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Facial responsiveness to odours in normal and pervasively developmentally disordered children
R Soussignan1, B Schaal, G Schmit
1Laboratoire de Psycho-Biologie du Développement, CNRS URA 315, EPHE, Paris, France.
Insights
Children with pervasive developmental disorder (PDD) show distinct facial responses to odors compared to neurotypical children. While PDD subjects display negative expressions, neurotypical children smile more, indicating altered social display of hedonic reactions.
Area of Science:
- Neuroscience
- Psychology
- Developmental Disorders
Background:
- Pervasive developmental disorder (PDD) is characterized by social and communication deficits.
- Understanding facial responsiveness in PDD is crucial for assessing sensory processing and social interaction.
- Olfactory stimuli provide a unique modality to investigate emotional and facial responses.
Purpose of the Study:
- To compare facial responsiveness to odors of varying hedonic valence in children with PDD and neurotypical (N) children.
- To investigate the accuracy of facial response classification in PDD subjects.
- To explore potential deficits in the socialization of hedonic facial displays in PDD.
Main Methods:
- Covert videotaping of facial responses in 10 PDD and 10 N children exposed to odors.
- Analysis of facial movements using the Facial Action Coding System (FACS).
- Observer ratings of facial behavior to classify odor pleasantness.
Main Results:
- PDD and N subjects exhibited distinct facial action units in response to unpleasant odors.
- PDD subjects showed more muscular actions indicating negative experiences, while N subjects displayed more smiles.
- Facial responses to unpleasant odors were classified more accurately in PDD than in N subjects.
Conclusions:
- Children with PDD possess a functional ability to sense odor hedonics.
- A deficit in the socialization of hedonic facial displays is suggested in individuals with PDD.
- Facial coding systems and observer ratings reveal differences in emotional expression related to olfactory stimuli.
Abstract:
The facial responsiveness of 10 mutic children with pervasive developmental disorder (PDD) and 10 normal (N) children matched for sex and chronological age were covertly videotaped while presented with a set of odours contrasted in hedonic valence. Hedonic ratings of the stimuli were obtained both from the group of N subjects and a panel of adults. Two methods were used to measure facial responses in the same subjects. The first method consisted in an analysis of facial movements with the Facial Action Coding System. Results show that PDD and N subjects displayed distinct action units in response to unpleasant odours. PDD subjects typically displayed muscular actions indexing negative experience, while N subjects showed more smiles. With the second method, odour-elicited facial behaviour was rated by a panel of observers, who were asked to judge whether the subjects were exposed a pleasant, neutral or unpleasant smell. The facial responses to unpleasant odours were classified more accurately in PDD than in N subjects. These findings suggest a functional ability to sense the hedonics attached to odours, but a deficit of socialization of hedonic facial displays in developmentally disordered subjects.