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the latest on dolphin language

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I wrote, or semi-podcasted, on the brain of the dolphin a while back, and much of my focus was on language, often described as the sine qua non of cerebral complexity and intelligence. In that piece, posted about eight months ago, I reported that there there was little clear evidence of any complex language in dolphins, but there had been some interesting research. Allow me to quote myself:

Dolphins do sometimes mimic the whistles of other dolphins too, particularly those of their closest relatives, but signature whistles as a form of recognition and differentiation, are a long way from anything like language. After all, many species can recognise their own mates or kin from the distinctive sounds they make, or from their specific odour, or from visual cues. However, a clever experiment carried out more recently, which synthesised these whistles through a computer, so that the whistle pattern was divorced from its distinctive sound, found that the dolphins responded to these patterns even when produced via a different sound. It seemed that they were recognising names. It’s undoubtedly intriguing, but clearly a lot more research is required.

So it was with some interest that I heard, on a recent SGU podcast, an account of what seemed an elaboration of the experiments conducted above, further confirming that dolphins recognised names. Or were they just reporting the same experiments? Having re-listened to the SGU segment, I find that they didn’t give any details of who did the study they were talking about, the only mention was to a news article. So I’ll just report on anything I can find, because it’s such a cool subject.

There’s a nice TED talk, from February 2013, on dolphin language and intelligence here, which is about researches over many years in the Bahamas with Atlantic spotted dolphins. As always, I suggest you listen to the talk and do the ‘research on the research’ yourself, as I’m not a scientist and I’m only doing this to educate myself, but hopefully I can also engage your interest.

Dolphins have a brain- to-body ratio (a rough but not entirely reliable guide to intelligence) second only to humans, they pass the mirror self-awareness test (another standard for intelligence that’s been questioned recently), they can be made to understand very basic artificial human language tests, and they’re at least rudimentary tool users. But the real interest lies in their own, obviously complex, vocal communication systems.

I probably misrepresented the information on signature whistles before: they’re only what we humans have been able to isolate from all the ‘noise’ dolphins make, because they’re recognisable and interpretable to us. Denise Herzing, in her TED talk, refers to ‘cracking the code’ of dolphins’ communication systems. She and her team have been working with the dolphins over the summer months for 28 years. They work with underwater cameras and hydrophones to correlate the sounds and behaviours of their subjects. This particular species is born without spots, but is fully black-and-white spotted by age 15. They go through distinct developmental phases making them easy to track over the years (dolphins live into their early 50s). The distinctive spotted patterns make them easy to track individually. Females are sexually mature by about age 9, males at around 15. Dolphins are very sexually active with multiple partners, so paternity is not always easy to determine, so this is worked out by collecting fecal matter and analysing its DNA. So, over 28 years, three generations have been tracked.

What really interests me about the dolphin communication question is their relation to sound and their use of sound compared to ours. Herzing describes them as ‘natural acousticians’ who make and hear sounds ten times as high as humans do. They also have highly developed vision, so they communicate via bodily signals, and they have taste and touch. Sound is of course a wave or vibration which can be felt in water, the acoustic impedance of tissue in water being much the same as on land. Tickling, of a kind, does occur.

Signature whistles are the most studied dolphin sounds, as the most easily measured. They’re used as names, in connecting mothers and calves for example.  But there are many other vocalisations, such as echo-location clicks (sonar), used in hunting and feeding, and also socially, in tightly-packed sound formations – buzzes, which can be felt in the water. They’re used regularly by males courting females. Burst-pulse sounds are used in times of conflict, and they are the least studied, most hard to measure of dolphin sounds.

Interestingly, Herzing notes that there’s a lot of interaction and co-operation in the Bahamas between spotted and bottle-nose dolphins, including baby-sitting each others’ calves, and combining to chase away sharks, but little mention is made, in this talk at least, of any vocal communication between the two species. When she goes on to talk about synchrony, I think she’s only talking about within-species rather than between species. Synchrony is a mechanism whereby the dolphins co-ordinate sounds and body postures to create a larger, stronger social unit.

As I’ve mentioned, dolphins make plenty of sounds beyond the range of human hearing. Underwater equipment is used to collect these ultrasonic sounds, but we’ve barely begun to analyse them. Whistle complexity has been analysed through information theory, and is highly rated even in relation to human languages, but virtually nothing is known about burst-pulse sounds, which, on a spectrogram, bear a remarkable similarity to human phonemes. Still, we have no Rosetta Stone for interpreting them, so researchers have developed a two-way interface, with underwater keyboards, with both visual and audible components. In developing communication, they’ve exploited the dolphins’ natural curiosity and playfulness. Dolphins, for example, are fond of mimicking the postures and vocalisations of humans, and invite the researchers into their play. Researchers have developed artificial whistles to refer to dolphins’ favourite toys, including sargassum, a kind of seaweed, and ropes and scarves, so that they can request them via the keyboard interface. These whistles were outside the dolphins’ normal repertoire, but easily mimicked by them. The experiment has been successful, but of course it isn’t known how much they understand, or what’s going through their minds with all this. What is clear, however, is that the dolphins are extremely interested in and focused on this type of activity, which sometimes goes on for hours.

This research group has lately been using an underwater wearable computer, known as CHAT (cetacean hearing and telemetry), which focuses on acoustic communication. Sounds are created via a forearm keyboard and an underwater speaker for real-time Q and A. This is still at the prototype stage, but it uses the same game-playing activity, seeking to empower dolphins to request toys, as well as human game-players, through signature whistles. It’s hoped that the technology will be utilisable for other species too in the future.

All of this is kind of by way of background to the research reported on recently. This was really about dolphin memory rather than language – or perhaps more accurately, memory triggered by language. Dolphins recognise the sounds of each others’ signature whistles, but would they recognise the whistle of a dolphin they’d not been in contact with for years. And for how many years? Researcher Jason Bruck tested this by collecting whistles of dolphins in captive facilities throughout the US. Dolphins are moved around a lot, and lose contact with friends and family. Sounds a bit like the foster-care system. Bruck found that when dolphins heard the signature whistles of old companions played to them through an underwater speaker, they responded with great attention and interest. One dolphin was able to recognise the whistle of a friend from whom he was separated at age two, after twenty years’ separation. As biologist Janet Mann put it, this is a big breakthrough but not so surprising, as dolphins are highly social animals whose lives, like ours, are criss-crossed by profound connections with others, with effects positive, negative and equivocal.  It’s important, too, for what it suggests – the capacity to remember so much more, in the  same coded way. in other words, a complex language, perhaps on a level with ours. Will we ever get to crack this code? Why not. Hopefully we won’t stop trying.


Written by stewart henderson

August 24, 2013 at 3:55 pm

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