The Recognition of Solid Object Shape: The Importance of Inhomogeneity

Abstract

A single experiment evaluated the haptic-visual cross-modal matching of solid object shape. One set of randomly shaped artificial objects was used (sinusoidally modulated spheres, SMS) as well as two sets of naturally shaped objects (bell peppers, Capsicum annuum and sweet potatoes, Ipomoea batatas ). A total of 66 adults participated in the study. The participants’ task was to haptically explore a single object on any particular trial and subsequently indicate which of 12 simultaneously visible objects possessed the same shape. The participants’ performance for the natural objects was 60.9 and 78.7 percent correct for the bell peppers and sweet potatoes, respectively. The analogous performance for the SMS objects, while better than chance, was far worse (18.6 percent correct). All of these types of stimulus objects possess a rich geometrical structure (e.g., they all possess multiple elliptic , hyperbolic , and parabolic surface regions). Nevertheless, these three types of stimulus objects are perceived differently: Individual members of sweet potatoes and bell peppers are largely identifiable to human participants, while the individual SMS objects are not. Analyses of differential geometry indicate that these natural objects (e.g., bell peppers and sweet potatoes) possess heterogeneous spatial configurations of distinctly curved surface regions, and this heterogeneity is lacking in SMS objects. The current results therefore suggest that increases in surface structure heterogeneity facilitate human object recognition.

Aging and temporal integration in the visual perception of object shape

“…Almost all surface regions on naturally occurring solid objects are either saddle-shaped ( hyperbolic ), bump- or dimple-like ( elliptic ), or cylindrical ( parabolic ). Many researchers have hypothesized that solid object shape is represented 34 – 38 as spatial configurations of these types of surface regions. In our current stimulus displays, only small portions of the objects are visible at any given time because of occluding surfaces (see Fig.…”

The importance of contours for visual object recognition and discrimination

“…Finally, parabolic surface regions are shaped like cylinders (curved in one direction, but not curved in a perpendicular direction). As an example, consider the solid object shown in Figure 3; this is a sweet potato (Ipomoea batatas) that I purchased in a grocery store and then laser-scanned in 3-D (Norman et al, 2019). This sweet potato has three prominent elliptic regions (indicated by green & blue) and two hyperbolic ones (indicated by red).…”

The integration of tactile and proprioceptive signals to achieve haptic object perception

“…We used a dissimilarity task over alternatives like object recognition or haptic search (van Polanen et al, 2014) for two reasons: First, we reasoned that dissimilarity tasks would be less susceptible to pop-out effects where specific features of objects can be used as cues to make judgments, thus ensuring that subjects attend to the whole object. It has been shown that pop-out effects indeed exist for both alternatives (Norman et al, 2019; van Polanen et al, 2014). Second, the dissimilarity rating paradigm can be used to quantitatively assess how two sources of information are combined, unlike recognition rates or search time, which exhibit a much more complex relationship with the sensory evidence.…”