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Do all components of a sign contribute equally to its recognition? In the present study, misperceptions in the sign-spotting task (based on the word-spotting task; Cutler & Norris, 1988) were analyzed to address this question. Three groups of deaf signers of British Sign Language (BSL) with different ages of acquisition (AoA) saw BSL signs combined with nonsense signs, along with combinations of two nonsense signs. They were asked to spot real signs and report what they had spotted. We will present an analysis of false alarms to the nonsense-sign combinations--that is, misperceptions of nonsense signs as real signs (cf. van Ooijen, 1996). Participants modified the movement and handshape parameters more than the location parameter. Within this pattern, however, there were differences as a function of AoA. These results show that the theoretical distinctions between form-based parameters in sign-language models have consequences for online processing. Vowels and consonants have different roles in speech recognition; similarly, it appears that movement, handshape, and location parameters contribute differentially to sign recognition.

Levelt (2002) argued that apparent effects of word frequency and age of acquisition (AoA) reported in recent picture naming studies might actually be confounded effects operating at the level of object recognition, rather than relevant to theories of lexical retrieval In order to investigate this issue, AoA effects were examined in an object recognition memory task (Experiments 1 and 2) and a word-picture verification task (Experiment 3) and compared with those found in naming tasks using the same pictures. Contrary to Levelts concerns, the results of the three experiments show that the AoA effect on picture naming has a lexical origin and does not simply result from a possible confound of object identification times.

We assess the importance of outline shape in mediating the recognition of living and nonliving things. Natural objects were presented as shaded line drawings or silhouettes, and were living and nonliving things. For object decision (deciding whether an object may be encountered in real life) there were longer response times (RTs) to nonliving than to living things. Importantly, this category difference was greater for silhouettes than for shaded line drawings. For naming, similar category and stimulus differences were evident, but were not as pronounced. We also examined effects of prior naming on subsequent object decision performance. Repetition priming was equivalent for nonliving and living things. However, prior presentation of silhouettes (but not shaded line drawings) reduced the longer RT to nonliving things relative to living things in silhouette object decision. We propose that outline contour benefits recognition of living things more than nonliving things: For nonliving things, there may be greater 2-D/3-D interpretational ambiguity, and/or they may possess fewer salient features.

The use of outline shape in recognizing objects was investigated in 4 experiments. In Experiment 1, participants matched a shaded image to either another shaded image or a silhouette. In Experiment 2, they initially named shaded images: later they named either shaded images or silhouettes. Performance in both experiments was predicted by changes in the outline shape of the stimuli. The same matching (Experiment 3) and priming (Experiment 4) paradigms were then used to investigate recognition with objects that were rotated between presentations so as to change the outline shape of the object. Recognition was predicted by changes to outline shape. These results place constraints on models of object recognition and are most compatible with viewpoint-dependent models of recognition.

Infants' recognition of contour-deleted figures was investigated in four experiments using a habituation procedure. The results indicate that 12-month-old infants could recognize line drawings of figures that were missing 33%, 50%, or even as much as 66% of their contour. This was so whether the contour-deleted versions were used on habituation or on test: Intact figures were recognized after habituation to contour-deleted exemplars, and in most cases contour-deleted ones were recognized after habituation to the intact figure. The single failure appeared to be due to difficulty in discriminating between two extremely impoverished test stimuli. Findings from the final experiment, in which infants recognized complements of contour-deleted stimuli but not scrambled versions, suggested that they fill in the gaps of the contour-deleted figures so as to create a figural whole.

In three experiments, we independently manipulated the angular disparity betwee objects to be compared and the angular distance between the central axis of the objects and the vertical axis in a mental rotation paradigm. There was a linear increase in reaction times that was attributable to both factors. This result held whether the objects were rotated (with respect to each other and to the upright) within the frontal-parallel plane (Experiment 1) or in depth (Experiment 2), although the effects of both factors were greater for objects rotated in depth than for objects rotated within the frontal-parallel plane (Experiment 3). In addition, the factors interacted when the subjects had to search for matching ends of the figures (Experiments 1 and 2), but they were additive when the ends that matched were evident (Experiment 3). These data may be interpreted to mean that subjects normalize or reference an object with respect to the vertical upright as well as compute the rotational transformations used to determine shape identity.

The speed and accuracy of perceptual recognition of a brieftly presented picture of an object is facilitated by its prior presentation. Picture priming tasks were used to assess whether the facilitation is a function of the repetition of: (a) the object's image features (viz., vertices and edges), (b) the object model (e.g., that it is a grand piano), or (c) a representation intermediate between (a) and (b) consisting of convex or singly concave components of the object, roughly corresponding to the object's part. Subjects viewed pictures with half their contour removed by deleting either (a) every other image feature from each part, or (b) half the components. On a second (primed) block of trials, subjects, saw: (a) the identical image that they viewed on the first block, (b) the complement which had the missing contours, or (c) a same name-different exemplar of the object class (e.g., a grand piano when an upright piano had been shown on the first block). With deletion of features, speed and accuracy of naming identical and complementary images were equivalent, indicating that none of the priming could be attributed to the actually present in the image. Performance with both types of image enjoyed an advantage over that with the different exemplars, establishing that the priming was visual, rather than verbal or conceptual. With deletion of the components, performance with identical images was much better than that with their complements. The latter were identical images was much better than that with their complements. The latter were equivalent to the different exemplars, indicating that all the visual priming of an image of an object is through the activation of a representation of its components in specified relations. In terms of a recent neutral net implementation of object recognition (Hummel & Biederman, in press), the results suggest that the locus of object priming may be at changes in the weight matrix for a geon assembly layer, where units have self-organized to represent combinations of convex or singly concave components (or geons) and their attributes (e.g., aspect ratio, orientation, and relations with other geons such as TOP-OF). The results of these experiments provide evidence for the psychological reality of intermediate representations in real-time visual object recognition.

This article reviews a number of approaches that perceptual psychologists have taken in attempting to understand 2-dimensional (2-D) shape recognition. Various strands in the literature are traced and current theoretical accounts are discussed in light of the earlier work. Today, it is generally accepted that the internal representation of shape is in the form of a structural description. Such a description is, in turn, couched in some form of abstract code. There is increasing interest in the notion that structural descriptions are critically determined by the imposition of a frame of reference. Although the discussion primarily deals with work on 2-D shapes, the underlying assumption is that this work is fundamental for theories of visual object recognition.

Subjects inspected sets of flat, separated orthographic projections of surfaces of potential three-dimensional objects. After solving problems based on these orthographic views, subjects discriminated between isometric views of the same objects and drawings of distractor structures. Recognition of the isometrics, which had never been shown during the problem solving phase of the experiment, was excellent. In addition, recognition of isometrics corresponding to problems that had been solved correctly when presented in orthographic form was significantly superior to recognition of isometrics based on problems solved incorrectly. In Experiment 2, conditions were included in which either orthographic or isometric views functioned as problem solving or recognition displays. Only in the case of orthographic for correctly-solved problems over incorrectly-solved problems obtained. The pattern of results suggests that viewers construct mental representations embodying structural information about integrated, three-dimensional objects when asked to reason about flat, disconnected projections.

The decomposition of three-dimensional (3-D) objects into shape primitives consisting of geometric volumes is a key proposal of some theories of object recognition. It implicitly assumes that recognition involves volumetric completion - the derivation of a three-dimensional structure that comprises inferred shape properties, such as surfaces, that are not directly visible due to self-occlusion. The goal of this study was to test this claim. In Experiment 1 participants memorized novel objects and then discriminated these from previously unseen objects. Targets were preceded by primes containing a subset of object surfaces that either matched those visible in the whole objects or that could only be inferred through volumetric completion. The results showed performance benefits through priming from visible surfaces but not from inferred surfaces. In Experiment 2, we found equivalent priming for part-primes containing two visible surfaces from the same volumetric part and for primes containing one surface from each of two volumes. These results challenge the view that 3-D object recognition is mediated by shape primitives comprising geometric volumes. Instead, the results support an alternative model that proposes that 3-D shapes are represented as a non-volumetric surface-based structural description.

Although, ordinarily, upright objects are readily recognized by observers who are tilted, it is hypothesized that this is achieved by a process of correction. The first stage of that process is held to be a description of the object in relation to the biologically more primitive system of retinal coordinates. In order to test this hypothesis, tilted subjects were required to view figures under conditions of inattention (Experiment 1) or divided attention (Experiment 2). Under such conditions description may not proceed beyond that first stage. The results showed that recognition description may not proceed beyond that first stage. The results showed that recognition was higher for figures that maintained their orientation with respect to the retina (although they were then tilted in the environment) than for figures that remained upright in the environment (although they were then disoriented with respect to the retina). This outcome is the very opposite of what occurs under conditions of attention.

How do we recognize objects despite differences in their retinal projections when they are seen at different orientations? Marr and Nishihara (1978) proposed that shapes are represented in memory as structural descriptions in object-centered coordinate systems, so that an object is represented identically regardless of its orientation. An alternative hypothesis is that an object is represented in memory in a single representation corresponding to a canonical orientation, and a mental rotation operation transforms an input shape into that orientation before input and memory are compared. A third possibility is that shapes are stored in a set of representations, each corresponding to a different orientation. In four experiments, subjects studied several objects each at a single orientation, and were given extensive practice at naming them quickly, or at classifying them as normal or mirror-reversed, at several orientations. At first, response times increased with departure from the study orientations. At first, response times increased with departure from the study orientations, with a slope similar to those obtained in classic mental rotation experiments. This suggests that subjects made both judgements by mentally transforming the orientation of the input shape to the one they had initially studied. With practice, subjects recognized the objects almost equally quickly at all the familiar orientations. At that point they were probed with the same objects appearing at novel orientations. Response times for these probes increased with increasing disparity from the previously trained orientations. This indicates that subjects had stored representations of the shapes at each of the practice orientations and recognized shapes at the new orientations by rotating them to one of the stored orientations. The results are consistent with a hybrid of the second (mental transformation) and third (multiple view) hypotheses of shape recognition: input shapes are transformed to a stored view, either the one at the nearest orientation or one at a canonical orientation. Interestingly, when mirror-images of trained shapes were presented for naming, subjects took the same time at all orientations. This suggests that mental transformations of orientation can take the shortest path of rotation that will align an input shape and its memorized counterpart, in this case a rotation in depth about an axis in the picture plane.