Matthews Joshua P, Mills Debra L, Sapir Ayelet
Bangor University, UK.
University of Greenwich, UK This paper has also been awarded the Early Career Best Paper Prize.
Iperception. 2025 Jul 13;16(4):20416695251350000. doi: 10.1177/20416695251350000. eCollection 2025 Jul-Aug.
Shading is an important monocular cue for three-dimensional (3D) perception, whereby 3D shape can be inferred from shading patterns across an object, in a process termed . Shape-from-shading has been characterised as a pre-attentive process that occurs in parallel across the visual field. Recent evidence, however, has challenged this notion, suggesting that it consists of an early pre-attentive process and a later stage of processing that is reliant on top-down attention. Here, we use event-related potentials (ERPs) to test this claim whilst participants were instructed either to ignore or to attend to shaded stimuli that could be perceived as two-dimensional (2D) and 3D. We found that 3D stimuli evoked a larger N1 component than 2D stimuli in both attended and unattended conditions, implying an early, pre-attentive processing stage in shape-from-shading. This activity was lateralised to the right hemisphere when participants attended to the stimuli, in accordance with the right hemisphere advantage in top-down attention. Further, when participants attended to the stimuli, a larger N2 component for 3D compared to 2D shape was found, suggesting a late, top-down process for identifying 3D shape. These findings provide evidence for two distinct stages of processing for shape-from-shading and suggest that attention is necessary for the perception of shape-from-shading.
阴影是三维（3D）感知的重要单眼线索，通过该线索，可以在一个称为“从阴影中感知形状”的过程中，从物体上的阴影图案推断出3D形状。从阴影中感知形状被认为是一种前注意过程，它在整个视野中并行发生。然而，最近的证据对这一观点提出了挑战，表明它由一个早期的前注意过程和一个后期依赖自上而下注意力的加工阶段组成。在这里，我们使用事件相关电位（ERP）来检验这一说法，同时指导参与者忽略或关注那些可以被感知为二维（2D）和三维的阴影刺激。我们发现，在被关注和未被关注的条件下，3D刺激诱发的N1成分都比2D刺激大，这意味着在从阴影中感知形状过程中存在一个早期的前注意加工阶段。当参与者关注刺激时，这种活动在右半球侧化，这与右半球在自上而下注意力方面的优势一致。此外，当参与者关注刺激时，发现3D形状的N2成分比2D形状的更大，这表明在识别3D形状时存在一个后期的自上而下过程。这些发现为从阴影中感知形状的两个不同加工阶段提供了证据，并表明注意力对于从阴影中感知形状是必要的。
