Psychology is not a unified paradigmatic science. That is, it lacks an overarching theory like evolution theory in biology. In a science without an empirically grounded paradigm, progress is made very much like evolution made progress in a process of trial and error. Some ideas may thrive for a moment, but if they are not fruitful, they are discarded. The emergence of a new idea is often characterized as a revolution, and psychology has seen its fair share of revolutions. Behaviorism replaced introspectionism and the cognitive revolution replaced behaviorism. For better or worse, cognitivism is dominating psychology at the moment. The cognitive revolution also had a strong influence on social psychology with the rise of social cognition research.

In the early days, social psychologists focussed on higher cognitive processes like attributions. However, in the 1980s, the implicit revolution shifted focus towards lower cognitive processes that may occur without awareness. This was not the first time, unconscious processes became popular. A special issue in the American Psychologists in 1992 called it the New Look 3 (Greenwald, 1992).

The first look was Freud’s exploration of conscious and unconscious processes. A major hurdle for this first look was conceptual confusion and a lack of empirical support. Puritan academic may also have shied away from the sexual content in Freudian theories (e.g., sexual desire directed at the mother).

However, the second look did try to study many of Freud’s ideas with empirical methods. For example, Silverman and Weinberger (1985) presented the phrase “Mommy and I are one” on a computer screen so quickly that participants were unable to say what they saw. This method is called subliminal priming. The idea was that the unconscious has a longing to be loved by mommy and that presenting this phrase would gratify the unconscious. Numerous studies used the “Mommy and I are one” priming method to see effects on behavior.

Greenwald (1992) reviewed this evidence.

Can subliminal presentations result in cognitive analyses of multiword strings? There have been reports of such effects, especially in association with tests of psychoanalytic hypotheses. The best known of these findings (described as subliminal psychodynamic activation [SPA], using “Mommy and I are One” as the text of a subliminal stimulus; Silverman & Weinberger, 1985) has been identified, on the basis of meta-analysis, as a reproducible phenomenon (Hardaway, 1990; Weinberger & Hardaway, 1990).

Despite this strong evidence, many researchers remain skeptical about the SPA result (see, e.g., the survey reported in Appendix B). Such skepticism is almost certainly due to the lack of widespread enthusiasm for the SPA result’s proposed psychodynamic interpretation (Silverman & Weinberger, 1985).

Because of the positive affective values of words in the critical stimulus (especially Mommy and I) , it is possible that observed effects might be explained by cognitive analysis limited to the level of single words. Some support for that interpretation is afforded by Hardaway’s demonstration (1990, p. 183, Table 3) that other affectively positive strings that include Mommy or One also produce significant effects. However, these other effects are weaker than the effect of the specific string, “Mommy and I are One.”

In summary of evidence from studies of subliminal activation, it is now well established that analysis occurs for stimuli presented at exposure conditions in a region between objective and subjective thresholds; this analysis can extract at least some semantic content of single words.

The New Look 3, however, was less interested in Freudian theory. Most of the influential subliminal priming studies used ordinary stimuli to study common topics in social psychology, including prejudice.

For example, Greenwald (1992) cites Devine’s (1989) highly influential subliminal priming studies with racial stimuli as evidence that “experiments using stimulus conditions that are clearly above objective thresholds (but presumably below subjective thresholds) have obtained semantic activation findings with apparent relative ease” (p. 769).

25 years later, in their Implicit Revolution article, Greenwald and Banaji feature Devine’s influential article.

“Patricia Devine’s (1989) dissertation research extended the previously mentioned subliminal priming methods of Bargh and Pietromonaco (1982) to automatic stereotypes. Devine’s article brought attention to the possibility of dissociation between automatic stereotype activation
and controlled inhibition of stereotype expression” (p. 865).

In short, subliminal priming has played an important role in the implicit revolution. However, subliminal priming is still rare. Most studies use clearly visible stimuli. This is surprising, given the clear advantages of subliminal priming to study unconscious processes. A major concern with stimuli that are presented with awareness is that participants can control their behavior. In contrast, if they are not even aware that a racial stimulus was presented, they have no ability to supress a prejudice response.

Another revolution explains why subliminal studies remain rare despite their obvious advantages. This revolution has been called the credibility revolution, replication revolution, or open science revolution. The credibility revolution started in 2011, after a leading social cognition journal published a controversial article that showed time-reversed subliminal priming effects (Bem, 2011). This article revealed a fundamental problem in the way social psychologists conducted their research. Rather than using experiments to see whether effects exist, they used experiments to accumulate evidence in favor of effects. Studies that failed to show the expected effects were hidden. In the 2010s, it has become apparent that this flawed use of the scientific method has produced large literatures with results that cannot be replicated. A major replication project found that less than 25% of results in social psychological experiments could be replicated (OSC, 2015). Given these results, it is unclear which results provided credible evidence.

Despite these troubling findings, social psychologists continue to cite old studies like Devine’s (1989) study (it was just one study!) as if it provided conclusive evidence for subliminal priming of prejudice. If we need any evidence for Freud’s theory of repression, social psychologists would be a prime example. Through various defense mechanisms they maintain the belief that old findings that were obtained with bad scientific practices provided credible evidence that can inform our understanding of the unconscious.

Here I show that this is wishful thinking. To do so, I conducted a modern meta-analysis of subliminal priming studies. Unlike traditional meta-analysis that do not take publication bias into account, this new method provides a strong test of publication bias and corrects for its effect on the results. While there are several new methods, z-curve has been shown to be superior to other methods (Brunner & Schimmack, 2020).

The figure shows the results. The red line at z = 1.96, corresponds to the significance criterion of .05. It is easy to see that this criterion acts like a censor. Results with z-scores greater than 1.96 (i.e., p < .05) are made public and can enter researchers awareness. Results that are not significant, z < 1.06, are repressed and may linger only in the unconscious of researchers who prefer not to think about their failures.

Statistical evidence of repression is provided by a comparison of the observed discovery rate (i.e., the percentage of published results that are significant) of 90% and the expected discovery rate based on the z-curve model (i.e., the grey curve in the figure) of 13%. Evidently, published results are selected from a much larger number of analyses that failed to support subliminal priming. This clear evidence of selection for significance undermines the credibility of individual studies in the subliminal priming literature.

However, there is some evidence of heterogeneity across studies. This is seen in the increasing numbers below the x-axis. Whereas studies with z-scores below 4, have low average power, studies with z-scores above 4, have a mean power greater than 80%. This suggests that replications of these studies could produce significant results. This information could be used to salvage a few solid findings from a pile of junk findings. Closer examination of these studies is beyond the purpose of this blog post, and Devine’s study is not one of them.

The main point of this analysis is that there is strong scientific evidence to support the claim that subliminal priming researchers did not use the scientific method properly. By selecting only results that support the existence of subliminal priming, they created only illusory evidence in support of subliminal priming. Thirty years after Devine’s (1989) subliminal prejudice study was published, we have no scientific evidence in support of the claim that racial stimuli can bypass consciousness and directly influence behavior.

However, Greenwald and other social psychologists who made a career out of these findings repress the well-known fact that published results in experimental social psychology are not credible and cite them as if they are credible evidence (Greenwald & Banaj, 2017).

Social psychologists are of course very familiar with deception. First, they became famous for deceiving participants (Milgram studies). In 2011, it became apparent that they were deceiving themselves. Now, it seems they are willing to deceive others to avoid facing the inconvenient truth that decades of research have produced no scientific results.

The inability to face ego-threatening information is of course not new to psychologists. Freud studied defense mechanisms and social psychologists studied cognitive biases and motivated reasoning. Right now, this trait is on display in Donald Trump and his supporters inability to face the fact that he lost an election. It is ironic that social psychologists have the same inability when their own egos are on the line.