Acoustic Measures of Prosody in Right-Hemisphere Damage: A Systematic Review and Meta-Analysis
The right hemisphere has often been claimed to be a locus for affective prosody, and people with right-hemisphere damage (RHD) have often been reported to show impairments in this domain. This phenomenon has been primarily investigated in terms of perception, more rarely in terms of production, and more rarely still using acoustic analysis. Our goal was to systematically review the papers reporting acoustic features of prosodic production in RHD, to identify strengths and weaknesses in this field, suggest guidelines for future research, and to support cumulative research by estimating the meta-analytic effect size of those features. We queried PubMed, PsychINFO, Web of Science, and Google Scholar, using the following combination of search terms: (prosody OR intonation OR inflection OR intensity OR pitch OR fundamental frequency OR speech rate OR voice quality) AND (RHD OR right hemisphere) AND (stroke) AND (acoustic). Standardized mean differences were extracted from all papers meeting inclusion criteria, and aggregated effect sizes were estimated using hierarchical Bayesian regression models. Sixteen papers met our inclusion criteria. We did not find strong evidence in the literature to indicate that the prosodic productions of people with RHD is substantially different from that of NBD controls, when measured in terms of acoustic features. However, the acoustic features of productions by people with RHD did differ from those of participants with NBD and LHD in some ways, notably in F0 variation and pause duration. Prosody type (emotional vs. linguistic) had very little effect. Taken together, currently available data show only a weak effect of RHD on prosody production. However, more accurate analyses are hindered by small sample sizes, lack of detail on lesion location, and divergent measuring techniques. Cumulative open science practices are recommended to overcome these issues.