Table 1.
Overview of studies included in the meta-analyses [EHI Edinburgh Handedness Inventory (Oldfield, 1971), LHfc left-handedness (forced choice), LHe left-handedness (extreme), MH mixed-handedness, NonRH non-right-handedness, Cont continuous data]
| Study | Handedness classification | Stuttering assessment | Handedness measurement | Males % | Mean age in years | Included in meta-analysis | Notes | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| LHfc | LHe | MH | NonRH | Cont | |||||||
| Ardila et al., 1994 | R-M-L | Adapted version of the questionnaire of Roberts et al. (1990) | Self report (“Are you right-handed, left-handed, or ambidextrous?”) | 52.16 | 22.55 | ● | ● | ● | |||
| Arnold et al., 2011 | R-L | Speech evaluation & Stuttering Severity Instrument 3 (Riley, 1994) | EHI | 66.67 | 4.54 | ● | ● | ||||
| Arnstein et al., 2011 | R-M-L | Stuttering Severity Instrument 3 (Riley, 1994) | Self-report on a three-choice item (“right-handed, “left-handed”, “mixed”) | 96.43 | 30.65 | ● | ● | ● | |||
| Brosch et al., 1999 | R-No preference-L | Stuttering Severity Instrument (Riley, 1972) | Laterality tests | 58.05 | 5.25 | ● | ● | ● | Children were classified as either right- or left-handed on the basis of how they threw a ball, drew a picture, grasped an object and kicked a ball. If two of the four tests were done with different hands or if they changed hands when the tests were repeated, the children were classified as ‘no hand preference’ | ||
| Bryngelson & Rutherford, 1937 | R-Ambidextrous-L | Speech evaluation | Not reported | 44.59 | 10 | ● | ● | ● | |||
| Bryngelson, 1940 | R-Ambidextrous-L | Speech evaluation | Not reported | 37.18 | 24.5 | ● | ● | ● | The sum of the percentages reported in Table 1 for the individuals who stutter was 104%, so we extrapolated to 100% | ||
| Cavenagh et al., 2015 | R-No preference-L | Speech evaluation & parental report & Stuttering Severity Instrument (Riley, 1994) | Parental report (“Is your child left- or right-handed?”) | 60.08 | 4.04 | ● | ● | ● | |||
| Chang et al., 2015 | R-Ambidextrous-L | Speech evaluation & Stuttering Severity Instrument 4 (Riley, 2009) | EHI | 55.98 | 6.35 | ● | ● | ● | ● | Categorical data are reported for 47 individuals who stutter and 42 controls, but continuous data are reported for 37 individuals who stutter and 40 controls | |
| Choo et al., 2016 | R-Ambidextrous-L | Stuttering Severity Instrument 4 (Riley, 2009) | EHI | 58.05 | 5.77 | ● | ● | ● | The handedness of two individuals who stutter and one control could not be determined. Authors kindly provided more data | ||
| Chrysanthis, 1947 | R-M-L | Speech evaluation | Not reported | Not reported | 10.5 | ● | ● | ● | Right-handed writers—Right-handed writers with characteristics of left-handedness—ambidextrous writers—Left-handed writers. The two middle categories were considered "mixed-handed" for the purposes of these analyses | ||
| Coalson & Byrd, 2015 (dataset 1) | Continuous | Self report & speech evaluation (O’Brian et al., 2004) | EHI | 63.63 | 21 | ● | Authors kindly provided the data | ||||
| Coalson & Byrd, 2015 (dataset 2) | Continuous | Self report & speech evaluation (O’Brian et al., 2004) | EHI | 63.63 | 22.5 | ● | Authors kindly provided the data | ||||
| Connally et al., 2014 | R-L | Stuttering Severity Instrument 3 (Riley, 1994) | Not reported | 67.29 | 23.45 | ● | ● | ||||
| Corbera et al., 2005 | R-L | DSM-IV (American Psychiatric Association (APA), 1994) & Self-report questionnaire [Conduct and Attitude Scale for the Assessment of Disfluencies (CASAD)] | EHI | 83.97 | 22.75 | ● | ● | ||||
| Cross, 1987 | R-L | Profile of Stuttering Behavior (Van Ripen, 1971) (not clear if questionnaire was used or based on sample evaluation) | EHI | 100 | 25.5 | ● | ● | ||||
| Cykowski et al., 2010 | Continuous | Self report & speech evaluation (Ingham et al., 1999) | EHI | 100 | 30.7 | ● | |||||
| Dellatolas et al., 1990 (dataset 1) | Continuous/R-L | Self report | 10 questions regarding hand preference | 51.75 | 34.5 | ● | The LIs are reported in the paper in a way that higher LIs corresponded to stronger left-handedness. We have transformed the scores so that higher scores correspond to stronger right-handedness, as was the case in the rest of the studies | ||||
| Dellatolas et al., 1990 (dataset 2) | Continuous/R-L | Self report | 10 questions regarding hand preference | 100 | 20.5 | ● | As above | ||||
| Desai et al., 2017 | R-Non-right | Speech evaluation & Assessment of the Child’s Experience of Stuttering (ACES) (Yaruss et al., 2006) & Overall Assessment of the Speaker’s Experience of Stuttering (OASES; Yaruss & Quesal, 2006) | EHI | 56.62 | 19.49 | ● | |||||
| Frankford et al., 2021 | R-Ambidextrous-L | Self report & Stuttering Severity Instrument (Riley, 2009) | EHI | 66.67 | 29.28 | ● | ● | ● | |||
| Friedmann, 1937 | R-Latent L-Manifest L | Not reported | Not reported | Not reported | Not reported | ● | ● | ● | The sum of percentages for the individuals who stutter was 102.8%, so we extrapolated to 100%. Both children and adults who stutter were included, whereas the control group consisted of children, thus the groups are not age-matched | ||
| Gough et al., 2018 | R-L | Stuttering Severity Instrument (Riley, 1994, 2009) | Not reported | 77.60 | 25.58 | ● | ● | ||||
| Hampton & Weber-Fox, 2008 | R-L | Stuttering Severity Instrument 3 (Riley, 1994) | EHI | 72.73 | 34.68 | ● | ● | ||||
| Hand & Haynes, 1983 | R-Sinistral (L) | Self report & Stuttering Severity Instrument (Riley, 1972) | Neurosensory Center Handedness Inventory (Varney & Benton, 1975) | 100 | 25 | ● | ● | ||||
| Jansson-Verkasalo et al., 2014 | R-L | Speech evaluation & Stuttering Severity Instrument 3 (Riley, 1994) | Not reported | 79.17 | 7.54 | ● | ● | ||||
| Jenson et al., 2018 | R-L | Stuttering Severity Instrument 4 (Riley, 2009) | EHI | 70.83 | 25.21 | ● | ● | ||||
| Kaganovich et al., 2010 | R-L | All criteria by Yairi & Ambrose, 1999 met | Parental report & 5 questions from EHI | 69.44 | 4.83 | ● | ● | ||||
| Koenraads et al., 2020 | R-L | Parental report | ΕΗΙ | 64.08 | 10 | ● | ● | Data from recovered stutterers are also reported, but we only included data from individuals with persistent stuttering | |||
| Kronfeld-Duenias et al., 2016 | R-L | Self report & Speech evaluation & Stuttering Severity Instrument 3 (Riley, 1994) | EHI | 82.11 | 32.5 | ● | ● | ● | Authors kindly provided raw data on EHI. We classified it into R-L using L > = 50 and R > 50 | ||
| Lescht et al., 2022 | R-Ambidextrous-L | Parental report & Stuttering Severuty Instrument (Riley, 2009) | Abbreviated EHI | 57.89 | 5.77 | ● | ● | ● | |||
| Liman et al., 2021 | Continuous | Stuttering Severity Instrument 3 (Riley, 1994) | EHI | 70 | 26.81 | ● | |||||
| Maruthy et al., 2017 | R-L | Self report & Stuttering Severity Instrument 3 (Riley, 1994) | Self report | 90 | 21.1 | ● | ● | ||||
| Max & Yudman, 2003 | R-M-L | Self report & Stuttering Severity Instrument 3 (Riley, 1994) | Lateral Preference Inventory (LPI; Coren, 1993) & Self report | 70 | 34.1 | ● | ● | ● | ● | We classified participants using information from Table 1 by assigning right for > 3 “right” responses, left for > 3 “left” responses and assigning the rest as mixed. We calculated the continuous score again using information from Table 1 and assigning 0 to “left”, 1 to” either” and 2 to “right” responses | |
| Maxfield et al., 2015 | R-L | Self report & speech evaluation & Overall Assessment of the Speaker's Experience with Stuttering (OASES) (Yaruss & Quesal, 2006) | Not reported | 71.05 | 25.46 | ● | ● | ||||
| Mohammadi & Papadatou-Pastou, 2020 | R-L & R-M-L | Speech evaluation & Stuttering Severity Instrument 3 (Riley, 1994) | EHI | 72.9 | 6.55 | ● | ● | ● | ● | ● |
Participants were classified as R-M-L using two cut-offs (- ± 80 and ± 60). Here we report the ± 80 cutoff point The R-L classification was used in the LHfc meta-analysis and the R-M-L classification in the rest of the categorical meta-analyses |
| Murase et al., 2016 | R-L | Self report & Speech evaluation | H.N. Handedness Inventory (Hatta, 1996) | 80.77 | 32.65 | ● | ● | ||||
| Okasha et al., 1974 | R-Left changed to R- L | Speech evaluation | Not reported | Not reported | 9 | ● | ● | ● | The "middle" category consists of "those who started left-handed and changed to right-handedness" as reported in the manuscript | ||
| Olander et al., 2010 | R-L | Speech evaluation (Yairi & Ambrose, 1999) | 5 questions from EHI | 72.85 | 4.88 | ● | ● | ||||
| Piispala et al., 2017 | R-L | Not reported | Not reported | 81.58 | 7.8 | ● | ● | ||||
| Porfert & Rosenfield, 1978 | R-Non-right | Self report | Self report (“Are you right-, mixed-, or left-handed?”) | 63.85 | 20.8 | ● | Handedness information on past stutterers and questionable stutterers were not included in the meta-analysis | ||||
| Preibisch et al., 2003a | R-Non-right | Recruitment from a treatment program | EHI | 75.63 | 31 | ● | |||||
| Preibisch et al., 2003b | R-Non-right | Self report & Speech evaluation | EHI | 100 | 31 | ● | |||||
| Records et al., 1977 | R-Ambidextrous-L | Not reported | Handedness questionnaire | 55.45 | Not reported | ● | ● | ● | Data were extracted from Table 3 (there were slight inconsistencies with other parts of the manuscript) | ||
| Rogic Vidakovic et al., 2016 | R-L | Recruitment from clinics & Stuttering Severity Instrument 3 (Riley, 1994) | EHI | 70.74 | 27.56 | ● | ● | ||||
| Sommer et al., 2002 | R-Non-right | Confirmation of diagnosis by pathologists/neurologists | EHI | 70 | 30.3 | ● | |||||
| Toyomura et al., 2011 | R-L | Stuttering Severity Instrument 4 (Riley, 2009) | Not reported | 91.67 | 27.5 | ● | ● | ||||
| Toyomura et al., 2018 | R-Ambidextrous-L | Recruitment from self-help group & Stuttering Severity Instrument 4 (Riley, 2009) | EHI | 75 | 29.7 | ● | ● | ||||
| Toyomura et al., 2020 | R-L | Speech evaluation | EHI | 65.63 | 23.75 | ● | ● | ||||
| Vanhoutte et al., 2015 | R-L | Self report & Speech evaluation & Stuttering Severity Instrument 4 (Riley, 2009) | EHI | 72.29 | 29.4 | ● | ● | ||||
| Vreeswijk et al., 2019 | Continuous | Recruitment from stuttering therapy and support groups & Speech evaluation & Stuttering Severity Instrument (Sandrieser & Schneider, 2008) | EHI | 79.29 | 29.29 | ● | |||||
| Walsh et al., 2019 | R-L | Speech evaluation (Yairi & Ambrose, 1999) & Test of Childhood Stuttering (TOCS; Gillam et al., 2009) | EHI | 76.43 | 4.65 | ● | ● | Authors kindly provided handedness data | |||
| Watkins et al., 2008 | R-L | Stuttering Severity Instrument 3 (Riley, 1994) | Not reported | 63.33 | 18 | ● | ● | ||||
| Whillier et al., 2018 | Continuous | Stuttering Severity Instrument 3 (Riley, 1994) | EHI | 70.92 | 25.09 | ● | |||||
| Wieland et al., 2015 | Continuous | Speech evaluation & Stuttering Severity Instrument 4 (Riley, 2009) | EHI | 47.06 | 8.75 | ● | |||||