Transfer of Learned Object Manipulations between Two- and Five-Digit Grasps

Successful object manipulation involves integrating object properties into a motor plan and scaling fingertip forces through learning. This study investigated whether learned manipulations using a two-digit grip transfer to a five-digit grip and vice versa, focusing on the challenges posed by added degrees of freedom in force distribution. The goal of the task was to exert the necessary compensatory torque (Tcom) and vertical forces to minimize object roll on a visually symmetrical object that with an asymmetrical mass distribution. To examine this, subjects performed blocked consecutive learning trials before switching grip type. Our results support the learning transfer between two-digits and five-digit grasp configurations despite challenges in maintaining perfect stability during the grip switch. Subjects adapted their grip forces (GF), center of pressure (CoP), and Tcom to minimize object roll, with significant improvements observed from novel (1 ^st ) to transfer (11 ^th ) trials. These findings suggest high-level, effector-independent representations of object manipulation that enable generalization across grip types, though some limitations in force distribution and digit position arise during transfers.