differences in subjective experience in humans. In grapheme–color synesthesia, written letters induce color sensations, accompanied by activation of color area V4. Competing hypotheses suggest that enhanced V4 activity during synesthesia is either induced by direct bottom-up cross-activation from grapheme processing areas within the fusiform gyrus, or indirectly via higher-order parietal areas. Synesthetes differ in the way synesthetic color is perceived: “projector” synesthetes experience color externally colocalized with a presented grapheme, whereas “associators” report an internally evoked association. Using dynamic causal modeling for fMRI, we show that V4 cross-activation during synesthesia was induced via a bottom-up pathway (within fusiform gyrus) in projector synesthetes, but via a top-down pathway (via parietal lobe) in associators. These findings show how altered coupling within the same network of active regions leads to differences in subjective experience. Our findings reconcile the two most influential cross-activation accounts of synesthesia.

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References (8)

Grossenbacher, P.G., and Lovelace, C.T. (2001). Trends Cogn. Sci. 5, 36-41.
Hubbard, E.M., Arman, A.C., Ramachandran, V.S., and Boynton, G.M. (2005). Neuron 45, this issue, 975-985.
Mattingley, J.B., Rich, A.N., Yelland, G., and Bradshaw, J.L. (2001). Nature 410, 580-582.
Palmeri, T.J., Blake, R.B., Marois, R., Flanery, M.A., and Whetsell, W.O. (2002). Proc. Natl. Acad. Sci. USA 99, 4127-4131.
Ramachandran, V.S., and Hubbard, E.M. (2001). Proc. R. Soc. Lond. B Biol. Sci. 268, 979-983.
Smilek, D., and Dixon, M.J. (2002). Psyche 8 (http://psyche.cs. monash.edu.au/v8/psyche-8-01-smilek.html).
Smilek, D., Dixon, M.J., Cudahy, C., and Merikle, P.M. (2001). J. Cogn. Neurosci. 13, 930-936.
DOI 10.1016/j.neuron.2005.03.007

The neuroanatomy of grapheme-color synesthesia

European Journal of Neuroscience, 2009

Grapheme-color synesthetes perceive particular colors when seeing a letter, word or number (grapheme). Functional neuroimaging studies have provided some evidence in favor of a neural basis for this type of synesthesia. Most of these studies have reported extra activations in the fusiform gyrus, which is known to be involved in color, letter and word processing. The present study examined different neuroanatomical features (i.e. cortical thickness, cortical volume and cortical surface area) in a sample of 48 subjects (24 grapheme-color synesthetes and 24 control subjects), and revealed increased cortical thickness, volume and surface area in the right and left fusiform gyrus and in adjacent regions, such as the lingual gyrus and the calcarine cortex, in grapheme-color synesthetes. In addition, we set out to analyze structural connectivity based on fractional anisotropy (FA) measurements in a subsample of 28 subjects (14 synesthetes and 14 control subjects). In contrast to the findings of a recent neuroanatomical study using modern diffusion tensor imaging measurement techniques, we did not detect any statistically significant difference in FA between synesthetes and non-synesthetes in the fusiform gyri. Our study thus supports the hypothesis of local anatomical differences in cortical characteristics in the vicinity of the V4 complex. The observed altered brain anatomy in grapheme-color synesthetes might be the anatomical basis for this particular form of synesthesia but it is also possible that the detected effects are a consequence (rather than the primary cause) of the lifelong experience of grapheme-color synesthesia.

Grapheme-color synesthesia subtypes: Stable individual differences reflected in posterior alpha-band oscillations

Grapheme-color synesthesia is a condition in which seeing letters and numbers produces sensations of colors (e.g., the letter R may elicit a sky-blue percept). Recent evidence implicates posterior parietal areas, in addition to lower- level sensory processing regions, in the neurobiological mechanisms involved in synesthesia. Furthermore, these mechanisms seem to differ for “projectors” (synesthetes who report seeing the color “out there in the real world”) versus “associators” (synesthetes who report the color to be only an internal experience). Relatively little is known about possible electrophysiological characteristics of grapheme-color synesthesia. Here we used EEG to investigate functional oscillatory differences among associators, projectors, and non-synesthetes. Projectors had stronger stimulus-related alpha-band (~10 Hz) power over posterior parietal electrodes, compared to both associators and non-synesthetes. Posterior alpha activity was not statistically signi␣cantly different between associators from non- synesthetes. We also performed a test-retest assessment of the projector-associator score and found strong retest reliability, as evidenced by a correlation coef␣cient of .85. These ␣ndings demonstrate that the projector-associator distinction is highly reliable over time and is related to neural oscillations in the alpha band.

Varieties of grapheme-colour synaesthesia: A new theory of phenomenological and behavioural differences

Consciousness and Cognition, 2007

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 (projector-associator distinction). Another suggestion is that they can be divided according to whether it is the perceptual or conceptual attributes of a stimulus that is critical (higher-lower distinction). 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.

Projectors, associators, visual imagery, and the time course of visual processing in grapheme-color synesthesia

Cognitive Neuroscience, 2017

In grapheme-color synesthesia, seeing particular letters or numbers evokes the experience of specific colors. We investigate the brain's real-time processing of words in this population by recording event-related brain potentials (ERPs) from 15 grapheme-color synesthetes and 15 controls as they judged the validity of word pairs ('yellow banana' vs. 'blue banana') presented under high and low visual contrast. Low contrast words elicited delayed P1/N170 visual ERP components in both groups, relative to high contrast. When color concepts were conveyed to synesthetes by individually tailored achromatic grapheme strings ('55555 banana'), visual contrast effects were like those in color words: P1/N170 components were delayed but unchanged in amplitude. When controls saw equivalent colored grapheme strings, visual contrast modulated P1/N170 amplitude but not latency. Color induction in synesthetes thus differs from color perception in controls. Independent from experimental effects, all orthographic stimuli elicited larger N170 and P2 in synesthetes than controls. While P2 (150-250ms) enhancement was similar in all synesthetes, N170 (130-210ms) amplitude varied with individual differences in synesthesia and visual imagery. Results suggest immediate cross-activation in visual areas processing color and shape is most pronounced in so-called projector synesthetes whose concurrent colors are experienced as originating in external space.

Components of Attention in Grapheme-Color Synesthesia: A Modeling Approach

PLOS ONE, 2015

Grapheme-color synesthesia is a condition where the perception of graphemes consistently and automatically evokes an experience of non-physical color. Many have studied how synesthesia affects the processing of achromatic graphemes, but less is known about the synesthetic processing of physically colored graphemes. Here, we investigated how the visual processing of colored letters is affected by the congruence or incongruence of synesthetic grapheme-color associations. We briefly presented graphemes (10-150 ms) to 9 grapheme-color synesthetes and to 9 control observers. Their task was to report as many letters (targets) as possible, while ignoring digit (distractors). Graphemes were either congruently or incongruently colored with the synesthetes' reported grapheme-color association. A mathematical model, based on Bundesen's (1990) Theory of Visual Attention (TVA), was fitted to each observer's data, allowing us to estimate discrete components of visual attention. The models suggested that the synesthetes processed congruent letters faster than incongruent ones, and that they were able to retain more congruent letters in visual short-term memory, while the control group's model parameters were not significantly affected by congruence. The increase in processing speed, when synesthetes process congruent letters, suggests that synesthesia affects the processing of letters at a perceptual level. To account for the benefit in processing speed, we propose that synesthetic associations become integrated into the categories of graphemes, and that letter colors are considered as evidence for making certain perceptual categorizations in the visual system. We also propose that enhanced visual short-term memory capacity for congruently colored graphemes can be explained by the synesthetes' expertise regarding their specific grapheme-color associations.

Color synesthesia. Insight into perception, emotion, and consciousness

Current opinion in neurology, 2015

Synesthesia is an extraordinary perceptual phenomenon, in which individuals experience unusual percepts elicited by the activation of an unrelated sensory modality or by a cognitive process. Emotional reactions are commonly associated. The condition prompted philosophical debates on the nature of perception and impacted the course of art history. It recently generated a considerable interest among neuroscientists, but its clinical significance apparently remains underevaluated. This review focuses on the recent studies regarding variants of color synesthesia, the commonest form of the condition. Synesthesia is commonly classified as developmental and acquired. Developmental forms predispose to changes in primary sensory processing and cognitive functions, usually with better performances in certain aspects and worse in others, and to heightened creativity. Acquired forms of synesthesia commonly arise from drug ingestion or neurological disorders, including thalamic lesions and senso...

Grapheme–Color Synesthesia Influences Overt Visual Attention

Journal of Cognitive Neuroscience, 2009

Synaesthesia is a fascinating condition in which ordinary stimuli elicit extraordinary sensory experiences. For example, specific tastes may elicit unusual tactile sensations and standard black letters may elicit highly specific colour experiences. These unusual experiences have been shown to have substantial impact on cognition, emotion, perception, and covert attention. Two experiments are presented which show that synaesthesia also influences overt visual attention. In these experiments two grapheme-colour synaesthetes viewed coloured letters while their eye movements were tracked.

Cross-modal, bidirectional priming in grapheme-color synesthesia

Consciousness and cognition, 2015

Grapheme-color synesthetes perceive achromatic graphemes to be inherently colored. In this study grapheme-color synesthetes and non-synesthetes discriminated (1) the color of visual targets presented along with aurally presented digit primes, and (2) the identity of aurally presented digit targets presented with visual color primes. Reaction times to visual color targets were longer when the color of the target was incongruent with the synesthetic percept reported for the prime. Likewise, discriminating aurally presented digit targets took longer when the color of the prime was incongruent with the synesthetic percept for the target. These priming effects were absent in non-synesthetes. We conclude that binding between digits and colors in grapheme-color synesthetes can occur bidirectionally across senses. The results are in line with the idea that synesthesia is the result of linking inducing stimuli (e.g. digits) to synesthetic percepts (colors) at an abstract - supra-modal - conc...

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Increased structural connectivity in grapheme-color synesthesia

Nature Neuroscience, 2007

Understanding grapheme personification: A social synaesthesia?

Journal of Neuropsychology, 2011

Much of synaesthesia research focused on colour, but not all cross-domain correspondences reported by synaesthetes are strictly sensory. For example, some synaesthetes personify letters and numbers, in additional to visualizing them in colour. First reported in the 1890s, the phenomenon has been largely ignored by scientists for more than a century with the exception of a few single-case reports. In the present study, we collected detailed self-reports on grapheme personification using a questionnaire, providing us with a comprehensive description of the phenomenology of grapheme personification. Next, we documented the behavioural consequences of personifying graphemes using a congruity paradigm involving a gender judgement task; we also examined whether personification is associated with heightened empathy as measured using Empathy Quotient and found substantial individual differences within our sample. Lastly, we present the first neuroimaging case study of personification, indicating that the precuneus activation previously seen in other synaesthesia studies may be implicated in the process. We propose that frameworks for understanding synaesthesia could be extended into other domains of cognition and that grapheme personification shares more in common with normal cognition than may be readily apparent. This benign form of hyper-mentalizing may provide a unique point of view on one of the most central problems in human cognition -understanding others' state of mind.

Synaesthesia for Finger Counting and Dice Patterns: A Case of Higher Synaesthesia?

Neurocase, 2007

Synaesthesia is often triggered by numbers, although it is conceivable that different aspects of numerical representation are responsible for different variants of synaesthesia. For individuals with "higher synaesthesia" it is assumed that number meaning (or numerosity) is responsible for the elicitation of synaesthetic experiences. This study documents a case study of a synaesthete, TD, who broadly fits this profile. TD reports that the same colours are elicited from physically different representations of number (digits, dice patterns and finger counting) provided that they share the same numerosity. The authenticity of his synaesthesia is established using Stroop-like priming and interference paradigms. Not only does synaesthetic colour interfere with veridical colour judgements, but also veridical colours can interfere with numerosity judgments. This suggests a close bi-directional coupling between numerosity and colour. Together, these findings constrain theories concerning the neural basis of synaesthesia.

Coming Unbound: Disrupting Automatic Integration of Synesthetic Color and Graphemes by Transcranial Magnetic Stimulation of the Right Parietal Lobe

Journal of Cognitive Neuroscience, 2006

& In some individuals, a visually presented letter or number automatically evokes the perception of a specific color, an experience known as color-grapheme synesthesia. It has been suggested that parietal binding mechanisms play a role in the phenomenon. We used a noninvasive stimulation technique, transcranial magnetic stimulation (TMS), to determine whether the posterior parietal lobe is critical for the integration of color and shape in color-grapheme synesthesia, as it appears to be for normal color-shape binding. Using a color-naming task with colored letters that were either congruent or incongruent with the synesthetic photism, we demonstrate that inhibition of the right posterior parietal lobe with repetitive TMS transiently attenuates synesthetic binding. These findings suggest that synesthesia (the induction of color from shape) relies on similar mechanisms as found in normal perception (where the perception of color is induced by wavelength). &

Grapheme–Color Synesthesia Influences Overt Visual Attention

Journal of Cognitive Neuroscience, 2009

When “3” is a Jerk and “E” is a King: Personifying Inanimate Objects in Synesthesia

Journal of Cognitive Neuroscience, 2007

& We report a case study of an individual (TE) for whom inanimate objects, such as letters, numbers, simple shapes, and even furniture, are experienced as having rich and detailed personalities. TE reports that her object-personality pairings are stable over time, occur independent of her intentions, and have been there for as long as she can remember. In these respects, her experiences are indicative of synesthesia. Here we show that TE's object-personality pairings are very consistent across test-retest, even for novel objects. A qualitative analysis of TE's personality descriptions revealed that her personifications are extremely detailed and multidimensional, and that her personifications of familiar and novel objects differ in specific ways. We also found that TE's eye movements can be biased by the emotional associations she has with letters and numbers. These findings demonstrate that synesthesia can involve complex semantic personifications, which can influence visual attention. Finally, we propose a neural model of normal personification and the unusual personifications that accompany object-personality synesthesia. &

Distinct colours in the ‘synaesthetic colour palette’

Philosophical Transactions of the Royal Society B: Biological Sciences

In grapheme-colour synaesthesia, particular linguistic elements evoke particular colour sensations. Interestingly, when asked, non-synaesthetes can also associate colours to letters, and previous studies show that specific letter-to-colour associations have similar biases to those of synaesthetes. However, it is an open question whether the colours reported by synaesthetes and non-synaesthetes differ overall : is there a ‘synaesthetic colour palette’? In this study, we visualize the overall distribution in colour space of colour concurrents in grapheme-colour synaesthetes, and colour associations in non-synaesthetic controls. We confirm the existence of a synaesthetic colour palette: colour concurrents in synaesthetes are different from colour associations in non-synaesthetes. We quantify three factors that distinguish the colour palette of synaesthetes and non-synaesthetes: synaesthetes have an increased over-representation of ‘pure’ (unmixed) hues, an increased presence of ‘warm’ ...