Cognitive dedifferentiation in eidetics and synaesthesia: hunting for the ghost once more

Both synaesthesia and eidetics have a common characteristic of cognitive de differentiation. Synaesthesia (eg colour-hearing) entails the dedifferentia tion of the sensory modalities, while eidetic imagery entails the dediffere ntiation of imagery and perception. One can profitably gain by investigatin g both within the same study. Moreover, some of the same issues have arisen in these, hitherto, separate research literatures. This behoves a common f ramework for analysis and investigation. We applied a technique previously used for identifying child eidetikers, for screening the adult population, looking at both phenomena in the same sample. After screening, we selected a total of twenty-nine individuals for controlled testing of both phenomena and their variants (structural eidetic imagery, typographic eidetic imager y, colour - hearing synaesthesia, colour - mood synaesthesia). Our particip ants also completed a number of questionnaires of relevance (absorption, di ssociation, and hallucination). We found that the personality trait of abso rption underlies the commonality of experience tapped by both typographic a nd structural eidetic imagery. Furthermore, the latter phenomena were found to have a common pseudohallucinatory experiential base. For subjects scori ng relatively high on the absorption scale, there is a negative correlation between structural eidetic imagery and colour-mood synaesthetic differenti ation, replicating to a degree results reported earlier.