Li Zhi, Durgin Frank H
Department of Psychology and Behavioral Sciences, Zhejiang University, Hangzhou, China.
Department of Psychology, Swarthmore College, Swarthmore, PA, USA.
Atten Percept Psychophys. 2018 Aug;80(6):1609-1618. doi: 10.3758/s13414-018-1536-5.
When one looks at a spot on level ground, the local optical slant (i.e., surface orientation relative to the line of sight) is geometrically equivalent to the angular declination (i.e., sagittal visual direction relative to horizontal). In theory, angular declination provides an unbiased proximal source of information for estimating optical slant on level ground. Two experiments were conducted to investigate whether human visual systems take advantage of this information. An aspect ratio task was used as an implicit measure for assessing perceived optical slant. Participants gave verbal estimates of the perceived aspect ratio of an L-shaped arrangement, formed by three balls on level ground or on slanted surfaces (hills). Gaze direction was held horizontal when viewing the stimuli on hills. Experiment 1 examined two optical slants (22° to 35°) at relatively short viewing distances (3.1 to 11.5 m), while Experiment 2 tested a shallow optical slant (6°) at relatively long viewing distances (5.7 to 17.2 m). No significant difference in perceived aspect ratio was found between the level-ground and the hill conditions in either experiment. These findings suggest that angular declination does not contribute to perceived optical slant on level ground. It seems that the perception of optical slant and of gaze declination are independent, and this may be because the two variables are normally used jointly to determine a higher order perceptual variable-geographical slant.
当一个人看向水平地面上的一个点时，局部光学倾斜度（即表面相对于视线的方向）在几何上等同于角偏斜度（即矢状视觉方向相对于水平方向）。理论上，角偏斜度为估计水平地面上的光学倾斜度提供了一个无偏差的近端信息源。进行了两项实验来研究人类视觉系统是否利用了这一信息。使用了一个长宽比任务作为评估感知到的光学倾斜度的隐性指标。参与者对由水平地面或倾斜表面（山丘）上的三个球形成的L形排列的感知长宽比进行口头估计。当在山丘上观察刺激物时，注视方向保持水平。实验1在相对较短的观察距离（3.1至11.5米）下检查了两种光学倾斜度（22°至35°），而实验2在相对较长的观察距离（5.7至17.2米）下测试了一种浅光学倾斜度（6°）。在两个实验中，水平地面条件和山丘条件下的感知长宽比均未发现显著差异。这些发现表明，角偏斜度对水平地面上感知到的光学倾斜度没有贡献。似乎光学倾斜度的感知和注视偏斜度的感知是相互独立的，这可能是因为这两个变量通常共同用于确定一个更高阶的感知变量——地理倾斜度。
