Boundary extension is constrained by naturalistic image properties

Boundary extension (BE) is a classical memory illusion in which observers remember more of a scene than was presented. According to predictive accounts, BE reflects the integration of visual input and expectations of what is beyond the boundaries of a scene. Alternatively, according to normalization accounts, BE reflects one end of a normalization process towards the typically-experienced viewing distance of a scene, such that BE and boundary contraction (BC) are equally common. Here, we show that BE and BC depend on depth-of-field (DOF), as determined by the aperture settings on a camera. Photographs with naturalistic DOF led to the strongest BE across a large stimulus set, while BC was primarily observed for unnaturalistic DOF. The relationship between DOF and BE was confirmed in three controlled experiments that isolated DOF from co-varying factors. In line with predictive accounts, we propose that BE is strongest for scene images that resemble day-to-day visual experience.

"Honey, I shrunk the scene": Decoupling the impact of distance from content on memory for scene boundaries

Memory often fills in what's not there. A striking example of this is boundary extension, whereby observers mistakenly recall a view that extends beyond what was actually seen. However, not all scenes induce boundary extension—suggesting that this process is triggered by specific scene properties. Revealing these properties is crucial for understanding how memory reshapes scene boundaries. Here we explored (in five experiments; N=500 adults) whether boundary extension is driven by perceived viewing distance. We created "fake-miniatures" by exploiting tilt-shift, a photographic effect which selectively reduces perceived distance while preserving other scene properties (e.g., making a distant railway appear like a model-train). Fake-miniaturization increased boundary extension for otherwise identical scenes: Participants who performed a scene-memory task misremembered fake-miniaturized views as farther than they actually were. This effect went beyond low-level image changes and generalized to a completely different distance manipulation. Thus, perceived distance modulates how scene boundaries are reshaped in memory.

Systematic transition from boundary extension to contraction along an object-to-scene continuum

After viewing a picture of an environment, our memory of it typically extends beyond what was presented—a phenomenon called boundary extension. But sometimes, memory errors show the opposite pattern—boundary contraction—and the relationship between these phenomena is controversial. We constructed virtual 3D environments, and created a series of views at different distances, from object close-ups to wide-angle indoor views, and tested for memory errors along this object-to-scene continuum. Boundary extension was evident for close-scale views, and transitioned parametrically to boundary contraction for far-scale views. However, this transition point was not tied to a specific position in the environment; instead, it tracked with judgments of the best looking view. We propose that boundary extension and contraction are in fact integrated phenomena, and we offer an account where competition between object-based and scene-based affordances determine whether a view will extend or contract in memory.