The researchers told the Himba several stories, each closely associated with a single emotion like sadness, fear or relief. Then they were played two records of a European’s voice, and the Himba were asked to choose which fit the story better. A group of Europeans were later tested the same way with recordings of a Himba voice.

Himba people were easily able to recognize sounds conveying negative emotions and the neutral sound of surprise. However they had trouble telling positive sounds, with the exception of laughter, the researchers report in the journal Proceedings of the National Academy of Sciences.

This was not so for the second experiment, since the European group was able to recognize the entire spectrum of signals voiced by the Himba. Sauter said the results indicate that positive non-verbal communication is more directed towards socializing among group members and requires practice inside a culture.