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The Last Show with David Cooper

Late Night Coffee and Impulsiveness

09 Apr 2026

Transcription

Chapter 1: What surprising effect does drinking coffee at night have?

4.486 - 31.309 David Cooper

The day is done. We're just getting started. The last show. Do you drink coffee to stay sharp, focused, and in control? I certainly do. But what if that late night cup you're grabbing secretly is doing the opposite of those things? It's nudging your brain towards impulsive, reckless decisions. Even fruit flies lose their cool when they're given coffee.

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31.689 - 39.538 David Cooper

Let's discuss all of this with biology professor at the University of Texas, El Paso, Kyung-An Han. Kay, welcome to the show.

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39.687 - 46.598 Kyung-An Han

Thank you for inviting me. I'm excited to talk to you about our recent study on caffeine's effect on behavior.

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46.958 - 55.772 David Cooper

Now, caffeine, using it to stay up late at work, to try to be focused. Is that a good idea? Did we think that was a good idea going into your study?

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Chapter 2: How does caffeine influence impulsive behavior?

56.073 - 76.731 Kyung-An Han

Well, what do you mean by good? I think good is really subjective. I mean, if your goal is to stay awake to study finals, obviously it's a good idea to drink coffee whenever you need it. But you just need to watch out not to drive afterwards because you don't want to drive through yellow lights.

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76.778 - 77.659 David Cooper

Okay.

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77.679 - 79.862 Kyung-An Han

Oh, I suppose that's what- That would be impulsivity.

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80.262 - 88.312 David Cooper

So let's talk about it. Let's talk about our favorite drug. We use it to stay sharp. It might be good at doing that, but what else is it doing to us?

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88.332 - 115.987 Kyung-An Han

Well, actually, caffeine has been used by people, athletes, to enhance their physical performance as well. So when caffeine acts on muscle, it increases production of ATP. So it is known as actually performance enhancer. Obviously, it's not really like other illegal kind of enhancer, but nonetheless, it has been helpful to some individuals.

116.547 - 124.839 Kyung-An Han

And obviously, it is also a cognitive enhancer as well, too, meaning it tends to increase your attention to the task.

Chapter 3: What insights does Kyung-An Han provide about their caffeine study?

124.859 - 154.378 Kyung-An Han

More importantly, it makes you be awake. So whenever you need to study last minute for final exam, or whether you need to work at night for night shift workers, this will help people to be awake. In that sense, it's really helpful. But like everything, every chemical that we intake, too much is always detrimental. But what we demonstrate is that also time of day is also critical as well too.

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154.958 - 181.192 Kyung-An Han

In our study, Drinking coffee during the daytime could be bad because it will make you not sleeping well because it reduces sleep time as well as quality of sleep, but nonetheless people sleep. But one drink coffee at night, I don't know, I do have a really good experience with it too. I had to drink a lot of coffee to finish my proposal. And then that was at work.

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181.312 - 200.982 Kyung-An Han

When I drove home, I had strong urge to drive through yellow light. I mean, this is exactly what food flies do. So when they get coffee at night, but not during the daytime, they become a little more impulsive. So in a condition where they need to control their behavior, like a strong airflow, which is like a wind,

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200.962 - 229.525 Kyung-An Han

or sound of predators then they need to stop not to get seen but they all of a sudden show impulsive flying so because they cannot control their behavior really well so i think this is a really good example of how caffeine interact with time of day to provide something that is not typically seen with what they typically do during the daytime.

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Chapter 4: Is it safe to drink coffee late at night for focus?

229.725 - 242.511 David Cooper

That's interesting. So impulsiveness for a fruit fly is like being more dangerous with predators, not flying properly when there's wind. What might nighttime impulsiveness look like for us if we drink too much coffee late into the evening?

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242.693 - 266.325 Kyung-An Han

Well, I can tell you this much. You don't want to talk to your parents about your obviously secret that you don't want to share with your parents, for example. Impulsivity can be cognition as well as movement. Obviously, we study impulsivity on movement because animal model that we are studying is foot flies.

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266.545 - 285.771 Kyung-An Han

So it's harder for us to ask them how well that they are controlling their cognition, although we measure their capacity to learn and remember. We haven't studied the effect of caffeine regarding its impact on their memory, but this is another step that we are approaching in the next step.

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285.791 - 293.541 Kyung-An Han

So at least in their performance, they cannot control their behavior, and then they become impulsive, which is

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293.521 - 320.676 David Cooper

negative in a way that you don't want to fly around when you do not you you're not supposed to now you mentioned the night shift workers where it might actually be useful because it keeps them awake alert better to focus all that exactly but there's some jobs where impulsiveness would be a terrible thing like maybe a surgeon an air traffic controller would you recommend for those folks maybe not drinking too much coffee late into the night

320.892 - 347.592 Kyung-An Han

Exactly. Maybe it's not a good idea for them to perform anything really critical after they stay awake, plus caffeine. Well, then what would be the best way to control their wakefulness at night? I cannot give you an answer for it, but at least we know that caffeine is not the best answer. So if you have important surgery at 7 o'clock in the morning after you do another surgery overnight,

347.572 - 360.686 Kyung-An Han

Then maybe it's a better idea not to drink caffeine at night, yet maybe try to get good sleep during the daytime before they get into night shift. So then maybe one way to control to be awake without caffeine.

361.347 - 374.541 David Cooper

Now, when I hear about experiments with fruit flies, I kind of naturally wonder how much of the results would translate into human behavior. How do we make that leap? How do we say, OK, we've observed it in fruit flies. We also suspect it might happen in humans, too.

374.757 - 401.659 Kyung-An Han

That's an excellent question. That's what everybody asks me. How close flies are to humans? In my opinion, they are really close to humans in many ways. They do have a majority of genes that cause diseases. And they are highly similar, those molecular functions. But more importantly, the way that the brain works in full flies is quite similar to the way that our brain works.

Chapter 5: What are the potential risks of nighttime caffeine consumption?

428.082 - 451.103 Kyung-An Han

to humans. So I think FlipFly is a really good model to study human brain, although there won't be some behaviors that can be exactly matching, but we can at least study fundamental mechanism, how brain control behavior and how anomaly in their brain function tend to cause diseases like autism or Alzheimer's diseases.

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451.184 - 464.888 David Cooper

Now, back to the research and looking at it at a high level. Caffeine, it's been a part of human culture for, I don't know, in some cultures, thousands of years and other centuries. Do you now think twice before having that late night coffee before you have to get something done?

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465.109 - 472.602 David Cooper

Would you recommend other people think twice and really think about what they're doing, making sure it's not driving or something where impulsivity would be a bad idea?

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472.835 - 498.012 Kyung-An Han

Right. I stopped drinking coffee after four o'clock because I want to have a really good night's sleep. Me too. I know for sure if I drink coffee after dinner, I cannot sleep well because there will be caffeine in my system and loss of sleep can be really bad too. So there will be a lot of side effects of having caffeine late at night, although there may be individual differences as well too.

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498.473 - 523.328 Kyung-An Han

I mean, you and I know that the way that we behave is based on our experiences as well too, beyond genetic makeup. So people who are highly resistant to the effect of caffeine, they may be okay because they've been doing it, body developed how to deal with it. So it may be okay with them. But for those who are new to caffeine,

523.308 - 550.986 Kyung-An Han

Maybe it's not a really good idea for them to use too much caffeine at night because it really does interact with a lot of molecular components that are active in the brain at night. And therefore, I think it could have a different way of controlling behavior than what we intended. So maybe many of the audience think, oh, flies are kind of different than humans.

550.966 - 562.539 Kyung-An Han

But we shall see in future how it does. Maybe you could maybe test how it influenced you by drinking coffee at night and see how impossible it can become.

562.859 - 570.988 David Cooper

All right. Maybe I'll be a research subject. Well, Kyung-An Han is a biology professor at the University of Texas at El Paso. Kay, I've enjoyed the chat. Thanks for being on the show.

571.348 - 572.89 Kyung-An Han

It was wonderful. Thank you for having me.

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