Horses can assign a human voice to the associated face. Picture: M. Grossmann /
Reading Many domesticated animals recognize their owners by voice or face. For the first time, British scientists were able to prove that horses can link the two sensory perceptions, just like humans. We humans not only recognize other people by the voice, but also connect the voice with an image stored in the brain. For a long time, scientists assumed that humans are the only creatures that recognize conspecifics in this way. Apparently, horses are capable of doing so. Leanne Proops and Karen McComb from the University of Sussex at Brighton had already demonstrated that horses can distinguish known human faces from unknown ones. In another study, the two researchers have now examined whether the animals can connect the voice and the face.

For this purpose, they set up a loudspeaker a few meters in front of the horses, to the right and left of which stood each the owner of the animal and an unknown person. For 15 seconds, the 32 quadrupeds then heard the two human voices. To test whether the horses were able to correctly assign the voice, the researchers recorded how fast, how often, and how long the animals looked at the person whose voice they were hearing.

Result: The horses paid much more attention to the person who heard them speak. There was little difference between owner and unknown person. Only when the owner was standing on the right side, the horses each looked at him for a longer time than to the stranger.

In a second experiment, Proops and McComb each presented two known humans to the animals. This time, the eyes of the animals rested much longer and more often on the person whose voice they were listening to - and the longest when that person was standing to the right of the speaker. In addition, some horses tried to run towards the person. The result is a clear sign that the horses can combine visual and acoustic sensory impressions, the scientists interpret. The fact that it was easier for the animals to assign the voice when the person was standing to their right suggests that the connection between the two senses is processed in the left hemisphere. Because the right half of the body is known to be controlled by the left hemisphere of the brain - as well as social interaction. The close proximity of these functions could additionally facilitate the recognition of humans by the animals. display

This could also be one of the reasons why mares generally looked at the person whose voice they were listening to longer, because they take care of the offspring and shape the social structure of the herd much more than stallions in the wild.
It was also noticeable that younger animals directed their gaze more quickly to the person whose voice they heard.

As mammals evolved together, Proops and McComb suggest that their observation is not just for horses, but that most mammals can recognize individuals of other species by linking two senses.

Leanne Proops and Karen McComb (University of Sussex, Brighton): Proceedings of the Royal Society / Biology Letters, doi: 10.1098 / rspb.2012.0626 © Marion Martin


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