Speaking of Psychology - Why numeracy counts in everyday life, with Ellen Peters, PhD

Episode Date: August 20, 2025

From deciding whether to buy a house to weighing the risks and benefits of taking a new medication, many important life decisions hinge on understanding numbers, statistics and probability. Ellen Peters, PhD, author of “Innumeracy in the Wild: Misunderstanding and Misusing Numbers” discusses what it means to be numerate; how numeracy affects people’s health, financial security and other life outcomes; and how can you improve your confidence and ability with numbers. Please take our listener survey at at.apa.org/SoPSurvey. Learn more about your ad choices. Visit megaphone.fm/adchoices

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The Hilton sale is on now. Book on Hilton.com or the Hilton app and save up to 20% to get the stay you expected. When you want savings, not surprises. It matters where you stay. Hilton, for the stay. It's hard to make good decisions if you don't understand numbers. Whether it's choosing a health insurance plan, deciding whether to buy a house,

or weighing the risks and benefits of taking a new medication, many important life decisions hinge on understanding numbers, statistics, or probability. Today we're going to talk to a psychologist who studies how people process numbers, perceive risk, and make decisions about what it means to be numerate and why numeracy matters. We'll discuss how common innumeracy is and how it affects people's health, financial security, and other life outcomes. We'll also talk about how you can improve your confidence and ability with numbers, even if you had many years past your last high school math class. Welcome to Speaking of Psychology, the flagship podcast of the American Psychological Association that examines the links between psychological science and everyday life. I'm Kim Mills.

My guest today is Dr. Ellen Peters, Director of the Center for Science Communication Research at the University of Oregon, and a professor in the Department of Psychology and the School of Journalism and Communication. She studies how people understand numerical information, perceive risk, and make decisions. She also studies how doctors, public officials, and other communicators can present numerical information in a way that helps people understand it better. Dr. Peters is an APA fellow and a fellow of the American. and Association for the Advancement of Science. She's the author of hundreds of peer-reviewed academic papers and of the 2020 book, Inumeracy in the Wild, misunderstanding and misusing numbers. Dr. Peters, thank you for joining me today. Kim, it's a pleasure to be here. Thanks for inviting me.

Let's start, as we often do on this podcast with a definition. What does it mean to be numerate or innumerate? How do you measure people's numeracy? So we call it objective numeracy. because it has to do with how well people answer problems in a math test. So objective numeracy is the ability to understand and use basic probability in mathematical concepts. And so it's kind of like numeracy is to numbers, like literacy is to words. Now, what are some of the most common ways that math and numbers come up in everyday life? And how well do people understand these things? Oh, gosh. So numbers come up in all kinds of ways. So I often work with people in health. I work with physicians or folks in public health, and it comes up when it comes to prescription drugs you take, for example. And even in a

couple of different ways. So just with prescription drugs alone, numbers come up when it comes to how likely you are to benefit from the drug or how likely you are to suffer from side effects. But numbers also come up when it comes to you figuring out when do I need to order my next round of medication. And so there's just kind of numbers all over the place. All kinds of other hazards too. We've been looking a bit lately at wildfire risks, for example, and other kinds of natural hazards. And the numeric information involved helps people better understand how likely might I end up in a situation like this. And how do they figure that out? I mean, what kind of data do you get to make that determination when we're talking about, say, wildfires?

So with wildfires, it's often more, it's often more visual. So it's a map. But sometimes that map will also come with a likelihood of how likely is my area, for example, to be at wildfire risk. So I know, for example, that there's an area of town that's quite near my daughter's house that's at a higher risk of wildfire than some of the rest of our city. So we can find out numerically, well, how likely is the risk at her house versus some other part of town? How common is enumeracy among U.S. adults and are there differences based on sex or other demographics? Yeah. So enumeracy is fairly common. It turns out that about a third of working age adults in the United States perform at what's considered the lowest proficiency level in numeracy. And so in some ways you can actually consider this about a third of working age adults functionally enumerate.

They can't do things, for example, or likely would not be able to do things, for example, like calculating the difference in percentages of patients who survive one treatment compared to another. They don't have the math skills that are necessary to understand that kind of information. And it's not that they can't do anything with numbers. These are often very smart people. But when it comes to numbers, they just don't have a lot of abilities. So they can do things, they can do sort of simple processes with numbers like counting and sorting the numbers or doing very simple arithmetic, like simple addition, for example. And it's not just a question of whether you can do it in your head, right?

I mean, even if you need a piece of paper, it's just that you understand the relationships and you can make calculation. Yeah, exactly. So when we give a numeracy test to people, for example, a lot of people do the math problems in their head, but they don't have to. They could actually pull out a piece of paper. and try to figure it out. And it is the case, you asked this a minute ago, and I kind of missed the question, but it is the case that some systematic differences in numeracy exist across the population. So you see things like women tend to be less numerate than men, controlling for other characteristics of them. But there are other things, too. We actually tend to become less numerate as we age. So as our minds slow down, our abilities with numeric processes that we haven't memorized, because if you've memorized, them, you've stored them in long-term memory, but if it's a new information that you have to

actually process, that's the kind of numeracy that tends to decline as we age. Less numerate people are also more likely to be lower in income, to have minority status, and of course to have lower education. That's actually one of the reasons I really value studying numeracy, because understanding numeracy and understanding how people process numbers also ends up being associated with understanding how we understand inequities that exist across our society. So how does numeracy compare with literacy? Are they on the same level? Are we as illiterate as we are enumerate in this country? Yeah, it's a good question. So it's a little hard to compare them. But the comparisons that I've seen are that we are more enumerate than we are illiterate.

And you can almost even see that just in how people talk about it. People are, people are quite embarrassed to be illiterate. They don't want to admit it, but everybody's willing to admit that they're enumerate. Like, I'm just bad at math and anyone could, and it's sort of an indication that enumeracy perhaps is more common, but it's also an indication that people might not understand how important it is and how important it is to be able to process numbers well in our information-rich society. How do we compare with other countries, like other European countries or Asian or African countries, are they as enumerate as we are in this country? I mean, one-third is a pretty high number.

Yeah, it is a pretty high number. So the last data that I know about are back in 2020. And there's more recent data available, but I don't know what the cross-country comparisons are. But back in 2020, we tended to be on the less numerate side. So if you look just at the proportion of people, for example, who are in that very low, those very low numeracy levels. At that point in time, the U.S. had about 29% of people in that very low numeracy levels. Countries like Italy were similar.

They had 32% in that least numerate. Spain had 31%. But then some other countries, and remember, we're comparing to the U.S. at 29%. Japan had only 8% of people in that least numerate. Finland, only 13%. Same with the Czech Republic, as well as the Netherlands. And so there actually are quite a few countries who are more numerate than the United States is.

And is this a failure of our educational system, or is there something else going on? Personally, I think it is about our education system. When I talked about the proportion of least numerous people in countries, we're talking about the people who are at the very lowest levels of math ability. You can also look at the other side. And we have a lot of extremely numerate people in the United States.

But we also have these big disparities of numeracy in the U.S. We also have big disparities in our educational system. And so to me, what it looks like is that our educational systems are failing portions of our population who end up being less numerate. What are some of the most common errors that people make when they're trying to understand numerical information? Not spending enough time on it. Just simply not looking at the numbers for very long, not trying to transform a number from one way of looking at it to another. And let me give you an example of that. So one of the things that we study, in my field of judgment and decision making is something called framing effects. So a framing effect is like 90% of people will survive if they get this treatment or in the alternative frame, 10% of people

will perish if they get this treatment. And they are logically equivalent. 90% surviving versus 10% dying is the exact same number. But what happens is to be able to understand that, you actually have to do that math. You actually have to take the 90% survival and say, oh, No, that means the 10% of the people die. But a lot of people, even if they can do that math, they don't do it. They just don't tend to look at the numbers and think about them. They don't, people who are less numerate in particular, just don't have the same habits with numbers that people who are highly numerate do.

Someone who is highly numerate will look at the 90% survival. And more or less, in fact, I would bet that you more or less automatically transformed it. The minute I said 90% survival, you thought 10% die. Not everybody does. Those kind of math operations aren't as easily accessible to them, and they're a little bit harder, and so they're just simply more likely to walk away from them. And so I think those are some of the biggest errors that people make. They don't put in the time, and it is a little more effort for them. And so as a result, they end up using other information that's not as helpful. So if they're given, if they're told about a treatment where they have a 10% chance of dying, they're going to feel much worse. that if they're told that they would have a 90% chance of survival, even though it's the same treatment. Right. We tend to latch on to the negative. We tend to latch onto the negative, but we also tend to latch onto information in the form it's given and without changing it. And by changing information, you get more meaningful information.

You get to understand the more complex set of information that's in front of you. It's not just that you're most likely to survive, but you might actually die. And by doing that transformation, you understand that in a deeper way. What about the concept of probability? How well do people understand that? I mean, I've heard people say, well, you know, everything's 50-50, either will or it won't. And that's not how probability works. Yeah, that is so interesting.

And it's actually a really interesting problem in medical decision-making. Because to an individual person, that is true. It's going to happen to me or it's not going to happen to me. But if you take a step back and you look at a population of people that's similar to that person, then you can get to predicted likelihood. So the predicted likelihood that a medication will help you, for example. And people are not very good with probabilities. It's one of the types of math that we tend to have the most problems with.

And in fact, most objective numeracy tests deal with probabilistic kinds of information because they tend to be harder and probabilities are, are important in a lot of everyday life events. You've done research that's looked at how numeracy affects people's health outcomes, their financial outcomes, and other aspects of life. What are the consequences in a day-to-day area of innumeracy? Yeah, so we actually kind of already started one of those. So one of the ways that numeracy seems to have impact on people's lives

has to do with their ability to make good decisions. even though everybody might get the same information, they might be given the exact same choice options. People have those different habits that we started talking about. For someone who's less numerate, numbers are harder, as we were talking about. And what research ends up showing is that their decisions end up being more vulnerable to their own emotional reactions, to how information is framed, to compelling stories that they're given or images that they're shown. And what this means when they're judging and deciding is that they will be more vulnerable to the framing effects we talked about. Or they'll be more vulnerable to using other cognitive shortcuts, heuristic shortcuts that people take.

They also may end up being, and in fact research shows that they'll end up being more susceptible just to how they're feeling in the moment, like their mood states. And then ultimately, studies show that they neglect numbers more, even if they think they're using them, they'll end up. up neglecting numbers more. The people who are highly numerate have a whole different set of habits. So they're more likely to seek out numbers. They're more likely to think longer about them, to transform numbers like we were talking about and do different calculations. They're even more likely to compare numbers and do just other kinds of operations with numbers that help them see a number that has meaning rather than see a number that's dry and feels irrelevant to them. So that's kind of the first way that numeracy has an impact.

And that has an impact on sort of everyday life. It's not just that math has to do with STEM education. Understanding and being able to use math has to do with the quality of your everyday life. And that then, as you started to mention, that then shows up in some of the consequences that people end up with. And my lab is not the only one that studies this. One study that we've done in our lab shows that people who are highly numerate make more money. And so for each individual problem, extra problem that a highly numerate person solved, they made $4,000 more in annual income after controlling for a whole slew of other demographics. People who are more numerate also end up being much wealthier. People on top of that, there's only one study that I know of on this, but people who are more numerate seem to be more likely to be employed rather than unemployed compared to people who are less numerate.

And then you get to health gaps, and there have been a whole bunch of different health gaps that have been studied. I'll mention just a couple. People who are less numerate are 40% more likely to have at least one chronic disease, and they also take 20% more prescription drugs, according to this study. And all of this is while having less ability to follow complex health regimens that involve numbers, because they're having difficulty with numbers. Now, this is a correlation, right? We're not talking causation in this instance.

For the most part, we're talking correlation. So most of the studies have been done with correlational data. A lot of them control for other non-numeric aspects of intelligence and for other demographics like education, but there's still correlational data. You're absolutely right about that. There have been a few studies that have looked at experimentally manipulating numeracy. And they've found those have found causal effects on risk perceptions. different kinds of behaviors, financial literacy.

So there's a few studies out there, but it's actually difficult to make a large impact on adult numeracy unless you put them through a very, very long, like a math course, unless you put them through sort of a long training course. We're going to take a short break, and when we return, we'll talk with Dr. Peters about whether our increasing reliance on technology is making us more or less numerate. It's peak pollination season, and my business is scaling fast. To keep the nectar flowing, I need a phone plan with top priority data speeds. That's why I chose GoogleFi wireless.

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And entertain all season with the Hampton Bay West Grove seven-piece outdoor dining set for only $49. This Memorial Day get low prices guaranteed at the Home Depot. Loss supplies last. Pricing valid May 14th or May 27th. U.S. only exclusions apply. See Home Depot.com slash price match for details. Is technology making us more enumerate or is it helping us be less enumerate? I'm asking just like in a day-to-day fashion, like you go to the grocery store and if the cashier doesn't see what the change is on the register, they have no idea how to make change anymore. I mean, I used to have to do that calculation in my head when I was a checker many years ago.

So I'm just astonished that people can't do these things. Yeah, I actually had a well-known psychologist actually told me a story once. He was at a checkout counter. Let's say the bill was 75 cents. How did that work? Basically, he was giving her money so that she would give him back a full dollar. And she couldn't do that on the fly, unfortunately. And so is technology helping or hurting?

I think it's both. So I think it's hurting in the sense that you're talking about. People are kind of losing that ability to make calculations on the fly. And that kind of thing, I suspect, will make people more vulnerable, even more vulnerable to framing effects, for example. Because if you don't do that change, that switch from 90% survival to 10% dying, then you're not going to have complete information. Or you're not going to be able to figure things out at the cashier, all of those kinds

of situations. I think technology helps in other ways, though. So technology can be used to help support people. If they're not going to understand the numbers, the technology can be that backup system so they don't get cheated or so that they better know what the meaning of information is. So, for example, in medical decision making, a lot of researchers and folks in the medical field have worked on decision aids. And those decision aids are very explicitly intended to help people better understand the numbers that underlie one cancer screening option versus a decision aids. another, for example, or one treatment option versus another. And so the technology also supports. So I'd say it's kind of a two-edged sword. You've done some research that's looked at people's

actual skill and their confidence with numbers and how those two things interact. What have you found? Yeah. So I just found this fascinating. We had started to study objective numeracy kind of early in my career. And then along the way, I came across this idea of numeric confidence. and realized that it's almost equally important to objective numeracy. So we did a set of two studies in one paper that came out in PNAS. And they're both correlational studies,

but what we did, one of them was in a financial domain and one was in a medical domain. And so we had access to people's self-reported financial outcomes, whether they had ever carried more than $5,000 in credit card debt, for example, whether they had ever defaulted on their mortgage, whether they had retirement savings. So some of the outcomes were positive and some were negative. We transformed it so that everything was about positive outcomes. In other words, so you have not defaulted on your mortgage is a positive outcome.

And then we measured their objective numeracy and we measured their numeric confidence. And what we found, and you can think about it in sort of two different ways. One thing that we found was that when people are high in numeric confidence, their objective numeracy matters. So if they're high in numeric confidence and they have high objective numeracy, they do really well in financial outcomes. But if they're high in numeric confidence and they're actually very low in ability, which does happen, those are the people who do the worst. And so when you're high in confidence, it can help you if you have the ability and it helps you to flourish. But if you're low in ability, what we think happens is that they go ahead and take charge of their own decisions because they're

confident. They can do it. But while they're confident they can do it, they may be making mistakes because they don't have the ability. And they may not be catching those mistakes, again, because they don't have the ability. And they may not be asking for help again because they think they have that ability. But then if you look at the people who are low in confidence, I found this fascinating. Objective ability almost made no difference to their financial outcomes, whether they are high or low in objective ability. When they had low confidence, it's like they just didn't step up to the plate. They just didn't try to use their numeric abilities. And because of that, their financial outcomes were about the same, whether they're low or high inability. Those were self-reported

financial outcomes. And so we're also really interested in, can we get to a more real outcome? Not that those aren't a real outcome, but they're self-reported. But I was working with a few rheumatologists at the time. This is a type of doctor who treats people with things like arthritis, But they also treat people who have lupus. And lupus is a very serious autoimmune disease that actually involves a lot of numeric processing because they have to figure out how to take medication. They have to understand the risks and benefits of their medication. They have to get to doctor's appointment.

There's just kind of a whole bunch of little numeric tasks that they have to do on an everyday basis. And so we're interested in taking a look at the same hypothesis with them. And in particular, because if they gave us a little, permission, we would have access into their medical records, and we could see how the physician thought they were doing in terms of how active their lupus was. And so we were with two rheumatologists helping out, we actually were able to access a sample of lupus patients who very kindly agreed to do our measures of numeracy and numeric confidence, and they allowed us, very kindly allowed us

access into their medical records. And we found the same result. The people who were low in confidence, their ability didn't make a difference. But if they were very high in numeric confidence, if they were high in ability, they did great. Their health was doing great. But if they were high in confidence, but they were low in ability, those are the people who are actually doing the worst. Their disease activity was the highest, and they're at most risk for long-term damage. What can people do to improve their numeracy? There's a number of things people can do. The first one has to do with what we were just talking about, that that interesting relationship between objective ability and numeric confidence, the first thing people can do is figure out who they are as a

math person because believing you're not skilled when you really are can hurt you because you're not doing as well. You're not taking advantage of the skills that you actually have. And so people need to be open to the possibility that they might be good at math so that they're more likely to use numbers in these everyday kinds of situations that we're talking about. But on the other hand, believing that you're skilled at math, when you really don't have those kind of math skills, that can really hurt, that can really hurt you. So encouraging people to figure out where they are, like, who am I as a math person? How can I match my level of numeric confidence with the level of ability that I actually have can really help? It means that you'll ask for help if you need it, and maybe you'll try harder

if you really have the skill, but you're just not confident about it. Something else. People can become more numerate. It takes practice. There's not a lot of research on this. So a little bit, this has to be taken with a little bit of a grain of salt. But people can take math classes. That would be the hardest thing. And that kind of practice would likely matter. We had done some research that suggests that just practicing in an easier way can help. You don't have to practice with particularly difficult math. But if you practice with simple math, like adding and subtracting numbers, practice by estimating the answers. You first have to estimate the answer before you see it

because you have to get feedback about whether you're right or wrong so that you can actually learn. It turns out the learning requires knowing what you've done correctly and what you've done incorrectly so you can do better the next time. But our research shows that even doing this in about six sessions of about 30 to 45 minutes, if I remember correctly, this can improve people's objective numeracy. and it actually did improve the consistency with which people perceived risks.

So we know that that helps. We need more research on it. But again, it is hard to manipulate numeracy among adults. Another thing, and then just sort of a long series of studies in my lab and others, suggests that that idea of developing good number habits may be important. And so people should pay attention to the numbers in their lives. Try not just to read over them. develop good number habits by spending more time, by transforming and calculating numbers, by comparing

numbers. Sometimes that makes all the difference. If you know how likely some treatment is to help you, take a look at some other plausible treatment and compare it and see which one might actually offer you more benefit. That'll help you derive more affective or emotional meaning from the numbers. And then the last thing kind of gets back to that technology question that you mentioned, Kim. And the idea is to advocate for yourself if you don't understand some number. Or if the person didn't provide a number and you feel like it might be helpful,

you can ask like a physician, how statistically likely is something? What is the probability of something happening? Or if you're given too many options or too much information, you can ask a professional to simplify, the information. So that to whatever is the most important information in their view. And by doing that, people actually will understand more. Sometimes less can be more. What about the people who need to convey numerical information, whether that's doctors talking to patients or maybe journalists explaining economic data, scientists who are trying to explain climate risk? How can they help people better understand the numbers they're putting out there so that we can make better decisions?

Yeah, so there's a series of recommendations that I would make from my lab and communicators will often make. The first one is to have a communication goal. And that sounds kind of silly in some ways, but I've been in all kinds of interviews where I'm sitting in like on a doctor's visit with a patient or a physical therapist's appointment with parents of a child who's not doing well. And they often go in with this like mound of information that they pick up and they put down in front of the patient. And without really thinking about what does this person really need to know? How can I facilitate how they understand? If you sit back and think first about what a communication goal is, that means that you can actually strategically choose what information to show. And then think about, again, strategically, how might I show it?

And then we get to the kinds of research that I do, which has to do with, how do you format information? What kinds of information might you show? And one of the first recommendations that I always have is to communicate with numbers, not only words. So there's this funny thing that happens where people often prefer communicating with verbal terms like common and unlikely, but people actually kind of prefer getting numbers. And not only do they prefer getting numbers, but they also better understand risks and they can react appropriately when numbers are discussed, so long as the numbers aren't too difficult. You don't want to provide too many numbers. But what ends up happening when you provide numeric information is not only do

people understand better, which helps to support informed consent processes and other things like that. But just the mere presence of numbers seems to increase people's trust in the message and their perceptions of the expertise of the messenger. And on social media, for example, people are more likely to share numbers that include numeric information compared to the exact same message minus the numbers. So that's one thing. Communicate with numbers, but you do have to make those numbers more manageable. And there's sort of two ways to do this. One is to provide less information. So remember that communication goal. You want to provide information that helps to meet the goal, but not more information than that if you can help it. Because more information means,

just a greater likelihood of losing somebody along the way. With less information, people do understand more. So you want to avoid cognitive overload. The other part of making numbers more manageable is do the math for people. We often give people information where they have to do a little bit of math and you lose so many people along the way. Another thing would be to make numbers more meaningful, you can provide context like we talked about this a little bit before too.

if you talk about 93% of patients will survive from treatment A, maybe you also want to give them a comparison. This is compared to 99% of people who would survive with treatment B. And by having that comparison, people can draw their own meaning. What are some of the other things? This goes back to more general communication advice from the literature. We often want to inform people and we want to help them better understand a situation that they're in so that they can make their own decisions. And you don't want to overwhelm them like we were saying. But in the end, we also often want to tell people what are the possible solutions here? And you want those solutions to be something that people think will work and that they're confident that they themselves can do. And so that kind of furnishing

of feasible solutions is really important. And we think about that a lot when it comes to communicating about hazards. So if you're communicating about earthquakes, for example, in the Pacific Northwest, you want to make sure not only that you can about the risk of an earthquake and what might happen, what the likelihood might be, what those consequences might be. But you also want to tell people, what can I do about it? What can I do? What can I do that will work? And what can I do that I'm confident that I can actually do? And so those are kind of some of the general things that I think about when it comes to communicating numbers, but also going beyond numbers to the idea that we're communicating to help people's lives. So you want to go beyond the numbers to things like furnishing solutions that are doable for people.

Well, that makes perfect sense. So what are the big questions you still want to answer? What are you working on right now? Oh, you know, we are still looking a bit at the mere presence of numbers. You know, I have to admit, I come from an engineering background originally. And so I'm a little bit of a geek when it comes to numbers. And so I just, I personally just find it fascinating that the mere presence of numbers can change how much people trust, how much people think someone's a number. expert. And I'm curious about why. So we're sort of delving into that a bit more. We just in the past probably a year or two have been looking more into how can we communicate more effectively about hazards that people face. And those are the earthquakes and the wildfires. And the reason for that is

I love doing psychological science. I love the brain candy of psychological science. It's just really interesting to find out how the human mind works. But I also wanted to make a difference. And so I want to make a difference in people's lives and hopefully, you know, help people to better understand something that's important to them and that will help, just help improve the quality of their life. And so that's why we've gone into some of the hazards research, because I think that's important. Well, Dr. Peters, I want to thank you for joining me today. It's been very enlightening. It has been very fun. Thank you again, Kim. It's been a pleasure. You can find previous episodes of Speaking of Psychology on our website at speakingof psychology.org

or on Apple, Spotify, YouTube, or wherever you get your podcasts. And if you like what you've heard, please follow us and leave a review. If you have comments or ideas for future podcasts, you can email us at speaking of psychology at APA.org. Speaking of psychology is produced by Lee Wynerman. Thank you for listening for the American Psychological Association. I'm Kim Mills. Relax and let Ralph's delivery handle your grocery shopping this week.

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