were able to show the dependence of the synesthetic percept from relatively
late perceptual integration processes. In contrast with the study of Bargary et al., we focused on the overall proportion of audiovisual fusions in the McGurk experiment. In the second experiment, speech comprehension in a noisy environment was analysed. Varying the signal-to-noise ratio (SNR) of the auditory input, it has been shown that even normal non-hearing impaired comprehenders take advantage from concurrent visual input. Also, an SNR can be found for which comprehension benefits most from the visual information (Ross, Saint-Amour, Leavitt, Javitt, & Foxe, 2007). Here, we tested whether synesthetes and controls benefit similarly from visual information during the perception of speech in a noisy environment. We predicted that if synesthetes have a generally overactive binding mechanism, they should report more fused syllables in the selleck screening library illusion experiment and outperform controls in the speech comprehension task. If, on the other hand, binding is restricted to the inducer–concurrent pairing, no differences should be observed in both experiments. All procedures had been approved
by the local Ethics Committee. All subjects gave informed consent and participated for a small monetary compensation. Participants were matched for age and gender. We divided our subjects into groups depending on the self-reported synesthetic experience. After an extensive interview, all Autophagy Compound Library price synesthetes were classified by self-reported localization of concurrent perception as ‘associators’ MCE公司 according to Dixon, Smilek, and Merikle (2004), that is, perceiving the synesthetic sensations in their ‘mind’s
eye’. In addition, our subjects were characterized by a modified offline version of the synesthesia battery (Eagleman, Kagan, Nelson, Sagaram, & Sarma, 2007) in which subjects have to indicate a colour related both to the presentation of tones of different instruments and different pitches and to the presentation of letters from A–Z and the numbers from 0 to 9. Control subjects were tested with the complete battery, whereas synesthesia subjects were tested only on those parts of the battery relevant for their self-reported inducer–concurrent pair (subjects showing both grapheme-colour and auditory-visual synesthesia performed on the corresponding parts of the battery). Thus, synesthetes were asked to choose the colour which matched their experienced synesthetic colour induced by the tone (letter, number) best and non-synesthetes were asked to select the colour which they thought to fit best to the presented item. After three presentations of the stimuli in a randomized order, the geometric distance in RGB (red, green, blue) colour space, indicated by the subject’s colour choices for each item during the three runs, was calculated. The mean values were then compared between groups.