Prosodic Entrainment in Conversations of Verbal Children and Teens on the Autism Spectrum

Abstract

Unusual speech prosody has long been recognized as a characteristic feature of the speech of individuals diagnosed with Autism Spectrum Disorders (ASD). However, research to determine the exact nature of this difference in speech prosody is still ongoing. Many individuals with verbal autism perform well on tasks testing speech prosody. Nonetheless, their expressive prosody is judged to be unusual by others. We propose that one aspect of this perceived difference in speech prosody in individuals with ASD may be due to a deficit in the ability to entrain-or become more similar-to their conversation partners in prosodic features over the course of a conversation. In order to investigate this hypothesis, 24 children and teens between the ages of 9 and 15 years participated in our study. Twelve of the participants had previously been diagnosed with ASD and the other 12 participants were matched to the ASD participants in age, gender, and non-verbal IQ scores. All participants completed a goal-directed conversation task, which was subsequently analyzed acoustically. Our results suggest (1) that youth diagnosed with ASD entrain less to their conversation partners compared to their neurotypical peers-in fact, children and teens diagnosed with ASD tend to dis-entrain from their conversation partners while their neurotypical peers tend to converge to their conversation partners' prosodic features. (2) Although age interacts differently with prosodic entrainment in youth with and without ASD, this difference is attributable to the entrainment behavior of the conversation partners rather than to those with ASD. (3) Better language skill is negatively correlated with prosodic entrainment for both youth with and without ASD. The observed differences in prosodic entrainment in children and teens with ASD may not only contribute to the perceived unusual prosody in youth with ASD but are also likely to be indicative of their difficulties in social communication, which constitutes a core challenge for individuals with ASD.

Keywords: adolescents; autism; children; conversational speech; prosody.

FIGURE 1

Illustration of the geometry associated with the proposed change in entrainment measurement. Each feature (k = 1,2) is parameterized by the (purple) vector drawn from the start point S^(k) = (S1${}_s^{(k)}$,S2${}_s^{(k)}$) which represents the value of both speaker’s f0 measurement over the first third of the conversation to the end point E^(k) = (S1${}_e^{(k)}$,S2${}_e^{(k)}$), which represents the value of both speaker’s f0 measurement over the last third of the conversation. The difference between the minimum distance from the point S^(k) to the line denoted as d${}_1^{(k)}$ and the minimum distance from the point E^(k) to the line denoted as d${}_2^{(k)}$ gives the change in entrainment measurement. Finally, the individual speaker contribution to the change in entrainment is assessed by computing the ratio of d${}_3^{(k)}$ = |S1${}_e^{(k)}$–S1${}_s^{(k)}$| and d${}_3^{(k)}$ = |S1${}_e^{(k)}$–S1${}_s^{(k)}$| to the sum d${}_3^{(k)}$ + d${}_4^{(k)}$, which represents the proportion of the change along the x-axis (Speaker 1) and y-axis (Speaker 2), respectively.

FIGURE 2

(A) Group differences between children and teens with Autism Spectrum Disorder (ASD) and their neurotypical peers (NT) in mean f0 entrainment. (B) Relationship between age in years and mean f0 entrainment and its group interaction.

FIGURE 3

(A) Group Differences between children and teens with Autism Spectrum Disorder (ASD) and their neurotypical peers (NT) in the contribution to mean f0 entrapment provided in percent of total entrainment (B) Relationship between language ability as measured by the Core Language sub-test of the CELF and contribution to mean f0 entrainment.

FIGURE 4

(A) Group Differences between children and teens with Autism Spectrum Disorder (ASD) and their neurotypical peers (NT) in the contribution to mean f0 entrapment adjusted for the overall amount of entrainment of the conversation. (B) Relationship between language ability as measured by the Core Language sub-test of the CELF and the adjusted mean f0 entrainment contribution. (C) The group interaction between age in years and adjusted contribution to mean f0 entrainment.