Why do some people not have an inner voice?

Editor's note: This segment was rebroadcasted on Jan. 7, 2024. Find that audio here. 

Do you have any inner voice or monologue? Chances are you do, but new research shows that we might all have very different ones and some of us might not have one at all.

The same research also shows that whether you have an inner voice and how strong it is might impact how memory and learning works for different people.

Lead researcher on the project and University of Wisconsin-Madison psychology professor Gary Lupyan tells us about the findings.

How do you test an inner voice? How do you know whether someone has an inner voice or not?

"We have to trust what people say. It's like other subjective experiences like pain. We can develop good instruments to make sure that when we ask these questions, different people agree on what it is that we’re asking them, but in the end, we have to rely on people's subjective report. If someone says that they're in pain, we trust they're in pain. And so same thing with the inner voice: We have various questions probing the kinds of format people's thoughts take. We find that as with visual imagery, some people have very vivid imagery. Other people have a hard time imagining anything. Inner voice has that same type of variability."

If someone isn't sure, can you explain what an inner voice is?

"If you assign it kind of a one to five scale, most people are at about a four. So, quite a bit. There are other people who say, 'It's all the time. I can't imagine not having it. Sometimes it's loud. Sometimes it's quiet, but of course it's always there.' But then there are others — and I am among them — who were shocked to find out that most people have this experience all the time. For myself, I certainly have it, but I wouldn't say that it's constant or that I need to work to shut it off. So, I learned something about myself in the course of doing this work."

What questions do you ask in conducting your experiments?

"Some questions relate to specific activities. For example, when people read silently, do you hear the words in kind of your mind's ear as you read them? Other questions relate to more casual activities like you're walking alone, thinking about some kind of problem in your head. Do you think of this in the form of a conversation? People vary in how they respond to this, and people are quite consistent. So, if you ask them the same or similar questions one time and then again six months later, they give very similar responses. It's not really about how they are feeling at the moment of answering."

We have a tendency to try to immediately decide whether something is better
or worse - Someone with an inner voice is automatically better or smarter. That's
not what research shows, right?

"Right. It’s good for some things, less good for other things. It's not a value
judgment."

A really fascinating part of your research is figuring out how an inner voice can help you and how not having one might help you. In which ways does having an inner voice possibly help you?

"One thing language is good at is categorizing — and in some cases, that's what
you want. For example, you are trying to remember a list of things and you don't
care about the details, you just care about the categories of those things, like a shopping list. Language is great at keeping that in memory. And in one of our experiments, we asked people to do exactly that, just remember a list of words and people who report having more inner speech were better at remembering those words.

"In other cases, language can get in the way. In some previous work, we found that if you have to remember a bunch of pictures, so for example, you see lots of pictures of different chairs and tables, and you have to label some of those pictures, you then have a harder time remembering which particular chair it is that you've seen. In that case, language, by nudging people to be more categorical, actually makes it harder to remember the details."

How does it help you going forward to understand the human mind?

"Learning that there is variation along this dimension is the first step to understanding what some of the cognitive consequences might be. Once we have the tools to measure different amounts of inner speech, we can then, as we did in this paper, start correlating them with performance on different kinds of tasks. In some cases, we find that people who report having less inner speech, but talked out loud to themselves, began to look like people who don't talk out loud to themselves, but who have more inner speech. It's a kind of a way of compensating for not experiencing this inner speech in this more silent way."

This kind of research might help with learning and especially with neurodivergence in learning.

"Indeed, and also just to make people on both sides realize that not everyone is
like them, and this is just part of natural variation in humans."

Thomas Danielian produced and edited this interview for broadcast with Todd Mundt. Danielian also adapted it for the web.