We examined how infants' categorization is jointly influenced by previous experience and how much they shift their gaze back and forth between stimuli. Extending previous findings reported by K. A. Kovack-Lesh, J. S. Horst, and L. M. Oakes (2008), we found that 4-month-old infants' (N = 122) learning of the exclusive category of "cats" was related to whether they had cats at home and how much they shifted attention between two available stimuli during familiarization. Individual differences in attention assessed in an unrelated task were not related to their categorization. Thus, infants' learning is multiply influenced by past experience and online attentional style. (Contains 4 tables, 2 figures and 3 footnotes.)