Table 1. .
Studies included in the review
| Reference | N | Age Range | Mean age | Degree of hearing loss | Hearing aid | Parent language use | How ToM tests were administered | Task(s) used | Main findings |
|---|---|---|---|---|---|---|---|---|---|
| Figueroa et al. (2020) | CI: 36 | 12–16 | 14;0 | Prelingually deaf | CIage = 2;3 | N/A | SpL | UT less verbal | TH > CI |
| TH: 54 | 12–16 | 13;6 | TH = CIearly; TH > CIlate | ||||||
| CIbilateral > CIunilateral; CIbilateral = TH | |||||||||
| Marschark et al. (2019) | CI: 46 | College students | N/A | N/A | CIage = 6;7 | NS: 9 | All groups in SL or SpL or both | Second order FB, sarcasm, dubble bluff; self-ratings of SL and SpL; Non-verbal IQ Woodcock-Johnson III | TH > CI or non-CI |
| No CI: 48 | HA: 43 | LS: 81 | |||||||
| TH :41 | No aid: 11 | ||||||||
| Meristo and Strid (2020) | NS: 9 | 2;2–6;2 | 4;3 | >80 dB | No aid | SL | Non-verbally, eye tracking | UT non-verbal | NS > LS |
| LS: 13 | 1;5–8;5 | 4;9 | >80 dB | CI | SpL | NS = TH | |||
| TH: 24 | SpL | NS and TH above chance | |||||||
| LS at chance | |||||||||
| Meristo et al. (2007) | NS: 24 | 7;4–16;1 | 12;3 | Prelingually deaf | N/A | SL | SL | UT, UC, second order FB, faux pas, strange stories (+ emotion understanding); RPM | Deaf children attended either a bilingual or an oralist school. |
| LS: 37 | 8;0–15;11 | 12;3 | SpL | SL | TH > LS Estonian bilingual | ||||
| TH: 26 | 6;1–15;4 | 10;9 | SpL | SpL | TH > LS Swedish bilingual | ||||
| TH > NS Estonian oralist | |||||||||
| NS > LS Estonian bilingual | |||||||||
| NS > LS Swedish bilingual | |||||||||
| NS > NS Estonian oralist | |||||||||
| TH = NS Estonian bilingual | |||||||||
| Meristo et al. (2012) | LS: 10 | 1;5–2;2 | 1;11 | Moderate to profound | 5CIage: 14 m | SpL | Non-verbally, eye tracking | UT | TH > LS in false belief trial |
| TH: 10 | 1;7–2;4 | 1;11 | 5HAage: 12 m | TH = LS in true belief trial | |||||
| Meristo et al. (2016) | CI: 8 | 3;11–8;5 | 6;5 | Profound | CIage: 1;9 | SpL | Non-verbally, eye tracking + verbally with toys in SpL | UT non-verbal | TH > CI or HA (non-verbal) |
| HA: 7 | 4;0–7;11 | 5;8 | 45–65 dB | HAage: 1;10 | SpL | UT × 3 verbal | CI and HA at chance (non-verbal) | ||
| TH: 15 | 4;1–8;11 | 5;11 | SpL | PPVT | TH above chance (non-verbal) | ||||
| Raven | TH = CI and TH > HA (verbal) | ||||||||
| Morgan and Kegl (2006) | LS: 22 | 7;0–39;0 | (1) 13;9 | Severely to profoundly deaf | N/A | SpL | SL | UC drawings | UC: Early learners > late learners |
| (2) 24;1 | Narrative task | ||||||||
| RPM | |||||||||
| Sign language – teacher ratings | |||||||||
| Netten et al. (2017) | HL: 44 | 3;4–5;10 | 4;9 | 35–70 dB; age at detection 0;0 to 4;6 | Bilateral HA-s all except one; Mean age at HA 2;2 | N/A | 89% spoken language, 11% sign-supported Dutch | UT, picture stimuli; Language skills – medical records and parent reports | TH > HL |
| TH: 101 | 3;4–5;10 | 4;9 | |||||||
| Peters et al. (2021) | CI: 25 | 3;0–6;4 | 4;9 | N/A | CIage = 12 m | SpL | UT & UC | TH = CI (UC and UT) | |
| TH: 25 | 3;6–5;11 | 4;8 | SpL | ToM Scale | TH = CI (ToM Scale) | ||||
| Language scales | |||||||||
| Peterson (2004) | CI: 13 | 4;2–11;2 | 8;0 | >91 dB | CIage = 2–5 y | SpL | 2× UT & 2× UC | TH > CI, HA or ASD | |
| HA: 13 | 5;0–12;1 | 7;6 | N/A | SpL | Verbal IQ; PPVT | CI = HA | |||
| ASD: 9 | 5;3–12;6 | 8;6 | Non-verbal IQ: the Goodenough-Harris | CI + HA = ASD | |||||
| TH: 17 | 4;1–5;8 | 4;10 | |||||||
| Peterson and Siegal (1995) | LS: 26 | 8;1–13;0 | 10;7 | Severely and profoundly prelingually deaf | SpL: 24 | Total communication, toy play | 2× UT; the Goodenough-Harris and Raven for non-verbal IQ + RPM | LS < Down syndrome | |
| SL: 2 | LS = ASD | ||||||||
| Peterson and Siegal (1999) | LS: 34 | 5;6–12;8 | 9;4 | Severe to profound | SpL | Each child’s prefered language for LS and NS | UT; UC; CA; the Goodenough-Harris for non-verbal IQ; teacher ratings of language for deaf. PPVT for TH | NS = OD = TH | |
| NS: 11 | 6;6–12;8 | 10;3 | Severe to profound | SL | NS or OD or TH > LS | ||||
| OD: 14 | 6;10–13;2 | 9;2 | Moderate to severe | SpL | SpL | LS = ASD | |||
| ASD: 22 | 6;2–13;9 | 9;6 | |||||||
| TH: 21 | 3;11–5;4 | 4;6 | |||||||
| Pluta et al. (2021) | CI: 45 | 3;3–8;3 | 5;5 | >90 dB | CIage = 13 m | SpL | UT less verbal | TH > CIyounger | |
| TH: 94 | 3;3–7;3 | 4;6 | prelingual | TH = CIolder | |||||
| Smogorzewska and Osterhaus (2021) | HL: 270 | Longitudinal study, ages 7;6 to 9;6 | 7;6 | Moderate to severe | All HL children used CI or HA | N/A | Written test battery | Second-order FB; Faux Pas | TD > DHH > MID |
| TH: 250 | 7;6 | Polish Language test for grammar, vocabulary, reading and writing | |||||||
| MID: 210 | 8;1 | ||||||||
| Sundqvist et al. (2014) | CIearly: 8 | 4;3–9;3 | 6;7 | All CI | CIage = 1;6 | SpL | SpL | UT | TH > CIearly or CIlate |
| CIlate: 8 | 4;5–9;6 | 7;1 | M = 88 dB | CIage = 3;4 | SpL | SpL | PPVT | CIearly = CIlate | |
| TH: 18 | 6;0–8;0 | 6;7 | SpL | SpL | RPM |
This study is missing in the table.
CA = changed appearance; UT = unexpected transfer; UC = unexpected contents; PPVT = Peabody Picture Vocabulary Test; RPM = Raven’s Progressive Matrices; LS = late signers (i.e., deaf children from hearing families); NS = native signers (i.e., deaf children from deaf families); OD = oral deaf children (i.e., children growing up with spoken language); TH = typically hearing children; ASD = autism spectrum disorder; HL = children with hearing loss; MID = mild intellectual disability; CI = cochlear implants, or children with cochlear implants; HA = conventional hearing aids, or children with conventional hearing aids; CIage = age of first cochlear implantation; HAage = age of initial hearing aid use; SL = sign language; SpL = spoken language.
Ages are provided in years and months (3;4 should be interpreted as 3 years and 4 months).
Degrees of hearing loss according to American Speech-Language-Hearing Association (mild 26 to 40 dB; moderate 41 to 55 dB; moderately severe 56 to 70 dB; severe 71 to 90 dB; profound 91+).