When listening to someone practicing piano, we readily perceive certain chords as pleasant, or consonant (e.g., perfect fifth), and other chords as unpleasant, or dissonant (e.g., minor second). These variations in perceptual experiences have been associated with processing advantages for consonant stimuli, which may be due to differences in the physical features of the musical intervals in consonant vs. dissonant chords, or to our experience with a musical system based on harmonic melodies.
In a new paper published in the Journal of Comparative Psychology, Crespo-Bojorque and Toro (2016) (PDF, 384KB) sought to disambiguate the role of physical features and experience by comparing auditory abstract rule learning in humans, who have experience producing and processing harmonic stimuli, and rats, who do not.
In the training phase, rats and humans were trained to make responses to sequences that followed an AAB pattern, and to withhold responses to sequences that followed an ABC pattern. Rats were rewarded with food for correct responses, and human participants received verbal feedback (correct or incorrect).
In a subsequent test phase, new AAB and ABC sequences were presented, and generalization was measured by the percentage of responses to new AAB sequences. There was no food reward or verbal feedback in the test phase.
Depending on the experiment, training and generalization sequences were either all consonant (e.g., octave-octave-fifth vs. octave-fifth-fourth) or all dissonant (e.g., minor second-minor second-tritone vs. minor second-tritone-minor ninth).
Both rats and people showed learning and generalization of abstract auditory rules. However, while rats showed no difference in performance based on consonance, people showed better generalization when sequences were consonant vs. dissonant.
Furthermore, people, but not rats, showed an additional advantage when consonant and dissonant intervals were intermixed within sequences (e.g., AAB was implemented as consonant-consonant-dissonant, or octave-octave-minor second), suggesting that consonance acted as a categorical anchor that differentiated between pattern elements, thereby facilitating structure abstraction.
Thus, although previous work has shown that rats can discriminate between consonant and dissonant intervals, this perceptual difference does not translate into a processing advantage for consonant intervals.
These results suggest that processing advantages based on consonance in human participants are due to experience with harmonic sounds, not their physical properties.
This hypothesis could be further supported by future work using either animal species that produce harmonic vocalizations, or experiments in which rats are given experience with harmonic music.
Citation:
- Crespo-Bojorque, P., & Toro, J. M. (2016). Processing advantages for consonance: A comparison between rats (Rattus norvegicus) and humans (Homo sapiens). Journal of Comparative Psychology, 130(2), 97–108. http://dx.doi.org/10.1037/com0000027
Note: This article is in the Basic / Experimental Psychology topic area. View more articles in the Basic / Experimental Psychology topic area.