Science Friday - Could ‘Season Creep’ Affect Human Behavior?

Episode Date: September 2, 2024

You might have noticed that the seasons don’t quite behave like they used to. In some places, fall and spring seem to fly by, while winter and summer are much longer and feel more intense. This shift is known as season creep, where the timing of the seasons starts to shift.This phenomenon is mostly due to climate change creating temperature imbalances and throwing weather patterns off kilter year-round. And it can cause problems for plants and animals as their natural cycles fall out of sync. But what does it mean for human behavior?Seasonal Affective Disorder, often called seasonal depression, 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.SciFri guest host Rachel Feltman is joined by Dr. Michael Varnum, social psychology area head and associate professor at Arizona State University, to discuss these questions.Transcripts for each segment will be available after the show airs on sciencefriday.com.   Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Did you know that seasons can influence our behavior? It's such a ubiquitous part of life that we've taken them for granted and not really thought and too concentrated away about what kinds of effects they may have. But with the timing of the seasons 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 SciFriot Radio Fellow Valeria Diaz.

You might have noticed that seasons don't feel the same anymore. Fall and spring seemed 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 SciFRI guest host Rachel Feldman with more. It's no surprise that the seasons can affect our mood. You've probably heard of seasonal affective 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 Varnum, 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 flies 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 in wintertime. 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 wintertime. 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 and 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 wintertime. 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 wintertime, 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 structurally. 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 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 do to our health and our psychology. In a recent review, this was by Roney 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, oh, 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 breeze. sort of false fall and then sort of normal August weather and now we've crept back up into heat wave 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 ten 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 my area feel like we go right from summer heat waves 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 worse than the spring. But maybe you're going to see more sort of year-round stability than 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, 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 effective disorder. So could you talk a little bit about what that is and why it happens? It seems like as 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, suggests that actually for a lot of people, we see these decreases in mood in the wintertime. 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 wintertime? 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 a 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 sleeps 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 houses.

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 Holer and Mark Schaller analyst, 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. 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. It seems like they might be good strategies to deal with these seasonal fluctuations in how we're feeling. And how can we prepare for seasons getting less predictable in the future with climate change? I mean, 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 how the seasons will change going forward, we might also be able to make some useful forecasts for things like 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 healthcare 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 researched or 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 and too concentrated away 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 Schaller and Ian Holm 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 collective or how motivated we are to find new romantic partners versus take care of family. And hopefully, you know, in another couple seasons, we'll have some answers for you. Yeah, absolutely. I can't wait to read the actual scientific research on cuffing season, as TikTok calls 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 helped make this show happen this week, including John Denkowski, Annie Niro, Jason Rosenberg, Rasha Auretti, Shoshana 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 Sci-Fi Radio Fellow by Leria Diaz. Thank you for listening.