(Extracted from《NATURE》, by Nobuo Masataka & Leonid Perlovsky) Contemporary cognitive and evolutionary musicology faces great controversies in attempting to identify the cognitive function ofmusic and its evolutionary origins. Arguments about the power of music over human psyche began long ago. Aristotle listed the power of music among the unsolved problems alongside finiteness of the world and existence of God. Kant was able to explain the epistemology of the beautiful by relating it to knowledge, but could not explain music: ‘‘it merely plays with senses.’’ Darwin noted that the human ability for music ‘‘must be ranked amongst the most mysterious with which(man) is endowed’’ because music is a human cultural universal that appears to serve no obvious adaptive purpose.

       Debates on the origins of consonance and dissonance in music have a long history. While some scientists argue that consonance judgments are an acquired competence based on exposure to the musical-system-specific knowledge of a particular culture, others favor a biological explanation for the observed preference forconsonance. Nobuo Masataka (Primate Research Institute, Kyoto University, Kanrin, Inuyama, Aichi, Japan) and Leonid Perlovsky (Athinoula A. Martinos Center for Biomedical Imaging, Harvard University, Charlestown, MA, USA) provide experimental confirmation that this preference plays an adaptive role in human cognition: it reduces cognitive interference.

       The experiment used a prototypical task known as the ‘‘Stroop interference task’’, which requires a person to respond to a specific dimension of a stimulus while suppressing a competing stimulus dimension. In the task, typically, a color word such as GREEN appears in an ink color such as red. If the participant’s task is to read the word and ignore the color (e.g. say ‘‘green’’), there is no evidence of difficulty reading the word compared to reading it when printed in standard black ink. However, if the participant’s task is to name the ink color and ignore the word (e.g. say ‘‘red’’), there is considerable difficulty relative to reading a color patch. Reading the word interferes with naming the color, but the color does not interfere with reading the word. This is the phenomenon of Stroop interference. Participants were asked to name the ink of a color word that designated a color incongruent with that of the ink of the word (Cognitive Interference Created). Also, the same participants were tested in a ‘Neutral testing session’, in which they were asked to name the ink of a color of a non-word string of letters (No Cognitive Interference). Both sessions were repeated under three conditions: (1) with exposure to music containing predominantly consonant intervals (Consonant condition), (2) with exposure to music containing predominantly dissonant intervals (Dissonant condition), and (3) without exposure to any music (Control condition). In every session and condition, the performance of the participants was measured as reaction time (RT) to response and error rate (ER) of the response. Children aged 8 to 9 years old and elderly adults aged 65 to 75 years old participated in this experiment.

The results of the experiment with the elderly adults were strikingly similar to those with the children, i.e. for the cognitive interference session, the cognitive interference under consonant condition was significantly lower than that under dissonant condition and control condition, while the cognitive interference under dissonant condition was significantly higher than that under consonant condition and control condition. The difference in ‘Neutral testing session’ (no cognitive interference) is not significant.

       The experiment concludes that consonant music may have an important cognitive function: help overcoming cognitive interference. Together with other recent experimental and theoretical publications, this gives tentative support for our hypothesis about the fundamental cognitive function of music: it helps to resolve cognitive interference, cognitive dissonance, and facilitates human evolution. (Annotation: Cognitive dissonance is discomfort caused by simultaneously holding conflicting cognitions. It usually leads to the depreciation and abandonment of conflicting knowledge. This theory is one of the most influential and widely studied theories in psychology. It is closely related to the entire human evolution. In the early stages of human evolution, the emergence of language led to the spread of cognitive dissonance. If they are not overcome, language and knowledge will be discarded, and further human evolution will also stop. This is why the ability of music to mitigate cognitive dissonance may be the foundation of music cognitive function and music evolution.)

       The experiment results support findings as well that the effect of music on cognitive dissonance depends on the hedonicity of music: pleasant music better helps to overcome cognitive dissonance than unpleasant music.

But the article also points out that, drawing conclusions about the connection between musical consonance and hedonicity requires caution since dissonant and sad music could also be sources of pleasure. The possible cognitive functions of musical dissonance is an unresolved issue in psychology and musicology. For example, one of the most popular pieces of western classical music is Adagio by Barber, which is sad, slow, and highly dissonant, like Adagio by Albinoni. A specific aspect of this question is why sad music is pleasurable. According to the hypothesis of the literature authors, sad music helps to overcome dissonance arising from difficult life conditions, including the ultimately death of close people (the dissonance between the feeling of the infinity of the spirit and the knowledge of death). In general, any two (or more) cognitions involve a cognitive dissonance. Possibly, the cognitive dissonance between any two cognitions involves its own shade of emotion, and overcoming each cognitive dissonance requires a special musical emotion (the literature authors do not differentiate here between emotion and mood). This hypothesis implies a potentially large number of musical emotions and also of cognitive dissonances and interferences. Music evolved for helping to overcome the predicament of stress that arises from holding contradictory cognitions, so that knowledge is not discarded, but rather can be accumulated, and human culture can evolve. The experimental results emphasize a need for further research studying multiple emotions and for determining the dimensionality of these emotional spaces. This problem has not been solved, and this paper reports a step in this direction. The consonance-dissonance dimension explored here is related to hedonicity (pleasure or displeasure) perceived in music; however, the potential pleasure from sad dissonant music makes this connection nontrivial. Possibly music is perceived as pleasant if it resolves cognitive dissonances and interferences important for a listener. This issue would have to be explored in future research.