What does it look like and what can it do? Category structure influences how infants categorize

Despite a large body of research demonstrating the kinds of categories to which infants respond, few studies have directly assessed how infants' categorization unfolds over time. Four experiments used a visual familiarization task to evaluate 10-month-old infants' (N = 98) learning of exemplars characterized by commonalities in appearance or function. When learning exemplars with a common function, infants initially responded to the common feature, apparently forming a category, and only learned the individual features with more extensive familiarization. When learning exemplars with a common appearance, infants initially learned the individual features and apparently only formed a category with more extensive familiarization. The results are discussed in terms of models of category learning.     

The future of infant categorization research: a process-oriented approach

We call for a shift from a content-oriented approach to a process-oriented approach to the study of categorization in infancy. Although gains have been made in our understanding of infant categorization by evaluating the categories to which infants respond, further understanding of infant categorization, and how categorization changes with development, requires that we more directly assess infants' category formation. We argue that two directions for future research will continue to enhance our understanding of categorization in infancy (and beyond). First, contextual variations (e.g., the effects of task, stimuli, and other factors) on infants' categorization must be better understood. Second, we must more directly evaluate the kinds of information infants use when forming categories, as well as how their use of such information changes with age, task, and so forth. We argue that these two foci will provide clearer understanding of the origins and early development of categorization.     

Parsing Items into Separate Categories: Developmental Change in Infant Categorization

Three experiments report developmental change in infants' tendency to parse exemplars into separate categories. In Experiment 1, a familiarization-novelty preference procedure was used. Fifty-four 4-, 7-, and 10-month-old infants were familiarized with members of two basic-level animal categories (cats and horses) and tested with novel members of the familiarized categories and with members of a third category (dogs). In Experiment 2, a habituation-dishabituation procedure was used. Forty-eight 7- and 10-month-old infants were habituated to examples of both male and female faces and tested with novel gender-typical and gender-ambiguous faces. In both experiments, 10-month-old infants appeared to form differentiated categories, whereas younger infants formed a single category to include the range of items presented during familiarization. Experiment 3 ruled out a priori stimulus preferences as an explanation for the 10-month findings in Experiment 2.     

Noncontingent stimulation, stimulus familiarization, and subsequent learning in young infants

2 experiments assessed the effects of prior noncontingent or familiarization experience on subsequent operant conditioning (kick-produced mobile movement) in young infants. In Experiment 1, infants received either long- or short-term noncontingent exposure to their own rotating mobile or simply viewed this mobile for several days while it remained motionless. In Experiment 2, long-term exposure was provided by the same novel mobile used for subsequent training. In both experiments, prior noncontingent experience did not interfere with subsequent conditioning. In Experiment 2, however, simple long-term familiarization with the training mobile precluded "evidence" of learning. The results indicated that infants develop expectancies regarding how stimuli occurring in particular contexts should behave based on their prior experiences with these stimuli.     

Time Course of Visual Attention in Infant Categorization of Cats Versus Dogs: Evidence for a Head Bias as Revealed Through Eye Tracking

Previous looking time studies have shown that infants use the heads of cat and dog images to form category representations for these animal classes. The present research used an eye-tracking procedure to determine the time course of attention to the head and whether it reflects a preexisting bias or online learning. Six- to 7-month-olds were familiarized with cats or dogs in upright or inverted orientations and then tested with a novel cat and novel dog in the same orientation. In the upright orientation, infants fixated head over body throughout familiarization; with inversion, no head preference was observed. These findings suggest that infant reliance on the head to categorize cats versus dogs results from a bias that pushes attention to the head.     

Infants' cross-modal transfer from solid objects to their graphic representations

12-month-old infants were familiarized either tactually or visually with objects and then tested for visual recognition memory using either (1) the familiar and a novel object, (2) colored pictures of the objects, or (3) outline drawings of them. In Study 1, infants showed recognition memory on all 3 visual intramodal problems but showed cross-modal transfer only when objects were used as test stimuli. With increased familiarization times in Study 2, transfer from tactually presented samples to both pictorial displays was achieved, indicating that after feeling an object the infants were able to recognize it visually solely on the basis of its contour. With reduced familiarization times in Study 3, there was no evidence for transfer from visually presented samples to the 2 pictorial displays, replicating the pattern of results observed cross-modally in Study 1 and suggesting that, at least in certain respects, cross-modal and intramodal perception follow similar principles.     

Development of Abstract Grammatical Categorization in Infants

This study examined abstract syntactic categorization in infants, using the case of grammatical gender. Ninety‐six French‐learning 14‐, 17‐, 20‐, and 30‐month‐olds completed the study. In a preferential looking procedure infants were tested on their generalized knowledge of grammatical gender involving pseudonouns and gender‐marking determiners. The pseudonouns were controlled to contain no phonological or acoustical cues to gender. The determiner gender feature was the only information available. During familiarization, some pseudonouns followed a masculine determiner and others a feminine determiner. Test trials presented the same pseudonouns with different determiners in correct (consistent with familiarization gender pairing) versus incorrect gender agreement. Twenty‐month‐olds showed emerging knowledge of gender categorization and agreement. This knowledge was robust in 30‐month‐olds. These findings demonstrate that abstract, productive grammatical representations are present early in acquisition.     

What Develops in Infants’ Spatial Categorization? Korean Infants’ Categorization of Containment and Tight‐Fit Relations

Korean‐learning infants’ categorization of two spatial categories, one consistent and one inconsistent with the Korean semantic category of “kkita,” was examined. Infants of 10 months (n = 32) and 18 months (n = 49) were tested on their categorization of containment or tight fit spatial relations. At 10 months, infants only formed a category of containment, but at 18 months, their categorization of tight fit was significantly stronger than containment. The results suggest that Korean infants benefit from their language environment in forming a category of tight fit when the exemplars are perceptually diverse. In particular, infants’ language environment may bolster their ability to generalize across diverse exemplars to form abstract categorical representations of spatial relations.     

Flexible and context-dependent categorization by eighteen-month-olds

One hundred 18-month-olds were tested using sequential touching and following 4 different priming contexts using sets of toys that could be simultaneously categorized at either the basic or global level. An exact expression of the expected mean sequence length for arbitrary categories was derived as a function of the number of touches made, and a finite mixture model analytic method was also used to explore individual variability in categorization. Toddlers could categorize flexibly and spontaneously selected the level of categorization as a function of the prior prime. Perceptual Variability emerged as a predictor of the level at which infants subsequently categorized. The infants were also able to classify objects as members of both basic- and global-level categories simultaneously.     

Categorization and memory retrieval by three-month-olds

84 3-month-olds were tested in 3 studies of the acquisition and long-term retention of category-specific information. Infants who were trained with a perceptibly different member of an alphanumeric category on each of 3 days generalized responding to a novel instance of the original training category but not a novel member of a novel category during a 24-hour novelty test. 2 weeks later, when infants displayed no evidence of remembering their prior training experience, categorization was reinstated if a novel exemplar from the original training category was used as the retrieval cue in a memory reactivation procedure. A novel exemplar from a novel category was not an effective retrieval cue. The effectiveness of the category-specific retrieval cue was a function of its physical similarity to the individual exemplars encountered during training, not testing. The background against which the alphanumeric exemplars were displayed during training was not an effective retrieval cue in either the 24-hour novelty test or the memory reactivation procedure, indicating that all invariant stimulus attributes do not contribute equally as category cues. These data are the first to document retention of category-specific information after extended intervals. A popular account of categorization holds that infants abstract invariant features from individual exemplars and form a schema or distinctive memory representation of these shared features against which subsequent exemplars are compared. The present data provide support for a more parsimonious account of categorization, based on the retrieval of information about individual exemplars, that does not require an assumption of prototype formation.     

Individual Differences in Infant Visual Attention: Four-Month-Olds' Discrimination and Generalization of Global and Local Stimulus Properties

Cognitive performance and development is negatively correlated with fixation duration patterns during infancy, and evidence suggests that long-looking infants may process visual information more slowly than short-looking infants. 3 experiments described here tested the possibility that these differences may be due to differential sensitivity to global and local visual information. Infants were administered discrimination and generalization tasks involving global and local information at varying levels of familiarization time. Results indicated that 4-month-olds process visual information in a global-to-local sequence. Both long- and short-looking infants were sensitive to both types of information, although long lookers required additional familiarization time to match the performance of short lookers. Finally, apparent "generalization" of global information at brief familiarization levels was traced to insensitivity to local stimulus properties. The results do not support the hypothesis that long- and short-looking infants are differentially sensitive to global versus local visual information at 4 months of age.     

Infant response to stimuli of similar hue and dissimilar shape: tracing the origins of the categorization of objects by hue

This study confirms that infants, like older children, are capable of responding "categorically" to stimuli of different shape if these are similar in hue. 24 infants (mean age 20.0 weeks) were familiarized to a stimulus in 1 hue (dominant wavelength 515 nm) and in either of 2 different shapes (face of a bear or a rabbit) and then presented with 4 main test comparisons in which the familiar stimulus was paired with a novel stimulus in either the familiar or the alternate (novel) shape and in a novel hue from the same or a different category (dominant wavelengths being 548 and 482 nm, respectively, and equally different from the familiar hue). Infants displayed a preference for the novel stimuli only in the new-category hue. Control tasks with a further 40 infants (same mean age as experimental group) eliminated alternative explanations of this pattern of response in terms of differential brightness of the hues, hue preferences, or inability to discriminate the shapes.     

Perceiving "outside the box" occurs early in development: evidence for boundary extension in three- to seven-month-old infants

This investigation examined whether infants display boundary extension-a tendency to remember more of a visual scene than was presented. Three- to 7-month-olds were familiarized with a photograph of a visual scene, and tested with wide-angle versus close-up views of the scene. Infants preferred the close-up, indicating that they perceived the wide angle (the one consistent with boundary extension) as more familiar. Converging experiments showed that: (a) infants did not spontaneously prefer the close-up, (b) adults did not judge the wide angle to be more similar to the familiarization stimulus, and (c) infants spontaneously preferred the close-up when the photographs depicted outline objects without backgrounds. The findings suggest that infants anticipate information that lies beyond the borders of a scene view.     

The Categorization of Above and Below Spatial Relations by Young Infants

3 experiments using the familiarization-novelty preference procedure were conducted to investigate whether 3-month-old infants could form categorical representations of the spatial relations above and below. In Experiment 1, one group of infants familiarized with exemplars depicting a dot in different positions above a horizontal bar displayed a subsequent visual preference for a novel category exemplar (dot below bar) that was paired with a familiar category exemplar (dot in novel position above bar). A second group of infants presented with exemplars in which the dot appeared in variable locations below the bar also responded preferentially to a novel category exemplar (dot above bar) when it was paired with a familiar category exemplar (dot in new position below bar). These preferences did not result from the salience of vertical up-down changes in dot position or the encoding of dot positions relative to an internal horizontal midline (Experiment 3) or from an inability to discriminate the members of each category (Experiment 2), but rather would seem to be a consequence of the ability to represent categorically the spatial relations above and below. The data provide evidence for early categorical organization in human spatial memory.     

Visual and verbal processes involved in the development of picture-recognition skills

4-5-year-old, 6-7-year-old, and 8-9-year-old children were given picture-recognition tasks in which recognition stimuli were systematically varied with respect to familiarization stimuli. Subjects were required either to verbalize or remain silent during familiarization and to identify either central figure only or whole picture recognition. Results suggested that (a) young children base recognition primarily on central figure whereas older children are more likely to utilize the entire stimulus array, and (b) younger children are more likely than older children to use spoken labels as a basis for recognition when they verbalize during familiarization.     

Evidence for knowledge-based category discrimination in infancy

Two studies examined whether infants' category discrimination in an object-examination task was based solely on an ad hoc analysis of perceptual similarities among the experimental stimuli. In Experiment 1A, 11-month-olds examined four different exemplars of one superordinate category (animals or furniture) twice, followed by a new exemplar of the familiar category and an exemplar of the contrasting category. Group A (N = 39) explored natural-looking toy replicas with low between-category similarity, whereas group B (N = 40) explored artificial-looking toy models with high between-category similarity. Experiment 1B (N = 40) tested a group of 10-month-olds with the same design. Experiment 1C (N = 20) reversed the order of test trials. For Experiment 2 (N = 20), the same artificial-looking toy animals as in Experiment 1 (group B) were used for familiarization), but no category change was introduced at the end of the session. Infants' responses varied systematically only with the presence of a category change, and not with the degree of between-category similarity. This supports the hypothesis that performance was knowledge based.     

Differential rates of visual information processing in full-term and preterm infants

This study investigated the effect of increasing familiarization time on the visual recognition memory of 6- and 12-month-old full-term and preterm infants. Infants were given trials in which they viewed a shape for either 10-, 15-, 20-, or 30-sec familiarization and were then tested for visual recognition memory using the paired comparison technique. While the older infants showed evidence of recognition memory after less familiarization time than the younger ones, at both ages preterms required considerably longer familiarization than full-terms. The pattern of performance replicates our earlier finding of developmental lags in the visual information processing of 6-month-old preterms and extends these findings to 12-month-olds. These results suggest that there are persistent differences between preterm and full-term infants throughout at least the first year of life in this very fundamental aspect of cognition.     

Generalized Discrimination of Positive Facial Expressions by Seven- and Ten-Month-Old Infants

The ability of 7- and 10-month-old infants to generalize their discrimination of facial expressions lacking featural consistency was investigated in a series of 4 experiments. Infants were habituated to models posing either prototypically positive displays (e.g., happy expressions) or positive expression blends (e.g., mock surprise). They were then tested for their ability to recognize a positive expression on the face of a novel model and to discriminate positive and negative facial expressions. Only in Experiment 1, in which infants were familiarized to a mix of happy and surprised facial expressions, did 10-month-olds demonstrate generalized discrimination of positive affect. When positive blends or happy expressions alone served as familiarization stimuli, both 7- and 10-month-old infants failed to dishabituate to a change in affective tone. 7-month-olds, in particular, showed consistent recovery of looking to the introduction of novel models. The pattern of results suggests that it is not until sometime after 7 months of age that dependence on the presence of expression-specific features for affect recognition and discrimination diminishes. By 10 months of age, however, infants are beginning to recognize the affective similarity of familiar positive facial expressions.     

正确理解“诚信”的基本涵义

诚信是重要的道德范畴之一,它是“诚”和“信”的统一体,我们在把握这个范畴时,不能把“诚”和“信”等同起来,不能把“信用”相混淆,不能局限在特定的范围内理解这个概念。正确理解诚信这个范畴,对于加强市场经济的信用建设和道德建设,具有重要的理论价值和实践意义。