The z-curve analysis of results in this journal shows (a) that many published results are based on studies with low to modest power, (b) selection for significance inflates effect size estimates and the discovery rate of reported results, and (c) there is no evidence that research practices have changed over the past decade. Readers should be careful when they interpret results and recognize that reported effect sizes are likely to overestimate real effect sizes, and that replication studies with the same sample size may fail to produce a significant result again. To avoid misleading inferences, I suggest using alpha = .005 as a criterion for valid rejections of the null-hypothesis. Using this criterion, the risk of a false positive result is below 2%. I also recommend computing a 99% confidence interval rather than the traditional 95% confidence interval for the interpretation of effect size estimates.
Given the low power of many studies, readers also need to avoid the fallacy to report non-significant results as evidence for the absence of an effect. With 50% power, the results can easily switch in a replication study so that a significant result becomes non-significant and a non-significant result becomes significant. However, selection for significance will make it more likely that significant results become non-significant than observing a change in the opposite direction.
The average power of studies in a heterogeneous journal like Frontiers of Psychology provides only circumstantial evidence for the evaluation of results. When other information is available (e.g., z-curve analysis of a discipline, author, or topic, it may be more appropriate to use this information).
Frontiers of Psychology was created in 2010 as a new online-only journal for psychology. It covers many different areas of psychology, although some areas have specialized Frontiers journals like Frontiers in Behavioral Neuroscience.
The business model of Frontiers journals relies on publishing fees of authors, while published articles are freely available to readers.
The number of articles in Frontiers of Psychology has increased quickly from 131 articles in 2010 to 8,072 articles in 2022 (source Web of Science). With over 8,000 published articles Frontiers of Psychology is an important outlet for psychological researchers to publish their work. Many specialized, print-journals publish fewer than 100 articles a year. Thus, Frontiers of Psychology offers a broad and large sample of psychological research that is equivalent to a composite of 80 or more specialized journals.
Another advantage of Frontiers of Psychology is that it has a relatively low rejection rate compared to specialized journals that have limited journal space. While high rejection rates may allow journals to prioritize exceptionally good research, articles published in Frontiers of Psychology are more likely to reflect the common research practices of psychologists.
To examine the replicability of research published in Frontiers of Psychology, I downloaded all published articles as PDF files, converted PDF files to text files, and extracted test-statistics (F, t, and z-tests) from published articles. Although this method does not capture all published results, there is no a priori reason that results reported in this format differ from other results. More importantly, changes in research practices such as higher power due to larger samples would be reflected in all statistical tests.
As Frontiers of Psychology only started shortly before the replication crisis in psychology increased awareness about the problem of low statistical power and selection for significance (publication bias), I was not able to examine replicability before 2011. I also found little evidence of changes in the years from 2010 to 2015. Therefore, I use this time period as the starting point and benchmark for future years.
Figure 1 shows a z-curve plot of results published from 2010 to 2014. All test-statistics are converted into z-scores. Z-scores greater than 1.96 (the solid red line) are statistically significant at alpha = .05 (two-sided) and typically used to claim a discovery (rejection of the null-hypothesis). Sometimes even z-scores between 1.65 (the dotted red line) and 1.96 are used to reject the null-hypothesis either as a one-sided test or as marginal significance. Using alpha = .05, the plot shows 71% significant results, which is called the observed discovery rate (ODR).
Visual inspection of the plot shows a peak of the distribution right at the significance criterion. It also shows that z-scores drop sharply on the left side of the peak when the results do not reach the criterion for significance. This wonky distribution cannot be explained with sampling error. Rather it shows a selective bias to publish significant results by means of questionable practices such as not reporting failed replication studies or inflating effect sizes by means of statistical tricks. To quantify the amount of selection bias, z-curve fits a model to the distribution of significant results and estimates the distribution of non-significant (i.e., the grey curve in the range of non-significant results). The discrepancy between the observed distribution and the expected distribution shows the file-drawer of missing non-significant results. Z-curve estimates that the reported significant results are only 31% of the estimated distribution. This is called the expected discovery rate (EDR). Thus, there are more than twice as many significant results as the statistical power of studies justifies (71% vs. 31%). Confidence intervals around these estimates show that the discrepancy is not just due to chance, but active selection for significance.
Using a formula developed by Soric (1989), it is possible to estimate the false discovery risk (FDR). That is, the probability that a significant result was obtained without a real effect (a type-I error). The estimated FDR is 12%. This may not be alarming, but the risk varies as a function of the strength of evidence (the magnitude of the z-score). Z-scores that correspond to p-values close to p =.05 have a higher false positive risk and large z-scores have a smaller false positive risk. Moreover, even true results are unlikely to replicate when significance was obtained with inflated effect sizes. The most optimistic estimate of replicability is the expected replication rate (ERR) of 69%. This estimate, however, assumes that a study can be replicated exactly, including the same sample size. Actual replication rates are often lower than the ERR and tend to fall between the EDR and ERR. Thus, the predicted replication rate is around 50%. This is slightly higher than the replication rate in the Open Science Collaboration replication of 100 studies which was 37%.
Figure 2 examines how things have changed in the next five years.
The observed discovery rate decreased slightly, but statistically significantly, from 71% to 66%. This shows that researchers reported more non-significant results. The expected discovery rate increased from 31% to 40%, but the overlapping confidence intervals imply that this is not a statistically significant increase at the alpha = .01 level. (if two 95%CI do not overlap, the difference is significant at around alpha = .01). Although smaller, the difference between the ODR of 60% and the EDR of 40% is statistically significant and shows that selection for significance continues. The ERR estimate did not change, indicating that significant results are not obtained with more power. Overall, these results show only modest improvements, suggesting that most researchers who publish in Frontiers in Psychology continue to conduct research in the same way as they did before, despite ample discussions about the need for methodological reforms such as a priori power analysis and reporting of non-significant results.
The results for 2020 show that the increase in the EDR was a statistical fluke rather than a trend. The EDR returned to the level of 2010-2015 (29% vs. 31), but the ODR remained lower than in the beginning, showing slightly more reporting of non-significant results. The size of the file drawer remains large with an ODR of 66% and an EDR of 72%.
The EDR results for 2021 look again better, but the difference to 2020 is not statistically significant. Moreover, the results in 2022 show a lower EDR that matches the EDR in the beginning.
Overall, these results show that results published in Frontiers in Psychology are selected for significance. While the observed discovery rate is in the upper 60%s, the expected discovery rate is around 35%. Thus, the ODR is nearly twice the rate of the power of studies to produce these results. Most concerning is that a decade of meta-psychological discussions about research practices has not produced any notable changes in the amount of selection bias or the power of studies to produce replicable results.
How should readers of Frontiers in Psychology articles deal with this evidence that some published results were obtained with low power and inflated effect sizes that will not replicate? One solution is to retrospectively change the significance criterion. Comparisons of the evidence in original studies and replication outcomes suggest that studies with a p-value below .005 tend to replicate at a rate of 80%, whereas studies with just significant p-values (.050 to .005) replicate at a much lower rate (Schimmack, 2022). Demanding stronger evidence also reduces the false positive risk. This is illustrated in the last figure that uses results from all years, given the lack of any time trend.
In the Figure the red solid line moved to z = 2.8; the value that corresponds to p = .005, two-sided. Using this more stringent criterion for significance, only 45% of the z-scores are significant. Another 25% were significant with alpha = .05, but are no longer significant with alpha = .005. As power decreases when alpha is set to more stringent, lower, levels, the EDR is also reduced to only 21%. Thus, there is still selection for significance. However, the more effective significance filter also selects for more studies with high power and the ERR remains at 72%, even with alpha = .005 for the replication study. If the replication study used the traditional alpha level of .05, the ERR would be even higher, which explains the finding that the actual replication rate for studies with p < .005 is about 80%.
The lower alpha also reduces the risk of false positive results, even though the EDR is reduced. The FDR is only 2%. Thus, the null-hypothesis is unlikely to be true. The caveat is that the standard null-hypothesis in psychology is the nil-hypothesis and that the population effect size might be too small to be of practical significance. Thus, readers who interpret results with p-values below .005 should also evaluate the confidence interval around the reported effect size, using the more conservative 99% confidence interval that correspondence to alpha = .005 rather than the traditional 95% confidence interval. In many cases, this confidence interval is likely to be wide and provide insufficient information about the strength of an effect.
Since 2011, it is an open secret that many published results in psychology journals do not replicate. The replicability of published results is particularly low in social psychology (Open Science Collaboration, 2015).
A key reason for low replicability is that researchers are rewarded for publishing as many articles as possible without concerns about the replicability of the published findings. This incentive structure is maintained by journal editors, review panels of granting agencies, and hiring and promotion committees at universities.
To change the incentive structure, I developed the Replicability Index, a blog that critically examined the replicability, credibility, and integrity of psychological science. In 2016, I created the first replicability rankings of psychology departments (Schimmack, 2016). Based on scientific criticisms of these methods, I have improved the selection process of articles to be used in departmental reviews.
1. I am using Web of Science to obtain lists of published articles from individual authors (Schimmack, 2022). This method minimizes the chance that articles that do not belong to an author are included in a replicability analysis. It also allows me to classify researchers into areas based on the frequency of publications in specialized journals. Currently, I cannot evaluate neuroscience research. So, the rankings are limited to cognitive, social, developmental, clinical, and applied psychologists.
2. I am using department’s websites to identify researchers that belong to the psychology department. This eliminates articles that are from other departments.
3. I am only using tenured, active professors. This eliminates emeritus professors from the evaluation of departments. I am not including assistant professors because the published results might negatively impact their chances to get tenure. Another reason is that they often do not have enough publications at their current university to produce meaningful results.
Like all empirical research, the present results rely on a number of assumptions and have some limitations. The main limitations are that (a) only results that were found in an automatic search are included (b) only results published in 120 journals are included (see list of journals) (c) published significant results (p < .05) may not be a representative sample of all significant results (d) point estimates are imprecise and can vary based on sampling error alone.
These limitations do not invalidate the results. Large difference in replicability estimates are likely to predict real differences in success rates of actual replication studies (Schimmack, 2022).
New York University
I used the department website to find core members of the psychology department. I found 13 professors and 6 associate professors. Figure 1 shows the z-curve for all 12,365 tests statistics in articles published by these 19 faculty members. I use the Figure to explain how a z-curve analysis provides information about replicability and other useful meta-statistics.
1. All test-statistics are converted into absolute z-scores as a common metric of the strength of evidence (effect size over sampling error) against the null-hypothesis (typically H0 = no effect). A z-curve plot is a histogram of absolute z-scores in the range from 0 to 6. The 1,239 (~ 10%) of z-scores greater than 6 are not shown because z-scores of this magnitude are extremely unlikely to occur when the null-hypothesis is true (particle physics uses z > 5 for significance). Although they are not shown, they are included in the meta-statistics.
2. Visual inspection of the histogram shows a steep drop in frequencies at z = 1.96 (dashed blue/red line) that corresponds to the standard criterion for statistical significance, p = .05 (two-tailed). This shows that published results are selected for significance. The dashed red/white line shows significance for p < .10, which is often used for marginal significance. There is another drop around this level of significance.
3. To quantify the amount of selection bias, z-curve fits a statistical model to the distribution of statistically significant results (z > 1.96). The grey curve shows the predicted values for the observed significant results and the unobserved non-significant results. The full grey curve is not shown to present a clear picture of the observed distribution. The statistically significant results (including z > 6) make up 20% of the total area under the grey curve. This is called the expected discovery rate because the results provide an estimate of the percentage of significant results that researchers actually obtain in their statistical analyses. In comparison, the percentage of significant results (including z > 6) includes 70% of the published results. This percentage is called the observed discovery rate, which is the rate of significant results in published journal articles. The difference between a 70% ODR and a 20% EDR provides an estimate of the extent of selection for significance. The difference of 50 percentage points is large. The upper level of the 95% confidence interval for the EDR is 28%. Thus, the discrepancy is not just random. To put this result in context, it is possible to compare it to the average for 120 psychology journals in 2010 (Schimmack, 2022). The ODR is similar (70 vs. 72%), but the EDR is a bit lower (20% vs. 28%), although the difference might be largely due to chance.
4. The EDR can be used to estimate the risk that published results are false positives (i.e., a statistically significant result when H0 is true), using Soric’s (1989) formula for the maximum false discovery rate. An EDR of 20% implies that no more than 20% of the significant results are false positives, however the upper limit of the 95%CI of the EDR, 28%, allows for 36% false positive results. Most readers are likely to agree that this is an unacceptably high risk that published results are false positives. One solution to this problem is to lower the conventional criterion for statistical significance (Benjamin et al., 2017). Figure 2 shows that alpha = .005 reduces the point estimate of the FDR to 3% with an upper limit of the 95% confidence interval of XX%. Thus, without any further information readers could use this criterion to interpret results published by NYU faculty members.
5. The estimated replication rate is based on the mean power of significant studies (Brunner & Schimmack, 2020). Under ideal condition, mean power is a predictor of the success rate in exact replication studies with the same sample sizes as the original studies. However, as NYU professor van Bavel pointed out in an article, replication studies are never exact, especially in social psychology (van Bavel et al., 2016). This implies that actual replication studies have a lower probability of producing a significant result, especially if selection for significance is large. In the worst case scenario, replication studies are not more powerful than original studies before selection for significance. Thus, the EDR provides an estimate of the worst possible success rate in actual replication studies. In the absence of further information, I have proposed to use the average of the EDR and ERR as a predictor of actual replication outcomes. With an ERR of 62% and an EDR of 20%, this implies an actual replication prediction of 41%. This is close to the actual replication rate in the Open Science Reproducibility Project (Open Science Collaboration, 2015). The prediction for results published in 120 journals in 2010 was (ERR = 67% + ERR = 28%)/ 2 = 48%. This suggests that results published by NYU faculty are slightly less replicable than the average result published in psychology journals, but the difference is relatively small and might be mostly due to chance.
6. There are two reasons for low replication rates in psychology. One possibility is that psychologists test many false hypotheses (i.e., H0 is true) and many false positive results are published. False positive results have a very low chance of replicating in actual replication studies (i.e. 5% when .05 is used to reject H0), and will lower the rate of actual replications a lot. Alternative, it is possible that psychologists tests true hypotheses (H0 is false), but with low statistical power (Cohen, 1961). It is difficult to distinguish between these two explanations because the actual rate of false positive results is unknown. However, it is possible to estimate the typical power of true hypotheses tests using Soric’s FDR. If 20% of the significant results are false positives, the power of the 80% true positives has to be (.62 – .2*.05)/.8 = 76%. This would be close to Cohen’s recommended level of 80%, but with a high level of false positive results. Alternatively, the null-hypothesis may never be really true. In this case, the ERR is an estimate of the average power to get a significant result for a true hypothesis. Thus, power is estimated to be between 62% and 76%. The main problem is that this is an average and that many studies have less power. This can be seen in Figure 1 by examining the local power estimates for different levels of z-scores. For z-scores between 2 and 2.5, the ERR is only 47%. Thus, many studies are underpowered and have a low probability of a successful replication with the same sample size even if they showed a true effect.
The results in Figure 1 provide highly aggregated information about replicability of research published by NYU faculty. The following analyses examine potential moderators. First, I examined social and cognitive research. Other areas were too small to be analyzed individually.
The z-curve for the 11 social psychologists was similar to the z-curve in Figure 1 because they provided more test statistics and had a stronger influence on the overall result.
The z-curve for the 6 cognitive psychologists looks different. The EDR and ERR are higher for cognitive psychology, and the 95%CI for social and cognitive psychology do not overlap. This suggests systematic differences between the two fields. These results are consistent with other comparisons of the two fields, including actual replication outcomes (OSC, 2015). With an EDR of 44%, the false discovery risk for cognitive psychology is only 7% with an upper limit of the 95%CI at 12%. This suggests that the conventional criterion of .05 does keep the false positive risk at a reasonably low level or that an adjustment to alpha = .01 is sufficient. In sum, the results show that results published by cognitive researchers at NYU are more replicable than those published by social psychologists.
Since 2015 research practices in some areas of psychology, especially social psychology, have changed to increase replicability. This would imply that research by younger researchers is more replicable than research by more senior researchers that have more publications before 2015. A generation effect would also imply that a department’s replicability increases when older faculty members retire. On the other hand, associate professors are relatively young and likely to influence the reputation of a department for a long time.
The figure above shows that most test statistics come from the (k = 13) professors. As a result, the z-curve looks similar to the z-curve for all test values in Figure 1. The results for the 6 associate professors (below) are more interesting. Although five of the six associate professors are in the social area, the z-curve results show a higher EDR and less selection bias than the plot for all social psychologists. This suggests that the department will improve when full professors in social psychology retire.
The table below shows the meta-statistics of all 19 faculty members. You can see the z-curve for each faculty member by clicking on their name.
Over the past two decades, social psychological research on prejudice has been dominated by the implicit cognition paradigm (Meissner, Grigutsch, Koranyi, Müller, & Rothermund, 2019). This paradigm is based on the assumption that many individuals of the majority group (e.g., White US Americans) have an automatic tendency to discriminate against members of a stigmatized minority group (e.g., African Americans). It is assumed that this tendency is difficult to control because many people are unaware of their prejudices.
The implicit cognition paradigm also assumes that biases vary across individuals of the majority group. The most widely used measure of individual differences in implicit biases is the race Implicit Association Test (rIAT; Greenwald, McGhee, & Schwartz, 1998). Like any other measure of individual differences, the race IAT has to meet psychometric criteria to be a useful measure of implicit bias. Unfortunately, the race IAT has been used in hundreds of studies before its psychometric properties were properly evaluated in a program of validation research (Schimmack, 2021a, 2021b).
Meta-analytic reviews of the literature suggest that the race IAT is not as useful for the study of prejudice as it was promised to be (Greenwald et al., 1998). For example, Meissner et al. (2019) concluded that “the predictive value for behavioral criteria is weak and their incremental validity over and above self-report measures is negligible” (p. 1).
In response to criticism of the race IAT, Greenwald, Banaji, and Nosek (2015) argued that “statistically small effects of the implicit association test can have societally large effects” (p. 553). At the same time, Greenwald (1975) warned psychologists that they may be prejudiced against the null-hypothesis. To avoid this bias, he proposed that researchers should define a priori a range of effect sizes that are close enough to zero to decide in favor of the null-hypothesis. Unfortunately, Greenwald did not follow his own advice and a clear criterion for a small, but practically significant amount of predictive validity is lacking. This is a problem because estimates have decreased over time from r = .39 (McConnell & Leibold, 2001), to r = .24 in 2009 ( Greenwald, Poehlman, Uhlmann, and Banaji, 2009), to r = .148 in 2013 (Oswald, Mitchell, Blanton, Jaccard, & Tetlock (2013), and r = .097 in 2019 (Greenwald & Lai, 2020; Kurdi et al., 2019). Without a clear criterion value, it is not clear how this new estimate of predictive validity should be interpreted. Does it still provide evidence for a small, but practically significant effect, or does it provide evidence for the null-hypothesis (Greenwald, 1975)?
Measures are not Causes
To justify the interpretation of a correlation of r = .1 as small but important, it is important to revisit Greenwald et al.’s (2015) arguments for this claim. Greenwald et al. (2015) interpret this correlation as evidence for an effect of the race IAT on behavior. For example, they write “small effects can produce substantial discriminatory impact also by cumulating over repeated occurrences to the same person” (p. 558). The problem with this causal interpretation of a correlation between two measures is that scores on the race IAT have no influence on individuals’ behavior. This simple fact is illustrated in Figure 1. Figure 1 is a causal model that assumes the race IAT reflects valid variance in prejudice and prejudice influences actual behaviors (e.g., not voting for a Black political candidate). The model makes it clear that the correlation between scores on the race IAT (i.e., the iat box) and scores on a behavioral measures (i.e., the crit box) do not have a causal link (i.e., no path leads from the iat box to the crit box). Rather, the two measured variables are correlated because they both reflect the effect of a third variable. That is, prejudice influences race IAT scores and prejudice influences the variance in the criterion variable.
There is general consensus among social scientists that prejudice is a problem and that individual differences in prejudice have important consequences for individuals and society. The effect size of prejudice on a single behavior has not been clearly examined, but to the extent that race IAT scores are not perfectly valid measures of prejudice, the simple correlation of r = .1 is a lower limit of the effect size. Schimmack (2021) estimated that no more than 20% of the variance in race IAT scores is valid variance. With this validity coefficient, a correlation of r = .1 implies an effect of prejudice on actual behaviors of .1 / sqrt(.2) = .22.
Greenwald et al. (2015) correctly point out that effect sizes of this magnitude, r ~ .2, can have practical, real-world implications. The real question, however, is whether predictive validity of .1 justifies the use of the race IAT as a measure of prejudice. This question has to be evaluated in a comparison of predictive validity for the race IAT with other measures of prejudice. Thus, the real question is whether the race IAT has sufficient incremental predictive validity over other measures of prejudice. However, this question has been largely ignored in the debate about the utility of the race IAT (Greenwald & Lai, 2020; Greenwald et al., 2015; Oswald et al., 2013).
Kurdi et al. (2019) discuss incremental predictive validity, but this discussion is not limited to the race IAT and makes the mistake to correct for random measurement error. As a result, the incremental predictive validity for IATs of b = .14 is a hypothetical estimate for IATs that are perfectly reliable. However, it is well-known that IATs are far from perfectly reliable. Thus, this estimate overestimates the incremental predictive validity. Using Kurdi et al.’s data and limiting the analysis to studies with the race IAT, I estimated incremental predictive validity to be b = .08, 95%CI = .04 to .12. It is difficult to argue that this a practically significant amount of incremental predictive validity. At the very least, it does not justify the reliance on the race IAT as the only measure of prejudice or the claim that the race IAT is a superior measure of prejudice (Greenwald et al., 2009).
The meta-analytic estimate of b = .1 has to be interpreted in the context of evidence of substantial heterogeneity across studies (Kurdi et al., 2019). Kurdi et al. (2019) suggest that “it may be more appropriate to ask under what conditions the two [race IAT scores and criterion variables] are more or less highly correlated” (p. 575). However, little progress has been made in uncovering moderators of predictive validity. One possible explanation for this is that previous meta-analysis may have overlooked one important source of variation in effect sizes, namely publication bias. Traditional meta-analyses may be unable to reveal publication bias because they include many articles and outcome measures that did not focus on predictive validity. For example, Kurdi’s meta-analysis included a study by Luo, Li, Ma, Zhang, Rao, and Han (2015). The main focus of this study was to examine the potential moderating influence of oxytocin on neurological responses to pain expressions of Asian and White faces. Like many neurological studies, the sample size was small (N = 32), but the study reported 16 brain measures. For the meta-analysis, correlations were computed across N = 16 participants separately for two experimental conditions. Thus, this study provided as many effect sizes as it had participants. Evidently, power to obtain a significant result with N = 16 and r = .1 is extremely low, and adding these 32 effect sizes to the meta-analysis merely introduced noise. This may undermine the validity of meta-analytic results ((Sharpe, 1997). To address this concern, I conducted a new meta-analysis that differs from the traditional meta-analyses. Rather than coding as many effects from as many studies as possible, I only include focal hypothesis tests from studies that aimed to investigate predictive validity. I call this a focused meta-analysis.
Focused Meta-Analysis of Predictive Validity
Coding of Studies
I relied on Kurdi et al.’s meta-analysis to find articles. I selected only published articles that used the race IAT (k = 96). The main purpose of including unpublished studies is often to correct for publication bias (Kurdi et al., 2019). However, it is unlikely that only 14 (8%) studies that were conducted remained unpublished. Thus, the unpublished studies are not representative and may distort effect size estimates.
Coding of articles in terms of outcome measures that reflect discrimination yielded 60 studies in 45 articles. I examined whether this selection of studies influenced the results by limiting a meta-analysis with Kurdi et al.’s coding of studies to these 60 articles. The weighted average effect size was larger than the reported effect size, a = .167, se = .022, 95%CI = .121 to .212. Thus, Kurdi et al.’s inclusion of a wide range of studies with questionable criterion variables diluted the effect size estimate. However, there remained substantial variability around this effect size estimate using Kurdi et al.’s data, I2 = 55.43%.
The focused coding produced one effect-size per study. It is therefore not necessary to model a nested structure of effect sizes and I used the widely used metafor package to analyze the data (Viechtbauer, 2010). The intercept-only model produced a similar estimate to the results for Kurdi et al.’s coding scheme, a = .201, se = .020, 95%CI = .171 to .249. Thus, focal coding does seem to produce the same effect size estimate as traditional coding. There was also a similar amount of heterogeneity in the effect sizes, I2 = 50.80%.
However, results for publication bias differed. Whereas Kurdi et al.’s coding shows no evidence of publication bias, focused coding produced a significant relationship emerged, b = 1.83, se = .41, z = 4.54, 95%CI = 1.03 to 2.64. The intercept was no longer significant, a = .014, se = .0462, z = 0.31, 95%CI = -.077 to 95%CI = .105. This would imply that the race IAT has no incremental predictive validity. Adding sampling error as a predictor reduced heterogeneity from I2 = 50.80% to 37.71%. Thus, some portion of the heterogeneity is explained by publication bias.
Stanley (2017) recommends to accept the null-hypothesis when the intercept in the previous model is not significant. However, a better criterion is to compare this model to other models. The most widely used alternative model regresses effect sizes on the squared sampling error (Stanley, 2017). This model explained more of the heterogeneity in effect sizes as reflected in a reduction of unexplained heterogeneity from 50.80% to 23.86%. The intercept for this model was significant, a = .113, se = .0232, z = 4.86, 95%CI = .067 to .158.
Figure 2 shows the effect sizes as a function of sampling error and the regression lines for the three models.
Inspection of Figure 1 provides further evidence that the squared-SE model. The red line (squared sampling error) fits the data better than the blue line (sampling error) model. In particular for large samples, PET underestimates effect sizes.
The significant relationship between sample size (sampling error) and effect sizes implies that large effects in small studies cannot be interpreted at face value. For example, the most highly cited study of predictive validity had only a sample size of N = 42 participants (McConnell & Leibold, 2001). The squared-sampling-error model predicts an effect size estimate of r = .30, which is close to the observed correlation of r = .39 in that study.
In sum, a focal meta-analysis replicates Kurdi et al.’s (2019) main finding that the average predictive validity of the race IAT is small, r ~ .1. However, the focal meta-analysis also produced a new finding. Whereas the initial meta-analysis suggested that effect sizes are highly variable, the new meta-analysis suggests that a large portion of this variability is explained by publication bias.
I explored several potential moderator variables, namely (a) number of citations, (b) year of publication, (c) whether IAT effects were direct or moderator effects, (d) whether the correlation coefficient was reported or computed based on test statistics, and (e) whether the criterion was an actual behavior or an attitude measure. The only statistically significant result was a weaker correlation in studies that predicted a moderating effect of the race IAT, b = -.11, se = .05, z = 2.28, p = .032. However, the effect would not be significant after correction for multiple comparison and heterogeneity remained virtually unchanged, I2 = 27.15%.
During the coding of the studies, the article “Ironic effects of racial bias during interracial interactions” stood out because it reported a counter-intuitive result. in this study, Black confederates rated White participants with higher (pro-White) race IAT scores as friendlier. However, other studies find the opposite effect (e.g., McConnell & Leibold, 2001). If the ironic result was reported because it was statistically significant, it would be a selection effect that is not captured by the regression models and it would produce unexplained heterogeneity. I therefore also tested a model that excluded all negative effect. As bias is introduced by this selection, the model is not a test of publication bias, but it may be better able to correct for publication bias. The effect size estimate was very similar, a = .133, se = .017, 95%CI = .010 to .166. However, heterogeneity was reduced to 0%, suggesting that selection for significance fully explains heterogeneity in effect sizes.
In conclusion, moderator analysis did not find any meaningful moderators and heterogeneity was fully explained by publication bias, including publishing counterintuitive findings that suggest less discrimination by individuals with more prejudice. The finding that publication bias explains most of the variance is extremely important because Kurdi et al. (2019) suggested that heterogeneity is large and meaningful, which would suggest that higher predictive validity could be found in future studies. In contrast, the current results suggest that correlations greater than .2 in previous studies were largely due to selection for significance with small samples, which also explains unrealistically high correlations in neuroscience studies with the race IAT (cf. Schimmack, 2021b).
Predictive Validity of Self-Ratings
The predictive validity of self-ratings is important for several reasons. First, it provides a comparison standard for the predictive validity of the race IAT. For example, Greenwald et al. (2009) emphasized that predictive validity for the race IAT was higher than for self-reports. However, Kurdi et al.’s (2019) meta-analysis found the opposite. Another reason to examine the predictive validity of explicit measures is that implicit and explicit measures of racial attitudes are correlated with each other. Thus, it is important to establish the predictive validity of self-ratings to estimate the incremental predictive validity of the race IAT.
Figure 2 shows the results. The sampling-error model shows a non-zero effect size, but sampling error is large, and the confidence interval includes zero, a = .121, se = .117, 95%CI = -.107 to .350. Effect sizes are also extremely heterogeneous, I2 = 62.37%. The intercept for the squared-sampling-error model is significant, a = .176, se = .071, 95%CI = .036 to .316, but the model does not explain more of the heterogeneity in effect sizes than the squared-sampling-error model, I2 = 63.33%. To remain comparability, I use the squared-sampling error estimate. This confirms Kurdi et al.’s finding that self-ratings have slightly higher predictive validity, but the confidence intervals overlap. For any practical purposes, predictive validity of the race IAT and self-reports is similar. Repeating the moderator analyses that were conducted with the race IAT revealed no notable moderators.
Only 21 of the 60 studies reported information about the correlation between the race IAT and self-report measures. There was no indication of publication bias, and the effect size estimates of the three models converge on an estimate of r ~ .2 (Figure 3). Fortunately, this result can be compared with estimates from large internet studies (Axt, 2017) and a meta-analysis of implicit-explicit correlations (Hofmann et al., 2005). These estimates are a bit higher, r ~ .25. Thus, using an estimate of r = .2 is conservative for a test of the incremental predictive validity of the race IAT.
Incremental Predictive Validity
It is straightforward to estimate the incremental predictive validity of the race IAT and self-reports on the basis of the correlations between race IAT, self-ratings, and criterion variables. However, it is a bit more difficult to provide confidence intervals around these estimates. I used a simulated dataset with missing values to reproduce the correlations and sampling error of the meta-analysis. I then regressed, the criterion on the implicit and explicit variable. The incremental predictive validity for the race IAT was b = .07, se = .02, 95%CI = .03 to .12. This finding implies that the race IAT on average explains less than 1% unique variance in prejudice behavior. The incremental predictive validity of the explicit measure was b = .165, se = .03, 95%CI = .11 to .23. This finding suggests that explicit measures explain between 1 and 4 percent of the variance in prejudice behaviors.
Assuming that there is no shared method variance between implicit and explicit measures and criterion variables and that implicit and explicit measures reflect a common construct, prejudice, it is possible to fit a latent variable model to the correlations among the three indicators of prejudice (Schimmack, 2021). Figure 4 shows the model and the parameter estimates.
According to this model, prejudice has a moderate effect on behavior, b = .307, se = .043. This is consistent with general findings about effects of personality traits on behavior (Epstein, 1973; Funder & Ozer, 1983). The loading of the explicit variable on the prejudice factor implies that .582^2 = 34% of the variance in self-ratings of prejudice is valid variance. The loading of the implicit variable on the prejudice factor implies that .353^2 = 12% of the variance in race IAT scores is valid variance. Notably, similar estimates were obtained with structural equation models of data that are not included in this meta-analysis (Schimmack, 2021). Using data from Cunningham et al., (2001) I estimated .43^2 = 18% valid variance. Using Bar-Anan and Vianello (2018), I estimated .44^2 = 19% valid variance. Using data from Axt, I found .44^2 = 19% valid variance, but 8% of the variance could be attributed to group differences between African American and White participants. Thus, the present meta-analytic results are consistent with the conclusion that no more than 20% of the variance in race IAT scores reflects actual prejudice that can influence behavior.
In sum, incremental predictive validity of the race IAT is low for two reasons. First, prejudice has only modest effects on actual behavior in a specific situation. Second, only a small portion of the variance in race IAT scores is valid.
In the 1990s, social psychologists embraced the idea that behavior is often influenced by processes that occur without conscious awareness. This assumption triggered the implicit revolution (Greenwald & Banaji, 2017). The implicit paradigm provided a simple explanation for low correlations between self-ratings of prejudice and implicit measures of prejudice, r ~ .2. Accordingly, many people are not aware how prejudice their unconscious is. The Implicit Association Test seemed to support this view because participants showed more prejudice on the IAT than on self-report measures. First studies of predictive validity also seemed to support this new model of prejudice (McConnell & Leibold, 2001), and the first meta-analysis suggested that implicit bias has a stronger influence on behavior than self-reported attitudes (Greenwald, Poehlman, Uhlmann, & Banaji, 2009, p. 17).
However, the following decade produced many findings that require a reevaluation of the evidence. Greenwald et al. (2009) published the largest test (N = 1057) of predictive validity. This study examined the ability of the race IAT to predict racial bias in the 2008 US presidential election. Although the race IAT was correlated with voting for McCain versus Obama, incremental predictive validity was close to zero and no longer significant when explicit measures were included in the regression model. Then subsequent meta-analyses produced lower estimates of predictive validity and it is no longer clear that predictive validity, especially incremental predictive validity, is high enough to reject the null-hypothesis. Although incremental predictive validity may vary across conditions, no conditions have been identified that show practically significant incremental predictive validity. Unfortunately, IAT proponents continue to make misleading statements based on single studies with small samples. For example, Kurdi et al. claimed that “effect sizes tend to be relatively large in studies on physician–patient interactions” (p. 583). However, this claim was based on a study with just 15 physicians, which makes it impossible to obtain precise effect size estimates about implicit bias effects for physicians.
Beyond Nil-Hypothesis Testing
Just like psychology in general, meta-analyses also suffer from the confusion of nil-hypothesis testing and null-hypothesis testing. The nil-hypothesis is the hypothesis that an effect size is exactly zero. Many methodologists have pointed out that it is rather silly to take the nil-hypothesis at face value because the true effect size is rarely zero (Cohen, 1994). The more important question is whether an effect size is sufficiently different from zero to be theoretically and practically meaningful. As pointed out by Greenwald (1975), effect size estimation has to be complemented with theoretical predictions about effect sizes. However, research on predictive validity of the race IAT lacks clear criteria to evaluate effect size estimates.
As noted in the introduction, there is agreement about the practical importance of statistically small effects for the prediction of discrimination and other prejudiced behaviors. The contentious question is whether the race IAT is a useful measure of dispositions to act prejudiced. Viewed from this perspective, focus on the race IAT is myopic. The real challenge is to develop and validate measures of prejudice. IAT proponents have often dismissed self-reports as invalid, but the actual evidence shows that self-reports have some validity that is at least equal to the validity of the race IAT. Moreover, even distinct self-report measures like the feeling thermometer and the symbolic racism have incremental predictive validity. Thus, prejudice researchers should use a multi-method approach. At present it is not clear that the race IAT can improve the measurement of prejudice (Greenwald et al., 2009; Schimmack, 2021a).
This article introduced a new type of meta-analysis. Rather than trying to find as many vaguely related studies and to code as many outcomes as possible, focused meta-analysis is limited to the main test of the key hypothesis. This approach has several advantages. First, the classic approach creates a large amount of heterogeneity that is unique to a few studies. This noise makes it harder to find real moderators. Second, the inclusion of vaguely related studies may dilute effect sizes. Third, the inclusion of non-focal studies may mask evidence of publication bias that is virtually present in all literatures. Finally, focal meta-analysis are much easier to do and can produce results much faster than the laborious meta-analyses that psychologists are used to. Even when classic meta-analysis exist, they often ignore publication bias. Thus, an important task for the future is to complement existing meta-analysis with focal meta-analysis to ensure that published effect sizes estimates are not diluted by irrelevant studies and not inflated by publication bias.
Enthusiasm about implicit biases has led to interventions that aim to reduce implicit biases. This focus on implicit biases in the real world needs to be reevaluated. First, there is no evidence that prejudice typically operates outside of awareness (Schimmack, 2021a). Second, individual differences in prejudice have only a modest impact on actual behaviors and are difficult to change. Not surprisingly, interventions that focus on implicit bias are not very infective. Rather than focusing on changing individuals’ dispositions, interventions may be more effective by changing situations. In this regard, the focus on internal factors is rather different from the general focus in social psychology on situational factors (Funder & Ozer, 1983). In recent years, it has become apparent that prejudice is often systemic. For example, police training may have a much stronger influence on racial disparities in fatal use of force than individual differences in prejudice of individual officers (Andersen, Di Nota, Boychuk, Schimmack, & Collins, 2021).
The present meta-analysis of the race IAT provides further support for Meissner et al.’s (2019) conclusion that IATs “predictive value for behavioral criteria is weak and their incremental validity over and above self-report measures is negligible” (p. 1). The present meta-analysis provides a quantitative estimate of b = .07. Although researchers can disagree about the importance of small effect sizes, I agree with Meissner that the gains from adding a race IAT to the measurement of prejudice is negligible. Rather than looking for specific contexts in which the race IAT has higher predictive validity, researchers should use a multi-method approach to measure prejudice. The race IAT may be included to further explore its validity, but there is no reason to rely on the race IAT as the single most important measure of individual differences in prejudice.
Funder, D.C., & Ozer, D.J. (1983). Behavior as a function of the situation. Journal of Personality and Social Psychology, 44, 107–112.
Kurdi, B., Seitchik, A. E., Axt, J. R., Carroll, T. J., Karapetyan, A., Kaushik, N., et al. (2019). Relationship between the implicit association test and intergroup behavior: a meta-analysis. American Psychologist. 74, 569–586. doi: 10.1037/amp0000364
After I posted this post, I learned about a published meta-analysis and new studies of incidental anchoring by David Shanks and colleagues that came to the same conclusion (Shanks et al., 2020).
“The most expensive car in the world costs $5 million. How much does a new BMW 530i cost?”
According to anchoring theory, information about the most expensive car can lead to higher estimates for the cost of a BMW. Anchoring effects have been demonstrated in many credible studies since the 1970s (Kahneman & Tversky, 1973).
A more controversial claim is that anchoring effects even occur when the numbers are unrelated to the question and presented incidentally (Criticher & Gilovich, 2008). In one study, participants saw a picture of a football player and were asked to guess how likely it is that the player will sack the football player in the next game. The player’s number on jersey was manipulated to be 54 or 94. The study produced a statistically significant result suggesting that a higher number makes people give higher likelihood judgments. This study started a small literature on incidental anchoring effects. A variation on this them are studies that presented numbers so briefly on a computer screen that most participants did not actually see the numbers. This is called subliminal priming. Allegedly, subliminal priming also produced anchoring effects (Mussweiler & Englich (2005).
Since 2011, many psychologists are skeptical whether statistically significant results in published articles can be trusted. The reason is that researchers only published results that supported their theoretical claims even when the claims were outlandish. For example, significant results also suggested that extraverts can foresee where pornographic images are displayed on a computer screen even before the computer randomly selected the location (Bem, 2011). No psychologist, except Bem, believes these findings. More problematic is that many other findings are equally incredible. A replication project found that only 25% of results in social psychology could be replicated (Open Science Collaboration, 2005). So, the question is whether incidental and subliminal anchoring are more like classic anchoring or more like extrasensory perception.
There are two ways to assess the credibility of published results when publication bias is present. One approach is to conduct credible replication studies that are published independent of the outcome of a study. The other approach is to conduct a meta-analysis of the published literature that corrects for publication bias. A recent article used both methods to examine whether incidental anchoring is a credible effect (Kvarven et al., 2020). In this article, the two approaches produced inconsistent results. The replication study produced a non-significant result with a tiny effect size, d = .04 (Klein et al., 2014). However, even with bias-correction, the meta-analysis suggested a significant, small to moderate effect size, d = .40.
The data for the meta-analysis were obtained from an unpublished thesis (Henriksson, 2015). I suspected that the meta-analysis might have coded some studies incorrectly. Therefore, I conducted a new meta-analysis, using the same studies and one new study. The main difference between the two meta-analysis is that I coded studies based on the focal hypothesis test that was used to claim evidence for incidental anchoring. The p-values were then transformed into fisher-z transformed correlations and and sampling error, 1/sqrt(N – 3), based on the sample sizes of the studies.
Whereas the old meta-analysis suggested that there is no publication bias, the new meta-analysis showed a clear relationship between sampling error and effect sizes, b = 1.68, se = .56, z = 2.99, p = .003. Correcting for publication bias produced a non-significant intercept, b = .039, se = .058, z = 0.672, p = .502, suggesting that the real effect size is close to zero.
Figure 1 shows the regression line for this model in blue and the results from the replication study in green. We see that the blue and green lines intersect when sampling error is close to zero. As sampling error increases because sample sizes are smaller, the blue and green line diverge more and more. This shows that effect sizes in small samples are inflated by selection for significance.
However, there is some statistically significant variability in the effect sizes, I2 = 36.60%, p = .035. To further examine this heterogeneity, I conducted a z-curve analysis (Bartos & Schimmack, 2021; Brunner & Schimmack, 2020). A z-curve analysis converts p-values into z-statistics. The histogram of these z-statistics shows publication bias, when z-statistics cluster just above the significance criterion, z = 1.96.
Figure 2 shows a big pile of just significant results. As a result, the z-curve model predicts a large number of non-significant results that are absent. While the published articles have a 73% success rate, the observed discovery rate, the model estimates that the expected discovery rate is only 6%. That is, for every 100 tests of incidental anchoring, only 6 studies are expected to produce a significant result. To put this estimate in context, with alpha = .05, 5 studies are expected to be significant based on chance alone. The 95% confidence interval around this estimate includes 5% and is limited at 26% at the upper end. Thus, researchers who reported significant results did so based on studies with very low power and they needed luck or questionable research practices to get significant results.
A low discovery rate implies a high false positive risk. With an expected discovery rate of 6%, the false discovery risk is 76%. This is unacceptable. To reduce the false discovery risk, it is possible to lower the alpha criterion for significance. In this case, lowering alpha to .005 produces a false discovery risk of 5%. This leaves 5 studies that are significant.
One notable study with strong evidence, z = 3.70, examined anchoring effects for actual car sales. The data came from an actual auction of classic cars. The incidental anchors were the prices of the previous bid for a different vintage car. Based on sales data of 1,477 cars, the authors found a significant effect, b = .15, se = .04 that translates into a standardized effect size of d = .2 (fz = .087). Thus, while this study provides some evidence for incidental anchoring effects in one context, the effect size estimate is also consistent with the broader meta-analysis that effect sizes of incidental anchors are fairly small. Moreover, the incidental anchor in this study is still in the focus of attention and in some way related to the actual bid. Thus, weaker effects can be expected for anchors that are not related to the question at all (a player’s number) or anchors presented outside of awareness.
There is clear evidence that evidence for incidental anchoring cannot be trusted at face value. Consistent with research practices in general, studies on incidental and subliminal anchoring suffer from publication bias that undermines the credibility of the published results. Unbiased replication studies and meta-analysis suggest that incidental anchoring effects are either very small or zero. Thus, there exists currently no empirical support for the notion that irrelevant numeric information can bias numeric judgments. More research on anchoring effects that corrects for publication bias is needed.
Social psychologists have failed to clean up their act and their literature. Here I show unusually high effect sizes in non-retracted articles by Sanna, who retracted several articles. I point out that non-retraction does not equal credibility and I show that co-authors like Norbert Schwarz lack any motivation to correct the published record. The inability of social psychologists to acknowledge and correct their mistakes renders social psychology a para-science that lacks credibility. Even meta-analyses cannot be trusted because they do not correct properly for the use of questionable research practices.
When I grew up, a popular German Schlager was the song “Aber bitte mit Sahne.” The song is about Germans love of deserts with whipped cream. So, when I saw articles by Sanna, I had to think about whipped cream, which is delicious. Unfortunately, articles by Sanna are the exact opposite. In the early 2010s, it became apparent that Sanna had fabricated data. However, unlike the thorough investigation of a similar case in the Netherlands, the extent of Sanna’s fraud remains unclear (Retraction Watch, 2012). The latest count of Sanna’s retracted articles was 8 (Retraction Watch, 2013).
WebOfScience shows 5 retraction notices for 67 articles, which means 62 articles have not been retracted. The question is whether these article can be trusted to provide valid scientific information? The answer to this question matters because Sanna’s articles are still being cited at a rate of over 100 citations per year.
Meta-Analysis of Ease of Retrieval
The data are also being used in meta-analyses (Weingarten & Hutchinson, 2018). Fraudulent data are particularly problematic for meta-analysis because fraud can produce large effect size estimates that may inflate effect size estimates. Here I report the results of my own investigation that focusses on the ease-of-retrieval paradigm that was developed by Norbert Schwarz and colleagues (Schwarz et al., 1991).
The meta-analysis included 7 studies from 6 articles. Two studies produced independent effect size estimates for 2 conditions for a total of 9 effect sizes.
Sanna, L. J., Schwarz, N., & Small, E. M. (2002). Accessibility experiences and the hindsight bias: I knew it all along versus it could never have happened. Memory & Cognition, 30(8), 1288–1296. https://doi.org/10.3758/BF03213410 [Study 1a, 1b]
Sanna, L. J., Schwarz, N., & Stocker, S. L. (2002). When debiasing backfires: Accessible content and accessibility experiences in debiasing hindsight. Journal of Experimental Psychology: Learning, Memory, and Cognition, 28(3), 497–502. https://doi.org/10.1037/0278-73126.96.36.1997 [Study 1 & 2]
Sanna, L. J., & Schwarz, N. (2003). Debiasing the hindsight bias: The role of accessibility experiences and (mis)attributions. Journal of Experimental Social Psychology, 39(3), 287–295. https://doi.org/10.1016/S0022-1031(02)00528-0 [Study 1]
Sanna, L. J., Chang, E. C., & Carter, S. E. (2004). All Our Troubles Seem So Far Away: Temporal Pattern to Accessible Alternatives and Retrospective Team Appraisals. Personality and Social Psychology Bulletin, 30(10), 1359–1371. https://doi.org/10.1177/0146167204263784 [Study 3a]
Sanna, L. J., Parks, C. D., Chang, E. C., & Carter, S. E. (2005). The Hourglass Is Half Full or Half Empty: Temporal Framing and the Group Planning Fallacy. Group Dynamics: Theory, Research, and Practice, 9(3), 173–188. https://doi.org/10.1037/1089-26188.8.131.52 [Study 3a, 3b]
Carter, S. E., & Sanna, L. J. (2008). It’s not just what you say but when you say it: Self-presentation and temporal construal. Journal of Experimental Social Psychology, 44(5), 1339–1345. https://doi.org/10.1016/j.jesp.2008.03.017 [Study 2]
When I examined Sanna’s results, I found that all 9 of these 9 effect sizes were extremely large with effect size estimates being larger than one standard deviation. A logistic regression analysis that predicted authorship (With Sanna vs. Without Sanna) showed that the large effect sizes in Sanna’s articles were unlikely to be due to sampling error alone, b = 4.6, se = 1.1, t(184) = 4.1, p = .00004 (1 / 24,642).
These results show that Sanna’s effect sizes are not typical for the ease-of-retrieval literature. As one of his retracted articles used the ease-of retrieval paradigm, it is possible that these articles are equally untrustworthy. As many other studies have investigated ease-of-retrieval effects, it seems prudent to exclude articles by Sanna from future meta-analysis.
These articles should also not be cited as evidence for specific claims about ease-of-retrieval effects for the specific conditions that were used in these studies. As the meta-analysis shows, there have been no credible replications of these studies and it remains unknown how much ease of retrieval may play a role under the specified conditions in Sanna’s articles.
The blog post is also a warning for young scientists and students of social psychology that they cannot trust researchers who became famous with the help of questionable research practices that produced too many significant results. As the reference list shows, several articles by Sanna were co-authored by Norbert Schwarz, the inventor of the ease-of-retrieval paradigm. It is most likely that he was unaware of Sanna’s fraudulent practices. However, he seemed to lack any concerns that the results might be too good to be true. After all, he encountered replicaiton failures in his own lab.
“of course, we had studies that remained unpublished. Early on we experimented with different manipulations. The main lesson was: if you make the task too blatantly difficult, people correctly conclude the task is too difficult and draw no inference about themselves. We also had a couple of studies with unexpected gender differences” (Schwarz, email communication, 5/18,21).
So, why was he not suspicious when Sanna only produced successful results? I was wondering whether Schwarz had some doubts about these studies with the help of hindsight bias. After all, a decade or more later, we know that he committed fraud for some articles on this topic, we know about replication failures in larger samples (Yeager et al., 2019), and we know that the true effect sizes are much smaller than Sanna’s reported effect sizes (Weingarten & Hutchinson, 2018).
Hi Norbert, thank you for your response. I am doing my own meta-analysis of the literature as I have some issues with the published one by Evan. More about that later. For now, I have a question about some articles that I came across, specifically Sanna, Schwarz, and Small (2002). The results in this study are very strong (d ~ 1). Do you think a replication study powered for 95% power with d = .4 (based on meta-analysis) would produce a significant result? Or do you have concerns about this particular paradigm and do not predict a replication failure? Best, Uli (email
His response shows that he is unwilling or unable to even consider the possibility that Sanna used fraud to produce the results in this article that he co-authored.
Uli, that paper has 2 experiments, one with a few vs many manipulation and one with a facial manipulation. I have no reason to assume that the patterns won’t replicate. They are consistent with numerous earlier few vs many studies and other facial manipulation studies (introduced by Stepper & Strack, JPSP, 1993). The effect sizes always depend on idiosyncracies of topic, population, and context, which influence accessible content and accessibility experience. The theory does not make point predictions and the belief that effect sizes should be identical across decades and populations is silly — we’re dealing with judgments based on accessible content, not with immutable objects.
This response is symptomatic of social psychologists response to decades of research that has produced questionable results that often fail to replicate (see Schimmack, 2020, for a review). Even when there is clear evidence of questionable practices, journals are reluctant to retract articles that make false claims based on invalid data (Kitayama, 2020). And social psychologist Daryl Bem wants rather be remembered as loony para-psychologists than as real scientists (Bem, 2021).
The problem with these social psychologists is not that they made mistakes in the way they conducted their studies. The problem is their inability to acknowledge and correct their mistakes. While they are clinging to their CVs and H-Indices to protect their self-esteem, they are further eroding trust in psychology as a science and force junior scientists who want to improve things out of academia (Hilgard, 2021). After all, the key feature of science that distinguishes it from ideologies is the ability to correct itself. A science that shows no signs of self-correction is a para-science and not a real science. Thus, social psychology is currently para-science (i.e., “Parascience is a broad category of academic disciplines, that are outside the scope of scientific study, Wikipedia).
The only hope for social psychology is that young researchers are unwilling to play by the old rules and start a credibility revolution. However, the incentives still favor conformists who suck up to the old guard. Thus, it is unclear if social psychology will ever become a real science. A first sign of improvement would be to retract articles that make false claims based on results that were produced with questionable research practices. Instead, social psychologists continue to write review articles that ignore the replication crisis (Schwarz & Strack, 2016) as if repression can bend reality.
Scientific advance relies on transparency, rigour and reproducibility. At PLOS ONE we have always supported the publication of rigorous research, in all its forms, positive or negative, as showcased in our earlier Missing Pieces Collection.
Today, the Children’s Tumor Foundation and PLOS ONE are pleased to announce a partnership to trial the integration of Registered Reports in the grant application and publication process: The Children’s Tumor Foundation (CTF) and
As of today, PLOS is retiring its two “Hubs”, which have respectively highlighted and brought together open-access content in two specific areas: Biodiversity and Clinical Trials. These sites were initially developed to experiment with how the open-access literature might be reorganised and filtered across journals, providing ways of enabling readers in particular fields to access material of interest to them. The Hub:Clinical Trials was dedicated to highlighting clinical trials research across the PLOS journals, as well as maintaining an archive of the original work previously published in PLOS Clinical Trials. Although the Hub will no longer exist, all unique articles originally published in PLOS Clinical Trials will continue to be openly available at http://www.plosclinicaltrials.org, as well as in PubMed Central. Trials research published in other PLOS journals will be available as usual on those journals’ sites. The decision in no way diminishes PLOS’s commitment to publishing all correctly conducted and reported clinical trials and we also intend to explore new ways of aggregating content in future. PLOS has always been committed to raising awareness about the effects of publication biases in relation to clinical trial data, and to providing ways of addressing those biases. This commitment now continues through a number of ongoing initiatives which PLOS journals continue to support.
Firstly, PLOS ONE continues its commitment to publishing the results of clinical trials research, irrespective of trial outcome. The journal’s publication criteria have always emphasised that for a paper to be published, following rigorous peer review, that work is technically sound and properly reported. In relation to clinical trials research, PLOS ONE (and other PLOS journals) requires authors to use CONSORT guidelines in reporting their study; to have prospectively registered their trial in a public, international registry such as clinicaltrials.gov; and to provide a copy of the original trial protocol as supporting information for editors, reviewers and readers to evaluate against the published report. The journal therefore provides a unique mechanism to rectify publication bias in the trials literature – a bias that has been described by the Alltrials Campaign as potentially “leading to bad treatment decisions, missed opportunities for good medicine, and trials being repeated”. Since January 2011, PLOS ONE has accepted for publication 406 articles classified as trials. Included amongst the papers published are frequent examples of well-conducted studies which fail to find “positive” effects of experimental interventions – such as this study looking at a complex intervention aimed at decreasing x-ray referrals for patients with acute low back pain; and this study evaluating the effects of an advocacy initiative aimed at reducing the risk of pedestrian injury.
Secondly, PLOS staff members continue to be involved in external initiatives which aim to address publication bias and to increase transparency in trial publication. Both Ginny Barbour (Editorial Director for Medicine at PLOS and Chief Editor, PLOS Medicine) and I have been involved in the European Medicines Agency’s Advisory Groups regarding its development of a new policy for making publicly available the original datasets for clinical trials which underpin drug regulatory decision making in Europe. The Agency has now released its draft policy which is open for public comment. The policy makes some important statements. For example, EMA does not consider clinical trial data to be commercially confidential, and the draft policy states that the interests of public health outweigh the considerations of commercial confidentiality. The draft policy would make all summary clinical trial data and documents (where there are no concerns about patient privacy) open access, at the time of the EMA’s report of a positive, negative or withdrawal decision on a drug indication.
PLOS is an initiating organisation behind the Alltrials initiative, which it endorses. Alltrials calls for “all trials to be registered and reported”. PLOS’s declaration of support for Alltrials can be read here. As a result of recent campaigning, some forward-thinking drug companies – such as GSK and Medtronic – have supported or developed initiatives to freely share individual patient level trial data with academic researchers for independent scrutiny.
Finally, PLOS journals (specifically PLOS Medicine and PLOS ONE) have recently declared support for a creative new approach for getting unreported trial results into the published literature. Both journals have stated that they will support the RIAT initiative, a proposal whereby authors independent of the original triallists or sponsors could revive unreported trials and independently publish their findings based on documents obtained through public-domain documents, such as via freedom of information requests.
These and other initiatives are beginning to change the trials landscape, but there is still a very long way to go before the public can be reassured that the findings of all trials will be made immediately available in an unbiased way to inform clinical decision making. PLOS editors will continue to support efforts aimed at ensuring the full and honest reporting of the results of all trials.
Last week BMJ published an article proposing a new initiative aimed at solving an age-old problem in medical publishing: that of the perennial failure of investigators and sponsors to publish all of the results of all their trials, accurately and transparently. The BMJ paper ups the ante and invites independent, “restorative authors” to step in and take charge of unpublished or misreported trials. It’s not so much “publish and be damned” as “publish or be published”. Restorative authors can now use as their data source the documentation from a trial (often many thousands of pages of protocols, clinical study reports, and individual patient datasets or analysed datasets) obtained through freedom of information requests. The RIAT proposers (Peter Doshi, Kay Dickersin, David Healy, S Swaroop Vedula and Tom Jefferson) describe in their table 1 the many documents and datasets they have already obtained for a large number of trials, and which they’re willing to share. Doshi et al invite collaborators to their enterprise:
“We call on others to join us, to contribute trial documents they have obtained from public sources that need publishing or republishing, and to help us with the writing. We need volunteers to act in place of those who should have but did not make trial reports visible and accessible.”
The initiative has already garnered support from our sister journal PLOS Medicine, which has co-signed an editorial announcing that they “commit to publishing restorative clinical trial submissions”. A detailed blog by PLOS Medicine editors discusses some of the hurdles that might need to be overcome for journals to publish restored trials by independent authors. For example, many “restored trials” may not have been originally registered in public trial registries, and restorative authors may have limited ability to establish whether the trials they are restoring were ethically conducted. Generally journals will only publish the results of trials which were publicly registered, and for which authors can take responsibility for ethical oversight and provide assurance to editors that their trial was carried out ethically. The PLOS Medicine editors invite feedback via their blog on these, and other issues.
The RIAT initiative is entirely concordant with PLOS ONE’s editorial aims and mission, which seeks to publish the results of all correctly reported, scientifically sound studies, irrespective of impact or the direction of results. PLOS ONE’s publication criteria do not discriminate against “negative results”, and the journal welcomes submission of re-analyses or replications of prior work, as well as analyses based on publicly available datasets. We do require that authors adhere to study-type-specific community standards for reporting, such as the CONSORT guidelines for reporting randomized trials (which has been adapted by the RIAT authors into a specific modification, the “RIATAR” tool for documenting the RIAT process).
Consequently, PLOS ONE now invites RIAT authors to consider submitting their “restored” trial reports to PLOS ONE for publication. These papers will be considered in the context of our existing publication criteria and editorial policies, although the editors are actively considering how the specific issues noted above in relation to trial registration and ethical integrity might best be interpreted. We ask RIAT authors to clearly identify when submitting (ideally in their cover letter) that they are responding to the RIAT initiative and are submitting a RIAT study. Authors should show that they have given the original triallists and sponsors an opportunity to publish their own study. They should do this by stating in their article methods section when they contacted the original triallists and sponsors, and by what date no response had been received. (If original triallists/sponsors have indicated they wish to restore their own trial, the RIAT proposal allows a “grace” period of a year, in which they should be allowed to publish without being scooped). We will also check Rapid Responses to the BMJ article to find out whether sponsors intend to restore their own trial. We also suggest that RIAT authors ensure they fully describe the methods that they have used to conduct RIAT, including the approaches to obtaining the datasets from the original trial, to reanalyze those data and through which they have come to their conclusions. This is particularly important if the trial has already been reported by the original triallists, and if RIAT authors are drawing different inferences based on a different approach to analysis. RIAT authors should take care to distinguish responsibility for the work they have done (in obtaining public data and conducting their reanalysis) from the work done by the original triallists (the conduct of the original trial), thereby establishing what authorship means in the context of a RIAT study.
Finally, the PLOS ONE editors have noted that PLOS ONE study is included in the list of clinical study reports amassed by the RIAT group (see Table 1, “Novartis FLUAD study, cited as reference 103 in the BMJ paper. PLOS ONE reference is given below). PLOS ONE is committed to correcting the publication record where necessary and therefore we will be in touch with the RIAT group to find out whether they can share with us any information on why this study is included in their list, and for what reasons a correction of the record may be needed. Quite separate from this, we also welcome any submission to PLOS ONE of a reanalysis of this trial from restorative authors, based on the clinical study reports that the RIAT group have obtained.