In stimulus-parity synaesthesia, a range of stimuli—for example, letters, numbers, weekdays, months, and colours (the inducers)—elicit an automatic feeling of oddness or evenness (the concurrent). This phenomenon was first described by , and has only recently been “rediscovered.” Here, we describe an individual who experiences a comparable phenomenon, but uses the labels negative and positive rather than odd and even. Stimulus-parity synaesthesia may be broader than first supposed, and it is important that assessments are sensitive to this breadth.
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