For infants, distinguishing between friends and strangers is a laughing matter

Infants as young as five months can differentiate laughter between friends and that between strangers, finds a new study by researchers at New York University and UCLA. The results suggest that the ability to detect the nature of social relationships is instilled early in human infancy, possibly the result of a detection system that uses vocal cues.

source https://www.lifetechnology.com/blogs/life-technology-news-blog/for-infants-distinguishing-between-friends-and-strangers-is-a-laughing-matter