Grove Philip M, Ashton Jessica, Kawachi Yousuke, Sakurai Kenzo
School of Psychology, The University of Queensland, St. Lucia, Queensland, Australia.
J Vis. 2012 Aug 7;12(8):5. doi: 10.1167/12.8.5.
With few exceptions, the sound-induced bias toward bouncing characteristic of the stream/bounce effect has been demonstrated via subjective responses, leaving open the question whether perceptual factors, decisional factors, or some combination of the two underlie the illusion. We addressed this issue directly, using a novel stimulus and signal detection theory to independently characterize observers' sensitivity (d') and criterion (c) when discriminating between objective streaming and bouncing events in the presence or absence of a brief sound at the point of coincidence. We first confirmed that sound-induced motion reversals persist despite rendering the targets visually distinguishable by differences in texture density. Sound-induced bouncing persisted for targets differing by as many as nine just-noticeable-differences (JNDs). We then exploited this finding in our signal detection paradigm in which observers discriminated between objective streaming and bouncing events. We failed to find any difference in sensitivity (d') between sound and no-sound conditions, but we did observe a significantly more liberal criterion (c) in the sound condition than the no-sound condition. The results suggest that the auditory-induced bias toward bouncing in this context is attributable to a sound-induced shift in criterion implicating decisional processes rather than perceptual processes determining responses to these displays.
除少数例外情况外，通过主观反应已证明了声音引发的对流/弹跳效应中弹跳特征的偏向，这使得知觉因素、决策因素或两者的某种组合是否构成这种错觉的基础这一问题悬而未决。我们直接解决了这个问题，使用一种新颖的刺激和信号检测理论，在有无重合点处的短暂声音的情况下，区分客观的流和弹跳事件时，独立地刻画观察者的敏感度（d'）和标准（c）。我们首先证实，尽管通过纹理密度差异使目标在视觉上可区分，但声音引发的运动反转仍然存在。声音引发的弹跳对于相差多达九个最小可觉差（JNDs）的目标仍然持续存在。然后，我们在信号检测范式中利用这一发现，让观察者区分客观的流和弹跳事件。我们未发现声音条件和无声条件下在敏感度（d'）上有任何差异，但我们确实观察到，与无声条件相比，声音条件下的标准（c）明显更宽松。结果表明，在这种情况下，听觉引发的对弹跳的偏向可归因于标准的声音引发的偏移，这涉及决策过程而非决定对这些显示反应的知觉过程。
