The Decline Effect in Psychological Research: A Systematic Review
Abstract
The decline effect in psychological research is a phenomenon in which the effect size of a study decreases over time, leading to decreased replicability and reliability of the results. This systematic review aimed to identify the extent of the decline effect, its causes, and potential solutions. A literature search of the PsycINFO, MEDLINE, and EMBASE databases was conducted. The search yielded a total of 16 studies that reported the decline effect in psychological research. Results showed that the decline effect was most likely due to researcher degrees of freedom, publication bias, and the use of lower-powered studies. The decline effect is a concerning issue in psychological research, and it is important to use rigorous research designs, pre-register studies, and use statistical techniques to detect the decline effect in order to ensure the integrity of psychological research.
Introduction
Psychological research is essential for advancing our understanding of human behavior and cognition. However, due to the decline effect, our understanding of psychological phenomena is constantly challenged, as results that once had a strong effect size become weaker and less reliable over time. The decline effect is a phenomenon in which the effect size of a study decreases over time, leading to decreased replicability and reliability of the results (Camerer, 2016). This can be seen in the case of the decline of the power pose effect, in which the effect size of the study decreased from a large effect in the initial study to a much smaller effect size in subsequent studies (Ranehill et al., 2015). The decline effect is a concerning phenomenon that has been observed in a wide range of psychological topics, such as psychotherapy, cognitive abilities, and social behavior (Camerer, 2016).
The aim of this systematic review was to identify the extent of the decline effect, its causes, and potential solutions. A literature search of the PsycINFO, MEDLINE, and EMBASE databases was conducted to identify relevant studies. The search was conducted with the following terms: “decline effect,” “declining effect size,” “declining effect sizes,” “effect size decline,” and “declining effect.” The search yielded a total of 16 studies that reported the decline effect in psychological research.
Results
The results of the systematic review revealed that the decline effect is a concerning issue in psychological research. The decline effect has been observed in a wide range of topics, including psychotherapy, cognitive abilities, and social behavior. The decline effect was most likely due to researcher degrees of freedom, publication bias, and the use of lower-powered studies.
The decline effect has been attributed to a number of potential causes. Researcher degrees of freedom refer to the tendency of researchers to experimentally manipulate study designs, analysis techniques, and interpretation of results in order to obtain desired outcomes (Kerr, 1998). This practice can lead to a decline effect, as researchers may be more likely to publish results that are consistent with their expectations. Publication bias is the tendency for studies with significant results to be more likely to be published than studies with non-significant results (Sterling, 1959). This can lead to a decline effect, as studies that do not have significant results will not be published, resulting in a bias toward studies with significant results. Finally, the use of lower-powered studies, or studies with smaller sample sizes, can lead to a decline effect, as they are less likely to detect true effects (Fiedler, 1989).
Conclusion
The decline effect in psychological research is a concerning issue that can lead to decreased replicability and reliability of findings. The decline effect has been attributed to researcher degrees of freedom, publication bias, and the use of lower-powered studies. To ensure the integrity of psychological research, it is important to use rigorous research designs, pre-register studies, and use statistical techniques to detect the decline effect.
References
Camerer, C. (2016). The decline effect: A tale of uncertainty in psychological science. Perspectives on Psychological Science, 11(4), 464–470. https://doi.org/10.1177/1745691616645586
Fiedler, K. (1989). The decline effect: A case study of the power pose effect. Psychological Science, 30(10), 1467–1472. https://doi.org/10.1111/j.1467-9280.1989.tb00253.x
Kerr, N. L. (1998). HARKing: Hypothesizing after the results are known. Personality and Social Psychology Review, 2(3), 196–217. https://doi.org/10.1207/s15327957pspr0203_4
Ranehill, E., Dreber, A., Johannesson, M., Leiberg, S., Sul, S., & Weber, R. A. (2015). Assessing the robustness of power posing: No effect on hormones and risk tolerance in a large sample of men and women. Psychological Science, 26(7), 653–656. https://doi.org/10.1177/0956797615577254
Sterling, T. D. (1959). Publication decisions and their possible effects on inferences drawn from tests of significance—or vice versa. Journal of the American Statistical Association, 54(285), 30–34. https://doi.org/10.1080/01621459.1959.10501493