This is known as “regression to the mean” (RTM) ( Galton, 1886). However, measurements vary from one time point to the next due to random error, and extreme values at the first measurement tend to approach the mean at the subsequent measurement. Researchers often make repeated measurements on unstable variables to obtain more accurate data or to assess change. Based on these findings we suggest several ways to control for the RTM effect in social psychology studies, such as adding the initial rating as a covariate in regression analysis, selecting a subset of stimuli for which the participant' initial ratings were matched across experimental conditions, and using a control group. Although these studies used methodologies similar to those used in earlier research, the social conformity and unrealistic optimism effects were no longer evident after controlling for RTM.
#I REGRESS MEANING SERIES#
In Study 2, 15 university students estimated and re-estimated their risk of experiencing a series of adverse life events as a test of the unrealistic optimism effect ( Sharot et al., 2011). In Study 1, 13 university students rated and re-rated the facial attractiveness of a series of female faces as a test of the social conformity effect ( Klucharev et al., 2009). Notable cases include studies on the phenomena of social conformity and unrealistic optimism ( Klucharev et al., 2009, 2011 Sharot et al., 2011, 2012b Campbell-Meiklejohn et al., 2012 Kim et al., 2012 Garrett and Sharot, 2014). However, insufficient attention is paid to RTM in most social psychological research. The wide use of repeated measurements in social psychology creates a risk that an RTM effect will influence results. If RTM is not fully controlled, it will lead to erroneous conclusions. It is common in repeated measurements for extreme values at the first measurement to approach the mean at the subsequent measurement, a phenomenon called regression to the mean (RTM). 2Scientific Laboratory of Economic Behaviors, School of Economics and Management, South China Normal University, Guangzhou, China.1Department of Psychology, School of Psychology and Center for Studies of Psychological Application, South China Normal University, Guangzhou, China.
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