Challenges with computing scalar and ad-hoc implicatures in Mandarin-speaking 4-8-year-old autistic children

Mixed findings have been reported about the computation of scalar or/and ad-hoc implicatures in primarily school-age autistic verbal children and adolescents: while some studies reported their struggles with both implicatures, others observed their strengths in computing scalar implicatures. This study extends the previous investigation by testing the derivation of scalar (including both number and quantifier) and ad-hoc implicatures of a younger group of Mandarin-speaking autistic 4-8-year-olds; moreover, we assess the biological, linguistic, and cognitive factors affecting children's implicature acquisition.

The participants included 22 4-8-year-old autistic verbal children (mean age = 67.64 months) and 19 typically developing (TD) children who did not significantly differ in age, receptive vocabulary, and non-verbal IQ. Both groups completed a computer-based Truth Value Judgment task, assessing their knowledge of scalar (involving the number 'three' and the quantifier 'some') and ad-hoc implicatures. We also examined whether their implicature computation was linked to age, receptive vocabulary, non-verbal IQ, and Theory of Mind (ToM).

Compared with the TD controls, autistic children derived significantly fewer scalar and ad-hoc implicatures. Specifically, TD children successfully computed number and ad-hoc implicatures, contrasting to the bimodal distribution of their pragmatic vs. logical responses to quantifier implicatures. Though autistic children performed better with number implicatures slightly above the chance level, they had difficulties in computing quantifier and ad-hoc implicatures. Further, autistic children's knowledge of the number and ad-hoc implicatures was linked to their ToM skills.

These findings underscore the overall delayed implicature knowledge of young autistic children, and their low sensitivity to the implicatures is related to the core ToM deficits. Furthermore, our data confirm the coherent pattern of the earlier acquisition of number over quantifier implicatures and illuminate the distinct mechanisms underlying the computation of scalar vs. ad-hoc implicatures.