Academic journal article Psychonomic Bulletin & Review

Making Sense of the Noise: Replication Difficulties of Correll's (2008) Modulation of 1/f Noise in a Racial Bias Task

Academic journal article Psychonomic Bulletin & Review

Making Sense of the Noise: Replication Difficulties of Correll's (2008) Modulation of 1/f Noise in a Racial Bias Task

Article excerpt

Published online: 11 November 2014

# Psychonomic Society, Inc. 2014

Abstract Correll (Journal of Personality and Social Psychology, 94, 48-59, 2008; Study 2) found that instructions to use or avoid race information decreased the emission of 1/f noise in a weapon identification task (WIT). These results suggested that 1/f noise in racial bias tasks reflected an effortful deliberative process, providing new insights regarding the mechanisms underlying implicit racial biases. Given the potential theoretical and applied importance of understanding the psychological processes underlying implicit racial biases - and in light of the growing demand for independent direct replications of findings to ensure the cumulative nature of our science - we attempted to replicate Correll's finding in two high-powered studies. Despite considerable effort to closely duplicate all procedural and methodological details of the original study (i.e., same cover story, experimental manipulation, implicit measure task, original stimuli, task instructions, sampling frame, population, and statistical analyses), both replication attempts were unsuccessful in replicating the original finding challenging the theoretical account that 1/f noise in racial bias tasks reflects a deliberative process. However, the emission of 1/f noise did consistently emerge across samples in each of our conditions. Hence, future research is needed to clarify the psychological significance of 1/f noise in racial bias tasks.

Keywords 1/f noise . Implicit racial bias . Weapon identification task . Independent direct replication

With an increasingly multicultural and global society, the study of racial bias becomes ever more important. In this context, social psychologists have increasingly relied on implicit measures to assess individuals' racial attitudes - such as the Implicit Association Test (IAT) or the Weapon Identification Task (WIT) - which aim to overcome limitations of direct measures including socially desirable responding and introspective limits (Gawronski, LeBel, & Peters, 2007). Many of these implicit measures involve assessing individuals' reaction times (RTs) to a series of words or photos related to the attitude object (e.g., photos of African-American or Caucasian faces). For such tasks, RTs to different trial types are typically averaged across trials to minimize external influences on any one trial. Correll (2008) argued, however, that aggregating across trials ignores a great deal of information about the variation in trialby-trial RTs and that considering such information from a 1/f noise perspective may shed new light about the psychological mechanisms underlying social psychological phenomena.

Correll (2008) investigated the potentially meaningful fluctuations in RTs across trials using an approach referred to as 1/f noise, which refers to non-random patterns of long-range correlations that manifest as waves in the fluctuations of RTs over time (Gilden, 2001; Gilden, Thornton, & Mallon, 1995; but see Wagenmakers, van der Maas, & Farrell, 2012). In recent years, 1/f noise - also known as flicker noise or pink noise - has been documented in a wide number of biological and physical systems including the fluctuations in tide heights, heartbeat, and firings of single neurons (Gilden, 2001; Press, 1978; for a review see Wijnants, 2014). From this perspective, the sequence of raw RTs can be represented as a complex waveform which can be decomposed into simpler component waves via a Fast Fourier transform (FFT). The log transformed frequency and power of each of these component waves can then be plotted; the slope between these two can then be estimated as power spectral density (PSD) slopes. If the variation in latencies is random then the PSD slope is not expected to differ from zero. However, PSD slopes that are negative, produced by lower frequency waves having more power than higher frequency waves, indicate 1/f noise. …

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