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On the Importance of Avoiding Shortcuts in Applying Cognitive Models to Hierarchical Data

This post summarizes the content of an article that is in press for Behavior Research Methods. The preprint is available on PsyArXiv.

Psychological experiments often yield data that are hierarchically structured. A number of popular shortcut strategies in cognitive modeling do not properly accommodate this structure and can result in biased conclusions. First, we considered a modeling strategy that ignores the hierarchical data structure, missing random effects on the participant-level. Our theoretical analysis indicates that this biases statistical results towards the null hypothesis. Second, we considered a modeling strategy that takes a two-step approach by first obtaining participant-level estimates from a hierarchical cognitive model and subsequently using these estimates in a follow-up statistical test. Our theoretical analysis indicates that this biases statistical results towards the alternative hypothesis. Using a simulation study for a two-group experiment, we demonstrate that both strategies result in considerable statistical biases when parameter estimation is based on little data; only hierarchical models of the multilevel data lead to correct conclusions. These results are particularly relevant for applications of hierarchical Bayesian cognitive models in settings with limitations on the size of the available data sets, such as clinical studies.


Musings on Preregistration: The Case of the Facial Feedback Effect

tl;dr. In 2016, the results of a multi-lab preregistered replication effort cast doubt on the idea, motivated by the “facial feedback hypothesis”, that holding a pen with one’s teeth (instead of with one’s lips) makes cartoons appear more amusing. The effect’s progenitor, Dr. Strack, critiqued the replication effort and suggested that the presence of a camera (put in place to confirm that participants held the pen as instructed) makes the effect disappear. This conjecture has recently received some empirical support from a preregistered experiment (Noah et al., 2018, JPSP). Overall, Noah et al. present a balanced account of their findings and acknowledge the considerable statistical uncertainty that remains. It may be the case that the camera matters, although we personally would currently still bet against it. Methodologically, we emphasize how important it is that the confirmatory analysis adheres exactly to what has been preregistered. In order to prevent the temptation of subtle changes in the planned analysis and at the same time eliminate the file drawer effect, we recommend the Registered Report over plain preregistration, although preregistration alone is vastly superior to registering nothing at all.

This tale starts in 2012. Doyen and colleagues had just published a bombshell paper, “Behavioral Priming: It’s All in the Mind, but Whose Mind?” (open access). Here is the first part of their abstract:

“The perspective that behavior is often driven by unconscious determinants has become widespread in social psychology. Bargh, Chen, and Burrows’ (1996) famous study, in which participants unwittingly exposed to the stereotype of age walked slower when exiting the laboratory, was instrumental in defining this perspective. Here, we present two experiments aimed at replicating the original study. Despite the use of automated timing methods and a larger sample, our first experiment failed to show priming. Our second experiment was aimed at manipulating the beliefs of the experimenters: Half were led to think that participants would walk slower when primed congruently, and the other half was led to expect the opposite. Strikingly, we obtained a walking speed effect, but only when experimenters believed participants would indeed walk slower.” (Doyen et al., 2012)


Karl Pearson’s Worst Quotation?

The famous statistician Karl Pearson was also a eugenicist, so there are a great many hair-raising quotations to choose from. I nominate the following two for being particularly shocking (for more information see Wikipedia and the Guardian). Brace yourself, here is quotation number one:


“History shows me one way, and one way only, in which a high state of civilization has been produced, namely, the struggle of race with race, and the survival of the physically and mentally fitter race. If you want to know whether the lower races of man can evolve a higher type, I fear the only course is to leave them to fight it out among themselves, and even then the struggle for existence between individual and individual, between tribe and tribe, may not be supported by that physical selection due to a particular climate on which probably so much of the Aryan’s success depended.” (Karl Pearson, 1901, pp. 19-20)


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