Casco Clara, Grieco Alba, Giora Enrico, Martinelli Massimiliano
Dipartimento di Psicologia Generale, Università di Padova, Via Venezia 8, 35131 Padova, Italy.
Vision Res. 2006 Mar;46(6-7):1091-8. doi: 10.1016/j.visres.2005.09.032. Epub 2005 Nov 9.
We found that a moving target line, more-vertical than 45 deg-oriented background lines, pops-out (d'=1.2) although it moves at the same speed of background elements and although it is invisible in static presentation (d'=.7). We suggest that the moving more-vertical target is more salient because the motion system responds to the orthogonal-velocity-component (V(perpendicular)=Delta d/Delta t sin theta) that is larger for the more-vertical target than for distracters. However, motion does not produce high d' when the target is more horizontal than background (d'=.6). This result is not expected if saliency resulted from the sum of saliency of orientation and motion independently coded but is instead predicted by visual search asymmetry. A line length effect on the moving target saliency also suggests that V(perpendicular) is extracted on the whole line and this operation is facilitated by line length in the same way for more-vertical and more-horizontal targets. Altogether, these results demonstrate that speed-based segmentation operating on V(perpendicular) not only affects speed and direction of motion discrimination, as previously demonstrated, but accounts for high saliency of image features that would otherwise prove undetectable of the basis of orientation-contrast.
我们发现，一条移动的目标线比45度取向的背景线更垂直，尽管它与背景元素以相同速度移动，且在静态呈现中不可见（d' = 0.7），但它仍能突显出来（d' = 1.2）。我们认为，移动的更垂直目标更显著，因为运动系统对正交速度分量（V(垂直)=Δd/Δt sinθ）做出反应，对于更垂直的目标，该分量比对干扰项更大。然而，当目标比背景更水平时，运动并不会产生高d'值（d' = 0.6）。如果显著性是由独立编码的方向和运动显著性之和产生的，那么这个结果是出乎意料的，而视觉搜索不对称性则可以预测这一结果。移动目标显著性的线长效应还表明，V(垂直)是在整条线上提取的，并且对于更垂直和更水平的目标，线长以相同方式促进了这一操作。总之，这些结果表明，基于V(垂直)的基于速度的分割不仅如先前所示影响运动辨别速度和方向，而且解释了图像特征的高显著性，否则这些特征在方向对比度基础上将无法检测到。
