• Miroslaw Sienkiewicz

Synaesthesia Honours Project: my survey about music instruments and research about geometric objects


Yesterday I asked a question on Synesthesia Facebook Group how different musical instruments impact visual stimuli.

As expected, everyone responded that they have associated colours to instruments. Another conclusion was that pitch of sound follow brightness: low pitch – dark shade, higher pitch – bright shade – which confirms what I deduced from literature that I read earlier. One respondent said that instruments have impact on shape, colour and extent texture. Colour stay the same but position of object (visual stimuli) and partially the shape is changing following the pitch and size changes with level (volume) of the sound.

One response was very detailed and stated that: pitch, instrument, loudness, distance, echo, chords (major/minor), tempo, voice (I’d call it a type of an instrument) and even lyrics have impact on visual stimuli.

What is interesting that three of them associated piano with blue colour. One respondent divided it into piano with reverb (blue) and without reverb (yellow).

Another association was:

bass – red

violin – orange

guitars – (more) gold(en)

Screenshot from Facebook:

This question came as a result of reading research report ‘Beyond colour perception: Auditory-visual synaesthesia induces experiences of geometric objects in specific locations’ (Chiou, Stelter and Rich, 2013)

At this point I know that cross-modal interactions are mostly the same for all of us but only for synesthetes it results in percept’s that does not exist in external world. Also, for synaesthetes they may occur in the same modality (grapheme-colour) different modality (auditory-visual).

Two hypotheses for this phenomenon exist:

  • Cross-activation hypothesis: synaesthesia is a result of excessive neural connections (between adjacent cortical areas)

  • Disinhibited-feedback hypothesis: synaesthesia is a result of malfunct of mechanism in brain that normally inhibit the crosstalk between brain areas in non-synaesthetes (e.g. multi-modal regions or areas involved in executive control or unimodal areas).

Usually experiments focus on synthetic colour but this one is focused on synesthetic coloured geometric objects located at specific spatial location.

Test in this research has been done on seven synaesthetes and 7 non-synaesthetes (control group). Synaesthetes were chosen when they proved that their synaesthesia is consistent.

They reported visual experiences like: geometric objects like cube, sphere and wavy line. Pitch, timbre and melody affected their perception of hue, brightness, shape and spatial location.

Conclusions from test:

  • Pitch affect position: low pitch – bottom position; high pitch – top position

  • Pitch affect brightness: low pitch: darker colour; high pitch - bright colour

  • Pitch affect size: low pitch: bigger; high pitch – smaller

Figure 1 Example of how pitch affect position, size and brightness (Chiou, Stelter and Rich, 2013)

Figure 2 (a) the relationship between pitch and size. (b) the relationship between pitch and brightness. (c) the relationship between auditory and location of the objects indicated by categorical codings of syneasthete's description (Chiou, Stelter and Rich, 2013)

Stimuli used for experiments: 16bit stereo files 44.1kHz and 65dB. 30 sounds consistent of: 10 piano notes, 10 flute notes and 10 violin notes: from C1 (33Hz) to Eb6 (1245Hz) separated by intervals of musical fifths (i.e., 700 cents). Notes: C1, G1, D2, A2, E3, B3, F#4, Db5, Ab5, and Eb6.

References:

Chiou, R., Stelter, M. and Rich, A. (2013). Beyond colour perception: Auditory–visual synaesthesia induces experiences of geometric objects in specific locations. Cortex, 49(6), p.1756.

Chiou, R., Stelter, M. and Rich, A. (2013). Beyond colour perception: Auditory–visual synaesthesia induces experiences of geometric objects in specific locations. Cortex, 49(6), p.1757.

Bibliography:

Chiou, R., Stelter, M. and Rich, A. (2013). Beyond colour perception: Auditory–visual synaesthesia induces experiences of geometric objects in specific locations. Cortex, 49(6), pp.1750-1763.

#objects #colour #pitch #spatiallocation #synaesthesia #test #experiment

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