The Human First Hypothesis: Identification of Conspecifics and Individuation of Objects in the Young Infant

doi:10.1006/cogp.2002.0779

Cognitive Psychology

Volume 44, Issue 4, June 2002, Pages 388-426

https://doi.org/10.1006/cogp.2002.0779 Get rights and content

Abstract

How do infants individuate and track objects, and among them objects belonging to their species, when they can only rely on information about the properties of those objects? We propose the Human First Hypothesis (HFH), which posits that infants possess information about their conspecifics and use it to identify and count objects. F. Xu and S. Carey [Cognitive Psychology,30(2), 111–153, 1996] argued that before the age of 1 year, infants fail to use property information. To explain their results, Xu and Carey proposed the Object First Hypothesis (OFH), according to which infants under 1 year of age have only the general concept of physical object to identify and count objects. We show that infants have a more extensive knowledge of sortals than that claimed by the OFH. When 10-month-olds see one humanlike and one non-humanlike object, they successfully identify and count them by using the contrast in their properties, as predicted by the HFH. We also show that infants succeed even when they make a decision based on differences between two close basic-level categories such as humanlike objects and doglike objects, but fail when they have to use differences within the human category. Thus, infants treat “human” as a basic sortal, as predicted by the HFH. We argue that our results cannot be accounted for by general purpose mechanisms. Neither the strong version of the OFH and its explanation in terms of object indexing mechanisms [A. M. Leslie, F. Xu, P. Tremoulet, & B. J. Scholl, Trends in Cognitive Sciences,2(1), 10–18, 1998] nor explanations in terms of task demands [T. Wilcox & R. Baillargeon, Cognitive Psychology,37(2), 97–155, 1998] are sufficient to explain our results.

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This paradigm – also known as the event-mapping paradigm – requires young infants to build expectations of how many objects are hidden behind the occluder and then map these expectations to an experimental outcome when the occluder is removed and the number of objects is revealed. Until 12-months of age, infants tested with this paradigm systematically fail to expect two objects on the basis of object property information (e.g., shape, color or size) (Xu & Carey, 1996), succeeding only when the objects show functional differences (Futo et al., 2010), belong to different highly relevant categories (e.g., human vs. non-human; Bonatti et al., 2002) or can be directly compared when simultaneously visible (Spelke, Kestenbaum, Simons, & Wein, 1995; Xu & Carey, 1996). Furthermore, even infants as old as 12 months of age continue to fail in individuating objects from the same category that differ in visual features (e.g., two ducks in different sizes) while succeeding when the objects are of different kind (e.g. a ball versus a duck) (Xu et al., 2004).
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.

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^☆

We thank Susan Carey for inspiration, discussion, and continuous support. Our gratitude to Rochel Gelman and Justin Halberda and to the anonymous referees for insightful comments on a first version of this paper, to Michel Dutat for technical support, to Susana Franck for correcting this manuscript, and to all the parents who volunteered to participate to the experiments. Some of these experiments were the core of E. Frot's Master's Dissertation (University of Paris VIII). During her work on the project, R. Zangl was funded by the FWF project J-1646-SPR.

Address correspondence and reprint requests to Luca Bonatti, SISSA-ISAS, Via Beirut 2/4, 34014 Trieste, Italy. E-mail: [email protected].

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Regular ArticleThe Human First Hypothesis: Identification of Conspecifics and Individuation of Objects in the Young Infant☆

Abstract

Cognition

Brain & Language

Cognition

Cognition

Trends in Cognitive Sciences

Cognitive Development

Cognitive Development

Cognitive Psychology

Cognition

Cognition

Cognition

Current Opinions in Neurobiology

Neuroscience Research

Cognitive Psychology

Cognition

Acta Psychologica

Cognitive Psychology

Cognition

Perception of biomechanical motions by infants: Implementation of various processing constraints

Journal of Experimental Psychology: Human Perception and Performance

The development of infant sensitivity to biomechanical motions

Child Development

Continuity and discontinuity in cognitive development

Anatomical variability in the cortical representation of first and second language

Neuroreport

Distinguishing between animates and inanimates: Not by motion alone

Regular Article
The Human First Hypothesis: Identification of Conspecifics and Individuation of Objects in the Young Infant☆