Not much is known about the language trajectories of non-verbal and minimally verbal children yet. However, the number of research studies are growing. Quite a few research studies have attempted to identify reliable predictors of good language outcomes. For example:
Predictors of language development in non-verbal and minimally verbal children
Saul and Norbury (2020) followed the expressive language progress of 27 minimally verbal children, aged three to five, for a year. At the end of the study, one-third no longer met the minimally verbal criteria at the end of the study. In this group of children, only one factor predicted language progress – the child's initial speech skills (the number of different speech sounds that the child made during an interaction). It means that there are factors other than social skills that influence language development in autism: persistent and severe expressive language difficulties may reflect an additional deficit in speech production, rather than a consequence of core autism features.
Chenausky et al. (2018) investigated baseline factors that predicted whether minimally verbal autistic children would improve after treatment for spoken language. Potential predictors tested were sex, age, expressive language, phonetic inventory (the number of speech sounds repeated correctly), autism severity, and nonverbal IQ. Phonetic inventory and (for some children) autism severity predicted children's posttreatment improvement whereas nonverbal IQ and expressive language ability did not predict improvement, nor did younger age, suggesting that some older children with autism may be candidates for speech therapy.
Morgan et al. (2020) determined the extent to which early social communication and vocabulary production predicted variance in language outcomes at 2 and 3 years of age. Measures of social communication between 18-21 months can predict language outcomes at 2 and 3 years. The strongest predictors of language outcomes at age 2 are measures of speech and vocabulary production. At age 3, social and symbolic communication played a more significant role in an expressive and receptive language outcome. A similar pattern emerged for the categorical prediction of language delay.
DiStefano et al. (2016) emphasize the crucial relationship between social engagement and expressive language development and highlight the need to include sustained communication interchanges in work with minimally verbal children. Minimally verbal autistic children can improve their play skills within a targeted intervention. Increases in symbolic play are associated with increases in expressive language skills (Chang et al. 2017).
The results of some studies are not very optimistic, for example:
Rose et al. (2016) explored outcomes for minimally verbal autistic children following a community based early intervention programme: Despite advances in early intervention, and access to services at a younger age:
around a quarter of children in this study exited early intervention with significant communication needs;
more than half of the children who entered the programme with minimal speech showed no improvement and exited the programme with a similar language profile.
a small percentage of children regressed in their language level over time.
Late talkers are a heterogeneous group of toddlers. And often it’s hard (if not impossible) to predict the outcome. Further research is needed.