Champion Rebecca A, Adams Wendy J
School of Psychology, University of Southampton, Southampton, UK.
J Vis. 2007 Oct 29;7(13):10.1-10. doi: 10.1167/7.13.10.
Studies of visual search performance with shaded stimuli, in which the target is rotated by 180 degrees relative to the distracters, typically demonstrate more efficient performance in stimuli with vertical compared to horizontal shading gradients. In addition, performance is usually better for vertically shaded stimuli with top-light (seen as convex) distracters compared to those with bottom-light (seen as concave) distracters. These findings have been cited as evidence for the use of the prior assumptions of overhead lighting and convexity in the interpretation of shaded stimuli and suggest that these priors affect preattentive processing. Here we attempt to modify these priors by providing observers with visual-haptic training in an environment inconsistent with their priors. Observers' performance was measured in a visual search task and a shape judgment task before and after training. Following training, we found a reduced asymmetry between visual search performance with convex and concave distracters, suggesting a modification of the convexity prior. However, although evidence of a change in the light-from-above prior was found in the shape judgment task, no change was found in the visual search task. We conclude that experience can modify the convexity prior at a preattentive stage in processing; however, our training did not modify the light-from-above prior that is measured via visual search.
对于带有阴影刺激的视觉搜索性能的研究，其中目标相对于干扰项旋转180度，通常表明与水平阴影梯度相比，垂直阴影梯度的刺激具有更高的效率。此外，与底部打光（视为凹形）的干扰项相比，顶部打光（视为凸形）的干扰项的垂直阴影刺激的性能通常更好。这些发现被引为证据，证明在对阴影刺激的解释中使用了头顶照明和凸性的先验假设，并表明这些先验影响前注意加工。在这里，我们试图通过在与他们的先验不一致的环境中为观察者提供视觉-触觉训练来修改这些先验。在训练前后，在视觉搜索任务和形状判断任务中测量观察者的表现。训练后，我们发现凸形和凹形干扰项的视觉搜索性能之间的不对称性降低，表明凸性先验发生了改变。然而，尽管在形状判断任务中发现了来自上方的光的先验发生变化的证据，但在视觉搜索任务中未发现变化。我们得出结论，经验可以在加工的前注意阶段修改凸性先验；然而，我们的训练并未修改通过视觉搜索测量的来自上方的光的先验。
