Categorization of Synaesthesia

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) there are types of synaesthesia acquired during adulthood (e.g., phantom or artificial synaesthesia), momentary synaesthesia triggered temporarily in people who do not show signs of synaesthesia every day (e.g., virtual, narcotic, or posthypnotic synaesthesia), and associational synaesthesia which, semantically speaking, refers to some universal sense relations (e.g., literary, artistic, and multimedia synaesthesia). There is a hypothesis that every kind of synaesthesia holds a different function—compensatory or integrative. It was suggested that synaesthesia can be described in one dimension, showing the intensity of this phenomenon. The stronger types of synaesthesia are: semantic, conceptual, intermodal, synthetic, comprehensive, external and bidirectional. The weaker types of synaesthesia are: sensory, perceptual, intramodal, analytic, partial, internal and unidirectional. There are huge individual differences in the manner that synaesthesia presents itself. By including a classification of kinds, types, and forms of synaesthesia into future experimental research will ensure a better understanding of the nature of this phenomenon, its mechanisms and the role that it plays in developing cognitive processes.