There’s lots of research suggesting that we may have something like a “number line” in our head: The SNARC effect says that if you normally read numbers from left to right, you’re faster to react to small numbers with your left hand, and big numbers with your right hand. Similar research has also found a SNARC effect for letters (a SLARC effect?).
So it might make sense that there would be a similar effect for musical notes. You might call it a SMARC effect, but if you only hear one note at a time it’s not really “music.” Undaunted, a team led by Pascale Lidji has conducted several experiments on what they call the SPARC effect (spatial pitch association of response codes). In many languages, “low” and “high” are used to describe both musical pitches and physical position. Low notes on a piano are played with the left hand, while high notes are played with the right.
Lidji’s team’s basic experiment is simple. Sixteen students listened to musical notes, and were told to press a button to the left if the note was played on a piano, and to the right if it was played on a violin (the button assignments were switched halfway through). They heard almost 200 notes, but they were selected from just four pitches: C3 (one octave below middle C on a piano), G3, E5, and B5. The students were all non-musicians, and their results were compared to the results for 16 musicians (some students, some professionals, all with over 8 years of musical training). Here are the results:
This graph shows the difference in right-hand versus left-hand reaction times — so if the right hand was slower to react, you see positive number, and if the left hand was slower, the number is negative. For non-musicians, there is no SPARC effect: there was no systematic difference in reaction time based on musical pitch. But for musicians, the right hand was slower to react to low notes and faster to react to high notes: that’s a bona-fide SPARC effect.
The researchers repeated the experiment, but this time, they re-oriented the buttons so that they were vertical instead of horizontal. The students and musicians were told to press the top button for notes played on a violin and the bottom button for notes played on a piano. Here are those results:
Now both musicians and non-musicians have a SPARC effect: the top hand is slower to react to low notes and faster to react to high notes. In several additional experiments, Lidji’s team did find a horizontal effect for non-musicians, but only when they were focusing on the pitch of the notes played rather than what instrument was playing them. They also tried to find a music-related effect, where listeners compared two different notes (they had to say whether the second not was higher or lower than the first), but the results were inconsistent; a SMARC effect was only found in one or two specialized instances.
What’s quite clear is that musicians do seem to have a left-to-right mapping of musical pitches, which is evident even when they’re not actively responding to the pitch of a note. Non-musicians have it too, but only when thinking specifically about pitch. Once multiple musical notes are involved, however, the phenomenon mostly disappears. In some ways, that’s not too surprising — it’d be like finding a SNARC effect for addition and subtraction.
Lidji, P., Kolinsky, R., Lochy, A., & Morais, J. (2007). Spatial associations for musical stimuli: A piano in the head? Journal of Experimental Psychology: Human Perception and Performance, 33 (5), 1189-1207 DOI: 10.1037/0096-15126.96.36.1999