VIII SEMESTRE
PERFIL DOCENTE Teóricos Prácticos Teórico- (*)
The current study was the first to investigate the modulation of the Interference Effect according to human and robot actor form and BM and CV in ASC. As with control participants, in our ASC group there was no modulation of the Interference Effect according to motion. However, whereas control adults exhibited a greater Interference Effect in response to human form compared to robot form, individuals with ASC did not exhibit this modulatory effect of form.
6.4.2.1 Modulation of Interference Effect according to motion
143 the control or ASC group, the current experiment demonstrated a marginally significant effect on movement variance by observed motion regardless of action congruency. In line with previous work (Bouquet et al., 2007; Gowen et al., 2008) the BM condition, compared to the CV condition, resulted in more variable arm movements for control participants. In contrast, there was no effect of motion type for individuals with ASC. Similarly, Gowen and colleagues (2008) reported that, regardless of
congruency, control participants made more variable movements when observing a dot that moved with BM compared to a dot moving with CV; individuals with ASC did not exhibit this pattern. For the current experiment such a finding is surprising since, unlike the stimuli employed by Gowen and colleagues (2008), our BM and CV movements followed identical trajectories and differed only in velocity profile. In Chapter 5: Experiment 1 participants were required to differentiate an animation that moved with MJ BM and the same animation degraded by CV perturbations. Relative to control participants, adults with ASC required a greater CV perturbation in order to successfully differentiate the two animations. This reduced sensitivity to the difference between BM and CV may relate to the absence of an effect of motion type on arm movement variance that we observe for individuals with ASC in the current study.
6.4.2.2 Modulation of Interference Effect according to form
Whereas control adults exhibited a greater Interference Effect in response to human form compared to robot form, individuals with ASC did not exhibit this modulatory effect of human form. This result is in line with Pierno and colleagues’ (2008) finding that visuomotor priming was greater for control children relative to children with ASC following observation of human actions. However, Pierno and colleagues (2008) also demonstrated that visuomotor priming was greater for children with ASC following
observation of robot actions. Based on these data one may expect a greater Interference Effect for robot action for the ASC group relative to the control group. However, we found no evidence of a greater Interference Effect for robot action for the ASC group. Interestingly, the results from the current study demonstrated that the ASC group showed no significant difference in the way they responded to either of the human form conditions and the way the control group responded to the robot condition (Figure 6.6). Thus, this suggests that the way the ASC group responded to human actions is similar to the way control participants responded to robotic actions. Differences in the predictability and repeatability of the movement stimuli could explain the discrepancy between the current findings and those of Pierno and colleagues (2008). The reach-to-grasp actions performed by Pierno and colleagues’ (2008) robotic actor followed smooth humanlike motion but the duration, average velocity and time to grip aperture were identical in every trial, making the robot movement more predictable than the human movements.
144 We found an interaction between group and actor form, which was driven by a higher Interference Effect from observing human compared with robot actions in the control group but not in the ASC group. It should be noted that there were no main effects of group in either of our analyses (Figure 6.5, Figure 6.6), suggesting that across the various conditions individuals with ASC and controls exhibited comparable levels of error plane variance. Coupled with the lack of a difference between the groups in the number of trials that had to be discarded from the analysis (Table 6), this suggests that our
participants with ASC understood the task instructions and performed the task in a similar way to control participants.
The lack of significant Interference Effects for individuals with ASC contrasts with previous studies (Bird et al., 2007; Gowen et al., 2008; Press et al., 2010). It is possible that the discrepancy between the current and previous studies is a result of the different action preparation affordances of the paradigms employed. In previous Interference Effect paradigms (Bird et al., 2007; Gowen et al., 2008; Press et al., 2010) participants were instructed to make one of two pre-specified actions upon presentation of a cue. In this situation the action not currently executed might be prepared for its imminent execution, and so the motor representation of the incongruent action will be active. Hence, a weak cortical motor response to action observation may be sufficient for motor activity to reach the motor execution threshold and be expressed as a typical Interference Effect. In contrast, in the current paradigm the participant was only ever instructed to execute one action type; therefore, action preparation for the incongruent action is unlikely.
The current results can be interpreted in a number of ways. Firstly, the lack of an Interference Effect in ASC is in line with the broken MNS hypothesis of ASC (Bernier et al., 2007; Dapretto et al., 2006; Oberman et al., 2005; Théoret et al., 2005; Williams et al., 2006). As demonstrated in Chapter 3 MNS activations during the observation of non-goal directed actions comprise automatic motoric simulations. It is this automatic motor simulation that is thought to interfere with action control (Blakemore and Frith, 2005). Following this logic, it maybe that the atypical Interference Effects here observed are a consequence of atypical MNS function in ASC. However, as discussed in the introduction to this thesis, it is important to consider non-imitation related components of a task when evaluating imitation (or Interference Effect) impairments. Correspondingly, an alternatively explanation for the lack of Interference Effect is that the social modulation of imitation is atypical in ASC. That is, human form acts as a ‘pro-social prime’ for typical individuals but not for individuals with ASC. Such pro-social priming could result in elevated imitation levels (Leighton et al., 2010; Cook and Bird, 2011) for the control group alone. Chapter 7 investigates whether the social modulation of imitation is atypical in
145 ASC.
6.4.3 Conclusion
This Chapter demonstrated that observing incongruent arm movements generated by actors with human form (virtual human agent, real human) results in an Interference Effect in ongoing executed actions in control participants. This effect was not seen for control participants when they observed incongruent movements conducted by a virtual agent with robot form. In contrast, individuals with ASC differed from controls in that they showed no Interference Effect when observing incongruent human or robot movements.
6.4.3.1 What next
A possible explanation, for the results presented in this Chapter, is that the social modulation of imitation is atypical in ASC hence the human form acts as a ‘pro-social prime’, elevating imitation levels for typical individuals but not for individuals with ASC. Chapter 7 investigates whether the social modulation of imitation is indeed atypical in adults with ASC.
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