Rajalakshmi Usha¹, Brad Wyble¹; ¹The Pennsylvania State University

Recreating observed movements is a critical part of learning dance, handicraft and sign languages. We report a new stimulus set and experimental design to study the nature of complex motor representations in working memory. Prior works typically used simple reaching movements or simple actions to demonstrate a motor-specific subcomponent within working memory (Smyth & Pendleton, 1990; Hillman et al., 2024; Wood, 2007), distinct from the visuospatial module. However because these studies used either highly discrete, repetitive motions or focused only on the spatial endpoint, the memories did not reflect complex patterns and may not have been motor plans per se. We created 30 unique, complex 2-D movement patterns containing curves and loops. Videos of a hand moving a computer mouse served as stimuli. Each video was also rotated to create a non-ego version, presenting the movement from an “other-person’’ viewpoint. Participants viewed each video and immediately recreated the movement using their own mouse. Regardless of viewing conditions, all reproductions were made from the participant’s own perspective. We predicted better performance in the ego condition as non-ego stimuli require mental rotation into an ego-centric motor plan. Twenty-five students (N = 25) from Pennsylvania State University participated in the experiment. We used dynamic time warping (DTW) in MATLAB to compare stimulus trajectories with participant recreations. After normalization, a paired-samples t-test (α = .05) showed significantly better matches in the ego condition (M = 209.96) than the non-ego condition (M = 236.2), t(24) = −2.544, p = .0178, indicating better performance for ego stimuli. Future work using concurrent motor and visual tasks will test whether this difference reflects the involvement of two distinct subsystems—one encoding egocentrically viewed movement directly as motor plans and another requiring mental rotation in the visual working memory prior to motor planning for non-egocentric movement.