How (if at all) would being able to speak and listen simultaneously alter the structure and development of language?

Question

Spoken communication requires human beings to be able to do two separate things:

The first is to understand what is being said to them (including isolating the sound of the other person's voice from all the other noises in the environment, resolving the sound to a set of words and pauses, and processing the words and pauses to extract meaning from them). The second is to communicate their own ideas to the other person (by formulating them into a sequence of words and pauses, and speaking these aloud in such a way that the other person can extract meaning from them).

Now, we are for the most part only able to do one of these things at a time (and often with a small pause in-between while we process what has been said to us and decide what we want to say in return). I'm wondering, if this wasn't the case, and both tasks could be done simultaneously without interfering with each other, would language have still developed in the way that it has? Would grammar still operate in the way that it does?

If not, what differences might we expect to see?

Answer 1

This is interesting to me because what you want to explore both happens and doesn't happen. As you have noticed, it's mighty difficult to hold a conversation when both parties are trying to talk over each other. However, we have plenty of examples in singing where we indeed are vocalizing over the top of someone while listening to them. There's no other way a barbershop quartet could maintain the locked down harmonies they need to sound as they do.

This points to something deeper in our psyche. Something about the way we think about communication causes us to choose not to speak in the way you describe. That makes it fun because this also suggests that this inability to speak and listen may be cultural, not biological. Cultural things are always fun to dig into, but first, some biology.

One key limitation with any human cognition is how slowly the brain processes novel stimuli. If it's prepared for a stimulus, the brain can respond within 106ms (that time was achieved by an Olympic athlete in a carefully structured test). However, if the brain is less prepared, it's slower. There's a pair of brainwaves scientists love to use in psychological experiments called P300a and P300b. Each of these occurs at roughly 300ms after a novel stimulus (hence P300). P300a is in response to an unexpected stimulus (such as a loud noise), while P300b is in response to an unexpected stimulus that is related to the current task at hand (such as a the stoplight turning yellow while you are driving). Scientists love these because they are very easy to distinguish, and are well correlated to cognition itself.

This shows a lower bound for communication "at the same time." If your stimulus needs to reach my upper cognitive functions, they don't even start processing until 300ms after you've made your sound and you'll probably need a few hundred milliseconds to process it. Most conversations are held at 110-150wpm (400-545ms per word), and while I don't have any scientific evidence to back it up... this sure looks like those two timelines are strongly related.

Another limit is that upper cognitive functions tend to be more serial and less parallel. Its a lot harder to be counting backwards from 100 by 7's while listening to someone speak than it is to do one or the other. This naturally serializes the conversation.

However, I did mention that we do listen while we speak, and gave singing as an example. Staying in tune is a lower cognitive function, in that singers aren't actively thinking about it most of the time. We singers tend to learn to automatically stay in tune. This means we don't need to have any of those slow P300 waves firing to stay in tune. We can use the lower and faster functions of the brain to communicate.

So what if we used those lower parts more when we communicated? I think there's a lot of room for interpretation there, because that part of the brain is not very well understood. We don't quite know what it would look like if it was communicating more directly than it does. However, we have a few examples of what it might be. There's a particular example that comes to mind, the Kecak style performances from Bali, Indonesia. It is believed to have its origins in an exorcism ritual. I will be the first to admit that, as a white US citizen, I don't fully understand what is going on here, but when I think about what it would look like for us to drop the walls we put up around our brain and let the lower functions communicate with one anothers', I get the impression it might look something like this. I don't know about you, but I get an eerie feeling when watching their dances, like they're reaching out to me in a way I don't fully comprehend. Maybe there's more to this than meets the eye.

Answer 2

Cort Ammon's answer is good, but I want to add comments and I have more commentary than the comment section will take.

Human language has the flexibility for simultaneous conversation

First, as he pointed out, the human language is very flexible. There are so many things that you can do with your voice above and beyond what we use to speak. For example, English speakers do not use tone like the Chinese do (while the Chinese don't use grammatical tense). There are at least 150 unique phonemes (sounds, roughly) that are used in speech by various human groups. !Xuun uses something like 141 of them; English uses up to 47 (21 vowels, 26 consonants, although not all dialects pronounce all sounds).

The point is, by using different sounds or tones two people could talk at the same time and be perfectly intelligible by not sharing similar sounds that would interfere with each other. A language could theoretically develop where there was a '1st speaker' and '2nd speaker' using different sounds and tones, so that two people could use one of the two speaker dialects to talk at the same time. '1st speaker' could use all short vowels and '2nd speaker' could use all long vowels for instance. Or it could be so easy in a tonal language like Chinese that the second speaker raises or lowers his voice a major fifth away from the first speaker, so their speech doesn't overlap on tones.

Regardless of the above, the human ear and brain is sufficient to track multiple conversations at once. It is hard to 'comprehend' two conversations at once, as we'll discuss next, but most people have picked out their own name in a converstion across the room. Further, anyone with kids can tell you that you can hear what your kids are saying even if you are talking to someone else.

The human brain is not set up for simultaneous conversation

Again, following Cort Ammon, our brains are not set up to process language at the same time as we speak it. Just try it, it is very hard to order your thoughts while you are listening, or even if you are reading.

It is interesting that expressive and receptive aphasia (inability to speak language, and comprehend language, respectively) are tied to different areas of the brain. So it is not that easy to assert that there is some shared hardward that is used for both expressing and recieving language that prevents us from doing both at the same time. But the proof is simply in testing it yourself. Try to read a sentance from this answer while reciting something you have memorized, then try to repeat what you just read. You just can't do it (at least I can't).

Conclusion

The human language is flexible enough to support simultaneously speaking and listening, but the brain just isn't up to it.

Answer 3

There's a real-life example of listening and speaking at the same time in the case of real-time translators. This is at a different time-scale than milliseconds; a translator typically needs to hear a few seconds of speech before they begin translating, and depending on the languages involved or if ambiguities arise may want to build up a longer backlog of speech. Note that although they are delaying their responses to initial stimulus by several seconds, they are speaking at the same time they are listening to the sentences they are going to translate a few seconds later.

If nothing else, it's proof that humans are capable of tasks like this; the rarity of it demonstrates more that it is not generally useful than that it is impossible. The reason it's not useful is elaborated on in other answers: most communication is serial, and we must hear the end of a question in order to answer it (unless we guess the end of the question correctly; but this is still a serial communication, because we at least need to hear the important parts before we answer).

Being able to speak and listen at the same time would only be useful for non-serial communication, and I'm not sure what the advantage of such communication would be. A group of people relaying status updates simultaneously might qualify, or holding two separate conversations at the same time. The latter happens often when there is a delay in responding, for instance in letters, emails, or chat rooms; it is not inconceivable that it could happen for spoken conversations, as you often know completely what you want to say before you finish saying it, which frees up your mind for listening to something else and formulating a reply to that, too. Again, it seems of limited benefit unless you have an interview with a lot of questions and not enough time to ask them all.

Answer 4

There is a reasonable case that this is exactly what does happen. Quite a lot of human verbal communication is a bit redundant purely in terms of the information content and in many cases the real conversation is more about more subtle cues of tone, context, inflection and body language and quite a lot of conversation is more or less automatic in terms of the mechanics of grammar and vocabulary.

Most of the time in casual conversation we are able to formulate concepts and inflect quite subtle nuances without really thinking much about it. Just thing about the difference in he way you talk to a good friend, a casual acquaintance, your boss, someone you are attracted to etc etc.

I saw a good example only today in the form of a theatrical audition workshop where people were asked to tell a story and were occasionally stopped and given new and unexpected context. For example mid sentence they might be stopped and asked to imaging that they were telling the same story but they were in a job interview or giving a speech at a wedding or trying to scare someone around a campfire. You could immediately see the proficient actors, not because they were able to make up new lines on the spot but because they were able to put themselves into that context and their whole delivery changed in a way that you might not notice in a written script.

They key point here is that a lot of the mechanics of language is entirely separate from conscious, rational thought and thinking about what you are going to say next while the other person is still speaking is an entirely normal part of conversation.

Indeed there is an argument that in a modern context where we have to deal with very complex concepts and technical information that we were never evolved for there is actually too much parallel speaking and listening and we would be better off with a language convention which didn't rely so much on a more or less instantaneous response.

Consider also that in most casual social contexts pauses in conversations are often considered as awkward (and acceptable pauses have been measures as being very small indeed) , this in itself implies that we are well able to start formulating a response long before the other person has finished speaking.

In some ways literature sums this up better than science and it would be worth looking at writers like Pratchett, Pinter, Austin and Wodehouse to get a sens of just how flexible and nuanced dialog can be.