1.4 Variability in Single Trials - It Can Be Systematic
While often dismissed as
measurement error, the EEG/ERP research community has long recognized
that information inherent within trial-to-trial variation is lost
through averaging (Jung et al., 2001; Walsh, Gunzelmann, & Anderson,
2017; Yajing et al., 2020). When trial-to-trial variability in either
latency or amplitude is systematic rather than random, analysis of
single trials can show valuable information such as the state of the
participant, the presence of a disability or disorder, or the ability to
learn over time (Jongsma et al.
2006; Pfefferbaum, Ford, Wenegrat, Roth, & Kopell, 1984; Pfefferbaum,
Wenegrat, Ford, Roth, & Kopell, 1984; Saville et al., 2015). Several
researchers have explored trial-to-trial variability (latency jitter)
using ST techniques and have shown individual or group differences,
especially in children or individuals with disabilities (Gavin et al.,
2019; Milne, 2011; Unsal & Segalowitz, 1995). Roth and colleagues
(2007) found increased latency and amplitude variability in participants
with schizophrenia compared to typical adults. ST analyses have also
been used to examine systematic changes in amplitude or latency across
the duration of the ERP task to identify informative patterns that may
represent learning over time (Quian Quiroga et al., 2007; Rey et al.,
2015). For example, Jongsma et al. (2006) observed slightly faster
response times with frequently presented targets versus infrequently
presented targets showing learning in healthy adults.