Researchers interpret pig emotions from the sounds they make

STEVE INSKEEP, HOST:

Some humans spend a lot of time teaching words to animals.

RACHEL MARTIN, HOST:

In recent years, Alex, the African gray parrot, developed a vocabulary of 150 words.

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(SOUNDBITE OF ARCHIVED RECORDING)

IRENE PEPPERBERG: What's here?

ALEX: Truck.

PEPPERBERG: That's a good boy. Truck - good boy.

ALEX: Want nut.

PEPPERBERG: Well, you can have a nut. Go choose your own.

MARTIN: Amazing. Also, in recent years, Koko the gorilla learned sign language.

INSKEEP: Other scientists try to figure out the languages that animals already have. Suppose we think of this as a form of expression.

(SOUNDBITE OF PIG GRUNTING)

MARTIN: Pigs are the subject of the study by Elodie Briefer. She's at Copenhagen University and a lead researcher for the SoundWel project.

ELODIE BRIEFER: What we did in this paper is to try to see if the calls produced in different situations vary.

MARTIN: They've been listening to the sounds a few pigs make from birth.

BRIEFER: So based on the behavior, we then classify them as emotionally positive, so which would be something that usually increase your chance of survival and that they would approach - or negative, which is where they would - situations they would avoid and which would decrease your chance of survival.

INSKEEP: Think about that. They identified four or five basic sounds that may give clues to how a pig feels.

BRIEFER: The main ones are their grunts.

(SOUNDBITE OF PIG GRUNTING)

BRIEFER: They have kind of low and closed and open-mouth grunts. And they have barks.

(SOUNDBITE OF PIG BARKING)

BRIEFER: And they have screams...

(SOUNDBITE OF PIG SCREAMING)

BRIEFER: ...And squeals.

(SOUNDBITE OF PIG SQUEALING)

INSKEEP: (Laughter) Amazing.

MARTIN: Wow. I don't really know what to say. Briefer says listening to pigs can help improve their welfare, which in turn helps a pig farmer.

INSKEEP: And at this point, we do have to just say it - pigs are mainly raised as a food source.

BRIEFER: We know that animals that have better welfare, they give better quality meat. So they have - they're usually less stressed. And stress triggers the release of cortisol, which gives a bad taste to the meat. So we know that better welfare leads to meat of better quality.

INSKEEP: OK. Briefer and her team believe that their method is about 92% accurate in discerning a pig's emotional state. And they plan to build some kind of tool, maybe an app, to help farmers listen to the pigs. Transcript provided by NPR, Copyright NPR.