The Influence of Initial and Final Precision on Motor Planning: Individual Differences in End-State Comfort During Unimanual Grasping and Placing

ABSTRACT

People will often grasp an object with an uncomfortable initial grasp if this affords more comfort at the end of the movement. The authors’ primary objective was to examine whether grasp planning is influenced by precision demands at the start and end of the movement. Twenty right-handed individuals performed a unimanual grasping and placing task in which the precision requirements at the start and end of the movement were either identical (low initial and final precision, high initial and final precision) or different (low initial and high final precision, high initial and low final precision). The major finding to emerge was the presence of individual differences. 50% of participants changed their initial grasps based on the precision requirements of the task, and were more likely to satisfy end-state comfort when the final precision requirements were high than when they were low. In contrast, 50% of participants generally planned their movements to satisfy end-state comfort (regardless of precision requirements). The authors hypothesized that the former group of participants was sensitive to the precision demands of the task, and participants planned their grips in accordance with these demands. In contrast, the latter group of participants reduced the cognitive costs by using previously successful grasp plans.

Keywords:

• end-state comfort
• grasping
• individual differences
• precision

ACKNOWLEDGMENTS

The authors thank an anonymous reviewer for the insightful comments on a previous version of this manuscript. Christian Seegelke gratefully acknowledges the financial support from Honda Research Institute Europe. This research was funded by the German Research Foundation (DFG; EC 277).

Notes

One participant did not employ a consistent strategy in the high initial and high final condition.

The results from the low initial and high final condition are similar to those reported in previous studies that use a similar experimental paradigm (Hughes & Franz, 2008; Seegelke et al., 2011).