Categorization is usually considered to be challenging for individuals with autism (e.g., Minshew et al., 2002), because they tend to focus on the details of objects rather than abstracting their overall category. However, Gastgeb et al. (2006) have recently demonstrated that high-functioning 10-year-olds and adolescents with autism behaved similarly to typical peers in responding more quickly and accurately to items that are typical of their category (e.g., robins for bird) compared to atypical items (e.g., ostriches).
The current study investigates the categorization speed and accuracy of 6-year-old children with ASD and compares these with their performance on standardized tests; we also include TD controls.
Eight children with ASD (M(age) = 6.6 years, SD = .287) and 13 TD children (M(age) = 5.76 years, SD = .414) participated as part of a longitudinal study. The children had been matched on language level at the onset of the study (4 years prior) but now differed in their TACL Q (M(TD) = 121.42, SD = 8.71; M(ASD) = 77.88, SD = 21.50), DAS (M(TD = 110.2, SD = 13.92; M(ASD) = 78.12, SD = 19.07), and Vineland composite (M(TD) = 108, SD = 6.85; M(ASD) = 76.11, SD = 13.9). The groups being unmatched for mental age, performance is primarily compared within groups.
The categorization task was modeled after Gastgeb et al. (2006). Children saw pictures of cars, cats, chairs, and birds, plus foil (e.g., house) items, presented on a laptop. For each category, some items were rated ‘highly Typical’ by naïve adults while others were rated ‘highly Atypical’. Coincident with each picture, children were asked “Is this a cat/car/bird/ chair?” Two-thirds of the items were designed to elicit ‘yes’ responses. Accuracy and response time (correct responses only) data were collected via E-prime using enlarged response buttons.
As expected, the TD children responded significantly more accurately for the Typical items (98%) than for the Atypical items (74%, p< .01), and significantly more quickly to the Typical items (M = 2.1 seconds) than the Atypical items (M = 3.1 seconds, p < .01). The children with ASD showed no typicality effects for the response time measures, but did respond significantly more accurately for the Typical items (90% correct) than for the Atypical items (68%, p < .05). Moreover, while the TD children responded more quickly to the foil items than did the ASD children, the groups did not differ on accuracy with these items (over 90% for both). Finally, the children with ASD who performed more accurately also had higher scores on the TACL, the DAS, and the Vineland (rs > .708, ps < .05).
These results suggest that some high-functioning children with ASD demonstrate sensitivity to the typicality organization of common categories as young as 6 years of age. This sensitivity is demonstrated by their decreased accuracy for atypical items, but not by any changes in response time. Further research will investigate how the children’s early variations in trajectory of language development might predict their ability to categorize.
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