Levelt, W. J. M. (1962). Motion breaking and the perception of causality. In A. Michotte (Ed.), Causalité, permanence et réalité phénoménales: Etudes de psychologie expérimentale (pp. 244-258). Louvain: Publications Universitaires.
Levelt, W. J. M., & Plomp, K.
(1968). The appreciation of musical intervals. In J. M. M. Aler (Ed.), Proceedings of the fifth International Congress of Aesthetics, Amsterdam 1964 (pp. 901-904). The Hague: Mouton.
As a preliminary to further research on musical consonance an explanatory investigation was made on the different modes of judgment of musical intervals. This was done by way of a semantic differential.
Subjects rated 23 intervals against 10 scales. In a factor analysis three factors appeared: pitch, evaluation and fusion. The relation between these factors and some physical characteristics has been investigated. The scale consonant-dissonant showed to be purely evaluative (in opposition to Stumpf's theory). This evaluative connotation is not in accordance with the musicological meaning of consonance. Suggestions to account for this difference have been given.