Do children preferentially mark unpredictable material? The case of optional plural marking.

Speakers tend to assign more linguistic material to less predictable elements. This tendency is typically explained by a bias for an efficient trade-off between production effort and understandability and is claimed to shape linguistic structures across languages. Recent work suggests this trade-off enters the linguistic system through learning processes with learners deviating from their input by increasing marking for less predictable elements. However, no study to date has tested whether child learners also show such predictability-based marking, an important gap seeing that children are the primary learners in real-life language acquisition. A recent study showed that adults increase predictability-based marking of an optional-plural marker, in line with communicative efficiency. Here, we ask if children show a similar pattern. Results show that children, unlike adults, do not show an efficient trade-off in their productions. We discuss implications for the role of different language learners on language change.