Does planning a different trajectory influence the choice of grasping points?

We examined whether the movement path is considered when selecting the positions at which the digits will contact the object's surface (grasping points). Subjects grasped objects of different heights but with the same radius at various locations on a table. At some locations, one digit crossed to the side of the object opposite of where it started. In doing so, it moved over a short object whereas it curved around a tall object. This resulted in very different paths for different objects. Importantly, the selection of grasping points was unaffected. That subjects do not appear to consider the path when selecting grasping points suggests that the grasping points are selected before planning the movements towards those points. © 2010 The Author(s)

Qaamuuska Af Soomaaliga Presentation: speakers' interviews

On the occasion of the Somali Monolingual Dictionary presentation, the Swedish journalist Lars Aberg interviewed the speakers: Prof. Annarita Puglielli, Prof. Cabdalla Cumar Mansuur, Axmed F. Cali Idaajaa, Maxamed Daahir Afrax.Munaasabada daahfurka Qaamuuska Af-soomaaliga ee ay diyaariyeen A. Puglielli iyo Cabdalla Mansuur ayaa suxufi Sweeden, Lars Aberg, la yeeshay wareysi: Annarita Puglielli, Prof. Cabdalla Cumar Mansuur, Axmed F. Cali Idaajaa, Maxamed Daahir Afrax.In occasione della presentazione del Grande Dizionario Somalo Monolingue, il giornalista svedese Lars Aberg ha intervistato i relatori: Prof. Annarita Puglielli, Prof. Abdalla Omar Mansur, Axmed F. Cali Idaajaa, Maxamed Daahir Afrax.Link Intervju Pr Abdalla: http://www.youtube.com/watch?v=ZNT4fF0V3RY&list=UUud8D2IV5qhAnQveScT4TsALink Intervju Pr Afrax: http://www.youtube.com/watch?v=kHt84rJJHakLink Intervju Pr Idaajaa: http://www.youtube.com/watch?v=VV-VcOGHrW0Link Intervju Pr Annarita Puglielli: https://www.youtube.com/watch?v=9d9OC7XnWs

Data from: Fixation biases towards the index finger in almost-natural grasping

We use visual information to guide our grasping movements. When grasping an object with a precision grip, the two digits need to reach two different positions more or less simultaneously, but the eyes can only be directed to one position at a time. Several studies that have examined eye movements in grasping have found that people tend to direct their gaze near where their index finger will contact the object. Here we aimed at better understanding why people do so by asking participants to lift an object off a horizontal surface. They were to grasp the object with a precision grip while movements of their hand, eye and head were recorded. We confirmed that people tend to look closer to positions that a digit needs to reach more accurately. Moreover, we show that where they look as they reach for the object depends on where they were looking before, presumably because they try to minimize the time during which the eyes are moving so fast that no new visual information is acquired. Most importantly, we confirmed that people have a bias to direct gaze towards the index finger’s contact point rather than towards that of the thumb. In our study, this cannot be explained by the index finger contacting the object before the thumb. Instead, it appears to be because the index finger moves to a position that is hidden behind the object that is grasped, probably making this the place at which one is most likely to encounter unexpected problems that would benefit from visual guidance. However, this cannot explain the bias that was found in previous studies, where neither contact point was hidden, so it cannot be the only explanation for the bias

Does postural stability affect grasping?

AbstractWe examined whether challenging upright stance influences the execution of a grasping task. Participants reached to grasp a small sphere while standing either on a stable surface or on foam. Before reaching for the sphere, participants exhibited more body sway and greater fluctuations in the centre of pressure when standing on foam. While reaching for the sphere, the overall body posture changed less when standing on foam than when standing on the stable surface. The digits’ and wrist's movements towards the sphere were no different when standing on foam than when standing on the stable surface. Presumably, the redundancy in the way movements can be performed is exploited to choose the most suitable changes in joint angles to achieve the desired movements of the digits under the prevailing conditions

Gaze when reaching to grasp a glass

People have often been reported to look near their index finger's contact point when grasping. They have only been reported to look near the thumb's contact point when grasping an opaque object at eye height with a horizontal grip-thus when the region near the index finger's contact point is occluded. To examine to what extent being able to see the digits' final trajectories influences where people look, we compared gaze when reaching to grasp a glass of water or milk that was placed at eye or hip height. Participants grasped the glass and poured its contents into another glass on their left. Surprisingly, most participants looked nearer to their thumb's contact point. To examine whether this was because gaze was biased toward the position of the subsequent action, which was to the left, we asked participants in a second experiment to grasp a glass and either place it or pour its contents into another glass either to their left or right. Most participants' gaze was biased to some extent toward the position of the next action, but gaze was not influenced consistently across participants. Gaze was also not influenced consistently across the experiments for individual participants-even for those who participated in both experiments. We conclude that gaze is not simply determined by the identity of the digit or by details of the contact points, such as their visibility, but that gaze is just as sensitive to other factors, such as where one will manipulate the object after grasping