This article is an attempt to synthesize the current knowledge about synaesthesia from many fields such as literature, arts, multimedia, medicine, or psychology. The main goal of this paper is to classify various types and forms of synaesthesia. Besides developmental synaesthesia being likely to play a crucial role in developing cognitive functions (constitutional or neonatal synaesthesia) ther...

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 synaesth...

Are we all synaesthetes? Weakening the case for 'weak synaesthesia' Synaesthesia quotient: individual index of expression of general neurocognitive aspects in developmental synaesthesia and its methodological implications Synaesthesia reclassified: From canonical to borderline cases of 'sensory unions' The sound of size: combined TMS-EEG results on pitch-size associations support the spectrum t...

Synaesthesia is a condition in which a sensory experience normally associated with one modality occurs when another modality is stimulated (Baron-Cohen and Harrison 1997). The commonest form of synaesthesia is colour-word synaesthesia, which is subdivided into a chromatic-graphemic type (the dominant letter in a word induces a letter-specific colour experience) and a chromatic-lexical type (eac...

Synaesthesia for time, numbers and space (TNS synaesthesia) is thought to have costs and benefits for recalling and manipulating time and number. There are two competing theories about how TNS synaesthesia affects cognition. The ‘magnitude’ account predicts TNS synaesthesia may affect cardinal magnitude judgements, whereas the ‘sequence’ account suggests it may affect ordinal sequence judgement...

Synaesthesia is a broadly defined neural phenomenon in which stimulation of a sense or concept triggers a second perception not normally associated with the stimulus. For example, letters or numbers may trigger a colour experience, sounds may trigger a taste sensation, or tastes may trigger a feeling of touch. Dozens of forms of synaesthesia have been reported, but the relationship between the ...

The term synaesthesia has been applied to a range of different sensory-perceptual and cognitive experiences, yet how these experiences are related to each other is not well understood. Not only are there disparate types of synaesthesia, but even within types there are vast individual differences in the way that stimuli induce synaesthesia and in the subjective synaesthetic experience. An invest...

The renaissance of synaesthesia research has produced many insights regarding the aetiology and mechanisms that might underlie this intriguing phenomenon, which abnormally binds features between and within modalities. Synaesthesia is interesting in its own right, but whether it contributes to our knowledge of neurocognitive systems that underlie non-synaesthete experience is an open question. I...

Although grapheme-colour synaesthesia is a well-characterized phenomenon in which achromatic letters and/or digits involuntarily trigger specific colour sensations, its underlying mechanisms remain unresolved. Models diverge on a central question: whether triggered sensations reflect (i) an overdeveloped capacity in normal cross-modal processing (i.e., sharing characteristics with the general p...

Synaesthesia is an unusual perceptual experience in which an inducer stimulus triggers a percept in a different domain in addition to its own. To explore the conditions under which synaesthesia evolves, we studied a neuronal network model that represents two recurrently connected neural systems. The interactions in the network evolve according to learning rules that optimize sensory sensitivity...