Vagnoni Eleonora, Andreanidou Vasiliki, Lourenco Stella F, Longo Matthew R
Department of Psychological Sciences, Birkbeck, University of London, London, UK.
Department of Clinical Educational and Health Psychology, University College London, London, UK.
Exp Brain Res. 2017 Sep;235(9):2729-2739. doi: 10.1007/s00221-017-5008-2. Epub 2017 Jun 12.
Time-to-collision (TTC) underestimation has been interpreted as an adaptive response that allows observers to have more time to engage in a defensive behaviour. This bias seems, therefore, strongly linked to action preparation. There is evidence that the observer's physical fitness modulates the underestimation effect so that people who need more time to react (i.e. those with less physical fitness) show a stronger underestimation effect. Here we investigated whether this bias is influenced by the momentary action capability of the observers. In the first experiment, participants estimated the time-to-collision of threatening or non-threatening stimuli while being mildly immobilized (with a chin rest) or while standing freely. Having reduced the possibility of movement led participants to show more underestimation of the approaching stimuli. However, this effect was not stronger for threatening relative to non-threatening stimuli. The effect of the action capability found in the first experiment could be interpreted as an expansion of peripersonal space (PPS). In the second experiment, we thus investigated the generality of this effect using an established paradigm to measure the size of peripersonal space. Participants bisected lines from different distances while in the chin rest or standing freely. The results replicated the classic left-to-right gradient in lateral spatial attention with increasing viewing distance, but no effect of immobilization was found. The manipulation of the momentary action capability of the observers influenced the participants' performance in the TTC task but not in the line bisection task. These results are discussed in relation to the different functions of PPS.
碰撞时间（TTC）低估被解释为一种适应性反应，它使观察者有更多时间参与防御行为。因此，这种偏差似乎与行动准备密切相关。有证据表明，观察者的身体健康状况会调节这种低估效应，以至于那些需要更多时间做出反应的人（即身体健康状况较差的人）表现出更强的低估效应。在这里，我们研究了这种偏差是否受观察者瞬间行动能力的影响。在第一个实验中，参与者在轻度固定（使用下巴托）或自由站立时估计威胁性或非威胁性刺激的碰撞时间。减少运动可能性导致参与者对接近的刺激表现出更多的低估。然而，相对于非威胁性刺激，这种效应在威胁性刺激中并不更强。在第一个实验中发现的行动能力效应可以解释为个人空间（PPS）的扩展。因此，在第二个实验中我们使用一种既定范式来测量个人空间大小，研究了这种效应的普遍性。参与者在使用下巴托或自由站立时从不同距离平分线条。结果复制了随着观察距离增加，横向空间注意力中经典的从左到右梯度，但未发现固定的影响。观察者瞬间行动能力的操纵影响了参与者在TTC任务中的表现，但对线平分任务没有影响。我们结合个人空间的不同功能对这些结果进行了讨论。
