Dissociating Slow Responses From Slow Responding

Gayatri Salunkhe; Bernd Feige; Christopher W N Saville; Maria Elena Stefanou; David Linden; Stephan Bender; Andrea Berger; Nikolaos Smyrnis; Monica Biscaldi; Christoph Klein

doi:10.3389/fpsyt.2020.505800

Dissociating Slow Responses From Slow Responding

Front Psychiatry. 2020 Oct 2:11:505800. doi: 10.3389/fpsyt.2020.505800. eCollection 2020.

Authors

Gayatri Salunkhe¹, Bernd Feige², Christopher W N Saville³, Maria Elena Stefanou^{1

4}, David Linden⁵, Stephan Bender⁶, Andrea Berger⁷, Nikolaos Smyrnis⁸, Monica Biscaldi¹, Christoph Klein^{1

6

8}

Affiliations

¹ Department of Child and Adolescent Psychiatry, Psychotherapy and Psychosomatics, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
² Department of Psychiatry and Psychotherapy, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
³ School of Psychology, Bangor University, Bangor, United Kingdom.
⁴ School of Psychology and Clinical Language Sciences, University of Reading, Reading, United Kingdom.
⁵ School for Mental Health and Neuroscience, Maastricht University, Maastricht, Netherlands.
⁶ Department of Child and Adolescent Psychiatry, Medical Faculty, University of Cologne, Cologne, Germany.
⁷ Department of Psychology, Ben-Gurion University of the Negev, Beer Sheva, Israel.
⁸ Department of Psychiatry, National and Kapodistrian University of Athens, Medical School, Eginition Hospital, Athens, Greece.

Abstract

Increased Intra-Subject Variability (ISV) is a candidate endophenotype of ADHD. ISV's relationship with response speed is highly relevant for ADHD as patients are highly variable but typically no slower than controls. This brief report addresses the relationship between variability and speed by employing dimensional analyses for differentiated performance measures, with a particular focus on the ex-Gaussian measures, across relevant ADHD studies and in young healthy adults (N = 70). For both patients with ADHD and healthy adults, we found that reaction time standard deviation and mean reaction time were strongly correlated, thus failing to dissociate, but ex-Gaussian tau (τ) shared only little variance with Gaussian mu (μ), thus dissociating slow responses (τ) from response speed or-if given-slow responding (μ). Our results highlight the utility of employing the ex-Gaussian measures to disentangle ISV and speed, particularly for ADHD data as patients make more slow responses but are not overall slower than typical controls.

Keywords: attention-deficit/hyperactivity disorder (ADHD); ex-Gaussian modeling; intra-subject variability; principal components analyses; response speed.