Implicit transfer of mirrored spatial structure in visuomotor sequence learning

Implicit transfer of mirrored spatial structure in visuomotor sequence learning Kanji Tanaka (kanji@fennel.rcast.u-tokyo.ac.jp) Research Center for Advanced Science and Technology, The University of Tokyo Japan Society for the Promotion of Science Katsumi Watanabe (kw@fennel.rcast.u-tokyo.ac.jp) Research Center for Advanced Science and Technology, The University of Tokyo Abstract Implicit transfer in sequential learning can occur with some spatio- temporal structures but not with others. Here, we investigated whether the consistent mirror-reversal of visuomotor sequences would lead to implicit transfer. A set comprised three sequential button presses and seven consecutive sets comprised a hyperset. Participants learned hypersets by trial and error with their right hand. Then, they learned another hyperset, in which each set was vertically mirrored, horizontally mirrored, or randomly generated. Even when the participants did not notice the mirrored rule, the mirrored hypersets led to implicit transfer in terms of accuracy for both vertical and horizontal reversals. Furthermore, the vertical reserval also led to implicit transfer of performance speed. Taken together, the present results suggest that people can implicitly apply their learned representations to the mirrored visuomotor sequences. Keywords: Implicit learning; Sequential learning; Transfer; Mirror symmetry; Speed, Accuracy Introduction Implicit learning of behavioral sequences play an important role in our daily life. Our cognitive abilities such as language usage, playing the piano, and driving a car can be improved by implicit acquisition or learning of skills (see reviews for implicit learning; Abrahamse, Jimenez, Verwey, & Clegg, 2010; Perruchet & Pacton, 2006). In fields of cognitive science, cognitive psychology, or experimental psychology, several implicit learning paradigms have been proposed (e.g., Serial Reaction Time (SRT) task, Nissen & Bullemer, 1987; artificial grammar learning (AGL), Reber, 1967; visuomotor button press task, Hikosaka, Rand, Miyachi, & Miyashita, 1995). Most studies have investigated whether people implicitly learn a sequence. In particular, some have insisted that people can learn both elements and a higher-order structure of a sequence. For example, Stadler and Neely (1997) showed that the structure of a sequence had a larger influence on learning in the SRT task than the length of that sequence, indicating that some structures tend to be easier to learn than others (see also Cohen, Ivry, & Keele, 1990). Some studies adopting the AGL task suggested that people might implicitly learn fragments or chunks of two, three, or four letters (Servan- Schreiber & Anderson, 1990; Perruchet & Pacteau, 1990). In the visuomotor button press task, Hikosaka et al. (1995) observed that participants performed slowly and inaccurately when a higher-order sequence was reversed, but individual elements remained identical. Thus, the previous studies pointed to the possibility that people learned certain levels of higher-order structure of a sequence. Transfer of motor learning refers that some movement controls are learned in one situation and transferred to another situation (e.g., Schmidt & Young, 1987). Experiments with key-pressing tasks have demonstrated transfer between sequences that require different arm or finger movements, suggesting that abstract representations underlie sequence production (e.g., Bapi et al., 2006; Kovacs et al., 2009). Namely, this implies that some representations used for motor execution appear to be independent of the effectors producing the action. Cohen et al. (1990), for example, found that transfer of speed occurs when participants learned a tapping task with their three fingers and then, the same tapping task with their index finger (they were not aware that the learning and transfer tasks were identical sequences due to a distraction task). Previous studies have reported that people implicitly detect reversed or mirrored structures of musical melodies, even when they are unaware of the structure (e.g., Dienes, Kuhn, Guo, & Jones, 2012). For example, Dienes and Longuet-Higgings (2004) used sequences comprised of twelve musical tones, where the first six tones were randomly generated and the second six tones were altered from the first tones with some specific alternations. During the learning phase, participants were told that the musical melody obeyed some specific rules and in the test phase, they required to answer whether the musical melody followed the rules or not. Results showed that participants who had background experience with atonal music could implicitly detect altered melodies (e.g., reversals and mirrors). Similarly, Kuhn and Dienes (2005) observed that trained participants preferred mirrored melodic structures to non-mirrored structures. Collectively, these results indicate that people could implicitly use the mirror symmetries of learned sequences. As well as the study of musical melody (e.g., Dienes & Longuet-Higgings, 2004), in the present study, we were interested in whether implicit transfer of visuomotor sequence learning occurred when learned sequences (i.e., visual configuration and finger movement of the sequence)