Parental sensitivity refers to a set of skills that enables a parent to be emotionally connected, in tune and responsive to their child’s needs, goals, and communicative attempts. A parent with a high level of sensitivity will be positive and accepting of their child and will strive for interactive congruence. Twenty-five (25) studies within the review assessed this aspect of parent behaviour (papers 19 to 45 in Table 1) and therefore it is the most frequently assessed aspect of PCI. Across papers parental sensitivity was described as a group of sub-skills. Parents were often assessed on each of these sub-skills using Likert-scales. These behaviours consisted:

Parental communication behaviours are language-focused strategies used by parents during moments of interaction with their deaf child. Though most are explicitly linked to exposing the child to signed or spoken language, some behaviours are centred around increasing the child’s access to spoken or signed language. Papers that only recorded and analysed parent’s verbal interactions were excluded (n = 43) and are listed in Appendix C. Thirteen papers assessed parents on a range of communicative behaviours (papers 40–52 in Table 1) and these are summarised below:

Increased access to language: Some papers assessed parents on their ability to communicate within the child’s line of sight or whilst being face to face; others observed parents’ use of timing, i.e., waiting for the child to look before communicating. Others observed parents’ use of child-directed speech or child-directed sign, i.e., where parents modify their speech or sign to be more child orientated. For example, a parent may adapt the palm orientation of a sign so the child can see more of the hand; they may increase the size and range of movement of signs, they may exaggerate the non-manual features of accompanying signs (facial expressions), use exaggerated vocal pitch or acoustic/sign highlighting, where the parent adapts their amplification of words or signs closer to the child.

Language input: This category refers to signed or spoken languages. Similar to parental sensitivity, parents were assessed on their contingent talk and number of connected turns, as well as their off-topic initiations (i.e., directives, requests and questions). Parents’ use of language stimulation was coded and assessed on how they: labelled items or feelings; commented; described; made accompanying sounds; interpreted their child’s behaviour with language; repeated their child’s utterance; expanded their child’s language by adding 1 or 2 new words, or rephrased it with correct grammar. Parents’ mean length of utterance (MLU) was assessed in one paper. Parents’ use of praise, affirmation and encouragement was assessed through language use, intonation, their gesture, and facial expressions. Assessment of less frequent behaviours included the parent modelling play, and the parent opposing the child, either by rejecting their communication, correcting their communication, or prohibiting their child’s behaviour.

The frequency and function of parents’ use of touch when interacting with their child was also assessed in a small set of studies (Papers 53–56 in Table 1). The authors of these papers were interested in the type, location, and duration of parent-initiated touch. One paper looked at the temporal alignment between touch and parents’ utterances [85]. Two papers also measured parental sensitivity [83,84] with Paradis and Koester [83] creating a coding system to analyse the function of parental touch, e.g., affectionate, attention-getting and instructive.

Five papers included in the review sit within this category (papers 57–61 in Table 1). Three papers [87,88,89] focused on the communication mode of parents (i.e., how often they signed, used gesture or spoke). One paper looked in detail into the type and function of gesture used [90] and another transcribed American Sign Language and documented eye gaze between mother and child [91].

Maternal sensitivity was positively correlated with expressive language and predicted language growth over time [14,76]. In their study of 285 deaf children with cochlear implants, Quittner and team found parents with above-average skills in maternal sensitivity and language stimulation had children with 1.52 years less of a language delay [14]. Dirks and Rieffe [20] also found positive relationships between parental sensitivity and receptive and expressive child language and total duration of joint engagement. Children with better language experienced longer interactions with their parents and this was linked to parents with higher levels of emotional sensitivity (ibid).

In their 1999 study, Pressman and colleagues found that maternal sensitivity was not correlated with children’s initial expressive language scores, but was positively correlated in their follow up assessments 12 months later [64]. In their regression analyses, maternal sensitivity positively predicted expressive language scores and accounted for 10% of the variance. In their 1998 study, they uncovered that maternal sensitivity had a larger positive effect on language in the sample of deaf children compared to their hearing sample [63].

2.3.3. Parental Communication Behaviours

In the study from Nicastri et al. [13], parents received nine whole-group sessions and three individual sessions of training over 10.5 months. The intervention was based on the ‘It Takes Two to Talk’ Hanen program [100] and involved video modelling, where parents had opportunities to put their training into practice at home. Strategies within the program included waiting and observing the child, following the child’s lead, interpreting the child’s behaviour, parallel talk, and expanding and recasting the child’s language. The authors reported significant gains in parent communication behaviours and parental sensitivity post-intervention and noted that parents in the treatment group had children with significantly better language skills, when formally assessed three years post treatment.

A pilot RCT [34] involved parents receiving weekly, hour-long sessions for six months, where they were explicitly taught to use strategies to promote early communication. The authors referred to methods such as enhanced milieu teaching [101], prelinguistic milieu teaching [102], and The Hanen Program It Takes Two to Talk [100]. Examples of strategies include sitting face to face, using gestures, imitating/mirroring the child’s actions, and turn taking. The study reported that parents in the treatment group increased their use of communication support strategies by 17% compared to 2% in the control group., There was a large effect size of 1.09 (p = 0.03) for the difference in gains in deaf children’s prelinguistic speech skills between the treatment and control groups.

3. Summary

The four main areas of PCI uncovered have some parallels with the review on children with language difficulties by Roberts and Kaiser [30], where the three most measured parent strategies were: parent responsiveness, use of language models and rate of communication. Similarly, a review by Holzinger and colleagues [104] on children with cochlear implants uncovered family involvement and parental linguistic input as key themes in their results. Additionally, within PCI research in the hearing population, the same set of behaviours are commonly measured [35].