Anisotropic visual awareness of shapes.

While object perception may feel instantaneous, it is an iterative process in which information is accumulated until ambiguity about identity and location is resolved. In theory, awareness of an object should depend on how efficiently this process occurs. Therefore, objects with inherently weak visual representations should be more susceptible to perceptual disruption. We tested this hypothesis by examining the perception of aspect ratio, a 2D feature of shapes with anisotropic representation (circular shapes are less robustly represented than elongated shapes in high-level visual areas). Observers viewed a target shape shown for 20-ms within an array of ellipses. The target, which varied from flat to tall, was either masked or unmasked. Observers indicated the target's aspect ratio and if it was visible. Observers reported seeing elongated shapes far more often than circular shapes, but only on trials with object-substitution masking. This effect replicated across five control experiments, even though the shapes were identical in basic image attributes (e.g., contrast, area). Our findings demonstrate that shapes with extreme aspect ratios are more readily available to awareness than shapes with ambiguous dimensionality. More generally, this work supports theories of object processing which suggest that strength of visual representation gates access to awareness.