Infants as young as five months can differentiate laughter between friends and that between strangers, finds a new study, suggesting 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.

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Infants as young as five months can differentiate laughter between friends and that between strangers, finds a new study, suggesting 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.