But, hey, it was published in the prestigious Proceedings of the National Academy of Sciences (PPNAS)! What could possibly go wrong?
Here’s what Erik Larsen writes:
In a paper published in the Proceedings of the National Academy of Sciences, People search for meaning when they approach a new decade in chronological age, Adam L. Alter and Hal E. Hershfield conclude that “adults undertake a search for existential meaning when they approach a new decade in age (e.g., at ages 29, 39, 49, etc.) or imagine entering a new epoch, which leads them to behave in ways that suggest an ongoing or failed search for meaning (e.g., by exercising more vigorously, seeking extramarital affairs, or choosing to end their lives)”. Across six studies the authors find significant effects of being a so-called 9-ender on a variety of measures related to meaning searching activities.
Larsen links to news articles in the New Republic,
Washington Huffington Post, Salon, Pacific Standard, ABC News, and the British Psychological Society, all of which are entirely uncritical reports, and continues:
I [Larsen] show that each of the six studies in the paper consist of at least one crucial deficiency hindering meaningful inferences. In several of the studies the results stems from the fact that the end digits are not comparable as 9, for example, is more likely to be found among younger age decades as the age range in all the studies is from 25 to 65. In other words, if people are more likely to engage in an activity at a younger age compared to later in life, higher end digits are more likely to measure such differences compared to lower end digits. When controlling properly for age the differences reported in some of the studies fails to reach statistical significance. In other studies, results were questionable due to empirical shortcomings.
Larsen conveniently made the data accessible via R code in this Github repository.
You can follow the link for all of Larsen’s comments but here are a few:
In Study 1, the authors use data from the World Values Survey. They conclude that “9-enders reported questioning the meaning or purpose of life more than respondents whose ages ended in any other digit”. However, if one take age decades into consideration, the 9-ender effects fails to reach statistical significance (p=0.71) despite the sample size of 42.063.
In the replication material, some respondents from the World Values Survey are excluded. In the full data set (obtained at http://www.worldvaluessurvey.org/WVSDocumentationWV6.jsp), there are 56,145 respondents in the age range 25-64. The difference between 9-enders and the other respondents on the Meaning variable is 0.001 and is non-significant . . .
In Study 2, age decades are less relevant due to the experimental design. Here the authors find significant effects of the experimental stimuli, and the effects seem robust. However, no randomization tests are reported. One sees that the experimental group differ systematically from both the baseline and control group on pre-randomization measured variables. People in the experimental group are, for example, on average over 6 years younger than the baseline group (p<0.001) and have a higher distance to a new decade than the control group (p=0.02), questioning the possibility to draw design-based inferences. . . . In Study 3, the authors argue that 9-enders are more likely to seek extramarital affairs. What did the authors do here? They "categorized 8,077,820 male users, aged between 25 and 64 years, according to the final digit of their ages. There were 952,176 9-enders registered on the site". Before looking at the data, one can ask two questions. First, whether those aged 30 are more likely to report the age of 29 and so on. The authors argue that this is not the case, but I am not convinced. Second, and something the authors doesn't discuss, whether age is a good proxy for the age users had when they signed up at the specific site (unless everybody signed up before in the months before November 2013). . . . In Study 4, the authors look at suicide victims across the United States between 2000 and 2011 and show that 9-enders are more likely to commit suicide. Interestingly, the zero-order correlation between suicide rate and 9-enders is non-significant. In the model conducted by the authors (which shows a significant result), when controlling properly for age, the effect of 9-enders fails to reach statistical significance (p=0.13). In Study 5, the authors show that runners who completed marathons faster at age 29 or 39. However, simple tests show that there is no statistical evidence that people run faster when they are 29 compared to when they are 30 (p=0.2549) or 31 (p= 0.8908) and the same is the case for when they are 39 compared to 40 (p=0.9285) and 41 (p=0.5254). Hence, there is no robust evidence that it is the 9-ender effect which drives the results reported by the authors. . . .
To relay these comments is not to say there is nothing going on: people are aware of their ages and it is reasonable to suppose that they might behave differently based on this knowledge. But I think that, as scientists, we’d be better off reporting what we actually see rather than trying to cram everything into a single catchy storyline.
Of all the news articles, I think the best was this one, by Melissa Dahl. The article was not perfect—Dahl, like everybody else who reported on this article in the news media, was entirely unskeptical—but she made the good call of including a bunch of graphs, which show visually how small any effects are here. The only things that jump out at all are the increased number of people on the cheating website who say they’re 44, 48, or 49—but, as Larsen says, this could easily be people lying about their age (it would seem like almost a requirement, that if you’re posting on a cheaters site, that you round down your age by a few years)—and the high number of first-time marathoners at 29, 32, 35, 42, and 49. Here’s Dahl’s summary:
These findings suggest that in the year before entering a new decade of life, we’re “particularly preoccupied with aging and meaningfulness, which is linked to a rise in behaviors that suggest a search for or crisis of meaning,” as Hershfield and Alter write.
Which just seems ridiculous to me. From cheaters lying about their ages and people more likely to do their first marathon at ages 29, 32, 35, 42, and 49, we get “particularly preoccupied with aging and meaningfulness”??? Sorry, no.
But full credit for displaying the graphs. Again, I’m not trying to single out Dahl here—indeed, she did better than all the others by including the graphs, it’s just too bad she didn’t take the next step of noticing how little was going on.
One problem, I assume, is the prestige of the PPNAS, which could distract a reporter from his or her more skeptical instincts.
Here, by the way, is that graph of suicide rates that appeared in Dahl’s news article:
According to the graph, more people actually commit suicide at 40 than at 39, and more do it at 50 than at 49, while more people kill themselves at 58 than 59. So, no, don’t call the suicide hotline just yet.
P.S. To get an image for this post, I started by googling “hype cycle” but all I got was this sort of thing:
All these are images of unidirectional curves; none are cycles! Then I went on wikipedia and found that “hype cycle” is “a branded graphical tool.” How tacky. If you’re going to call something a cycle, you gotta make it return to its starting point!
The hype cycle
The “cycle” of which I speak goes something like this:
1. Researcher is deciding what to work on.
2. He or she hears about some flashy paper that was published in PNAS under the auspices of Susan Fiske, maybe something like himmicanes and hurricanes. The researcher, seeing this, sees that you can get fame and science chits by running a catchy psych experiment or statistical analysis and giving it a broad interpretation with big social implications.
3. The analysis is done, it’s submitted to PNAS.
4. PNAS sends it to Susan Fiske, who approves it.
5. The paper appears and gets huge exposure and uncritical media attention, both in general and (I’m sorry to say) within the field of psychology.
Return to 1: Another researcher is deciding what to work on. . . .
That’s the hype cycle: The press attention and prestige publication motivates more work of this kind.
P.S. Let me emphasize: I’m not opposed to this sort of work. I think the age analysis is clever (and I mean that in a good way), and I think it’s great that this sort of thing is being done. But, please, can we chill on the interpretations? And, journalists (both in general and within our scientific societies), please report this with a bit of skepticism? I’m not saying you need to quote an “opponent” of the study, just don’t immediately jump to the idea that the claims are generally valid, just because they happened to appear in a top journal.
Remember, PNAS published the notorious “himmicanes and hurricanes” study.
Remember, the Lancet published the notorious Iraq survey.
Remember, Psychological Science published . . . ummm, I think you know where I’m going here.
Reporting with skepticism does not require “debunking.” It’s just a matter of being open-minded about the possibility that claimed results to not really generalize to the larger populations or questions of interest, in the above case it would imply questioning a claim such as, “We know that the end of a perceived era prompts us to make big life decisions,” which is hardly implied by some data that a bunch of 42-year-olds and 49-year-olds are running marathons.