Bimodal distribution of performance in discriminating major/minor modes

Abstract

This study investigated the abilities of listeners to classify various sorts of musical stimuli as major vs minor. All stimuli combined four pure tones: low and high tonics (G5 and G6), dominant (D), and either a major third (B) or a minor third (B[symbol: see text]). Especially interesting results were obtained using tone-scrambles, randomly ordered sequences of pure tones presented at ≈15 per second. All tone-scrambles tested comprised 16 G's (G5's + G6's), 8 D's, and either 8 B's or 8 B[symbol: see text]'s. The distribution of proportion correct across 275 listeners tested over the course of three experiments was strikingly bimodal, with one mode very close to chance performance, and the other very close to perfect performance. Testing with tone-scrambles thus sorts listeners fairly cleanly into two subpopulations. Listeners in subpopulation 1 are sufficiently sensitive to major vs minor to classify tone-scrambles nearly perfectly; listeners in subpopulation 2 (comprising roughly 70% of the population) have very little sensitivity to major vs minor. Skill in classifying major vs minor tone-scrambles shows a modest correlation of around 0.5 with years of musical training.

Scale-sensitivity: A cognitive resource basic to music perception

“…These results suggest that the ability to discriminate major vs minor musical modes may conform to a bimodal distribution. Chubb et al (2013) provided direct evidence that this is true. In this experiment, listeners were asked to classify as major versus minor a new class of stimuli called "tonescrambles."…”

“…The finding of Chubb et al (2013) implies that there exists a cognitive resource relevant to the major vs minor tone-scramble classification task that different listeners possess in dramatically different measures. The central question of the current study is: What is the nature of this resource?…”

“…Although the tone-scramble task used by Chubb et al (2013) partitions listeners very cleanly into high-vs lowperformers, many important questions concerning the nature of the sensitivity mediating performance remain unanswered. The tone-scrambles used by Chubb et al (2013) differed only in the third scale degree, which is central to the difference between the major vs minor diatonic scales.…”

“…The tone-scrambles used by Chubb et al (2013) differed only in the third scale degree, which is central to the difference between the major vs minor diatonic scales. It is thus tempting to conclude that the sensitivity separating the high-performing listeners of Chubb et al (2013) from the low-performing listeners is specific to the notes that differentiate the major vs minor diatonic scales. These critical notes occur at scale degrees 3, 6, and (possibly) 7.…”

“…The point of using tone-scrambles as stimuli (as opposed to actual melodies) is to isolate musical qualities due to variations in the set of notes used to make up a scale from the other aspects of musical structure (e.g., rhythmic and sequential regularities) that characterize well-structured musical melodies. The major tone-scrambles used by Chubb et al (2013) contained eight tones of each of the notes G 5 (lower tonic), D 6 (dominant, i.e., 5th scale degree), G 6 (upper tonic), and B 5 (major third); the minor tone-scrambles included the same numbers of G 5 's, D 6 's, and G 6 's as the major tone-scrambles but included eight B[ 5 's (minor thirds) instead of B 5 's. Participants strove to classify the tone-scramble presented on each trial as either major or minor, and received feedback after each trial.…”