The continuous end-state comfort effect: weighted integration of multiple biases

Abstract

The grasp orientation when grasping an object is frequently aligned in anticipation of the intended rotation of the object (end-state comfort effect). We analyzed grasp orientation selection in a continuous task to determine the mechanisms underlying the end-state comfort effect. Participants had to grasp a box by a circular handle-which allowed for arbitrary grasp orientations-and then had to rotate the box by various angles. Experiments 1 and 2 revealed both that the rotation's direction considerably determined grasp orientations and that end-postures varied considerably. Experiments 3 and 4 further showed that visual stimuli and initial arm postures biased grasp orientations if the intended rotation could be easily achieved. The data show that end-state comfort but also other factors determine grasp orientation selection. A simple mechanism that integrates multiple weighted biases can account for the data.

It's in the eyes: Planning precise manual actions before execution

“…When we want to execute a task with a particular object, it appears that we first find the target object and then extract the manipulation-relevant features for the selection of an appropriate grasp. However, this grasp selection does not appear to be purely habitual (Herbort & Butz, 2011), but it jointly depends on the current state of the object, the final goal, and the proprioceptive and haptic anticipation of its weight and 3D shape (Herbort & Butz, 2012;Herbort, Butz, & Kunde, 2014).…”

Prospective motor control on tabletops

“…Our studies are mostly inspired by the continuous-tasks ap proach [6,7] rather than discrete-tasks approach of Rosen baum et al [18,19,20]. The former is more generic and can describe situations with uncertainty about the final grasp orientation of a movement and the costs associated with a cer tain object acquisition strategy.…”

“…Herbort [6] argues that it is un clear how precisely someone can anticipate a final posture of a movement and its associated costs, and therefore, optimal planning may not always be feasible. To account for the var ious biases that determine a grasp selection, he proposes the Weighted Integration of Multiple Biases (WIMB) model [7]. In its simplest form, the model can be expressed as follows: According to the model, two different biases contribute to the initial grasp orientation p initial .…”

End-state comfort effect in manipulative motor actions of typical and atypical children: a systematic review

“…Planning an action involves a complex process in which the individual selects a sequence of particular movements among infinite possibilities to perform an action 1,2 . More specifically, the best strategy to grasp a particular object needs to be formulated when planning a manipulative action, considering the objective of the task, the current restrictions to perform it and the physical properties of the object grasped, allowing the most efficient production of movements or performance of sequential actions 3,4 . Determining how a movement or a combination of movements in particular is selected involves the degrees of freedom problem described by Bernstein 5 .…”