The Dynamics of Looking and Smiling Differ for Young Infants at Elevated Likelihood for ASD

Abstract

Social smiling is the earliest gained social communication skill, emerging around 2 months of age. From 2 to 6-months, infants primarily smile in response to caregivers. After 6 months, infants coordinate social smiles with other social cues to initiate interactions with the caregiver. Social smiling is reduced in older infants with autism spectrum disorder (ASD) but has rarely been studied before 6 months of life. The current study therefore aimed to understand the component parts of infant social smiles, namely look to caregiver and smile, during face-to-face interactions in 3 and 4-month-old infants at elevated (EL) and low likelihood (LL) for ASD. We found that EL and LL infants looked to their caregiver and smiled for similar amounts of time and at similar rates, suggesting that social smiling manifests similarly in both groups. A nuanced difference between groups emerged when considering temporal dynamics of looking and smiling. Specifically, 3-month-old EL infants demonstrated extended looking to the caregiver after smile offset. These findings suggest that social smiling is largely typical in EL infants in early infancy, with subtle differences in temporal coupling. Future research is needed to understand the full magnitude of these differences and their implications for social development.

Keywords: autism spectrum disorder; infancy; parent‐child interaction; social attention; social smiling.

FIGURE 1 |

Caregivers and infants engaged in a face-to-face interaction with each other for 5 min. Infant looks to caregiver and smiles were coded.

FIGURE 2 |

(A) The overall percent of the session looking to caregiver, (B) number of looks per minute, and (C) duration of looks were assessed. Each dot represents one participant, while the bar graphs and error bars represent the mean and standard error. Generalized linear mixed effects models revealed that (A) despite similar proportions of the session spent looking to the caregiver (B–C) older infants generate more, shorter looks to the caregiver’s face than younger infants.

FIGURE 3 |

(A) The overall percent of the session smiling, (B) number of smiles per minute, and (C) duration of smiles were assessed. Each dot represents one participant, while the bar graphs and error bars represent the mean and standard error. Generalized linear mixed effects models revealed that smiling increased with age, driven by more frequent smiles.

FIGURE 4 |

(A) Look-smile episodes are defined as unbroken periods of time where the infant is either looking to or smiling at the caregiver. (B) We examined the coordination patterns of co-occurring looks and smiles based on which behavior started first and based on which behavior ended first. Episodes that started with a look were considered for onset temporal dynamics analyses, and episodes where smiles ended first were considered for offset temporal dynamics analyses. When calculating the onset and offset latency, onset was calculated as time from look onset to onset of the first smile and offset was calculated as the time from the last smile offset to look offset.

FIGURE 5 |

The probability that the infant is looking to the caregiver in the (A) 10 s before smile onset and (B) 10 s after smile offset is displayed as cumulative lognormal distribution functions. Dotted lines represent data from 3-month-old participants and dashed lines represent data from 4-month-old participants. (A) An age effect shows that 4-month-old infants are more temporally coupled at look-smile onset than 3-month-old infants. (B) A group by age interaction effect shows that the look-smile offset for 3-month-old EL infants is less coupled than for all other infants.