Articulation rate in Swedish child-directed speech increases as a function of the age of the child even when surprisal is controlled for

TL;DR

This study shows that in Swedish child-directed speech, articulation rate increases with the child's age, independent of surprisal, suggesting adults adapt their speech rate to the child's linguistic capacity.

Contribution

It demonstrates that the increase in articulation rate with age persists even when controlling for surprisal and other factors, highlighting adaptive speech modifications.

Findings

Articulation rate in CDS is lower than in ADS for the youngest children.

There is a negative correlation between articulation rate and surprisal in ADS.

The increase in CDS articulation rate with age remains after controlling for surprisal.

Abstract

In earlier work, we have shown that articulation rate in Swedish child-directed speech (CDS) increases as a function of the age of the child, even when utterance length and differences in articulation rate between subjects are controlled for. In this paper we show on utterance level in spontaneous Swedish speech that i) for the youngest children, articulation rate in CDS is lower than in adult-directed speech (ADS), ii) there is a significant negative correlation between articulation rate and surprisal (the negative log probability) in ADS, and iii) the increase in articulation rate in Swedish CDS as a function of the age of the child holds, even when surprisal along with utterance length and differences in articulation rate between speakers are controlled for. These results indicate that adults adjust their articulation rate to make it fit the linguistic capacity of the child.