Synesthesia-like mappings of lightness, pitch, and melodic interval.

Synesthesia-like mappings between visual lightness and auditory pitch and between visual lightness and melodic interval were examined. When subjects rated how visual lightnesses and auditory pitches "fit together," lighter stimuli fit better with higher pitches, and darker stimuli fit better with lower pitches. These patterns were stronger against black than against white visual backgrounds; however, effects of visual background were eliminated when subjects had a large set of lightness levels from which to choose the visual lightness level that best fit a given auditory pitch or melodic interval. When subjects chose which visual lightness best fit or matched a melodic interval, lighter stimuli were chosen for ascending melodic intervals, and darker stimuli were chosen for descending melodic intervals. Larger melodic intervals produced more extreme (lighter or darker) choices. Auditory pitch exhibits meaningful synesthesia-like mappings with visual lightness when unidimensionally varied in frequency and when multidimensionally varied in interval size and direction.