It may be possible to diagnose autism by giving children a sniff test, a new study suggests.

Most people instinctively take a big whiff when they encounter a pleasant smell and limit their breathing when they encounter a foul smell.

Children with autism spectrum disorder do not make this natural adjustment, said Liron Rozenkrantz, a neuroscientist at the Weizmann Institute of Science in Israel and one of the researchers involved with the study.

She and her colleagues reported their findings in the journal Current Biology.

They presented 18 children who had an autism diagnosis and 18 typically developing children with pleasant and unpleasant odors and measured their sniff responses. The pleasant smells were rose and soap; the unpleasant smells were sour milk and rotten fish.

Typically developing children adjusted their sniffing almost immediately — within about 305 milliseconds. Children with autism did not respond as rapidly. As they were exposed to the smells, the children were watching a cartoon or playing a video game.