Synesthesia

[…] R. H. Gault's case of synesthesia in a deaf and blind girl, who could distinguish colors by the sense of smell, […]

Because of this, SSDs are one of the first technologies to meaningfully demonstrate just what synesthesia – or at least one kind of it – might feel like to those who have never had it.

[S]ynesthetes themselves can provide the indispensable cues to design a structured qualitative questionnaire: color synesthesias and their variations during sexual arousal, direct physical stimulation, and orgasm […] can help scientists differentiate the specific triggers and their characteristics.