Wu Jun, He Zijiang J, Ooi Teng Leng
University of Louisville, Louisville, Kentucky 40292, USA.
Percept Psychophys. 2008 May;70(4):707-13. doi: 10.3758/pp.70.4.707.
Our visual space does not appear to change when we scan or shift attention between locations. This appearance of stability implies that the depth information selection process is not crucial for constructing visual space. But we present evidence to the contrary. We focused on space perception in the intermediate distance, which depends on the integration of depth information on the ground. We propose a selection hypothesis that states that the integration process is influenced by where the depth information is selected. Specifically, the integration process inaccurately represents the ground when one samples depth information only from the far ground surface, instead of sequentially from the near to the far ground. To test this, observers matched the depth/length of a sagittal bar (test) to the width of a laterally oriented bar (reference) in three conditions in a full-cue environment that compelled the visual system to sample from different parts of the ground. These conditions had the lateral reference bar placed (1) adjacent to the test bar, (2) at the far ground, and (3) at the near ground. We found that the sagittal bar was perceived as shorter in conditions (1) and (2) than in Condition 3. This finding supports the selection hypothesis, since only Condition 3 led to more accurate ground surface integration/representation and less error in relative distance/depth perception. Also, we found that performances in all three conditions were similar in the dark, which has no depth information on the ground, indicating that the results cannot be attributed to asymmetric visual scanning but, rather, to differential information selection.
当我们在不同位置之间扫描或转移注意力时，我们的视觉空间似乎并没有改变。这种稳定性表明深度信息选择过程对于构建视觉空间并非至关重要。但我们提供了相反的证据。我们关注的是中等距离的空间感知，这依赖于地面上深度信息的整合。我们提出了一种选择假设，即整合过程受深度信息选择位置的影响。具体而言，当一个人仅从远处地面表面采样深度信息，而不是从近处到远处地面依次采样时，整合过程会不准确地呈现地面。为了验证这一点，在一个全线索环境中，观察者在三种条件下将矢状条（测试条）的深度/长度与横向条（参考条）的宽度进行匹配，这种环境迫使视觉系统从地面的不同部分进行采样。这些条件包括将横向参考条放置在（1）与测试条相邻处，（2）远处地面，以及（3）近处地面。我们发现，在条件（1）和（2）下，矢状条被感知为比条件3下更短。这一发现支持了选择假设，因为只有条件3导致了更准确的地面表面整合/呈现以及相对距离/深度感知中的更少误差。此外，我们发现，在黑暗中，所有三种条件下的表现都相似，黑暗中地面没有深度信息，这表明结果不能归因于不对称的视觉扫描，而应归因于不同的信息选择。
