Social Rewards Enhance Offline Improvements in Motor Skill Sho K. Sugawara1,2, Satoshi Tanaka1,3, Shuntaro Okazaki1, Katsumi Watanabe4,5, Norihiro Sadato1,2* 1 Division of Cerebral Integration, National Institute for Physiological Sciences, Okazaki, Aichi, Japan, 2 School of Life Sciences, The Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa, Japan, 3 Center for Fostering Young and Innovative Researchers, Nagoya Institute of Technology, Nagoya, Japan, 4 Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan, 5 Japan Science and Technology Agency, CREST, Kawaguchi, Saitama, Japan Abstract Motor skill memory is first encoded online in a fragile form during practice and then converted into a stable form by offline consolidation, which is the behavioral stage critical for successful learning. Praise, a social reward, is thought to boost motor skill learning by increasing motivation, which leads to increased practice. However, the effect of praise on consolidation is unknown. Here, we tested the hypothesis that praise following motor training directly facilitates skill consolidation. Forty- eight healthy participants were trained on a sequential finger-tapping task. Immediately after training, participants were divided into three groups according to whether they received praise for their own training performance, praise for another participant’s performance, or no praise. Participants who received praise for their own performance showed a significantly higher rate of offline improvement relative to other participants when performing a surprise recall test of the learned sequence. On the other hand, the average performance of the novel sequence and randomly-ordered tapping did not differ between the three experimental groups. These results are the first to indicate that praise-related improvements in motor skill memory are not due to a feedback-incentive mechanism, but instead involve direct effects on the offline consolidation process. Citation: Sugawara SK, Tanaka S, Okazaki S, Watanabe K, Sadato N (2012) Social Rewards Enhance Offline Improvements in Motor Skill. PLoS ONE 7(11): e48174. doi:10.1371/journal.pone.0048174 Editor: Michael Taffe, The Scripps Research Institute, United States of America Received June 11, 2012; Accepted September 20, 2012; Published November 7, 2012 Copyright: 2012 Sugawara et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by Grant-in-Aid for Scientific Research S21220005 to N.S. and S24680061 to S.T. from the Japan Society for the Promotion of Science and CREST to K.W. from the Japan Science and Technology Agency. Part of this study is the result of the project ‘‘Development of biomarker candidates for social behavior’’, carried out under the Strategic Research Program for Brain Sciences by the Ministry of Education, Culture, Sports, Science and Technology of Japan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: sadato@nips.ac.jp Introduction Praise is the positive evaluation of another’s products, perfor- mance, or attributes, where the evaluator presumes the validity of the standards on which the evaluation is based [1]. Praise can boost self-efficacy [2,3], enhance feelings of competence and autonomy [4], create positive feelings [5], strengthen the association between responses and their positive outcomes [6], and provide incentives for task engagement [7]. In motor skill learning, for example, praise is hypothesized to provide feedback about the level of participant competence [8], which serves as an incentive to enhance practice efforts [9]. Thus, praise accelerates motor skill performance by enhancing motivation [8,10,11]. This is reasonable because motor skills are initially acquired by repeatedly performing an action during practice. However, learning a motor skill continues to evolve once practice ends [12,13,14] through consolidation, which is essential for skill formation and long-term retention [15,16,17]. There have been no investigations into the effects of praise on skill consolidation. Here, we hypothesize that praise influences the skill consolidation process directly, as opposed to indirectly through motivating further practice. In the present study we tested this hypothesis through a behavioral experiment designed to manipulate both the timing of the praise given and the participants’ expectation of a future test. First, to examine the effects of praise on offline rather than online performance improvements during training, participants were praised only after training was completed. Second, after a 24-h retention interval, all participants performed a ‘‘surprise’’ retest of the trained sequence. This minimized the possibility that the participants either physically or mentally practiced the trained sequence prior to the retest. These special considerations allowed us to investigate the direct benefits of praise on skill consolidation. Results Performance of the trained sequence Forty-eight right-handed participants came to the laboratory on two subsequent days (Figure 1). All participants were trained on a sequential finger-tapping task, for which offline improvement (a form of consolidation) has been described elsewhere [16–21]. Performance was defined as the number of correctly tapped sequences per 30-s trial. Immediately after training, in order to manipulate praise as an independent variable, participants were divided into three groups (Figure 2): in the ‘‘Self group’’ (n = 17), participants watched a movie in which the evaluators praised their own performance; in the ‘‘Other group’’ (n = 15), participants watched the same movie as the Self group, but were told that it represented the evaluation of another participant’s performance; and in the ‘‘No-praise group’’ (n = 16), participants neither PLOS ONE | www.plosone.org 1 November 2012 | Volume 7 | Issue 11 | e48174