Brouwer Anne-Marie, Brenner Eli, Smeets Jeroen B J
Erasmus University Rotterdam, Rotterdam, The Netherlands.
Percept Psychophys. 2002 Oct;64(7):1160-8. doi: 10.3758/bf03194764.
To investigate whether visual judgments of acceleration could be used for intercepting moving targets, we determined how well subjects can detect acceleration when the presentation time is short. In a differential judgment task, two dots were presented successively. One dot accelerated and the other decelerated. Subjects had to indicate which of the two accelerated. In an absolute judgment task, subjects had to adjust the motion of a dot so that it appeared to move at a constant velocity. The results for the two tasks were similar. For most subjects, we could determine a detection threshold even when the presentation time was only 300 msec. However, an analysis of these thresholds suggests that subjects did not detect the acceleration itself but that they detected that a target had accelerated on the basis of the change in velocity between the beginning and the end of the presentation. A change of about 25% was needed to detect acceleration with reasonable confidence. Perhaps the simplest use of acceleration for interception consists of distinguishing between acceleration and deceleration of the optic projection of an approaching ball to determine whether one has to run backward or forward to catch it. We examined the results of a real ball-catching task (Oudejans, Michaels, & Bakker, 1997) and found that subjects reacted before acceleration could have been detected. We conclude that acceleration is not used in this simple manner to intercept moving targets.
为了研究视觉对加速度的判断是否可用于拦截移动目标，我们确定了在呈现时间较短时，受试者检测加速度的能力如何。在差异判断任务中，先后呈现两个点。一个点加速，另一个点减速。受试者必须指出两个点中哪个加速了。在绝对判断任务中，受试者必须调整一个点的运动，使其看起来以恒定速度移动。两个任务的结果相似。对于大多数受试者，即使呈现时间仅为300毫秒，我们也能确定检测阈值。然而，对这些阈值的分析表明，受试者并非检测到加速度本身，而是根据呈现开始和结束之间的速度变化检测到目标已经加速。需要大约25%的变化才能有合理把握地检测到加速度。或许，加速度在拦截中的最简单应用是区分接近球的视觉投影的加速和减速，以确定是必须向后跑还是向前跑去接球。我们检查了一项真实接球任务的结果（奥德扬斯、迈克尔和巴克，1997年），发现受试者在能够检测到加速度之前就做出了反应。我们得出结论，在拦截移动目标时，不会以这种简单方式使用加速度。
