The relative weight of shape and non-rigid motion cues in object perception: A model of the parameters underlying dynamic object discrimination

Abstract

Shape and motion are two dominant cues for object recognition, but it can be difficult to investigate their relative quantitative contribution to the recognition process. In the present study, we combined shape and non-rigid motion morphing to investigate the relative contributions of both types of cues to the discrimination of dynamic objects. In Experiment 1, we validated a novel parameter-based motion morphing technique using a single-part three-dimensional object. We then combined shape morphing with the novel motion morphing technique to pairs of multipart objects to create a joint shape and motion similarity space. In Experiment 2, participants were shown pairs of morphed objects from this space and responded "same" on the basis of motion-only, shape-only, or both cues. Both cue types influenced judgments: When responding to only one cue, the other cue could be ignored, although shape cues were more difficult to ignore. When responding on the basis of both cues, there was an overall bias to weight shape cues more than motion cues. Overall, our results suggest that shape influences discrimination more than motion even when both cue types have been made quantitatively equivalent in terms of their individual discriminability.

The contribution of nonrigid motion and shape information to object perception in pigeons and humans

“…Not surprisingly, researchers have begun to investigate the role of motion in object perception. In particular, research has now focused on the contribution of different types of motion (Aggarwal, Cai, Liao, & Sabata, 1998), such as rigid (e.g., translation) and nonrigid object motion that is displayed by moving objects and organisms (e.g., Friedman, Vuong, & Spetch, 2009;Liu & Cooper, 2003;Newell, Wallraven, & Huber, 2004;Setti & Newell, 2010;Stone, 1998;Vuong, Friedman, & Plante, 2009;Vuong, Friedman, & Read, 2012;Vuong & Tarr, 2004.…”

“…Studies show that humans can use nonrigid motion in object recognition. For example, nonrigid movement has a facilitative effect on face recognition (Knappmeyer et al, 2003;O'Toole, Roark, & Abdi, 2002;Xiao et al, 2014) and novel object recognition (Chuang, Vuong, & Bülthoff, 2012;Vuong et al, 2012).…”

“…In spite of the prevalence of nonrigid motion in nature, relatively little is known about how nonrigid motion is utilized in conjunction with shape information for object recognition in general. Recently, Vuong et al (2012) investigated the relative contribution of nonrigid motion and shape information for object recognition in human observers. Participants were asked to determine whether two objects were the same or different.…”

“…When both shape and motion were used, participants weighted shape more heavily than motion. That is, Vuong et al (2012) showed that humans are able to use either shape or nonrigid motion to differentiate between objects, but they show a shape bias when both cues were available.…”

“…It is currently unknown how nonhuman animals use nonrigid motion for object recognition. Furthermore, it is not known whether the biases reported by Vuong et al (2012) and are representative of a fundamental difference in the way the mammalian and avian brains process shape and motion for object recognition. That is, when nonrigid motion is used in conjunction with shape to identify an object, do humans still show greater sensitivity to shape information and pigeons to motion information?…”