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Adults use both first-order, or categorical, relations among features (e.g., the nose is above the mouth), and second-order, or fine spatial relations (e.g., the space between eyes), to process faces. Adults' expertise in face processing is thought to be based on the use of second-order relations. In the current study, 5-month-olds detected second-order changes, but 3-month-olds failed to detect second-order changes induced by 2 different manipulations. Three-month-olds did detect first-order changes, however. Also, inversion affected 5-month-olds' processing of second-order but not first-order information. These results suggest that, although sensitivity to first-order relations is available by 3 months or earlier, sensitivity to second-order information may not develop until sometime between 3 and 5 months of age.
Bhatt et al. (Sat,) studied this question.