Hearing a crying baby can make any adult feel distressed, but some crying bouts are more likely than others to rouse worry and anxiety.

New research published 14 June in Research in Developmental Disabilities shows that adults report feeling more distress when hearing the cries of babies who are later diagnosed with autism than those of typical infants.

People with autism have communication difficulties such as problems taking turns during conversation. To track this social behavior back to its origins, the researchers examined crying as one of the first forms of communication babies acquire.

Research dating back to the 1960s shows that babies with autism produce cries that are distinct from and higher-pitched than those of other babies. 

An analysis from the new study shows that short pauses between cries cause the most distress in some adult listeners. A high pitch is the second-most distressing factor, although other studies have found it to be the most important factor.

The researchers recorded the cries of 13-month-old Caucasian babies — ten controls and ten babies later diagnosed with autism at 36 months of age. The researchers played the recordings to two groups: 80 adults from Italy and 80 from Japan. Half of these adults are parents of typically developing children and half do not have children.

The adults used a seven-point scale to rate the babies’ cries, both on how much distress they thought the babies were feeling and on how distressing the cries were to hear.

The babies with autism not only sounded more agitated when they cried, according to the adults, but also made them feel more anxious than the cries of the typical babies did.

Researchers also measured the number of cries within a 15-second clip, independent of the pause length. The Japanese adults felt less anxious when babies made seven or more cries during this clip than when the babies made fewer cries. The Italian group did not show this preference.

The onomatopoeic word for a baby crying in Japan is “ann-ann,” in comparison with the Italian sound “nguee.” It’s possible that the repetition in the Japanese interpretation gives the Japanese listeners familiarity with hearing more cries, the researchers suggest.

Overall, the results have greater implications than the momentary distress listeners may feel. Parents will go to great lengths to soothe a crying baby, but they may be less likely to interact with the child if they are upset by the wails, the researchers suggest.

This lack of interaction may contribute to the later social deficits — such as difficulty taking turns during conversations — in children with autism, the researchers say.

The new study has some limitations. It is small, and did not test parents of children with autism. These parents may be used to hearing their babies’ cries, and may not feel as much distress as other adults do.