What Can Illusory Conjunctions Reveal about Synaesthetic Bindings?

Isabel Arend, Avishai Henik

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The visual system successfully binds the shapes and colours of objects; therefore, our visual experience regarding the objects around us is coherent. However, this binding process can break down when attention is diverted, producing illusory conjunctions (ICs); for example, when presented with a red 2 and a green 5, the observer may report a green 2 and a red 5. The strongest observation of binding in human cognition is found in synaesthesia. In grapheme-colour synaesthesia, linguistic stimuli (e.g., letters or numbers) are strongly associated with colours. It is debatable whether these highly stable bindings constitute a form of early binding that occurs outside the focus of attention. We examined for the first time the occurrence of ICs in grapheme-colour synaesthesia. Experiment 1 replicated our previous finding, showing the effects of numerical distance on ICs (Arend et al., Psychon. Bull. Rev. 2013, 20, 1181-1186). Participants viewed a display containing two centrally presented letters and two coloured numbers and were asked to report: (1) whether the letters were same/different, (2) the colour of the larger number, and (3) the level of confidence concerning the colour of the number. Experiment 2 used a modified version of this task. Synaesthetes (N=5) and controls (N=15) viewed number-colour pairs that were congruent or incongruent with that of the synaesthetic association. Grapheme-colour synaesthesia significantly affected ICs on incongruent but not on congruent trials. Our findings strongly support the notion that shape and colour are free-floating features in synaesthesia, similar to what is observed in normal cognition.

Original languageEnglish
Pages (from-to)235-251
Number of pages17
JournalMultisensory Research
Issue number3-5
StatePublished - 1 Jan 2017


  • Synaesthesia
  • feature integration
  • illusory conjunctions
  • spatial attention

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Ophthalmology
  • Sensory Systems
  • Computer Vision and Pattern Recognition
  • Cognitive Neuroscience


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