Reporting and Interpreting Working Memory Performance in n-back Tasks

Working memory is an executive function, which involves holding information in mind and mentally working with it (Diamond, 2013). A widely used measure for the assessment of working memory function is the n-back task (Owen et al., 2005). Here, participants are typically instructed to monitor a series of stimuli and to respond whenever a stimulus is presented that is the same as the one presented n trials previously. Common versions are 2-back and 3-back tasks, in which participants have to respond to stimuli that have been presented two or three trials earlier. Zero-back and 1-back versions are also often used as control conditions. In most studies, participants are required to respond with a button press to the relevant stimuli (= targets) and to withhold responses to distractor stimuli (= non-targets). Yet, there are also studies, in which participants are required to indicate for each trial whether the stimulus represents a target or a non-target (e.g., by pressing two different buttons; Jonides et al. have also been used in recent years. As dependent variables, most studies report response latencies (= reaction times) and accuracy (in %) or the number of errors. With increasing task difficulty (i.e., with increasing ns), reaction times usually increase and accuracy decreases (e. Similarly, reaction times and accuracy are usually negatively correlated (e.g., Carter et al., 1998). In other words, higher reaction times are associated with a higher number of errors. Although this relationship exists, it appears that reaction times and accuracy have dissociable correlates. For example, Jaeggi et al. (2010) examined various n-back tasks and found several dissociations between reaction times and accuracy. For instance, higher accuracy (but not reaction times) in visuospatial, auditory, and dual 3-back tasks was correlated with higher fluid intelligence as measured with the Raven test. In visuospatial n-back tasks, reaction times (but not accuracy) were associated with reading span and digit span forward performance. In addition to these findings, a recent study by Hur et al. (in press) further highlights the role of reaction times vs. accuracy. In that study, pictures of emotional scenes were used in a 0-back task (labeled as perception task) and a 2-back task (labeled as working memory task). The authors argued that there was a ceiling effect in accuracy and more meaningful variation in reaction times in the perception task and, thus, they focused on interpreting reaction time results. In the working memory task, however, there …