Don’t try to control your golf club for better putting performance

Tool-body interaction induces a perceived alteration in the sensorimotor body schema (BS) as the tool becomes integrated like a new body part. This phenomenon fosters a sense of ownership and agency over the tool, known as tool embodiment. In this study, we investigated whether also in golfers, extensive and consistent use of a golf club over years of practice can lead to it being perceived as an extension of their arm. More specifically, we explored whether golfers incorporate their golf club into their hand's BS and whether the development of a sense of ownership and agency over the golf club is associated with changes in their BS and perceived peripersonal space (PPS). We recruited ten amateur golfers with many years of experience and regular training several hours per week. Semi-professional handballers served as a control group. While golfers performed a putting test to induce and assess their control over the club, handballers did a ball throwing task. To assess changes in the forearm BS, before and after the putting or throwing test, respectively, participants performed a tactile distance judgment task (TDJ) where they judged distances between two tactile stimuli applied to their right forearm in a proximodistal orientation. A reaching distance estimation (RDE) task was performed to assess the felt extent of the PPS. Golfers also rated their ownership and agency over the golf club as perceived during the putting task. Our results revealed that at baseline both golfers and handballers underestimated the distance of two points on their arm, with no difference between the groups and no change in the post-test. With respect to the PPS, both groups overestimated their reaching distance with the golfers making smaller estimation errors. After the putting and throwing test, respectively, the estimation error was further reduced. Additionally, golfers demonstrated a sense of ownership and agency over the golf club emerging during the putting task. Smaller RDE and TDJ errors were associated with higher levels of perceived ownership over the golf club, while the association of ownership with smaller TDJ errors became only marginally significant. Together these findings indicate that more accurate body image and estimation of reach contributed to a stronger sense of embodiment but not sense of agency. Interestingly, better performance in the putting task predicted lower ownership and agency ratings. No correlation between performance and TDJ or RDE estimation errors were observed. We therefore conclude that less control over the golf club and less BS integration led to better golf putting performance after year-long putting. Keywords: Tool embodiment, golfers, handballers, peripersonal space, body schema, ownership, sense of agency