Methods matter: your measures of explicit and implicit processes in visuomotor adaptation affect your results

Abstract

Visuomotor rotations are frequently used to study cognitive processes underlying motor adaptation.Explicit aiming strategies and implicit recalibration are two of these processes. A large body of literature indicates that these two processes are dissociable and perhaps even independent components. Various direct and indirect methods have been used to dissociate the two processes.Discrepancies have been found between these different methods. They may arise for different reasons, but one reason may be that the different measures reflect different components of explicit and implicit knowledge. They may also be because of effects of the measurements themselves on the amount of explicit and implicit learning. The goal of this study was to directly compare verbal reporting, a direct measure of explicit knowledge, with indirect measures. We thus compared three different measures in two different conditions: during consistent reporting and during intermittent reporting. Our results show that our two conditions lead to a dissociation between the measures. In the consistent reporting group, all measures showed similar results. However, in the intermittent reporting condition, verbal reporting showed less explicit and more implicit knowledge than our two indirect methods. Verbal reporting seems to be insensitive to the changes in explicit knowledge caused by reporting. These findings suggest that verbal reporting reflects different components of explicit knowledge than those reflected in our indirect measures. A more sophisticated approach, including multiple components of explicit knowledge, may be necessary in order to fully understand motor adaptation. New and noteworthyExplicit and implicit processes during adaptation to visuomotor rotations can be captured using different types of measures. Here, we show that different methods may capture different processes and moreover, measurement may confound estimates of explicit and implicit knowledge. We suggest that at least two explicit components -one that is verbalizable and the other controllable -exist which can be captured by using the report and the AI, respectively.Reporting affects explicit knowledge in visuomotor rotations

External error attribution dampens efferent-based predictions but not proprioceptive changes in hand localization

“…Here, participants make open-loop reaches with (implicit and explicit) or without (implicit) the strategy they learned. This process dissociation procedure (PDP 16 ) is consistent with similar tasks 53,55 , has been used in previous studies 17,18,43,56 , and doesn't seem to evoke additional explicit learning unlike other methods [56][57][58] . While explicit learning does not necessarily correspond to external error attribution, it is likely that external error attribution is accompanied by more explicit adaptation.…”

External error attribution dampens efferent-based predictions but not proprioceptive changes in hand localization

“…We ask people to make open-loop reaches to targets after adaptation, while either using the strategy they just learned (implicit and explicit), or not using it (only implicit). We use this measurement task as it doesn't seem to evoke additional explicit learning itself, as other methods do (Leow et al, 2017;de Brouwer et al, 2018;Maresch and Donchin, 2019), and to keep results comparable to earlier work from our lab (Modchalingam et al, 2019). While explicit learning does not necessarily lead to external error attribution, it is likely that external error attribution is accompanied with more explicit adaptation.…”

“…Previous studies have shown that awareness of the nature of the perturbation increases the contribution of explicit learning during adaptation, on top of rather stable implicit learning (Heuer and Hegele, 2008;Benson et al, 2011;Ivry, 2011, 2012;Taylor et al, 2014;Bond and Taylor, 2015;McDougle et al, 2015;Werner et al, 2015;Modchalingam et al, 2019). Here we measure implicit and explicit learning using a process dissociation procedure (PDP; adapted from Werner et al, 2015), which we and others have done before (Neville and Cressman, 2018;Maresch and Donchin, 2019;Modchalingam et al, 2019) and is consistent with findings from a similar task quantifying explicit learning (Hegele and Heuer, 2013). We ask people to make open-loop reaches to targets after adaptation, while either using the strategy they just learned (implicit and explicit), or not using it (only implicit).…”

Competition between parallel sensorimotor learning systems

“…A similar phenomenon can be observed in other experiments where participants are provided with visual landmarks scattered on either side of the target. When participants use these landmarks to report their intended aiming direction, reporting frequency increases explicit strategy use, but decreases implicit adaptation [66][67][68] . Furthermore, participants themselves exhibit varying degrees of strategy, leading to negative subject-to-subject associations between implicit and explicit learning 15,16,41 (Fig.…”