In a series of studies, young infants have been shown to form category representations for a variety of animal species and furniture artifacts (reviewed in Quinn, 2002c). In the experiments investigating young infants' category representations of various animal species, 3- and 4-month-olds familiarized with instances of 12 domestic cats, representing different breeds and depicted in a variety of stances, will generalize familiarization to novel instances of domestic cats, but show novel category preferences for birds, dogs, horses, tigers, and even female lions (Eimas & Quinn, 1994; Eimas, Quinn, & Cowan, 1994; Quinn, Eimas, & Rosenkrantz, 1993). Examples of the cats and dogs are shown in Figure 5.7.
In addition, same-aged infants familiarized with 12 horses will generalize to novel horses, but display novel category preferences for cats, giraffes, and zebras (Eimas & Quinn, 1994). These findings indicate that young infants can form separate representations for cats and horses each of which excludes instances of the other along with exemplars from a number of basic-level categories from the same superordinate animal category.
Behl-Chadha (1996) extended the findings of early basic-level categorization among animal species to furniture. Three- and 4-month-olds familiarized with 12 pictorial instances of chairs (including arm chairs, desk chairs, kitchen chairs, rocking chairs, and stuffed chairs, depicted in a variety of colors and viewpoints) generalized their familiarization to novel chairs, but displayed novel category preferences for couches, beds, and tables. In addition, 3- and 4-month-olds presented with 12 couches generalized their familiarization to novel couches, but showed novel category preferences for chairs, beds, and tables. These results indicate that 3- and 4-month-olds can form individuated representations for chairs and couches, each of which excludes instances of the other as well as beds and tables. Overall, the findings provide evidence that young infants are capable of forming category representations for both natural kind animal species and artifactual items of furniture at a near basic-level of exclusiveness.
The findings of early categorization are significant because they suggest that young infants divide the world of objects appropriately into perceptual cluster representations that later come to have conceptual significance for adults. That is, the category distinctions made by quite young infants are often the same distinctions that later in life come to have a conceptual nature. As such, this early veridical parsing of the world should permit infants to begin to incorporate new "nonobvious" knowledge into category representations initially constructed on the basis of perceptual experience. For example, if young infants possess abilities to form a category representation for cats (e.g., one that is based on observable surface attributes including overall body shape, parts, markings, head and face information, communicative sounds, and motion), then more abstract information that is learned later (e.g., that cats have the verbal label or name "cat," are meat eaters, possess cat DNA, give birth to kittens, and like to play string games) can be used to enrich the early perceptually based category representation and allow for the development of a conceptually based representation (i.e., a concept) for cats. The conceptual representations found in children and adults can thus be viewed as informational enrichments of young infants' perceptual category representations (Quinn, 2002b; Quinn & Eimas, 1997, 2000). By this view, the abilities that young infants have to form perceptual category representations may form the primitive base from which adult conceptions of objects develop.
One clarification that may be helpful at this point in the discussion is to acknowledge that the infants who are presented with exemplars of nonhuman animals (e.g., cats) and form category representations in the laboratory are not necessarily leaving the laboratory with long-term representations for cats that will themselves represent the start-up structures into which subsequent experience and knowledge can be incorporated. The claim is more that the infants are demonstrating parsing skills in the laboratory that may be successfully deployed to form representations for classes of real objects when those objects are encountered in the natural environment. It is the latter group of representations that may serve as the actual supports for further knowledge acquisition.
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