Category Archives: The Trait-State Continuum

Around here, the Fall semester starts in just a few weeks. This means the MSU subject pool will soon be teeming with “volunteers” eager to earn their research participation credits. Like many of my colleagues, I have often wondered about the pros and cons of relying so heavily on college sophomores in the laboratory (e.g., Sears, 1986, 2008). Regardless of your take on these issues, it is hard to imagine that subject pools will go away in the near future. Thus, I think it is important to try to learn more about the characteristics of participants in these subject pools and to think more carefully about issues that may impact the generalizability of these types of studies. I still think college student subject pools generate convenience samples even if a certain researcher disagrees.

I did a paper with my former graduate student Edward Witt and our undergraduate assistant (Matthew Orlando) about differences in the characteristics of subject pool members who chose to participate at different points in the semester (Witt, Donnellan, & Orlando, 2011). We also tested for selection effects in the chosen mode of participation by offering an online and in-person version of the same study (participants were only allowed to participate through one mode).  We conducted that study in the Spring of 2010 with a total sample size of 512 participants.

In the original report, we found evidence that more extraverted students selected the in-person version of the study (as opposed to the online version) and that average levels of Conscientiousness were lower at the end of the semester compared to the beginning. In other words, individuals with relatively lower scores on this personality attribute were more likely to show up at the end of term. Continue reading →

I wanted to re-read Cronbach (1957) and I stumbled across this letter to the American Psychologist in 1957 from Ardie Lubin with the title of this post: Replicability as a publication criterion.

Just a quick excerpt: “Replicability and generalizability, of course, are not new criteria, and assuredly all editors employ them now in judging the soundness of an article. The only novelty here is the weight which would be placed on the question of whether the results are replicable. Every author would be asked to show some attempt in this direction. Articles using replication designs which are not satisfactory to the editor could be given lowest publication priority. Articles with no attempt at replication would be rejected.”

Ulrich Schimmack has a paper in press at Psychological Methods that should be required reading for anyone producing or consuming research in soft psychology (Title: “The Ironic Effect of Significant Results on the Credibility of Multiple-Study Articles”).  Sadly, I doubt this paper will get much attention in the popular press.  Uli argues that issues of statistical power are critical for evaluating a package of studies and his approach also fits very nicely with recent papers by Gregory Francis.  I am excited because it seems as if applied researchers are beginning to have access to a set of relatively easy to use tools to evaluate published papers.

(I would add that Uli’s discussion of power fits perfectly well with broader concerns about the importance of study informativeness as emphasized by Geoff Cumming in his recent monograph.)

Uli makes a number of recommendations that have the potential to change the ratio of fiction to non-fiction in our journals.  His first recommendation is to use power to explicitly evaluate manuscripts.  I think this is a compelling recommendation.  He suggests that authors need to justify the sample sizes in their manuscripts. There are too many times when I read papers and I have no clue why authors have used such small samples sizes.  Such concerns do not lend themselves to positive impressions of the work.

Playing around with power calculations or power programs leads to sobering conclusions. Continue reading →

Are state-level rates of diabetes really linked with violent crime?  DeWall et al. (2011) seem to think so because they published a package in Aggressive Behavior that pushed the idea of a connection between diabetes and aggression. The title was catchy: “Sweetened blood cools hot tempers: Psychological self-control and aggression.”

The basic argument is that glucose metabolism is associated with self-control and low self-control is associated with aggression.   Diabetes is a deficiency in metabolizing glucose so therefore diabetics should be aggressive.  This work draws on the glucose as brain fuel argument that received attention in the New York Times last Fall.  Robert Kurzban has an interesting critique of this work on his blog.  See links at the end of my post.

(Full Disclose: I find Kurzban’s perspective compelling on this issue.  Likewise, I am not sure how to square the DeWall arguments with other observations about diabetes, age, and crime.  It also seems to me that the causal arrow could go from low self-control to both adult crime and adult-onset diabetes but I do not want to get off track.  This post is about evidence in the DeWall paper. Continue reading →