Simplicity and generalization: Short-cutting abstraction in children's object categorizations

Development in any domain is often characterized by increasingly abstract representations. Recent evidence in the domain of shape recognition provides one example; between 18 and 24 months children appear to build increasingly abstract representations of object shape [Smith, L. B. (2003). Learning to recognize objects. Psychological Science, 14, 244-250]. Abstraction is in part simplification because it requires the removal of irrelevant information. At the same time, part of generalization is ignoring irrelevant differences. The resulting prediction is this: simplification may enable generalization. Four experiments asked whether simple training instances could shortcut the process of abstraction and directly promote appropriate generalization. Toddlers were taught novel object categories with either simple or complex training exemplars. We found that children who learned with simple objects were able to generalize according to shape similarity, typically relevant for early object categories, better than those who learned with complex objects. Abstraction is the product of learning; using simplified - already abstracted instances - can short-cut that learning, leading to robust generalization.     

The role of surface-based representations of shape in visual object recognition

This study contrasted the role of surfaces and volumetric shape primitives in three-dimensional object recognition. Observers (N?=?50) matched subsets of closed contour fragments, surfaces, or volumetric parts to whole novel objects during a whole–part matching task. Three factors were further manipulated: part viewpoint (either same or different between component parts and whole objects), surface occlusion (comparison parts contained either visible surfaces only, or a surface that was fully or partially occluded in the whole object), and target–distractor similarity. Similarity was varied in terms of systematic variation in nonaccidental (NAP) or metric (MP) properties of individual parts. Analysis of sensitivity (d′) showed a whole–part matching advantage for surface-based parts and volumes over closed contour fragments—but no benefit for volumetric parts over surfaces. We also found a performance cost in matching volumetric parts to wholes when the volumes showed surfaces that were occluded in the whole object. The same pattern was found for both same and different viewpoints, and regardless of target–distractor similarity. These findings challenge models in which recognition is mediated by volumetric part-based shape representations. Instead, we argue that the results are consistent with a surface-based model of high-level shape representation for recognition.     

Clarifying the role of shape in children's taxonomic assumption.

When asked to find a new referent of a novel label children tend to ignore thematic relations (e.g., the relation between a spider and its web) and focus instead on taxonomic relations (e.g., the relation between a spider and a snake). The precise nature of children's taxonomic assumption has not been clear, however. One possibility is that the taxonomic assumption reduces to a "similar-shape rule": perhaps children tend to select objects of the same taxonomic kind when asked to extend new labels simply because these objects are more similar in shape than objects which are only thematically related. Sixty children between 3 and 5 years of age participated in three studies which examined children's attention to thematic relations, similarity of shape, and taxonomic relations when extending novel object labels. The findings indicated that shape has some primacy in children's expectations about object label reference, yet when shape is not available as a guide, children also take taxonomic kind into consideration when searching for new referents of novel labels. Thus children make use of a relatively rich and somewhat varied set of expectations to guide their inferences about object label reference.     

The role of surface discontinuity and shape in 4-month-old infants' object segregation

This research examined whether 4-month-old infants use a discontinuity in an object's front surface to visually segregate a display into two separate objects, and whether object shape enables its use. In Experiment 1, infants saw a three-dimensional display composed of two parts with distinctly different shapes. Two groups of infants saw a display in which these two shapes were divided by a visible discontinuity in the front surface (i.e., a boundary between the two objects). One of these groups saw the display move apart at the discontinuity when a gloved hand pulled one object; the second group saw the two objects move together as a single unit. A third group saw a modified version of this display that had no discontinuity present. The results suggested that infants regarded the discontinuity as an indication that the display could be composed of more than one object. In Experiment 2, infants saw the same display, but with a shape that did not highlight the discontinuity. The infants in this study showed no evidence of using the discontinuity. Together, the findings suggest that 4-month-old infants use the surface discontinuity between two objects as an indication that multiple objects could be present in a display, but only when scanning the outer edges of the display leads them to attend to it.     

The role of expectations in children's experience of novel events

The expectations children bring to interactions, as well as the information they receive prior to them, may be important for children's experiences of new adults. In this study, 148 children (8-13years old) reported on their expectations of adults, received one of three types of information about a new adult (positive, realistic, or control), and then "interacted" with a videotaped "controlling" adult. The effect of information type depended on children's age and prior expectations, with expectancy effects emerging in the context of positive information at the younger end of our age range and in the context of realistic information at the older end of our age range. Furthermore, the more expectations exceeded perceptions (i.e., the more disappointment), the lower children's rapport, affect, and prosocial intentions were and the more internal causal attributions they made. Results are discussed in terms of their theoretical and applied contributions.     

The role of comparison in preschoolers’ novel object categorization

We examined the role of the comparison process and shared names on preschoolers’ categorization of novel objects. In our studies, 4-year-olds were presented with novel object sets consisting of either one or two standards and two test objects: a shape match and a texture match. When children were presented with one standard, they extended the category based on shape regardless of whether the objects were named. When children were presented with two standards that shared the same texture and the objects were named with the same noun, they extended the category based on texture. The opportunity to compare two standards, in the absence of shared names, led to an attenuation of the effect of shape. These findings demonstrate that comparison plays a critical role in the categorization of novel objects and that shared names enhance this process.     

Encoding color and shape from different parts of an object in visual short-term memory

Can we find an object-based encoding benefit in visual short-term memory (VSTM) when the features to be remembered are from different parts of an object? Using object parts defined by either figure-ground separation or negative minima of curvature, results from five experiments in which the visual change detection paradigm was used showed that the object-based encoding benefit in VSTM is modulated by how features are assigned to parts of an object: Features are best retained when the color and shape features to be remembered belong to the same part of an object. Although less well retained in comparison, features from different parts of an object are still better remembered than features from spatially separated objects. An object-based feature binding therefore exists even when the color and shape features to be remembered are from different parts of an object.     

Early word meanings: The case of object names

It has been claimed that young children use object names overgenerally and undergenerally because they do not have notions of objects of particular kinds, but rather, complexive notions of objects and their habitual actions or locations. However, for overgeneral uses in particular, it is difficult to differentiate word meaning from word use because communicative functions are not explicitly expressed in single-word speech. In the present paper, we identify three types of overgeneral uses, and argue that two of these reflect communicative functions rather than complexive meanings. We obtained production data from 10 children in the single-word period, using a standardized method of recording utterance contexts. Most uses of object names were for appropriate instances of the adult categories. Of the overgeneral uses, most were attributable to communicative functions rather than complexive meanings, and there was no evidence of undergeneral use. The results provide strong evidence that, from the very start, children's object names, like those of adults, apply to objects of particular kinds.     

The role of part structure in the perceptual localization of a shape

The process of object localization may be accomplished with respect to a particular reference location, such as the center of gravity, COG (eg Vishwanath and Kowler, 2003 Vision Research 43 1637-1653). Here, we investigated how part structure affects an object's reference location. The reference location was evaluated with a measure of the illusory displacement of an internal target element embedded within a larger object (Morgan et al, 1990 Vision Research 30 1793-1810). To examine whether the reference location is different for shapes with part structure, two shapes were tested: circle (small and large; no part structure) and bell (shape with two parts, one larger than the other). Results were examined with respect to two predictions: either the location of an object is based on its shape as a whole, disregarding part structure (ie a single, overall COG), or the parts are processed separately (different COGs). With the circles, the results showed a systematic illusory displacement of the internal target toward the COG. With the bell, the illusion was significantly weaker than with both circles--even though the main part of the bell had the same size as the small circle, and its horizontal axis had the same extent as the large circle. Moreover, the distance judgments for the bell were consistent with a (weaker) reference point being located at the COG of the larger part, rather than at the COG of the entire bell. These results show that the part structure of a shape plays a role in the representation of its location, and that for complex shapes the perceived location of an embedded element depends more on the parts within which it is embedded, rather than on the whole shape.     

Early activation of object names in visual search

In a visual search experiment, participants had to decide whether or not a target object was present in a fourobject search array. One of these objects could be a semantically related competitor (e.g.,shirt for the targettrousers) or a conceptually unrelated object with the same name as the target—for example,bat (baseball) for the targetbat (animal). In the control condition, the related competitor was replaced by an unrelated object. The participants’ response latencies and eye movements demonstrated that the two types of related competitors had similar effects: Competitors attracted the participants’ visual attention and thereby delayed positive and negative decisions. The results imply that semantic and name information associated with the objects becomes rapidly available and affects the allocation of visual attention.     

Essentialism in Brazilian children's extensions of animal names

The present study investigates whether Brazilian children have essentialist beliefs about animal categories. Two groups of Brazilian 4-year-olds (middle class and from shantytowns) were told that 2 animals share either internal or superficial properties. They were then taught labels for the animals. Across conditions, children from both groups were equally likely to interpret the labels as referring to mutually exclusive categories of animals, but they differed on how likely they were to maintain an inclusion relation between the labels. More important, children from both groups were more likely to accept a common label for animals sharing internal than superficial properties, indicating that internal property information convinced children that the animals were of the same kind. These findings were comparable to the results of a recent study by G. Diesendruck, S. A. Gelman, and K. Lebowitz (1998) with North American 4-year-olds.     

The role of Hebrew letter names in early literacy: the case of multiphonemic acrophonic names

English-speaking children spell letters correctly more often when the letters' names are heard in the word (e.g., B in beach vs. bone). Hebrew letter names have been claimed to be less useful in this regard. In Study 1, kindergartners were asked to report and spell initial and final letters in Hebrew words that included full (CVC), partial (CV), and phonemic (C) cues derived from these letter names (e.g., kaftor, kartis, kibepsilonl, spelled with /kaf/). Correct and biased responses increased with length of congruent and incongruent cues, respectively. In Study 2, preschoolers and kindergartners were asked to report initial letters with monosyllabic or disyllabic names (e.g., /kaf/ or /samepsilonx/, respectively) that included the cues described above. Correct responses increased with cue length; the effect was stronger with monosyllabic letter names than with disyllabic letter names, probably because the cue covered a larger ratio of the letter name. Phonological awareness was linked to use of letter names.     

Long-lasting semantic context effects in the spoken production of object names

A number of recent studies have found that objects are named more slowly in the context of same-category items than in the context of items from various semantic categories. Several experiments reported here indicated that this semantic effect is relatively persistent because it was essentially unaffected by the presence of interspersed filler items. The authors suggest that the effect is specific to the retrieval of lexical-semantic codes and characterize mechanisms that could support the effect at this processing level, such as incremental learning in the links between conceptual and lexical codes and the temporary increase of lexical resting levels. The results underscore the necessity of incorporating mechanisms of long-term adaptation into current models of spoken production.     

The visual and haptic perception of natural object shape

In this study, we evaluated observers' ability to compare naturally shaped three-dimensional (3-D) objects, using their senses of vision and touch. In one experiment, the observers haptically manipulated 1 object and then indicated which of 12 visible objects possessed the same shape. In the second experiment, pairs of objects were presented, and the observers indicated whether their 3-D shape was the same or different. The 2 objects were presented either unimodally (vision-vision or haptic-haptic) or cross-modally (vision-haptic or haptic-vision). In both experiments, the observers were able to compare 3-D shape across modalities with reasonably high levels of accuracy. In Experiment 1, for example, the observers' matching performance rose to 72% correct (chance performance was 8.3%) after five experimental sessions. In Experiment 2, small (but significant) differences in performance were obtained between the unimodal vision-vision condition and the two cross-modal conditions. Taken together, the results suggest that vision and touch have functionally overlapping, but not necessarily equivalent, representations of 3-D shape.     

The influence of object size and surface shape on shape constancy from stereo

The failure of shape constancy from stereoscopic information is widely reported in the literature. In this study we investigate how shape constancy is influenced by the size of the object and by the shape of the object's surface. Participants performed a shape-judgment task on objects of five sizes with three different surface shapes. The shapes used were: a frontoparallel rectangle, a triangular ridge surface, and a cylindrical surface, all of which contained the same maximum depth information, but different variations in depth across the surface. The results showed that, generally, small objects appear stretched and large objects appear squashed along the depth dimension. We also found a larger variance in shape judgments for rectangular stimuli than for cylindrical and ridge-shaped stimuli, suggesting that, when performing shape judgments with cylindrical and ridge-shaped stimuli, observers rely on a higher-order shape representation.     

The role of object recognition in young infants' object segregation

Needham's (2001, this issue) new results confirm that young infants draw on experientially derived representations in resolving individuation ambiguities due to shared boundaries between adjacent objects. They extend previous findings in a surprising way: The memory representations that infants draw upon have bound together information about shape, color, and pattern. Our commentary on these important results draws a distinction between two senses of "recognition" and asks in which sense object recognition contributes to object individuation in these experiments.