Synesthetic Associations Research Articles

Graphemic and Semantic Pathways of Number-Color Synesthesia: A Dissociation of Conceptual Synesthesia Mechanisms.

Number–color synesthesia is a condition in which synesthetes perceive numbers with concurrent experience of specific, corresponding colors. It has been proposed that synesthetic association exists primarily between representations of Arabic digit graphemes and colors, and a secondary, semantic connection between numerosity and colors is built via repeated co-activation. However, this distinction between the graphemic and semantic pathways of synesthetic number–color connection has not been empirically tested. The current study aims to dissociate graphemic and semantic aspects of color activations in number–color synesthesia by comparing their time courses. We adopted a synesthetic priming paradigm with varied stimuli onset asynchronies (SOAs). A number (2–6, prime) was presented in one of three notations: digit, dice, or non-canonical dot pattern, and a color patch (target) appeared with an SOA of 0, 100, 300, 400, or 800 ms. Participants reported the color as quickly as possible. Using the congruency effect (i.e., shorter reaction time when target color matched the synesthetic color of number prime) as an index of synesthetic color activation level, we revealed that the effect from the graphemic pathway is quick and relatively persistent, while the effect from the semantic pathway unfolds at a later stage and is more transient. The dissociation between the graphemic and semantic pathways of synesthesia implies further functional distinction within “conceptual synesthesia”, which has been originally discussed as a unitary phenomenon. This distinction has been demonstrated by the differential time courses of synesthetic color activations, and suggested that a presumed, single type of synesthesia could involve multiple mechanisms.

Face-Processing Differences Present in Grapheme-Color Synesthetes.

Grapheme‐color synesthesia is a heterogeneous neurological phenomenon whereby the experience of a grapheme automatically and involuntarily elicits an experience of color. While the majority of synesthesia research has focused on inducer‐specific influences of synesthetic associations, more recent efforts have examined potential broader differences. Based on spontaneous reports from synesthetes detailing problems with face recognition, in conjunction with the geographical proximity of neurological regions relevant to both synesthesia and face processing, we sought to examine whether synesthetes demonstrated atypical face‐processing abilities.A total of 16 grapheme‐color synesthetes and 16 age‐and‐gender matched controls (±3 years) completed the Cambridge Face Memory Test (CFMT; Duchaine & Nakayama, 2006) of face memory, the Vanderbilt Holistic Face Processing Task (VHPT‐F; Richler, Floyd, & Gauthier, 2014) of holistic face processing, as well as a standardized self‐report questionnaire the Faces and Emotions Questionnaire (Freeman, Palermo, & Brock, 2015). The results revealed significantly poorer performance in synesthete's ability to recognize faces in the CFMT that was driven by a reduction in upright advantage. Results also revealed a significant reduction in overall accuracy on the VHPT‐F for synesthetes, who despite this displayed a comparable holistic processing advantage compared to matched controls. Finally, synesthetes also rated themselves as significantly worse at face recognition. We suggest that this pattern may reflect differences in the development of individualized perceptual strategies.

Do the colors of your letters depend on your language? Language-dependent and universal influences on grapheme-color synesthesia in seven languages

Grapheme-color synesthetes experience graphemes as having a consistent color (e.g., “N is turquoise”). Synesthetes’ specific associations (which letter is which color) are often influenced by linguistic properties such as phonetic similarity, color terms (“Y is yellow”), and semantic associations (“D is for dog and dogs are brown”). However, most studies of synesthesia use only English-speaking synesthetes. Here, we measure the effect of color terms, semantic associations, and non-linguistic shape-color associations on synesthetic associations in Dutch, English, Greek, Japanese, Korean, Russian, and Spanish. The effect size of linguistic influences (color terms, semantic associations) differed significantly between languages. In contrast, the effect size of non-linguistic influences (shape-color associations), which we predicted to be universal, indeed did not differ between languages. We conclude that language matters (outcomes are influenced by the synesthete’s language) and that synesthesia offers an exceptional opportunity to study influences on letter representations in different languages.

Consistency and strength of grapheme-color associations are separable aspects of synesthetic experience

Consistency of synesthetic associations over time is a widely used test of synesthesia. Since many studies suggest that consistency is not a completely reliable feature, we compared the consistency and strength of synesthetes’ grapheme-color associations. Consistency was measured by scores on the Synesthesia Battery and by the Euclidean distance in color space for the specific graphemes tested for each participant. Strength was measured by congruency magnitudes on the Implicit Association Test. The strength of associations was substantially greater for synesthetes than non-synesthetes, suggesting that this is a novel, objective marker of synesthesia. Although, intuitively, strong associations should also be consistent, consistency and strength were uncorrelated, indicating that they are likely independent, at least for grapheme-color synesthesia. These findings have implications for our understanding of synesthesia and for estimates of its prevalence since synesthetes who experience strong, but inconsistent, associations may not be identified by tests that focus solely on consistency.

Consistency of synesthetic association varies with grapheme familiarity: A longitudinal study of grapheme-color synesthesia

Grapheme-color synesthesia is a condition in which the visual perception of letters or numbers induces a specific color sensation. The consistency of grapheme-color association has been considered as a fundamental characteristic of synesthesia. However, recent studies have indicated that this association can change across the adult lifespan, and it has become necessary to investigate the factors behind the changes within each synesthete. We conducted a longitudinal study of Japanese adult synesthetes to investigate long-term (5–8 years) changes in color responses to 300 graphemes (alphanumeric and Japanese characters). Graphemes with lower long-term consistency of synesthetic association also tended to have lower short-term consistency, indicating that grapheme-color association's consistency is determined for each grapheme. Further, less familiar graphemes had less consistent associations with their synesthetic colors. These findings suggest that a stronger grapheme-color association is formed for more familiar graphemes, leading to the consolidation of synesthetic color for such graphemes.

Grapheme-Color Synesthesia in an Abugida: a Bengali Case Study.

Grapheme-color synesthetes experience graphemes (e.g., letters of the alphabet) as having a specific, consistent color. Most studies of grapheme-color synesthesia have only examined synesthetes in English, leaving underexplored the question of how synesthetic phenomenology might differ in languages that do not use alphabets. In particular, grapheme-color synesthesia in an abugida (a segmental writing system in which vowels are added to consonant graphemes using 'accent'-like diacritical marks) has never been studied. Here, we present a case study of a Bengali synesthete, MJ, the first report of a grapheme-color synesthete in an abugida. First, we show that for MJ, diacritics influence the overall color of the consonant grapheme they modify, 'pulling' it toward the color she experiences for the vowel. Second, we describe and analyze the complex synesthetic experiences reported by MJ for conjunct graphemes, a unique orthographic feature of Brahmi-derived scripts (such as Bengali) in which multiple graphemes are visually combined into a single 'merged' grapheme. Finally, we show that in addition to these language-specific features, MJ's synesthetic associations are influenced by some of the same linguistic properties (such as orthography and phonology) that influence synesthetic associations in other languages. We conclude that the idiosyncratic features of MJ's synesthesia reflect unique properties of the Bengali writing system, that more studies of synesthesia in non-alphabetic scripts are needed, and that synesthetic phenomenology can offer insights into how linguistic properties shape grapheme representation in the brain.

Adaptation to a New Tuning Standard in a Musician with Tone-color Synesthesia and Absolute Pitch

ABSTRACT Developmental synesthesia is a neurological condition in which certain perceptions or cognitions trigger atypical supplementary perceptions (e.g., tones evoke specific colors). Tone-color synesthesia is prevalent in musicians and is associated with enhanced music processing and increased connectivity in auditory cortex. We report the case of NTM, a professional violinist with tone-color synesthesia as well as absolute pitch. When she switched from modern (A440 tuning standard) to baroque (A415 tuning standard) interpretation, NTM experienced a serious incongruence in her synesthesia and absolute pitch which severely interfered with her musical performance. However, through explicit self-training over months using color cues from her synesthesia, she learned new pitch associations for her note concepts which canceled this interference. This ability was validated through a second evaluation four years after the initial evaluation. NTM can now switch between both standards with little interference. She also reported changes in her non-musical synesthesia and developed new synesthesia to a tonal language (mandarin). This case indicates that synesthetic associations can be used as anchors to learn a new tuning standard when interference is high. It also suggests that tone concepts can undergo important perceptual modifications and still maintain their stability as inducers of synesthesia.

The Texture of Type: Nabokov’s Sensory Perception of Alphabetical Letters: The Semanticized Graphic Form

ABSTRACT My paper investigates how Nabokov’s synesthetic perception of typographic letters as images was expanded into a special letter-coding semanticizing practice and discusses the important questions raised by this strategy with regard to the theory and practice of literary analysis. I argue that Nabokov reconceives and expands his biologically determined binary (letter-with-color) synesthetic associations in a cross- and self-referential system of motifs permeating the whole oeuvre. Consciously controlling his personal experience of his synesthetic mind, Nabokov extrapolates it by adding images and objects and how in this artistic method he attaches symbolic or emblematic notions to letters through color- and object-associations. This complex meaning of letters can be unfolded from supporting codes, metaphors and motifs that trigger adequate contextual interpretations. His prose invites the same meticulous text-decoding methodology demanded by Symbolist and avant-garde prose art that helps to discover a similar segment in the theory of art of these two literary tendencies reputed as antithetical. 1 1 The article was written in the framework of the project “The Border Zone Paradigm: Crossroads in Culture” (2018–2020) funded by the Russian Foundation for Fundamental Research (No. 18–512–23002).

ПСИХОЛОГИЧЕСКИЙ АСПЕКТ СИНЕСТЕЗИИ И ОСОБЕННОСТИ СИНЕСТЕТИЧЕСКОГО ВОСПРИЯТИЯ НЕСЛЫШАЩИХ

The article is devoted to synesthesia, its study from the point of view of psychology and neuropsychology, features of synesthetic perception and importance of synesthesia for deaf people. The author refers to the works of modern researchers of synesthesia in the field of psychology and neuropsychology and examines various types of synesthetic reactions and associations. Synesthesia researchers study this phenomenon comprehensively, in the sensoryperceptual- cognitive continuum. Synesthetic stimuli and reactions are related to perception and can be considered in terms of its emotional component. It is emphasized that synesthesia affects the individual’s memory, in particular, A. R. Luria, who investigated the phenomenon of synesthesia, believes that synesthetic sensations contribute to better memorization of information, especially perceived from hearing. A. R. Luria notes that at hearing perception of a word, its phonetic component remains on the last place, and the dominant meaning is semantic. In synesthesia, a brighter visual and auditory image is attached to the perception of meaning. When memorizing, the visual component of the image remains the leading one. For deaf people, the meaning itself, perceived with the help of sign language, is already assigned to the visual component. But this is not always a visual image. The author refers to the testimonies of deaf people, who describe their synesthetic experience, showing that the absence of hearing is not an obstacle to the perception of sound, which can be felt by other senses, touch and vision.

Synesthetes perseverate in implicit learning: Evidence from a non-stationary statistical learning task.

Synesthetes automatically and consistently experience additional sensory or cognitive perceptions in response to particular environmental stimuli. Recent evidence suggests that the propensity to develop synesthesia is genetic while the particular associations experienced by a given synesthete are influenced by learning. Despite the potential role of implicit learning in the formation of synesthetic associations, there has been minimal investigation of synesthetes' implicit learning abilities. In this study, we examine linguistic-colour synesthetes' ability to implicitly learn from and adjust to non-stationary statistics in a domain unrelated to their particular form of synesthesia. Engaging participants in a computer game Whack-the-mole, we utilise the online measure of reaction time to assess the time course of learning. Participants are exposed to "worlds" of probabilities that, unbeknownst to them, undergo unannounced changes, creating unpredictable statistical shifts devoid of accompanying cues. The same small set of probability worlds are repeated throughout the experiment to investigate participants' ability to retain and learn from this repetitive probabilistic information. The reaction time data provide evidence that synesthetes require more information than nonsynesthetes to benefit from the non-stationary probability distributions. These findings demonstrate that linguistic-colour synesthetes' implicit learning abilities-in a domain far from their synesthetic experiences-differ from those of nonsynesthetes.

Paratextual programming of ensemble works by Ukrainian composers: semantic and semiotic-expressive aspects of synesthetic associations

The purpose of the article is to study the Ukrainian chamber creativity of the late 20th – early 21st centuries from the point of view of analyzing the methods of paratextual programming of ensemble pieces for various types of thematic and meaningful representativeness and related processes of music inheritance of some artistic and expressive functions «transposed» from unrelated arts. Methodology. Used a set of methodological approaches of textological, semantic, synesthetic, cultural analysis. Scientific novelty. The study of paratextual programming of the compositions of the chamber art of Ukraine of the late XX – early XXI centuries allowed, on the one hand, to emphasize thematic areas of representation in music of artistic images (plots, themes, motifs) from works of other arts. On the other hand, it made it possible to detect the presence of interaction between different types of art not only at the semantic but also at the semiotic-expressive levels, which is implemented through the introduction of specific techniques of the semiotic «translation» of semantic and structural «cliches» of rhetorical, graphic, plastic, theatrical expression. Conclusions. Systematization of methods of paratextual programming of chamber art works in Ukraine in the late ХХ and early ХХІ centuries allows us to single out several groups of their thematic representativeness on the principle of interaction in musical-literary, -visual, - theatrical and -movie correlations. The intersemiotic semantic connection of the musical text with its paratextual component (reflected in names, auto-commentaries, remarks, epigraphs, dedications) is often emphasized in a semiotic and expressive manner. The study of this process reveals that at an semiotic level of comparison and identification of stylistic techniques (which initially have a non-musical species origin and a method of artistic and material embodiment) is carried out by means of technical and compositional operation with rich sound-visual resources of music. The potential of their disclosure (using intonation, microtonic, timbre, phonical, textural, polyphonic means, including «voiced silence») is aimed at obtaining a synesthetic perceptual effect that creates the illusion of semiotic conformity and a kind of «transfer» to the audible space of ensemble compositions of extra-musical artistic and expressive techniques and functions.

Synesthesia improves sensory memory, when perceptual awareness is high

Empirical evidence suggests that synesthesia is associated with enhanced sensory processing. A separate body of empirical literature suggests that synesthesia is linked to a specific profile of enhanced episodic and working memory performance. However, whether sensory (iconic) memory performance is also affected by synesthesia remains unknown. Therefore, we tested 22 grapheme-color synesthetes and compared their performance in a partial-report paradigm with 22 individually matched non-synesthete controls. Participants were briefly presented with a circular-letter array and required to report the identity of the letter at a probed target location after various delays. Furthermore, they were required to indicate the subjective clarity of the target letter after every trial. The results suggest that sensory memory performance is enhanced in synesthesia, but only when subjective clarity of the target letter is high. Additional exploratory analyses revealed that synesthetic consistency, which is widely used to confirm the genuineness of synesthesia, correlated significantly with performance in the partial report paradigm. We conclude that synesthesia does not generally enhance sensory memory performance, but that synesthetic experiences may enhance sensory memory performance when perceptual awareness of the target is high. Furthermore, the stability of synesthetic associations may be linked to sensory memory performance.

Musical Stained-glasses by Olivier Messian

Musical Stained-glasses by Olivier Messian

Absolute pitch is not necessary for pitch class-color synesthesia.

Sounds evoke color sensations in sound-color synesthesia. Recently, we showed that pitch classes (do, re, mi, etc.) have rainbow hues and that colors are linked to the names of pitch classes rather than to their sounds in 15 subjects who had "pitch class-color synesthesia." However, all synesthetes in our previous study had high levels of absolute pitch (AP); therefore the effects of AP on the condition remained unclear. The present study investigated 18 additional pitch class-color synesthetes who had no or lower levels of AP, and confirmed the generality of the above findings. Furthermore, behavioral experiments indicated a two-step process underlying color sensations: pitches are first associated with their pitch class names, and then the pitch class names evoke color sensations. Two separable brain functions underlie pitch-to-color conversion in pitch class-color synesthesia: a musical function of pitch class identification, and the synesthetic association between pitch class and color.

Rare variants in axonogenesis genes connect three families with sound–color synesthesia

Synesthesia is a rare nonpathological phenomenon where stimulation of one sense automatically provokes a secondary perception in another. Hypothesized to result from differences in cortical wiring during development, synesthetes show atypical structural and functional neural connectivity, but the underlying molecular mechanisms are unknown. The trait also appears to be more common among people with autism spectrum disorder and savant abilities. Previous linkage studies searching for shared loci of large effect size across multiple families have had limited success. To address the critical lack of candidate genes, we applied whole-exome sequencing to three families with sound-color (auditory-visual) synesthesia affecting multiple relatives across three or more generations. We identified rare genetic variants that fully cosegregate with synesthesia in each family, uncovering 37 genes of interest. Consistent with reports indicating genetic heterogeneity, no variants were shared across families. Gene ontology analyses highlighted six genes-COL4A1, ITGA2, MYO10, ROBO3, SLC9A6, and SLIT2-associated with axonogenesis and expressed during early childhood when synesthetic associations are formed. These results are consistent with neuroimaging-based hypotheses about the role of hyperconnectivity in the etiology of synesthesia and offer a potential entry point into the neurobiology that organizes our sensory experiences.

Coordinated neural, behavioral, and phenomenological changes in perceptual plasticity through overtraining of synesthetic associations

Synesthesia is associated with additional perceptual experiences, which are automatically and consistently triggered by specific inducing stimuli. Synesthesia is also accompanied by more general sensory and cortical changes, including enhanced modality-specific cortical excitability. Extensive cognitive training has been shown to generate synesthesia-like phenomenology but whether these experiences are accompanied by neurophysiological changes characteristic of synesthesia remains unknown. Addressing this question provides a unique opportunity to elucidate the neural basis of perceptual plasticity relevant to conscious experiences. Here we investigate whether extensive training of letter-color associations leads not only to synesthetic experiences, but also to changes in cortical excitability. We confirm that overtraining synesthetic associations results in synesthetic phenomenology. Stroop tasks further reveal synesthesia-like performance following training. Electroencephalography and transcranial magnetic stimulation show, respectively, enhanced visual evoked potentials (in response to untrained patterns) and lower phosphene thresholds, demonstrating specific cortical changes. An active (using letter-symbol training) and a passive control confirmed these results were due to letter-color training and not simply to repeated testing. Summarizing, we demonstrate specific cortical changes, following training-induced acquisition of synesthetic phenomenology that are characteristic of genuine synesthesia. Collectively, our data reveal dramatic plasticity in human visual perception, expressed through a coordinated set of behavioral, neurophysiological, and phenomenological changes.

Why is the synesthete's “A” red? Using a five-language dataset to disentangle the effects of shape, sound, semantics, and ordinality on inducer–concurrent relationships in grapheme-color synesthesia

Grapheme-color synesthesia is a neurological phenomenon in which viewing a grapheme elicits an additional, automatic, and consistent sensation of color. Color-to-letter associations in synesthesia are interesting in their own right, but also offer an opportunity to examine relationships between visual, acoustic, and semantic aspects of language. Research using large populations of synesthetes has indeed found that grapheme-color pairings can be influenced by numerous properties of graphemes, but the contributions made by each of these explanatory factors are often confounded in a monolingual dataset (i.e., only English-speaking synesthetes). Here, we report the first demonstration of how a multilingual dataset can reveal potentially-universal influences on synesthetic associations, and disentangle previously-confounded hypotheses about the relationship between properties of synesthetic color and properties of the grapheme that induces it. Numerous studies have reported that for English-speaking synesthetes, “A” tends to be colored red more often than predicted by chance, and several explanatory factors have been proposed that could explain this association. Using a five-language dataset (native English, Dutch, Spanish, Japanese, and Korean speakers), we compare the predictions made by each explanatory factor, and show that only an ordinal explanation makes consistent predictions across all five languages, suggesting that the English “A” is red because the first grapheme of a synesthete's alphabet or syllabary tends to be associated with red. We propose that the relationship between the first grapheme and the color red is an association between an unusually-distinct ordinal position (“first”) and an unusually-distinct color (red). We test the predictions made by this theory, and demonstrate that the first grapheme is unusually distinct (has a color that is distant in color space from the other letters' colors). Our results demonstrate the importance of considering cross-linguistic similarities and differences in synesthesia, and suggest that some influences on grapheme-color associations in synesthesia might be universal.

One-shot Synesthesia.

Synesthesia is commonly thought to be a phenomenon of fixed associations between an outside inducer and a vivid concurrent experience. Hence, it has been proposed that synesthesia occurs due to additional connections in the brain with which synesthetes are born. Here we show that synesthesia can be a much richer and more flexible phenomenon with a capability to creatively construct novel synesthetic experiences as events unfold in people’s lives. We describe here cases of synesthetes who occasionally generate novel synesthetic experience, called one-shot synesthesias. These synesthetic experiences seem to share all the properties with the classical synesthetic associations except that they occur extremely rarely, people recalling only a few events over the lifetime. It appears that these one-shots are not created at random but are instead responses to specific life events. We contrast the properties of those rare synesthetic events with other, more commonly known forms of synesthesia that also create novel synesthetic experiences, but at a high rate—sometimes creating novel experiences every few seconds. We argue that one-shot synesthesias indicate that synesthetic associations are by their nature not prewired at birth but are dynamically constructed through mental operations and according to the needs of a synesthetic mind. Our conclusions have implications for understanding the biological underpinnings of synesthesia and the role the phenomenon plays in the lives of people endowed with synesthetic capacities.

Commonalities between grapheme-color and sound-color synesthetic association based on phonetic information

Commonalities between grapheme-color and sound-color synesthetic association based on phonetic information

Beyond the subjective experience of colour: An experimental case study of grapheme–texture synesthesia

ABSTRACTThis study was a case investigation of grapheme–texture synestheste TH, a female who subjectively reported experiencing a visual association between grapheme and colour/texture. First, we validated the existence of a synesthetic association in an objective manner. Involuntarily elicited experience is a major hallmark that is common to different types of synesthetes. Our results indicated interference between physical and synesthetic texture, suggesting the involuntary occurrence of synesthetic textural experience. We analysed the behavioural measures using the EZ diffusion model. The result suggested that TH’s synesthetic experience was dissociable from that of briefly trained associative processing of non-synesthetes. Second, we investigated how the synesthetic experience of colour and texture dimensions was bound in the visual representation. We found that the interference effects of colour and texture were not independent. This suggested that in the elicited experience, the colour and texture features construct an integrated representation.