Goat bleats not only sound remarkably human, they are also key to revealing feelings to their companions, according to new research that deepens our understanding of the animals' emotional complexity.

As part of a study published in Frontiers of Zoology on Tuesday, scientists played the ruminants a series of calls from a hidden speaker that were either happy or sad.

To obtain the positive calls, they approached goats with buckets of food. For the negative calls, they recorded goats that were frustrated at not being fed while others were.

When they switched from playing one type of bleat to the other, the goats were more likely to look toward the source of the sound and walk about, suggesting they were able to distinguish its emotional content.

What's more, readings of heart-rate variation taken from the goats corresponded to a positive, more relaxed state when they were played the happy calls, and a distressed state when the sad calls were played.

"It is quite crucial for us because often we talk about animal welfare and how we can improve the animal life in a farm setting," Luigi Baciadonna, lead author of the study from Queen Mary University of London, told AFP.

It means that if some goats in a group are distressed, or content, that can cause a ripple effect among others.

Baciadonna would next like to investigate whether goats are able to respond to different emotions displayed by humans.