Object individuation and labelling in 6-month-old infants

The ability to determine how many objects are involved in physical events is fundamental for reasoning about the world that surrounds us. Previous studies suggest that infants can fail to individuate objects in ambiguous occlusion events until their first birthday and that learning words for the objects may play a crucial role in the development of this ability. The present eye-tracking study tested whether the classical object individuation experiments underestimate young infants’ ability to individuate objects and the role word learning plays in this process. Three groups of 6-month-old infants (N = 72) saw two opaque boxes side by side on the eye-tracker screen so that the content of the boxes was not visible. During a familiarization phase, two visually identical objects emerged sequentially from one box and two visually different objects from the other box. For one group of infants the familiarization was silent (Visual Only condition). For a second group of infants the objects were accompanied with nonsense words so that objects’ shape and linguistic labels indicated the same number of objects in the two boxes (Visual & Language condition). For the third group of infants, objects’ shape and linguistic labels were in conflict (Visual vs. Language condition). Following the familiarization, it was revealed that both boxes contained the same number of objects (e.g. one or two). In the Visual Only condition, infants looked longer to the box with incorrect number of objects at test, showing that they could individuate objects using visual cues alone. In the Visual & Language condition infants showed the same looking pattern. However, in the Visual vs Language condition infants looked longer to the box with incorrect number of objects according to linguistic labels. The results show that infants can individuate objects in a complex object individuation paradigm considerably earlier than previously thought and that linguistic cues enforce their own preference in object individuation. The results are consistent with the idea that when language and visual information are in conflict, language can exert an influence on how young infants reason about the visual world.     

Object individuation and object identity in infancy: the role of spatiotemporal information, object property information, and language.

Recent work on object individuation and object identity in infancy indicates that at least three sources of information may be used for object individuation and object identity: spatiotemporal information, object property information, and object kind information. Several experiments have shown that a major developmental change occurs between 10 and 12 months of age (Xu & Carey, 1996; Xu, Carey & Welch, in press; Van de Walle, Prevor & Carey, under review; Xu, Carey & Quint, in preparation): Infants at 10 months and younger readily use spatiotemporal information in object individuation and object identity tasks, but not until about 12 months of age are infants able to use object property or object kind information to do so. This paper proposes a two-part conjecture about the mechanism underlying this change. The first part borrows ideas from object-based attention and the distinction between "what" and "where" information in visual processing. The hypothesis is that (1) young infants encode object motion and location information separately from object property information; and (2) toward the end of the first year, infants integrate these two sources of information. The second part of the conjecture posits an important role for language. Infants may take distinct labels as referring to distinct kinds of objects from the onset of word learning, and infants use this information in solving the problem of object individuation and object identity. Evidence from human adults, infants, and non-human primates is reviewed to provide support for the conjecture.     

Training experts: individuation without naming is worth it

There is growing evidence that individuation experience is necessary for development of expert object discrimination that transfers to new exemplars. Individuation training in human studies has primarily used label association tasks where labels are learned at both the individual and more abstract (basic) level, and expertise criterion requires that individual-level judgments become as fast as basic-level judgments. However, there are training situations when the use of labels is not practical (e.g., with animals or some clinical populations). Moreover, labeling itself can facilitate object discrimination, thus it is unclear what role labels play in the acquisition of expertise in such training paradigms. Here, participants completed an online game that did not require labels in which they interacted with novel objects (Greebles) or control objects (Yufos). Games either required individuation or categorization. We then assessed the impact of this exposure on an abridged Greeble training paradigm. As expected, participants who played Yufo games or Greeble categorization games showed a significant basic-level advantage for Greebles in the abridged training paradigm, typical of novices. However, participants who played the Greeble identity game showed a reduced basic-level advantage, suggesting that individuation without labels may be sufficient to acquire perceptual expertise.     

Memory load affects object individuation in 18-month-old infants

Accurate representation of a changing environment requires individuation-the ability to determine how many numerically distinct objects are present in a scene. Much research has characterized early individuation abilities by identifying which object features infants can use to individuate throughout development. However, despite the fact that without memory featural individuation would be impossible, little is known about how memory constrains object individuation. Here, we investigated infants' ability to individuate multiple objects at once and asked whether individuation performance changes as a function of memory load. In three experiments, 18-month-old infants saw one, two, or three objects hidden and always saw the correct number of objects retrieved. On some trials, one or more of these objects surreptitiously switched identity prior to retrieval. We asked whether infants would use this identity mismatch to individuate and, hence, continue searching for the missing object(s). We found that infants were less likely to individuate objects as memory load grew, but that infants individuated more successfully when the featural contrast between the hidden and retrieved objects increased. These results suggest that remembering more objects may result in a loss of representational precision, thereby decreasing the likelihood of successful individuation. We close by discussing possible links between our results and findings from adult working memory.     

Labeling guides object individuation in 12-month-old infants

A new manual search method was used to investigate the impact of naming on object individuation in 12-month-old infants. In Experiment 1, on a two-word trial, an experimenter looked into a box while the infant was watching and provided two labels (e.g., "Look, a fep!" and "Look, a wug!"). On a one-word trial, the experimenter instead repeated the same label (e.g., "Look, a zav!"). After the infant retrieved one object from the box, subsequent search behavior was recorded. Infants searched more persistently (i.e., for a longer duration) after hearing two labels than one, suggesting that hearing two labels led the infants to expect two objects inside the box. In Experiment 2, infants' search behavior did not differ depending on whether they heard one or two emotional expressions, suggesting that the facilitation effect observed in Experiment 1 may be specific to linguistic expressions. Thus, we provide the first evidence that infants as young as 12 months are able to use intentional and referential cues to guide their object representations. These findings also suggest that a rudimentary version of the mutual-exclusivity constraint may be functional by the end of the first year.     

A review of object individuation in infancy

The present review of object individuation in infancy is divided into five sections. The first section is a brief history of the field and an outline of the development of efficient methods for studying object individuation among infants. Sections 2 and 3 are structured around the empirical evidence obtained by using two different kinds of basic and widely used experiments: infants' responses to (apparently) disappearing objects (Section 2), and infants' responses to objects that (apparently) change into other objects (Section 3). In the fourth section, theories of object individuation are presented and discussed. The final section takes a look ahead to the future and proposes a few experiments that may help in resolving some of the most important disputes regarding object individuation in infancy.     

The emergence of kind-based object individuation in infancy

Four experiments investigated whether 12-month-old infants use perceptual property information in a complex object individuation task, using the violation-of-expectancy looking time method (Xu, 2002; Xu & Carey, 1996). Infants were shown two objects with different properties emerge and return behind an occluder, one at a time. The occluder was then removed, revealing either two objects (expected outcome, if property differences support individuation) or one object (unexpected outcome). In Experiments 1-3, infants failed to use color, size, or a combination of color, size, and pattern differences to establish a representation of two distinct objects behind an occluder. In Experiment 4, infants succeeded in using cross-basic-level-kind shape differences to establish a representation of two objects but failed to do so using within-basic-level-kind shape differences. Control conditions found that the methods were sensitive. Infants succeeded when provided unambiguous spatiotemporal information for two objects, and they encoded the property differences during these experiments. These findings suggest that by 12 months, different properties play different roles in a complex object individuation task. Certain salient shape differences enter into the computation of numerical distinctness of objects before other property differences such as color or size. Since shape differences are often correlated with object kind differences, these results converge with others in the literature that suggest that by the end of the first year of life, infants' representational systems begin to distinguish kinds and properties.     

Infant individuation and identification of objects

Recent studies of the infant's object concept have focused on the role of property information in individuation. We draw a distinction between individuation and identification. By individuation, we mean the setting up of an object representation (OR). By identification, we mean using the information stored in an OR to decide which, if any, previously individuated object is presently encountered. We investigate this distinction in experiments with 12-month-old infants. We find that for infants of this age, a shape difference between two objects has a large effect on both individuation and identification. However, a color difference between two objects has a large effect on individuation, but little or no effect on identification. This suggests that, somewhat surprisingly, information used to establish an OR may not always be incorporated into that representation.     

Ape metaphysics: object individuation without language

Developmental research suggests that whereas very young infants individuate objects purely on spatiotemporal grounds, from (at latest) around 1 year of age children are capable of individuating objects according to the kind they belong to and the properties they instantiate. As the latter ability has been found to correlate with language, some have speculated whether it might be essentially language dependent and therefore uniquely human. Existing studies with non-human primates seem to speak against this hypothesis, but fail to present conclusive evidence due to methodological shortcomings. In the present experiments we set out to test non-linguistic object individuation in three great ape species with a refined manual search methodology. Experiment 1 tested for spatiotemporal object individuation: Subjects saw 1 or 2 objects simultaneously being placed inside a box in which they could reach, and then in both conditions only found 1 object. After retrieval of the 1 object, subjects reached again significantly more often when they had seen 2 than when they had seen 1 object. Experiment 2 tested for object individuation according to property/kind information only: Subjects saw 1 object being placed inside the box, and then either found that object (expected) or an object of a different kind (unexpected). Analogously to Experiment 1, after retrieval of the 1 object, subjects reached again significantly more often in the unexpected than in the expected condition. These results thus confirm previous findings suggesting that individuating objects according to their property/kind is neither uniquely human nor essentially language dependent. It remains to be seen, however, whether this kind of object individuation requires sortal concepts as human linguistic thinkers use them, or whether some simpler form of tracking properties is sufficient.     

Infants' ability to use object kind information for object individuation.

The present studies investigate infants reliance on object kind information in solving the problem of object individuation. Two experiments explored whether adults, 10- and 12-month-old infants could use their knowledge of ducks and cars to individuate an ambiguous array consisting of a toy duck perched on a toy car into two objects. A third experiment investigated whether 10-month-old infants could use their knowledge of cups and shoes to individuate an array consisting of a cup perched on a shoe into two objects. Ten-month-old infants failed to use object kind information alone to resolve the ambiguity with both pairs of objects. In contrast, infants this age succeeded in using spatiotemporal information to segment the array into two objects, i.e. they succeeded if shown that the duck moved independently relative to the car, or the cup relative to the shoe. Twelve-month-old infants, as well as adults, succeeded at object individuation on the basis of object kind information alone. These findings shed light on the developmental course of object individuation and provide converging evidence for the Object-first Hypothesis [Xu, F., Carey, S., 1996; Xu, F., 1997b]. Early on, infants may represent only one concept that provides criteria for individuation, namely physical object; kind concepts such as duck, car, cup, and shoe may be acquired later in the first year of life.     

Do Early Nouns Refer to Kinds or Distinct Shapes? Evidence From 10-Month-Old Infants

ABSTRACT— What is the nature of early words? Specifically, do infants expect words for objects to refer to kinds or to distinct shapes? The current study investigated this question by testing whether 10-month-olds expect internal object properties to be predicted by linguistic labels. A looking-time method was employed. Infants were familiarized with pairs of identical or different objects that made identical or different sounds. During test, before the sounds were demonstrated, paired objects were labeled with one repeated count-noun label or two distinct labels. Results showed that infants expected objects labeled with distinct labels to make different sounds and objects labeled with repeated labels to make identical sounds, regardless of the objects' appearance. These findings indicate that the 10-month-olds' expectations about internal properties of objects were driven by labeling and provide evidence that even at the beginning of word learning, infants expect distinct labels to refer to different kinds.     

Temporal buffering and visual capacity: The time course of object formation underlies capacity limits in visual cognition

Capacity limits are a hallmark of visual cognition. The upper boundary of our ability to individuate and remember objects is well known but—despite its central role in visual information processing—not well understood. Here, we investigated the role of temporal limits in the perceptual processes of forming “object files.” Specifically, we examined the two fundamental mechanisms of object file formation—individuation and identification—by selectively interfering with visual processing by using forward and backward masking with variable stimulus onset asynchronies. While target detection was almost unaffected by these two types of masking, they showed distinct effects on the two different stages of object formation. Forward “integration” masking selectively impaired object individuation, whereas backward “interruption” masking only affected identification and the consolidation of information into visual working memory. We therefore conclude that the inherent temporal dynamics of visual information processing are an essential component in creating the capacity limits in object individuation and visual working memory.     

Do 9-month-old infants expect distinct words to refer to kinds?

In 3 experiments, 9-month-old infants' expectations for what distinct count noun labels refer to were investigated. In Experiment 1, a box was opened to reveal 2 objects inside during familiarization: either 2 identical objects or 2 different objects. Test trials followed the same procedure, except before the box was opened, the contents were described using 2 distinct labels ("I see a wug! I see a dak!") or the same label twice ("I see a zav! I see a zav!"). Infants who heard a label repeated twice looked longer at 2 different objects versus 2 identical objects, whereas infants who heard 2 distinct labels showed a different pattern of looking. Experiments 2 and 3 presented infants with object pairs that only differed in shape or color, and it was found that infants expected the different-shaped (but not the different-colored) objects to be labeled by distinct count nouns. Because the property of shape is a cue to kind membership and the property of color is not, these results suggest that even at the beginning of word learning, infants may expect distinct labels to refer to distinct kinds of objects.     

语言标签和自我关联对新颖客体类别知觉的影响

类别知觉(Categorical perception)是人类最基本的认知活动之一, 探讨语言对类别知觉的影响是心理语言学领域的热门话题之一。在这个研究的3个实验中, 分别在高、低不同的语言标签表征强度下、高、低不同的客体自我关联程度下观察新颖客体类别知觉的过程。研究发现, 语言标签表征程度的增强可促进新颖客体类别知觉的右视野优势效应; 客体与自我关联程度的提高会促进左、右视野的类别知觉效应; 语言标签的表征程度和客体与自我关联程度同时增强时, 语言标签的作用依旧表现出来, 但与自我关联的影响产生权衡分配, 且其影响力并不足以产生右视野优势效应。     

Primates do not spontaneously use shape properties for object individuation: a competence or a performance problem?

Several recent studies have documented that non-human primates can individuate objects according to property and/or kind information in much the same way as human infants do from around one year of age when they begin to acquire language. Some studies suggest, however, that only some properties are used for the individuation of food items: color, but not shape. The present study investigated whether these findings reveal a true competence problem with shape properties in the food domain or whether they merely reveal a performance problem (e.g., lack of attention to shapes). We tested 25 great apes (chimpanzees, bonobos and gorillas) in two food individuation tasks. We manipulated subjects’ experience with differences in color and shape properties of food items. Results indicated (i) that all subjects, regardless of their prior experience, solved the color-based object individuation task and (ii) that only the group with previous experience with different shape properties succeeded in the shape-based individuation task. Great apes can thus be primed to take shape into account for individuating food objects, and this results clearly speaks in favor of a performance (rather than a competence) problem in using shape for object individuation of food items.     

The shape of words in the brain

The principle of arbitrariness in language assumes that there is no intrinsic relationship between linguistic signs and their referents. However, a growing body of sound-symbolism research suggests the existence of some naturally-biased mappings between phonological properties of labels and perceptual properties of their referents (Maurer, Pathman, & Mondloch, 2006). We present new behavioural and neurophysiological evidence for the psychological reality of sound-symbolism. In a categorisation task that captures the processes involved in natural language interpretation, participants were faster to identify novel objects when label–object mappings were sound-symbolic than when they were not. Moreover, early negative EEG-waveforms indicated a sensitivity to sound-symbolic label–object associations (within 200 ms of object presentation), highlighting the non-arbitrary relation between the objects and the labels used to name them. This sensitivity to sound-symbolic label–object associations may reflect a more general process of auditory–visual feature integration where properties of auditory stimuli facilitate a mapping to specific visual features.     

Infants' individuation of agents and inert objects

Using the violation-of-expectancy method, we investigated 10-month-old infants' ability to rely on dynamic features in object individuation processes. Infants were first familiarized to events in which two different objects repeatedly appeared and disappeared, one at a time from behind a screen; at test, the screen was removed, revealing either one or two objects. In Experiment 1, one self-moving non-rigid agent and one inert object were involved in each trial, while in Experiment 2 two different agents were presented. Infants preferred to look at one-object outcomes in Experiment 1, but they did not show any preference for one- or two-object outcomes in Experiment 2. The results suggest that infants can use dynamic information to detect agents in complex individuation tasks before they can rely on shape or surface features. We propose that the sortals agent and inert object appear in development before 12 months without a substantial contribution of linguistic experience. These findings may motivate a revision of current theories on the development of kind-based individuation and object files.     

Shifting ontological boundaries: how Japanese‐ and English‐speaking children generalize names for animals and artifacts

Past research shows that young language learners know something about the different category organizations of animals, objects and substances. The three experiments reported here compare Japanese‐speaking and English‐speaking children's novel name generalizations for two kinds of objects: clear instances of artifacts and objects with ambiguous features suggestive of animates. This comparison was motivated by the very different nature of individuation in the two languages and by the boundary shift hypothesis that proposes that entities that straddle the individuation boundary of a language are assimilated toward the individuated side. The results of the three experiments support the hypothesis. An explanation in terms of mutually reinforcing correlations among language, perceptual properties and category structure is proposed.     

Object individuation in 3-day-old chicks: use of property and spatiotemporal information

Object individuation was investigated in newborn domestic chicks. Chicks' spontaneous tendency to approach the larger group of familiar objects was exploited in a series of five experiments. In the first experiment newborn chicks were reared for 3 days with objects differing in either colour, shape or size. At test, each chick was presented with two groups of events: two objects differing in one property vs. two presentations of the same object. In both cases, all objects involved in the same group of events were sequentially presented and eventually concealed in a different spatial location, and the number of events taking place at each location was equalized. Chicks spontaneously approached the two different objects rather than the single object seen twice. Chicks did not just prefer the more varied set as they did not choose it when the two elements of each group of events were simultaneously presented (Experiment 2). Chicks succeeded when two different objects simultaneously presented were confronted with three identical ones simultaneously presented (Experiment 3), though they failed with sequential presentation of two different objects vs. one object presented three times if they had been familiarized with up to three identical objects (Experiment 4). Chicks instead succeeded if they had been familiarized with objects that were all different from one another (Experiment 5). These young birds thus proved able to use property and spatiotemporal information for object individuation.     

Object manipulation facilitates kind-based object individuation of shape-similar objects

Five experiments investigated the importance of shape and object manipulation when 12-month-olds were given the task of individuating objects representing exemplars of kinds in an event-mapping design. In Experiments 1 and 2, results of the study from Xu, Carey, and Quint (2004, Experiment 4) were partially replicated, showing that infants were able to individuate two natural-looking exemplars from different categories, but not two exemplars from the same category. In Experiment 3, infants failed to individuate two shape-similar exemplars (from Pauen, 2002a) from different categories. However, Experiment 4 revealed that allowing infants to manipulate objects shortly before the individuation task enabled them to individuate shape-similar objects from different categories. In Experiment 5, allowing object manipulation did not induce infants to individuate natural-looking objects from the same category. These findings suggest that object manipulation facilitates kind-based individuation of shape-similar objects by 12-month-olds.