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kinds of effects they may have. But with the timing of the season is changing more and more every year. How could that impact our psychology? It's Monday, September 2nd. It's Labor Day and this is Science Friday. I'm Sifre Radio Fellow by Lady of the S. You might have noticed that seasons don't feel the same anymore. Fall and Spring seem to sit by while winter and summer drag on and hit harder. This is called season creep, a shift in the timing of the seasons due to
climate change messing with temperatures and weather patterns. This phenomenon is throwing plants, animals and even us out of sync. But what does it mean for human behavior? Here is Sifre guest host Rachel Feldman with more. It's no surprise that the seasons can affect our mood. You've probably heard of seasonal effective disorder often called seasonal depression which tends to hit during the cold, dark winter
months. But as the seasons start changing more quickly and unpredictably, the shift could have a wide range of effects on us that we're only just beginning to understand. Joining me today to try to answer some of these questions is Dr. Michael Varnam, social psychology area head and associate professor at Arizona State University. Welcome to Science Friday. Thanks so much for joining us. Hi, thanks so much for having me Rachel.
So you and your colleagues recently wrote a paper on the topic of human seasonality. Could you explain what that means and why it's an important topic to unpack? Sure thing. So we got interested in this question of, you know, when we look at many other non-human animals, if we think about, you know, brown bears and squirrels that hibernate in the winter or Canada geese which fly south in the fall in search of warmer weather, we
look across the animal kingdom and we look at plants as well. And we see a wide range of seasonal effects on their physiology and behavior. And when we think about ourselves, most of us are aware of some of these seasonal shifts in mood, but in fact, it turns out that we're fairly seasonal creatures as well. Yeah. So what are some of the ways that seasons can influence human behavior? A lot of things seem to follow seasonal patterns
in our species. So it's not just this sort of tendency to increase feelings of depression and winter time. Recent work by some of my collaborators actually suggests that anxiety seems to peak in spring and fall. And we also see changes in things like aggressive behavior. So we've known for some years looking at crime statistics and other sources of data that people get a little more violent and aggressive in the summertime. But it also turns
out if we look at generosity, that tends to peak in the winter time. There's a bump in charitable giving and even how much people leave as tips at restaurants around the Christmas holidays. And beyond that, we see changes in everything from the kinds of foods we eat in levels of exercise to our preferences for different kinds of colors and even our sexual
behavior. So it turns out in the summertime and also again around the holidays, a variety of sources of data looking at sort of large surveys of people's frequency of sex as well as internet searches for things like pornography and condom sales. These seem to show biannual peaks as well. Wow, that's so interesting. Do we have any idea why seasons can affect us in these ways? Yeah, so some of these changes probably have to do with the way amounts
of sunlight and heat affect our neurotransmitters and our hormones. There's emerging evidence suggesting that you know, serotonin tends to start to bottom out in the winter time and sex hormones like estrogen and testosterone according to large analyses of medical records seem to have biannual peaks in the winter and summer as well. But more broadly, we also see, you know, when we think about seasonal changes, it's not just the temperature or
whether we're getting snow or how much light we're getting the changes. Other aspects of our environment that have been shown to affect our behavior also shift. So if we think about the winter time, right, this is cold and flu and now COVID season. So the threat of infectious disease tends to follow cyclical patterns and that's been linked from everything to our tendency to conform to how willing we are to try new things to whether folks are
suspicious of people who are unfamiliar or don't look like them. We also see shifts, for example, in places like Arizona where I live, we get influxes of guests and tourists in our winter months because it's a lot nicer here than, say, up in Canada or the Midwest. And so the density of population can shift seasonally and that can affect the extent to which we engage in long-term planning. And in addition to this, seasons also have kind
of cultural associations, right? Christmas, Hanukkah, a lot of other holidays fall in those December months, but we also see, right, we can think about the cycles of the school year and other ways in which our lives are sort of structured in these seasonal patterns. And likely some of these effects that have been observed are due to kind of a complex interplay of these factors.
And it's interesting that you mentioned, you know, sort of respiratory disease spikes. I know there's been a lot of talk this summer in particular about COVID spikes in the summer and I've seen some public health experts speculate that maybe as summers are getting more oppressively hot and people are spending more time indoors in the AC, you know, the sort of traditional wisdom about viral transmission being lower in the summer because everyone's
enjoying the high-mount side might be, you know, less of a truth these days. Do you have any thoughts on other ways that climate change and season creep could be impacting those effects on our behavior and is anyone researching that specific question? Yeah, those are great questions. So, you know, one of the big effects of climate change aside from season creep is that our summers are not only getting longer, but they're getting
hotter. And there's emerging research on sort of what do extreme high temperatures and exposure to them due to our health and our psychology. You know, recent review, this was by Roni and Alamegir found that we get more irritable when we're exposed to these
really hot temperatures, which kind of makes sense, right? But also that our sleep tends to be disrupted, we tend to experience decreased motivation and increased feelings of helplessness, which, you know, living in the Phoenix Valley when it's been above 110 for over a month and a half straight. Sometimes, yeah, we do feel pretty gloomy about life in general and like we're doomed. So, a lot of things might be responding to this increase in extreme heat.
Yeah, absolutely. I know in the New York City area, we had a brief sort of false fall and then sort of normal August weather. And now we've cupped back up into heatwave territory. And I am definitely feeling less hopeful, but I, you know, I hope that autumn is still in sight. So, how can seasons happening earlier or later disrupt our behavior patterns?
So, there's some research emerging for other species, right? If we look at migratory birds over the past few decades, they're actually starting to shift those migration patterns by about five to 10 days over the past few decades. Animals that hibernate are sort of arising from their stupor about two weeks earlier than they were earlier in this, about half a century
ago or so. Insect populations are sort of emerging and hitting their peaks later. And so, you know, again, it's not just these other animals that are likely to be affected by these shifts and seasons and their timing, but a lot of the effects we talked about just a few moments ago in humans, we might expect the timing of those to begin to change as well.
Yeah. And what about sort of the actual shift from season to season itself? You know, I know a lot of folks in, in my area, if you like, we go right from summer heatwaves that last way longer than they used to. And then suddenly it's dark and it's cold. And we haven't had that, you know, autumn time to recover. How might that impact our behavior
based on what we know about human seasonality? I think that's a fascinating question. So, you know, we might expect that some of these effects that we see in terms of psychological or behavioral changes that seem to be strongest in spring and fall, I guess they might become muted. So, for example, you know, it turns out studies of college students suggest that working memory is best in the fall and worst in the spring. But maybe you're going to see more sort of year-round
stability in some of these cognitive effects. I'm not entirely certain, but I think these are fascinating questions for us to begin to look into and track. And maybe things that, you know, with enough archival data, right, climate change isn't exactly new. We may be able to look back and see evidence, right, of shifts in sort of the strength or timing of these peaks in things like aggressive behavior or changes in mood or, you know, changes in our memory and cognition.
And as we touched on earlier, you know, one commonly known psychological effect of season shifting is seasonal affective disorder. So, could you talk a little bit about what that is and why it happens? It seems like our best we can understand it. Our bodies seem to respond to
the amount of sunlight we're exposed to. And as the days shorten, we're exposed to less of it, and we seem to make less serotonin, which appears to have effects on our mood for some people that leads to clinical levels of depression, but large-scale surveys and also analysis of data from, you know, what people are posting on social media and what they're searching for. So, just that actually for a lot of people, we see these decreases in mood in the winter time. You know,
scientists have speculated a bit about, you know, why might this be? Is there perhaps some adaptive property of why we get a little sad in the winter time? And it actually, if we step back from it, there's a lot of parallels to what happens in hibernating animals. And so, for most of our history, we didn't have very good climate control, right? We didn't have electric heat or air
conditioning. We didn't have grocery stores, so food might have become scarce in the winter. So, it would have been adaptive, at least in latitudes where you really had these very cold months where not a lot of stuff would grow, for us to kind of conserve energy. And this might explain the sort of decrease in motivation. It might explain why we're sort of moving and exercising less, why we're eating more and packing on the pounds. When we're feeling happier, we tend to be more energetic,
we burn more calories. And so, this might in some ways be a holdover from sort of most of our evolutionary history. Yeah, that's super interesting. On my podcast, The Weirdest Thing I learned this week, we've talked a few times about the idea of second sleep, you know, before electric light, a lot of people, a lot of cultures had these, you know, two phases of sleep and it was like
the sun's going down, so why would you stay up? But you're getting more sleep than you need, so you wake up in the middle of the night, you do a couple of things with your one candle and then go back to bed. And I remember reading some scholars from the time actually said that, you know, the best time to try to conceive a child was between your two sleeves because your
energy would be at its highest level. So, yeah, I love thinking about just the ways that our routines have changed so much now that, you know, we can control when we have light and how warm our house is. And yeah, I think it's important to remember that, you know, maybe our bodies are really trying to help us out by getting us to slow down in the winter. But what about the other side of the coin? You know, what are some positive impacts or benefits that seasons changing can
bring us? Well, if we look at the data that Ian, home and Mark, shall are analyzed on anxiety, I mean, I was kind of surprised to read these results, but that, you know, anxiety seems to be peaking in fall and spring when they look at this sort of annual cycles of it. And so maybe we'll get less anxious if we have less fall and spring. I don't know. Interesting. And how would you suggest that people prepare for seasonal mood changes? So, I think it may be helpful for a lot of people to
realize that these are kind of natural cycles we go through in mood. You know, I imagine in the therapeutic context, knowing that, you know, maybe what's going on in terms of your feelings isn't entirely due to, you know, something idiosyncratic in your life that's awful or oppressing or depressing, but that this is part of, you know, sort of a wave that goes up and down in a regular fashion. And that, you know, it's likely to pass as the sun comes creeping back out again.
I'm not a clinician, but I imagine knowing that would probably be somewhat helpful. We also know, right, because in this modern world where we have all these conveniences, we can purposefully engage in more exercise, which is one thing that's been shown to be really, really effective at improving
our mood, reducing feelings of depression and anxiety. So maybe, you know, knowing that this is coming, that it's natural, but also proactively taking some steps to do things that we know will improve mood, seem like they might be good strategies to deal with these seasonal fluctuations in our field. Science Friday is supported by NetSweep. Quick math. Unless your business spends on operations, on multiple systems, on delivering your product or service, the more margin you have and the more
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author Brian Green updates his classic work with a new preface and epilogue. Therely accessible and entertaining, The Elegent Universe brings us closer than ever to comprehending how the universe works. Now available, wherever books are sold. Science Friday is supported by newscientist.com. The destination for science stories that matter. If you haven't yet discovered new scientist,
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less predictable in the future with climate change? I mean, that's that's a tough one. You know, in one line of work, I'm interested in looking at sort of long patterns of societal and psychological change and thinking about how we can maybe forecast the future of these. So we do have good meteorological and climate data. We have decent archival data going back at least long
enough to detect some of these seasonal effects. So I imagine if we can model what these seasonal, how the seasons will change going forward, we might also be able to make some useful forecasts for things like, you know, birth rates and reproductive behavior, rates of crime, changes in sort of mental illness, symptomology that, you know, should be helpful for policymakers, those in the health care industry, folks, you know, trying to decide how to allocate resources to deal with these issues.
Yeah. Well, and I suppose there are parts of the world that already have a lot less seasonal change than I'm used to having grown up on, you know, in the Northeast. So maybe I can pick up some tips from folks in Arizona and California. What would you like to see research doors studied about this in the future? Well, you know, I think seasons are an interesting question in the behavioral
sciences. It's one of those where it's such a ubiquitous part of life that we've taken them for granted and not really thought into concentrated a way about what kinds of effects they may have. And so it's pretty common for psychologists now to report, you know, where in the world they gather their data and how old their participants were and what their, you know, demographic backgrounds are because we know this stuff matters. But we don't really pay attention to when we conduct our
research. And if seasons affect this wide range of behaviors and mental states, you know, everything from mood to sexuality to aggression, then it might be important to start paying a little more attention to that. And also to be thinking about, you know, can we make some predictions for how things that might be a little less obvious might change over the course of the year?
My colleagues and I, Mark Schauer, any in home at UBC, we're actually running some big longitudinal studies right now looking at, you know, whether there might be seasonal shifts in things like xenophobia or seasonal changes in our orientation to individualism or collectivism or how motivated we are to find new romantic partners versus take care of family. And hopefully, you know, in another couple of seasons we'll have some answers for you. Oh, yeah, absolutely. I can't wait
to read the actual scientific research on a cuffing season as to talk about it. Thank you so much for joining us. This has been super interesting. My pleasure. Thank you so much for inviting me on today. And that's all the time we have for now. A lot of folks help make this show happen this week, including John Dinkosky, Annie Nero, Jason Rosenberg, Russia Reedy, Shishana Bucksbaum, and many more. In tomorrow's episode, we'll dig into the science of rogue worlds, objects that
float freely in the cosmos. Scientists just identify six new ones right here in the Milky Way. But for now, I'm sorry I really fell over, but I did it. Thank you for listening. Science Friday is supported by newscientist.com. The destination for science stories that matter. If you haven't yet discovered new scientists, now's the chance to expand your mind and feed your curiosity. Every week, a global community of more than five million people feast on the most important science and technology
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