There is ample evidence of impaired sensory-motor acquisition in autism. Combined with anecdotal olfactory-behavioral reports, this suggests that individuals with autism may exhibit a specific olfactory profile. In the current study, Noam Sobel and his colleagues assessed olfactory performance in children undergoing diagnosis for autism. Their measure of performance was nasal airflow during sniffing of odorants. Given that sniffs are odorant-specific, such an assay provides a nonverbal measure of performance.
Sobel and his team developed a mobile device consisting of an olfactometer and airflow measurement apparatus, which was deployed at the autism diagnostic center at Assaf HaRofeh Hospital in Israel. In a complete experiment, a child received up to 26 olfactory stimulation trials, half consisting of the unpleasant odor butyric acid, and half consisting of the pleasant odor phenyl-ethyl alcohol. The inter-trial interval was 30 seconds, and the total study duration was no longer than 15 minutes. The task involved mere exposure to the odorants, and measurement of the ensuing sniff. There were no task instructions to follow, and no active task to complete.
Compliance in children in the diagnostic setting was low. Out of 26 children who started the experiment (24 boys, mean age 6.3±2.7 years), only 10 completed it, and only 6 children completed a sufficient number of trials to allow analysis (all boys, mean age 6.6±1.9 years). Nevertheless, in these six children there was a striking correlation (R2=0.99, p< 0.05) between their composite sniff-response score (i.e., difference in sniffs in response to pleasant vs. unpleasant odors) and their independently obtained autism severity scores (as assessed using the Autism Diagnostic Observation Schedule).
The results of this study imply an association between olfactory performance and autism, which may help researchers develop a nonverbal diagnostic marker. That said, the diagnostic device must be modified so as to improve compliance. Thus, these results can be viewed as a pilot that strongly merits replication and extension.