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W G Hayward

Publications and source records attributed to W G Hayward.

6 recordsLinked to original sources
PubMed2000

Viewpoint dependence and object discriminability.

In an attempt to reconcile results of previous studies, several theorists have suggested that object recognition performance should range from viewpoint invariant to highly viewpoint dependent depending on how easy it is to differentiate the objects in a given recognition situation. The present study assessed recognition across depth rotations of a single general class of novel objects in three contexts that varied in difficulty. In an initial experiment, recognition in the context involving the most discriminable object differences was viewpoint invariant, but recognition in the least discriminable context and recognition in the intermediate context were equally viewpoint dependent. In a second experiment, utilizing gray-scale versions of the same stimuli, almost identical viewpoint-cost functions were obtained in all three contexts. These results suggest that differences in the geometry of stimulus objects, rather than task difficulty, lie at the heart of previously discrepant findings.

Adult↗
PubMed1999

Recognizing silhouettes and shaded images across depth rotation.

Outline-shape information may be particularly important in the recognition of depth-rotated objects because it provides a coarse shape description which gives first-pass information about the structure of an object. In four experiments, we compared recognition of silhouettes (showing only outline shape) with recognition of fully shaded images of objects, by means of a sequential-matching task. In experiments 1 and 2, the first stimulus was always a shaded image, and the second stimulus was either a shaded image or a silhouette. Recognition costs associated with a change in viewpoint were no greater for silhouettes than they were for shaded images. Experiments 3 and 4 replicated the design of the earlier experiments, but showed a silhouette as the initial stimulus, rather than a shaded image. In these cases, recognition costs associated with a change in viewpoint were greater for silhouettes than for shaded images. Combined, these results indicate that, while visual representations clearly include additional information, outline shape plays an important role in object recognition across depth rotation.

Cognition↗
PubMed1997

Testing conditions for viewpoint invariance in object recognition.

Based on the geon structural description approach, I. Biederman and P.C. Gerhardstein (1993) proposed 3 conditions under which object recognition is predicted to be viewpoint invariant. Two experiments are reported that satisfied all 3 criteria yet revealed performance that was clearly viewpoint dependent. Experiment 1 demonstrated that for both sequential matching and naming tasks, recognition of qualitatively distinct objects became progressively longer and less accurate as the viewpoint difference between study and test viewpoints increased. Experiment 2 demonstrated that for single-part objects, larger effects of viewpoint occurred when there was a change in the visible structure, indicating sensitivity to qualitative features in the image, not geon structural descriptions. These results suggest that the conditions proposed by I. Biederman and P.C. Gerhardstein are not generally applicable, the recognition of qualitatively distinct objects often relies on viewpoint-dependent mechanisms, and the molar features of view-based mechanisms appear to be image features rather than geons.

Adult↗
PubMed1995

Spatial language and spatial representation.

This study explores the commonalities between linguistic and visual representations of space. In particular, because common types of spatial relations, specifically closed-class spatial forms in language and qualitative spatial relations in perception, have been proposed in both representational systems, we investigate whether they share underlying structural similarities. Moreover, while visual spatial relations are a basic element of several theories of object representation, they have been characterized mainly in terms of their linguistic counterparts and without direct evidence about their organization. In order to illuminate the nature of these structures, as well as demonstrate possible correspondences between the two systems, we compare how the spatial relationship between pairs of objects in a scene is encoded linguistically and visually. Spatial language was investigated by having subjects either generate (Experiment 1) or rate the applicability of (Experiment 2) spatial terms for describing the spatial relationship between object pairs. Both the frequency of use and the applicability of spatial terms were highest when the two objects were in vertical or in horizontal alignment. Spatial representation was investigated by paradigms in which subjects either recalled the position of one object relative to the other (Experiment 3) or judged whether one object presented sequentially was in the same or a different position relative to the other (Experiment 4). The accuracy of position estimates and the sensitivity to shifts in position were both highest when the rated object was in a spatial location where spatial terms had been judged to have high applicability in Experiments 1 and 2. These results indicate that the structure of space as encoded by language may be determined by the structure of spatial relations in visual representation.

Adult↗