The End-State Comfort Effect in Bimanual Grip Selection

Abstract

During a unimanual grip selection task in which people pick up a lightweight dowel and place one end against targets at variable heights, the choice of hand grip (overhand vs. underhand) typically depends on the perception of how comfortable the arm will be at the end of the movement: an end-state comfort effect. The two experiments reported here extend this work to bimanual tasks. In each experiment, 26 right-handed participants used their left and right hands to simultaneously pick up two wooden dowels and place either the right or left end against a series of 14 targets ranging from 14 to 210 cm above the floor. These tasks were performed in systematic ascending and descending orders in Experiment 1 and in random order in Expiment 2. Results were generally consistent with predictions of end-state comfort in that, for the extreme highest and lowest targets, participants tended to select opposite grips with each hand. Taken together, our findings are consistent with the concept of constraint hierarchies within a posture-based motion-planning model.

Combined effects of planning and execution constraints on bimanual task performance

“…As expected, and in line with previous studies on bimanual object manipulations (Fischman et al 2003;Weigelt et al 2006) partici- pants chose to end comfortably, regardless of whether the comfortable end posture was reached by symmetric or asymmetric rotations of the forearms. Interestingly, the end-state comfort eVect predominantly aVected the right hand.…”

“…However, more recently researchers have also focused their attention on the end-state comfort eVect in bimanual tasks (Fischman et al 2003;Weigelt et al 2006;Hughes and Franz 2008). As an example, Fischman et al (2003) showed that participants adjusted the height of their start grips whenever they had to place a dowel at a very low target location (prompting a high start grip) or at a very high target location (eliciting a low start grip). In line with this, Weigelt et al (2006) showed in a bimanual object manipulation task a strong tendency for both hands to end comfortably.…”

Effects of stimulus cueing on bimanual grasp posture planning

“…Although the majority of participants performed the task in a similar fashion to the semi-symbolic group, there was a subset of participants (40 %) in both the symbolic and direct cueing groups who grasped the two objects using an overhand grip in virtually all trials, regardless of condition. Individual differences in end-state comfort sensitivity have been reported in previous studies (Fischman et al 2003;Janssen et al 2010;Rosenbaum et al 1990Rosenbaum et al , 1996, and as in those previous studies, the mechanisms that influenced the individual differences in movement strategies cannot be readily explained by personal factors. Specifically, the age of the participants and proportions of males and females were similar regardless of the chosen planning strategy.…”

“…This end-state comfort effect has been observed in a variety of unimanual tasks (for an overview, see Rosenbaum et al 2006) and provides evidence that final goal postures are represented and planned prior to movement execution. Since the initial report (Rosenbaum et al 1990), more recent studies have examined whether the end-state comfort effect extends to simultaneous bimanual movements (Fischman et al 2003;Hughes and Franz 2008;Hughes et al 2011a, b;Weigelt et al 2006;van der Wel and Rosenbaum 2010). Bimanual movements provide an interesting scenario in which to examine grasp posture planning, as the sensitivity toward end-state comfort often competes with the strong tendency for the two hands to grasp objects with identical postures (bimanual spatial coupling).…”

Prospective and retrospective effects in human motor control: planning grasps for object rotation and translation

“…Several studies demonstrated the end-state comfort eVect for reaching toward an object to be rotated (e.g., Fischman, Stodden, & Lehman, 2003;Haggard, 1998;Herbort & Butz, 2010;Short & Cauraugh, 1997), and one study extended the investigation of the end-state comfort eVect to whole-body movements (Lam, McFee, Chua, & Weeks, 2006). Two other studies showed that the end-state comfort eVect is manifested in nonhuman animals (Chapman, Weiss, & Rosenbaum, 2010;Weiss, Wark, & Rosenbaum, 2007).…”