Time filter

Source Type

Seegelke C.,Bielefeld University | Seegelke C.,Research Institute for Cognition and Robotics CoR Laboratory | Seegelke C.,CITEC | Hughes C.M.L.,Nanyang Technological University | And 5 more authors.
Experimental Brain Research | Year: 2014

The present experiment examined the influence of final target position on grasp posture planning during a three-segment object manipulation task in which the required object orientation at the first target position was unconstrained. Participants grasped a cylindrical object from a home position, placed it at an intermediate position in a freely chosen orientation, and subsequently placed it at one of four final target positions. Considerable inter-individual differences in initial grasp selection were observed which also led to differences in final grasp postures. Whereas some participants strongly adjusted their initial grasp postures to the final target orientation, and thus showed a preference for end-state comfort, other participants showed virtually no adjustment in initial grasp postures, hence satisfying initial-state comfort. Interestingly, as intermediate grasp postures were similar regardless of initial grasp adjustment, intermediate-state comfort was prioritized by all participants. These results provide further evidence for the interaction of multiple action selection constraints in grasp posture planning during multi-segment object manipulation tasks. Whereas some constraints may take strict precedence in a given task, other constraints may be more flexible and weighted differently among participants. This differentiated weighting leads to task- and subject-specific constraint hierarchies and is reflected in inter-individual differences in grasp selection. © 2014, Springer-Verlag Berlin Heidelberg.


Hughes C.M.L.,Bielefeld University | Hughes C.M.L.,Research Institute for Cognition and Robotics CoR Laboratory | Hughes C.M.L.,CITEC | Hughes C.M.L.,TU Munich | And 9 more authors.
PLoS ONE | Year: 2012

There is ample evidence that people plan their movements to ensure comfortable final grasp postures at the end of a movement. The end-state comfort effect has been found to be a robust constraint during unimanual movements, and leads to the inference that goal-postures are represented and planned prior to movement initiation. The purpose of this study was to examine whether individuals make appropriate corrections to ensure comfortable final goal postures when faced with an unexpected change in action goal. Participants reached for a horizontal cylinder and placed the left or right end of the object into the target disk. As soon as the participant began to move, a secondary stimuli was triggered, which indicated whether the intended action goal had changed or not. Confirming previous research, participants selected initial grasp postures that ensured end-state comfort during non-perturbed trials. In addition, participants made appropriate on-line corrections to their reach-to-grasp movements to ensure end-state comfort during perturbed trials. Corrections in grasp posture occurred early or late in the reach-to-grasp phase. The results indicate that individuals plan their movements to afford comfort at the end of the movement, and that grasp posture planning is controlled via both feedforward and feedback mechanisms. © 2012 Hughes et al.


Lee Hughes C.M.,Bielefeld University | Lee Hughes C.M.,Research Institute for Cognition and Robotics CoR Laboratory | Lee Hughes C.M.,CITEC | Seegelke C.,Bielefeld University | And 4 more authors.
Journal of Motor Behavior | Year: 2012

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.Copyright © 2012 Taylor and Francis Group, LLC.


Hughes C.M.L.,TU Munich | Seegelke C.,Bielefeld University | Seegelke C.,CITEC | Seegelke C.,Research Institute for Cognition and Robotics CoR Laboratory
Journal of Motor Behavior | Year: 2013

The authors examined the effects of perturbations in action goal on bimanual grasp posture planning. Sixteen participants simultaneously reached for 2 cylinders and placed either the left or the right end of the cylinders into targets. As soon as the participants began their reaching movements, a secondary stimulus was triggered, which indicated whether the intended action goal for the left or right hand had changed. Overall, the tendency for a single hand to select end-state comfort compliant grasp postures was higher for the nonperturbed condition compared to both the perturbed left and perturbed right conditions. Furthermore, participants were more likely to plan their movements to ensure end-state comfort for both hands during nonperturbed trials, than perturbed trials, especially object end-orientation conditions that required the adoption of at least one underhand grasp posture to satisfy bimanual end-state comfort. Results indicated that when the action goal of a single object was perturbed, participants attempted to reduce the cognitive costs associated with grasp posture replanning by maintaining the original grasp posture plan, and tolerating grasp postures that result in less controllable final postures. © 2013 Copyright Taylor and Francis Group, LLC.


Hinte S.,Bielefeld University | Lohse M.,Research Institute for Cognition and Robotics CoR Laboratory
Proceedings - IEEE International Workshop on Robot and Human Interactive Communication | Year: 2011

When and how do users interrupt the interaction with a robot and turn to the experimenter? Usually it is assumed that experimenters affect the interaction negatively and should ideally not be present at all. However, in interaction situations with autonomous systems and inexperienced users this is often not possible for safety reasons. Thus, the participants indeed at times switch their focus of attention from the robot to the experimenter. Instead of seeing this as something purely negative, we argue that answering the questions of when, why and how this happens actually bears important information about the state of the interaction and the users' understanding of it. Therefore, we analyzed a study conducted in a home tour scenario with this respect and indeed discovered certain situations when the users turned away from the robot and towards the experimenter. © 2011 IEEE.


Hughes C.M.L.,Bielefeld University | Hughes C.M.L.,Research Institute for Cognition and Robotics CoR Laboratory | Hughes C.M.L.,CITEC | Hughes C.M.L.,TU Munich | And 5 more authors.
Experimental Brain Research | Year: 2012

The purpose of the present study was to investigate whether difficulties in bimanual grasp posture planning arise from conflicts in response selection. Forty-five participants were assigned to one of three groups (symbolic cueing, semi-symbolic cueing, and direct cueing) and instructed to reach for, grasp, and place two objects on a board in various end-orientations, depending on condition. In general, the tendency to adopt initial grasps that resulted in end-state comfort was significantly higher for the semi-symbolic, than that for the other two groups. There were, however, noticeable individual differences in grip behavior in the symbolic and direct cueing groups. Although the majority of participants performed the task in a similar fashion to the semi-symbolic group, therewas a subset of participants (40 %in each group) who grasped the two objects using an overhand grip in virtually all trials, regardless of condition. It is hypothesized that the observed individual differences in grasp posture strategy arise from differences in motor planning abilities, or the strategies participants employ in order to comply with task demands. A secondary finding is that the degree of interlimb coupling was larger for congruent, than incongruent, conditions irrespective of stimulus cueing. This finding indicates that the interference in the execution of bimanual grasping and placing tasks arises from interference during the specificationofmovement parameters specific to planning and execution of bimanual movements, or neuronal cross-talk in efferent pathways, rather than response selection conflicts. © Springer-Verlag 2012.


Hughes C.M.L.,Nanyang Technological University | Seegelke C.,Bielefeld University | Seegelke C.,Research Institute for Cognition and Robotics CoR Laboratory | Seegelke C.,CITEC | Reissig P.,University of Tasmania
Brain and Cognition | Year: 2014

The purpose of the current experiments was to examine whether the problems associated with grasp posture planning during bimanually incongruent movements are due to crosstalk at the motor programming level. Participants performed a grasping and placing task in which they grasped two objects from a table and placed them onto a board to targets that required identical (congruent) or non-identical degrees of rotation (incongruent). The interval between the presentation of the first stimulus and the second stimulus (stimulus onset asynchrony: SOA) was manipulated. Results demonstrate that the problems associated with bimanually incongruent grasp posture planning are reduced at SOA durations longer than 1000. ms, indicating that the costs associated with bimanual incongruent movements arise from crosstalk at the motor programming level. In addition, reach-to-grasp times were shorter, and interlimb limb coupling was higher, for congruent, compared to incongruent, object end-orientation conditions in both Experiment 1 and 2. The bimanual interference observed during reach-to-grasp execution is postulated to arise from limitations in the visual motor system or from conceptual language representations. The present results emphasize that bimanual interference arises from constraints active at multiple levels of the neurobiological-cognitive system. © 2014 Elsevier Inc.


Westerholz J.,CITEC | Westerholz J.,Bielefeld University | Schack T.,CITEC | Schack T.,Bielefeld University | And 3 more authors.
PLoS ONE | Year: 2013

Recent research has shown that neurophysiological activation during action planning depends on the orientation to initial or final action goals for precision grips. However, the neural signature for a distinct class of grasping, power grips, is still unknown. The aim of the present study was to differentiate between cerebral activity, by means of event-related potentials (ERPs), and its temporal organization during power grips executed with an emphasis on either the initial or final parts of movement sequences. In a grasp and transportation task, visual cues emphasized either the grip (the immediate goal) or the target location (the final goal). ERPs differed between immediate and final goal-cued conditions, suggesting different means of operation dependent on goal-relatedness. Differences in mean amplitude occurred earlier for power grips than for recently reported precision grips time-locked to grasping over parieto-occipital areas. Time-locked to final object placement, differences occurred within a similar time window for power and precision grips over frontal areas. These results suggest that a parieto-frontal network of activation is of crucial importance for grasp planning and execution. Our results indicate that power grip preparation and execution for goal-related actions are controlled by similar neural mechanisms as have been observed during precision grips, but with a distinct temporal pattern. © 2013 Westerholz et al.


Seegelke C.,Bielefeld University | Seegelke C.,Research Institute for Cognition and Robotics CoR Laboratory | Seegelke C.,CITEC | Hughes C.M.L.,TU Munich | And 3 more authors.
PLoS ONE | Year: 2013

Action plans are not generated from scratch for each movement, but features of recently generated plans are recalled for subsequent movements. This study investigated whether the observation of an action is sufficient to trigger plan recall processes. Participant dyads performed an object manipulation task in which one participant transported a plunger from an outer platform to a center platform of different heights (first move). Subsequently, either the same (intra-individual task condition) or the other participant (inter-individual task condition) returned the plunger to the outer platform (return moves). Grasp heights were inversely related to center target height and similar irrespective of direction (first vs. return move) and task condition (intra- vs. inter-individual). Moreover, participants' return move grasp heights were highly correlated with their own, but not with their partners' first move grasp heights. Our findings provide evidence that a simulated action plan resembles a plan of how the observer would execute that action (based on a motor representation) rather than a plan of the actually observed action (based on a visual representation). © 2013 Seegelke et al.


Lohse M.,Research Institute for Cognition and Robotics CoR Laboratory
Proceedings - IEEE International Workshop on Robot and Human Interactive Communication | Year: 2011

What users expect of a robot strongly influences their ratings of the interaction. If the robot satisfies the expectations, the users are usually pleased. If not, their experience of the interaction is negative. We as robot designers strive to design for positive interaction experiences. Therefore, users' expectations need to be taken into account. However, in this paper we argue that not all expectations are equally important. Based on a semantic differential questionnaire, we show a correlation between the perceived importance of users' expectations and the difficulty to satisfy them in interaction. The paper argues that this correlation allows to identify the most important improvements that should be made to robot systems but also to find attributes which the robot is quite good at already. © 2011 IEEE.

Loading Research Institute for Cognition and Robotics CoR Laboratory collaborators
Loading Research Institute for Cognition and Robotics CoR Laboratory collaborators