According to Bob Fink of Greenwich Publishing, musical scales developed due to the nature of the brain to seek resolution in music. Certain tones, such as the leading tone of a melody, have a natural inclination to resolve a certain way to a listener's brain, such as a half step higher in the case of the leading tone. Because of this, medieval musicians developed musical scales as a means of dividing tones in a system logically relative to each other. A scale can start on any of the 11 existing tones, and regardless of its starting point, a scale of one type will always be relative in regard to the distances between pitches. A major scale in C will have the same pitch relationships between its tones as a major scale in A, even though they have different starting points. This is an example of how our brain has a natural tendency to organize music and scales by auditory relationships.
The Mozart Effect is a popular and controversial example of musical scales and their effect on the brain. According to the Indiana University Human Intelligence website, some scientists believe that exposing young humans to music, even while still in the womb, can increase spatial awareness, reasoning and overall intelligence. According to a Canadian study on six-year-old children taking piano lessons, as cited in a Forbes article, the children who received music lessons had larger increases in IQ than the control group.
According to New Scientist, the type of musical scale used in a piece of music has a great effect on the response it evokes from a listener. Music that uses major scales often suggests emotions of happiness, excitement, celebration and triumph. Music with minor scales is perceived as brooding, depressing, contemplative and pensive. When these two main types of scales are mixed within the same piece, ambivalent and provocative emotions and imagery can be produced in the human brain.
According to University of Washington's Neuroscience for Kids website, music can have powerful effects on the development and upkeep of human memory. Since all scales consist of quantifiable auditory relationships, the mere act of listening to music involves subconscious memory usage through the brain organizing different pitches in a scale and the rhythms they are played with. Whether listeners realize it or not, the process of experiencing music engages memory and cognition centers in the brain that help make sense of the noise coming from a recording or live band.
The significance of musical scales lies in their ability to encapsulate the tendencies that certain pitch relationships have in our brain. Why these pitch relationships have natural tendencies to humans is still not entirely known to scientists, though it has been suggested by Sociology Central that it may be part of the socialization humans experience during growth and development, since music is primarily a social and cultural activity passed down through generations.