Bootstrapping in Psychophysiology
Bootstrapping is a data-based simulation technique for making statistical inferences (Efron & Tibshirani, 1994). It is especially useful for estimating the repeatability and reliability of a statistical result. Over 30 years ago, Wasserman and Bockenholt (1989) introduced bootstrapping to the field of psychophysiology. It has been shown to be useful in a variety of applications, including research on event-related potentials (ERP) such as the P300 waveform (e.g., Fabbiani et al., 1998). More recently, it has been used to interrogate psychophysiological methods, such as computing standard measurement errors to obtain a universal metric of ERP data quality (Luck et. al. 2021).
Although bootstrapping is used in a variety of fields, it is commonly utilized in the detection of concealed information. For instance, the P300-based Concealed Information Test (P300-CIT), has been studied for over 30 years and reliably uses the bootstrapped P300 to detect concealed knowledge of privileged, typically crime-related, information (Rosenfeld, 2020). In the P300-CIT, a series of crime relevant(Probe) and crime irrelevant (Irrelevant) stimuli are presented to a participant, and based on their responses to these stimuli one can classify them as being knowledgeable or unknowledgeable of crime relevant information. Another stimulus called a Target is used to maintain the attention of the participants by asking them to produce a unique response (e.g., on a keyboard) everytime they see it (Rosenfeld et al., 2006; Gamer & Berti, 2012). Guilty/knowledgeable individuals will have a differential psychophysiological response to crime relevant information compared to crime irrelevant information. For instance, the probe, which is crime relevant, would be salient only to someone who is “guilty” resulting in a larger P300 for probes in comparison to irrelevants. For this reason, the probe-irrelevant difference (i.e., “CIT effect”) is used to determine if the individual is “Guilty” (i.e., knowledgeable) or “Innocent” (i.e., unknowledgeable) (Rosenfeld, 2020).