Boffins have discovered that babies can recognise SAD voices from neutral ones from as young as three-months-old.
Conducting a study on three-to-seven month old tots, researchers at two London universities found that the part of a baby's brain responsible for processing emotion lit up more when the infants heard unhappy voices.
They also discovered the babies were more attuned to human noises like coughing or yawning, than familiar non-human sounds like those made by toys.
Evelyne Mercure from University College London said: "Our results suggest that the infant temporal cortex is more mature than previously reported.
"It is a rare demonstration that specialised areas exist in the brain very early in development."
Anna Blasi of King's College London added: "It is probably because the human voice is such an important social cue that the brain shows an early specialisation for its processing. This may represent the very first step in social interactions and language learning."
Her colleague Declan Murphy said the findings could feasibly be used "to accurately identify babies who will go on to suffer from disorders such as autism".
Does your baby react differently to different tones in your voice? Have you noticed changes in your baby's behaviour if you raise your voice or are unhappy?