Our paper on bathing/showering habits and loneliness has been accepted (Donnellan, Lucas, & Cesario, in press). The current package has 9 studies evaluating the correlation between trait loneliness and a preference for warm showers and baths as inspired by Studies 1a and 1b in Bargh and Shalev (2012; hereafter B & S). In the end, we collected data from over 3,000 people and got effect size estimates that were considerably smaller than the original report. Below are some random reflections on the results and the process. As I understand the next steps, B & S will have an opportunity to respond to our package (if they want) and then we have the option of writing a brief rejoinder.
1. I blogged about our inability to talk about original B & S data in the Fall of 2012. I think this has been one of my most viewed blog entries (pathetic, I know). My crew can apparently talk about these issues now so I will briefly outline a big concern.
Essentially, I thought the data from their Study 1a were strange. We learned that 46 of the 51 participants (90%) reported taking less than one shower or bath per week. I can see that college students might report taking less than 1 bath per week, but showers? The modal response in each of our 9 studies drawn from college students, internet panelists, and mTurk workers was always “once a day” and we never observed more than 1% of any sample telling us that they take less than one shower/bath per week. So I think this distribution in the original Study 1a has to be considered unusual on both intuitive and empirical grounds.
The water temperature variable was also odd given that 24 out of 51 participants selected “cold” (47%) and 18 selected “lukewarm” (35%). My own intuition is that people like warm to hot water when bathing/showering. The modal response in each of our 9 samples was “very warm” and it was extremely rare to ever observe a “cold” response.
My view is that the data from Study 1a should be discarded from the literature. The distributions from 1a are just too weird. This would then leave the field with Study 1b from the original B & S package based on 41 community members versus our 9 samples with over 3,000 people.
2. My best meta-analytic estimate is that the correlation between trait loneliness and the water temperature variable is .026 (95% CI: -.018 to .069, p = .245). This is based on a random effects model using the 11 studies in the local literature (i.e., our 9 studies plus Studies 1a and 1b – I included 1a to avoid controversy). Researchers can debate about the magnitude of correlations but this one seems trivial to me especially because we are talking about two self-reported variables. We are not talking about aspirin and a life or death outcome or the impact of a subtle intervention designed to boost GPA. Small effects can be important but sometimes very small correlations are practically and theoretically meaningless.
3. None of the original B and S studies had adequate power to detect something like the average .21 correlational effect size found across many social psychological studies (see Richard et al., 2003). Researchers need around 175 participants with power set to .80 for the r = .21 expectation. If one takes sample size as an implicit statement about researcher expectations about the underlying effect sizes, it would seem like the original researchers thought the effects they were evaluating were fairly substantial. Our work suggests that the effects in question are probably not.
In the end, I am glad this paper is going to see the light of day. I am not sure all the effort was worth it but I hope our paper makes people think twice about the size of the connection between loneliness and warm showers/baths.
25 Jan 2014: Corrected some typos.