CAUDAL MAXIMO HORARIO (QMH)

As stated in the introduction, to date it is not clear whether motor resonance and thus motor interference need a tight match between one’s own and the observed agent’s physical features

10

Parts of the text used in this chapter have been published as “Kupferberg A, Huber M, Helfer B, Lenz C, Knoll A, Glasauer S. (2012) Moving Just Like You: Motor Interference Depends on Similar Motility of Agent and Observer. PLoS ONE 7(6): e39637. doi:10.1371/journal.pone.0039637”

30 to emerge during action observation. These features could be, for example, presence of certain morphological features (a body, head, face, and extremities), ability to move determined by joint configuration (motility) or movement kinematics (trajectory, velocity and variability). In the original study, which tested the influence of movement observation on the movement of the observer [166], motor interference (MI) appeared in case of human movement but not in case of artificial movement produced by an industrial robot (see Figure 6b). Interestingly, two later studies have demonstrated MI when subjects watched a humanoid robot performing movements based on implemented prerecordings of motion in a human experimenter (see Figure 6c) [62,212]. Interestingly, this MI disappeared when the same robot moved with a constant-velocity profile. However, it is still unclear which aspect of human motion, absent in robotic movements, was responsible for evoking MI while observing movements based on human prerecordings. Thus, the interference effect in [62,212] might have been triggered by either non-constant velocity (acceleration and deceleration), or variability of movement amplitude and trajectory (e.g. due to fatigue or constraints caused by anatomy of the human arm) during repeatedly presented movements. Further, previous studies which indicated the importance of biological velocity [62,212] were not able to disentangle whether biological motion is the only requirement for MI or whether other morphological similarities between agent and observer have to be present. Finally, previous studies have compared only biological vs. constant velocity profiles but have not investigated whether an artificial approximation of the biological velocity might be sufficient.

Thus, in the absence of top-down cues, the question remains which basic features of the observed agent and the observer have to match for MI to occur. In this study we investigated what aspects in the appearance (for example, head and body), motility (ability to move resulting from the joint configuration) and movement kinematics (variability, velocity) of the observed agent are responsible for triggering MI during observation of incongruent movements (see Table 2). With motility, we mean the ability to move. Thus, with “similar motility” we refer to the capacity of an agent to move in a similar way as another agent. As an example, although a dolphin and a shark have a similar body shape, they swim using different styles: due to the different configuration of their body, sharks swim in a side to side motion and dolphins swim in an up and down motion. In my study, when using the robots, we manipulated the configuration of the robot arm “JAHIR” relative to the observer.

If artificial motility and appearance were sufficient, we expected to see an effect of MI on movement production while viewing videos of incongruent movements performed by an industrial robot arm JAHIR. Alternatively, absence of MI during observation of artificial motion of an industrial robot arm might be caused by either its artificial motility, which results from the joint configuration that does not match the one of the human arm, or its artificial appearance. To test for the role of biological motility, we presented subjects with the rotated video of the industrial robot arm (JAHIR 90°), which in respect to joint configuration now resembled more a human arm (see Figure 8). In the comparison between the two videos of the industrial robot arm, the kinematics of the end effector (the gripper) of the robot arm did not change relative to the observer, but the kinematics of the joints relative to the observer did, since the video was turned by 90°. To test for the importance of human-like body shape,

31 we presented the subjects with a humanoid robot which had the same industrial arm mounted in a human-like configuration, but additionally had a torso and a head. In case that the biological motility but not the appearance is required for MI, we expected to see MI both for JAHIR 90° and JAST. In case that only human-like appearance is required for eliciting MI, we expected to see MI only in case of humanoid robot and human, but not when observing an industrial robot.

In case that movement variability is not important for triggering MI, we expect the interference effect to be present during observation of incongruent movements of at least the humanoid robot which had human-like appearance and motility. Otherwise, if movement variability is important, the MI would be present only for the observation of the human agent.

Movement kinematics (biological velocity and

movement variability) Human-like appearance Human-like motility Human (MH) + + +

Humanoid robot (JAST) - + +

Industrial robot arm, human-like configuration (JAHIR 90°)

- - +

Industrial robot arm, artificial configuration (JAHIR)

- - -

Table 2: Summary of agent characteristics in the MI study.

2.2

Neural correlates of goal attribution during action observation– an fMRI