1 3 Exp Brain Res (2013) 227:93–100 DOI 10.1007/s00221-013-3488-2 RESEARCH ARTICLE Are reaction times obtained during fMRI scanning reliable and valid measures of behavior? Jan Willem Koten · Robert Langner · Guilherme Wood · Klaus Willmes Received: 11 October 2012 / Accepted: 14 March 2013 / Published online: 7 April 2013 © Springer-Verlag Berlin Heidelberg 2013 across sessions. Thus, for the range of tasks used, test–retest reliability and criterion validity of performance during scan- ning were satisfactory. Further, the pattern of between-task relations did not change within the scanner, attesting to the construct validity of performance measurements during scanning. In some tasks, however, RTs obtained from fMRI conditions were significantly shorter than those observed under normal laboratory conditions. In summary, RTs obtained during fMRI scanning appear to be largely reliable and valid measures of behavior. The observed RT speed-up during scanning might reflect task-specific interactions with a slightly different neuro-cognitive state, indicating some limits to generalizing brain–behavior relations observed with fMRI. These findings encourage further efforts in fMRI research to establish the external validity of within- scanner task performance. Keywords fMRI · Scanner effects on performance · Test–retest reliability · Validity · Stress Introduction It is often assumed that participants in neuroimaging experi- ments act “normally” (i.e., validly) and reliably (Koch et al. 2003). More specifically, brain–behavior relations observed during functional magnetic resonance imaging (fMRI) are usually taken to be comparable to brain–behavior relations assumed for traditional laboratory conditions or observed using different imaging modalities such as electroencepha- lography. Ultimately, this assumption is not testable because it is not possible to scan the brain without a scanner. Nev- ertheless, it is very well possible to compare the behavior of an individual in- and outside the scanner. Behavioral differences that arise from differences in environmental Abstract Assuming that behavior observed during func- tional magnetic resonance imaging (fMRI) is comparable with behavior outside the scanner appears to be a basic tenet in cognitive neuroscience. Nevertheless, this assumption has rarely been tested directly. Here, we examined the reliability and validity of speeded performance during fMRI scanning by having the same 30 participants perform a battery of five reaction time (RT) tasks in two separate fMRI sessions and a standard laboratory (i.e., outside-scanner) session. Medium- to-high intra-class correlations between the three sessions showed that individual RT differences were conserved Jan Willem Koten and Robert Langner contributed equally. Electronic supplementary material The online version of this article (doi:10.1007/s00221-013-3488-2) contains supplementary material, which is available to authorized users. J. W. Koten (*) · K. Willmes Neuropsychology Section, Department of Neurology, Medical School, RWTH Aachen University, Universitätsklinikum Aachen, Pauwelsstr. 30, 52074 Aachen, Germany e-mail: Jan.Koten@gmx.de J. W. Koten · G. Wood Neuropsychology Section, Department of Psychology, Karl Franzens University, Graz, Austria R. Langner (*) Institute of Clinical Neuroscience and Medical Psychology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany e-mail: r.langner@fz-juelich.de R. Langner Research Centre Jülich, Institute of Neuroscience and Medicine (INM-1), Jülich, Germany Author's personal copy