de la Malla Cristina, López-Moliner Joan
Vision and Control of Action Group, Departament de Psicologia Bàsica, Universitat de Barcelona, Barcelona, Catalunya, Spain.
Exp Brain Res. 2015 Sep;233(9):2507-15. doi: 10.1007/s00221-015-4321-x. Epub 2015 May 24.
Hitting a moving target requires that we do not miss the target when it is around the aimed position. The time available for us not to miss the target when it is at the position of interest is usually called the time window and depends on target's speed and size. These variables, among others, have been manipulated in previous studies but kept constant within the same trial or session. Here, we present results of a hitting task in which targets underwent simple harmonic motion, which is defined by a sinusoidal function. Target velocity changes continuously in this motion and so does the time window which is shorter in the centre (peak velocity) and longer at the turning points (lowest velocity) within a single trial. We studied two different conditions in which the target moved with a reliable (across trials) amplitude displacement or reliable peak velocity, respectively, and subjects were free to decide where and when to hit it. Results show that subjects made a compromise between maximum and minimum target's speed, so that they did hit the target at intermediate speed values. Interestingly, the reliability of target peak velocity (or displacement) modulated the point of interception. When target's peak velocity was more reliable, subjects intercepted the target at positions with smaller temporal windows and the reverse was true when displacement was reliable. Subjects adapted the interceptive behaviour to the underlying statistical structure of the targets. Finally, in a control condition in which the temporal window also depended on the instant size and not only on speed, subjects intercepted the target when it moved at similar speeds than when the size was constant. This finding suggests that velocity rather than the temporal window contributed more to controlling the interceptive movements.
击中移动目标要求我们在目标处于瞄准位置附近时不要失手。当目标处于感兴趣的位置时，我们不失手的可用时间通常称为时间窗口，它取决于目标的速度和大小。在之前的研究中，除其他因素外，这些变量已被操控，但在同一次试验或实验环节中保持不变。在此，我们展示了一项击打任务的结果，其中目标进行简谐运动，简谐运动由正弦函数定义。在这种运动中，目标速度持续变化，时间窗口也如此，在单次试验中，时间窗口在中心处（峰值速度）较短，在转折点处（最低速度）较长。我们研究了两种不同条件，分别是目标以可靠的（跨试验）振幅位移或可靠的峰值速度移动，并且受试者可以自由决定何时何地击中目标。结果表明，受试者在目标的最大和最小速度之间进行了权衡，以便他们确实能在中间速度值时击中目标。有趣的是，目标峰值速度（或位移）的可靠性调节了拦截点。当目标的峰值速度更可靠时，受试者在时间窗口较小的位置拦截目标，而当位移可靠时情况则相反。受试者根据目标的潜在统计结构调整拦截行为。最后，在一个控制条件下，时间窗口不仅取决于速度，还取决于即时大小，当目标以与大小恒定时相似的速度移动时，受试者会拦截目标。这一发现表明，速度而非时间窗口对控制拦截动作的贡献更大。
