Characteristic	Variable name	Domain	Criteria set	No. of studies (% total studies)	Citations
Sound distortions; phonetic errors	Sound distortions	Segmental	ASRS, McNeil, Wambaugh	28 (66.7)	Ballard et al., 2016, 2018; Ballard, Savage, et al., 2014; Bartle-Meyer et al., 2009; Basilakos et al., 2015, 2017; Bislick et al., 2017; Botha et al., 2015, 2018; Croot et al., 2012; Duffy et al., 2017; Haley et al., 2013, 2012; Jacks, 2008; Jacks & Haley, 2015; Jacks et al., 2010; Jonkers et al., 2017; Josephs et al., 2014, 2013, 2012; Maas et al., 2015; Mailend & Maas, 2013; New et al., 2015; Robin et al., 2008; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Slow overall speech/articulation rate a	Slow rate	Suprasegmental	ASRS, McNeil, Wambaugh	28 (66.7)	Ballard et al., 2016, 2018; Ballard, Savage, et al., 2014; Basilakos et al., 2015, 2017; Bislick et al., 2017; Botha et al., 2015, 2018; Cunningham et al., 2016; Haley et al., 2013, 2012; Haley et al., 2017; Itabashi et al., 2016; Jacks, 2008; Jacks & Haley, 2015; Jonkers et al., 2017; Josephs et al., 2014, 2013, 2012; Maas et al., 2015; Mailend & Maas, 2013; Melle & Gallego, 2012; New et al., 2015; Robin et al., 2008; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Distorted substitutions; other substitution errors (phonemic)	Distorted substitutions	Segmental	ASRS, McNeil, Wambaugh	25 (59.5)	Ballard et al., 2018; Basilakos et al., 2015, 2017; Bislick et al., 2017; Botha et al., 2015, 2018; Croot et al., 2012; Duffy et al., 2017; Haley et al., 2013, 2012; Itabashi et al., 2016; Jacks, 2008; Jacks & Haley, 2015; Jacks et al., 2010; Jonkers et al., 2017; Josephs et al., 2014, 2013, 2012; Maas et al., 2015; Mailend & Maas, 2013; Melle & Gallego, 2012; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Syllable segmentation/syllable segregation (including within words or across words in phrases/sentences)	Syllable segmentation	Suprasegmental	ASRS, McNeil	20 (47.6)	Ballard et al., 2016, 2018; Ballard, Savage, et al., 2014; Basilakos et al., 2015, 2017; Bislick et al., 2017; Botha et al., 2015; Croot et al., 2012; Itabashi et al., 2016; Josephs et al., 2014, 2013, 2012; Mailend & Maas, 2013; Melle & Gallego, 2012; New et al., 2015; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Lengthened intersegment durations (between sounds, syllables, words, or phrases; possibly filled, including intrusive schwa)	Lengthened pauses	Suprasegmental	ASRS, McNeil	20 (47.6)	Ballard et al., 2018; Basilakos et al., 2015, 2017; Bislick et al., 2017; Botha et al., 2015, 2018; Itabashi et al., 2016; Jacks & Haley, 2015; Jacks et al., 2010; Josephs et al., 2014, 2013, 2012; Maas et al., 2015; Melle & Gallego, 2012; New et al., 2015; Robin et al., 2008; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Lengthened vowel and/or consonant segments; other sound prolongations	Inc. seg. dur	Segmental	ASRS, McNeil	20 (47.6)	Ballard et al., 2018; Bartle-Meyer et al., 2009; Basilakos et al., 2015, 2017; Botha et al., 2015, 2018; Haley et al., 2013, 2012; Jacks, 2008; Jacks & Haley, 2015; Jacks et al., 2010; Josephs et al., 2014, 2013, 2012; Maas et al., 2015; Robin et al., 2008; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Audible or visible articulatory groping, speech initiation difficulty, false starts/restarts	Groping	Motor	ASRS, McNeil, Wertz	18 (42.9)	Ballard et al., 2016, 2018; Basilakos et al., 2015, 2017; Botha et al., 2015, 2018; Duffy et al., 2017; Haley et al., 2012; Itabashi et al., 2016; Jacks, 2008; Josephs et al., 2014, 2013, 2012; Melle & Gallego, 2012; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Increased sound distortions or distorted sound substitutions with increased utterance length or increased syllable/word articulatory complexity	Complexity effect	Segmental	ASRS	16 (38.1)	Ballard et al., 2016, 2018; Basilakos et al., 2015, 2017; Botha et al., 2015, 2018; Duffy et al., 2017; Jacks, 2008; Josephs et al., 2014, 2013, 2012; Melle & Gallego, 2012; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Deliberate, slowly sequenced, segmented, and/or distorted (including distorted substitutions) speech SMRs in comparison to speech AMRs; sequencing errors	SMRs < AMRs	Segmental	ASRS	14 (33.3)	Ballard et al., 2016, 2018; Basilakos et al., 2015, 2017; Botha et al., 2015, 2018; Josephs et al., 2014, 2013, 2012; Robin et al., 2008; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Sound or syllable repetitions	Repetitions	Segmental	ASRS	14 (33.3)	Ballard et al., 2018; Basilakos et al., 2015, 2017; Botha et al., 2015, 2018; Haley et al., 2012; Josephs et al., 2014, 2013, 2012; Melle & Gallego, 2012; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Distorted sound additions (not including intrusive schwa)	Distorted additions	Segmental	ASRS	14 (33.3)	Ballard et al., 2018; Basilakos et al., 2015, 2017; Botha et al., 2015, 2018; Duffy et al., 2017; Itabashi et al., 2016; Josephs et al., 2014, 2013, 2012; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Altered/abnormal prosody; dysprosody; equal/excess stress	Dysprosody	Suprasegmental	McNeil, Wambaugh, Wertz	13 (31.0)	Ballard et al., 2018; Ballard, Savage, et al., 2014; Bartle-Meyer et al., 2009; Bislick et al., 2017; Croot et al., 2012; Haley et al., 2012; Jacks, 2008; Jacks et al., 2010; Jonkers et al., 2017; Maas et al., 2015; Mailend & Maas, 2013; New et al., 2015; Robin et al., 2008
Increased sound distortions or distorted sound substitutions with increased speech rate	Rate effect	Segmental	ASRS, McNeil	12 (28.6)	Ballard et al., 2018; Basilakos et al., 2015, 2017; Botha et al., 2015, 2018; Josephs et al., 2014, 2013, 2012; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Reduced words per breath group relative to maximum vowel duration	Reduced phrase length	Suprasegmental	ASRS	11 (26.2)	Basilakos et al., 2015, 2017; Botha et al., 2015, 2018; Josephs et al., 2014, 2013, 2012; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Inaccurate (off-target in place or manner) speech AMRs	Inaccurate AMRs	Segmental	ASRS	11 (26.2)	Basilakos et al., 2015, 2017; Botha et al., 2015, 2018; Josephs et al., 2014, 2013, 2012; Whitwell, Duffy, Strand, Xia, et al., 2013; Utianski et al., 2019; Utianski, Whitwell, Schwarz, Duffy, et al., 2018; Utianski, Whitwell, Schwarz, Senjem, et al., 2018
Errors consistent in type/invariable in location; consistent errors over repeated productions	Consistent errors	Segmental	McNeil, Wambaugh	7 (16.7)	Ballard et al., 2016; Jacks, 2008; Jonkers et al., 2017; Maas et al., 2015; Mailend & Maas, 2013; Robin et al., 2008
Articulator inconsistency/inconsistent errors over multiple repetition	Inconsistent errors	Suprasegmental	Wertz	2 (5.1)	Ballard et al., 2016; Haley et al., 2012
“Syllabic speech output”b	—	Suprasegmental	—	1 (2.4)	Bartle-Meyer et al., 2009
PVI thresholdb (< 112)	—	Suprasegmental	—	1 (2.4)	Ballard et al., 2018
Words of increasing length error thresholdb (> 0.17)	—	Segmental	—	1 (2.4)	Ballard et al., 2018

Note. Em dashes indicate data not available. Out of 53 total AOS articles, 42 articles were included in this analysis of inclusion criteria. Five were excluded from current analysis because they were published before 2007; four were excluded (Caso et al., 2014; Duncan et al., 2019; Mandelli et al., 2014; Wilson et al., 2010) because they used traditional primary progressive aphasia inclusion criteria and specification of AOS as a separate subgroup is not addressed or is addressed as part of the review article's analyses/results rather than as a means of participant inclusion. One was excluded (Strand et al., 2014) because it introduces the ASRS. One was excluded (Haley & Jacks, 2019) because specific inclusion criteria for diagnosis of the AOS group is not listed. Percentages listed are based on the 42 articles charted. ASRS = Apraxia of Speech Rating Scale (Strand et al., 2014); McNeil = criteria set introduced in McNeil et al. (2009); Wambaugh = criteria set introduced in Wambaugh et al. (2006); Wertz = criteria set introduced in Wertz et al. (1984); SMRs = sequential motion rates; AMRs = alternating motion rates; PVI = pairwise variability index.

^aWord syllable duration from Cunningham et al. (2016) and Haley et al. (2013, 2017) considered as rate measure.

^b Measures mentioned as inclusion criteria in only one study were excluded from Figure 2b for ease of interpretation of the figures.