Social psychology textbook like colorful laboratory experiments that illustrate a theoretical point. As famous social psychologist Daryl Bem stated, he considered his experiments more illustrations of what could happen than empirical tests of what actually happens. Unfortunately, social psychology textbooks make it less obvious that the results of highlighted studies should not be generalized to real life.
Myers and Twenge (2019) tell the story of fishy smells.
In a laboratory experiment, exposure to a fishy smell caused people to be suspicious of each other and cooperate less—priming notions of a shady deal as “fishy” (Lee & Schwarz, 2012). All these effects occurred without the participants’ conscious awareness of the scent and its influence.
They don’t even mention some other fun facts about this study. To make sure that the effect is not just a mood effect induced by bad odors in general, fishy smells were contrasted with fart smells, and the effect seemed to be limited to fishy smells.
The article was published in the top journal for experimental social psychology (JPSP:ASC) and is relatively highly cited.
However, the studies reported in this article smell a bit fishy and should be consumed with a grain of salt and a lot of lemon. The problem is that all of the results are significant, which is highly unlikely unless studies have very high statistical power (Schimmack, 2012).
And it even works the other way around.
And making people think about suspicion, also makes them think about fish, in theory.
Suspicion also makes you be more sensitive to fishy smells.
Undergraduate students may not realize what the problem with these studies is. After all, they all worked out; that is they produced a p-value less than .05, which is supposed to ensure that no more than 1 out of 20 studies are a false positive result. As all of these studies are significant, it is extremely unlikely that all of them are false positives. So, we would have to infer that suspicion is related to fishy smells in our minds.
However, since 2012 it is clear that we have to draw another conclusion. The reason is that results in social psychology articles like this one smell fishy and suggest that the authors are telling us a fun story, but they are not telling us what really happened in their lab. It is extremely unlikely that the authors reported all of their studies and data analyses that they conducted. Instead they may have used a variety of so-called questionable research practices that increase the chances of reporting a significant result. Questionable research practices are also known as fishing for significance. These questionable research practices have the undesirable effect that they increase the type-I error rate. Thus, while the reported p-values are below .05, the risk of a false positive result is not and could be as high as 100%.
To demonstrate that researchers used questionable research practices, we can conduct a bias test. The most powerful bias test for small sets of studies is the Test of Insufficient Variance. When most p-values are just significant , p < .05 and p > .005, but always significant the results are not trustworthy because sampling error should produce more variability than we see.
The table lists the test statistics, converts the two-tailed p-values into z-scores and computes the variance of the z-scores. The variance is expected to be 1, but the actual variance is only 0.14. A chi-square test shows that this deviation is significant with p = .01. Thus, we have scientific evidence to claim that these results smell a bit fishy.
Unfortunately, these results are not the only fishy results in social psychology textbooks. Thus, students of social psychology should read textbook claims with a healthy dose of skepticism. They should also ask their professors to provide information about the replicability of textbook findings. Has this study been replicated in a preregistered replication attempt? Would you think you could replicate this result in your own lab? It is time to get rid of the fishy smell and let the fresh wind of open science clean up social psychology.
We can only hope that sooner than later, articles like this will sleep with the fishes.