The effects of varying melodic intervals in melodic intonation therapy for persons with aphasia

Abstract

Background Melodic Intonation Therapy (MIT) is an evidence-based treatment for persons with non-fluent aphasia. The contribution of rhythm within MIT has been frequently studied, though little research has been completed to determine the role melodic intervals play in this therapy.

Aim The purpose of this study was to evaluate the effects of melodic intervals on the efficacy of MIT by using two different melodic intervals to intone target phrases: the consonant minor third and the dissonant tritone. These researchers hypothesized that participants would have greater success in therapy when phrases were intoned on the minor third due to the interval’s familiarity and perceived pleasantness as opposed to the unfamiliar and perceptually unpleasant tritone.

Methods & Procedures Using a single-subject, multiple-baseline design, two participants with expressive aphasia were exposed to phrases intoned on both intervals while participating in MIT across eight weeks. Spoken probe phrases were elicited and quantitatively scored on intelligibility prior to, during, and after treatment to measure progress made for phrases intoned on each interval. An effect size was calculated for each interval using a formula created for single-subject, multiple baseline aphasia research studies (Beeson & Robey, 2006).

Outcome & Results The effect size of the tritone was greater than the effect size of the minor third for both participants: this was contrary to the researchers’ hypothesis. Due to COVID-19, treatment was completed via teletherapy, the first time this method has been used to conduct an MIT treatment study. It was determined that MIT provided in this format resulted in improvement in trained phrases.

Conclusion This research suggests that contrary to the MIT protocol, therapy may be more efficacious if phrases are sung using dissonant or unfamiliar melodic intervals rather than pleasant, familiar intervals. However, generalization of this study is restricted due to several limitations. Further research should be completed to evaluate the effects of various intervals within MIT and the complex interaction between rhythm and pitch.